Estrogen action and male fertility: roles of the sodium/hydrogen exchanger-3 and fluid reabsorption in reproductive tract function

Metastasis-associated protein 1 participates in regulating luminal acidification of the epididymis via repressing estrogen receptor alpha transcription

BACKGROUND

As a component of the nucleosome remodeling and deacetylating (NuRD) complex, metastasis-associated protein 1 (MTA1) has been reported to be abundant in male reproductive system and might participate in spermatogenesis and sperm maturation, whereas the precise functional role of MTA1 in these processes is still undetermined.

OBJECTIVE

To investigate the effect and potential function of MTA1 in male fertility.

MATERIALS AND METHODS

Mta1 knockout mice (Mta1-/- ) were employed to detect their reproductive phenotype. The pH value of Mta1-/- epididymal luminal fluid was measured, and the potential mechanism of MTA1 involved in regulating luminal acidification was detected in vivo and in vitro. A vasectomy model with abnormal pH of epididymal lumen was established to further detect the effect of MTA1 on epididymal luminal microenvironment.

RESULTS

Mta1-/- mice were fertile without any detectable defects in spermatogenesis or sperm motility while the deficiency of MTA1 could acidify the initial segment of epididymis to a certain extent. MTA1 could interact with estrogen receptor alpha (ERα) and inhibit the transcription of ERα target gene, hydrogen exchanger 3 (NHE3), and ultimately affect the epididymal luminal milieu. After vasectomy, the Mta1-/- mice presented a more acidic epididymal lumen which was closer to the normal state compared to the wild-type model.

DISCUSSION AND CONCLUSION

MTA1 is dispensable for male fertility in mice, but plays a potentially important function in regulating luminal acidification of the epididymis.

Alkylphenols disrupt estrogen homeostasis via diradical cross-coupling reactions: A novel pathway of endocrine disruption

Estrogen, being an essential class of sex hormone, is an important target of endocrine disruption chemicals. It is well known that environmental disruptors could activate or inhibit estrogen receptors, acting as agonists or antagonists, and thus affect the circulating estrogen concentrations. Here, we report enzyme-mediated diradical cross-coupling reactions between alkylphenols (e.g., 2,4-di-tert-butylphenol [DBP], 4-nonylphenol [4-NP], and 4-tert-octylphenol [4-t-OP]) and estrogens (e.g., estradiol [E2]) that generate coupling metabolites and disrupt estrogen homeostasis. Among the phenolic xenobiotics, the screening of metabolic products revealed that alkylphenols had the highest reaction activities and generated coupling metabolites with high abundances (DBP-O-E2, 4-t-OP-O-E2, and 4-NP-O-E2). The coupling reactions were catalyzed by cytochrome P450 3A4 (CYP3A4) and verified by the detection of the coupling products in general populations. In vitro and in vivo exposures together with CYP3A4 inhibition demonstrated that cross-coupling reactions of phenols and E2 significantly reduced the normal levels of E2. We further established a unique spin-trapping-based high-throughput screening method to show the existence of diradicals in the coupling reaction. Density functional theory calculations revealed that spin aromatic delocalization was the fundamental cause of the high rebound barrier and sufficient lifetime of phenoxy radicals that enabled phenolic cross-coupling triggered by cytochrome P450. The identified mechanistic details for diradical cross-coupling reactions provide a novel pathway for phenolic chemicals to disrupt estrogen homeostasis.

Na+/H+ Exchangers (NHEs) in Mammalian Sperm: Essential Contributors to Male Fertility

Na+/H+ exchangers (NHEs) are known to be important regulators of pH in multiple intracellular compartments of eukaryotic cells. Sperm function is especially dependent on changes in pH and thus it has been postulated that NHEs play important roles in regulating the intracellular pH of these cells. For example, in order to achieve fertilization, mature sperm must maintain a basal pH in the male reproductive tract and then alkalize in response to specific signals in the female reproductive tract during the capacitation process. Eight NHE isoforms are expressed in mammalian testis/sperm: NHE1, NHE3, NHE5, NHE8, NHA1, NHA2, NHE10, and NHE11. These NHE isoforms are expressed at varying times during spermatogenesis and localize to different subcellular structures in developing and mature sperm where they contribute to multiple aspects of sperm physiology and male fertility including proper sperm development/morphogenesis, motility, capacitation, and the acrosome reaction. Previous work has provided evidence for NHE3, NHE8, NHA1, NHA2, and NHE10 being critical for male fertility in mice and NHE10 has recently been shown to be essential for male fertility in humans. In this article we review what is known about each NHE isoform expressed in mammalian sperm and discuss the physiological significance of each NHE isoform with respect to male fertility.

Aquaporins in Reproductive System

AQP0-12, a total of 13 aquaporins are expressed in the mammalian reproductive system. These aquaporins mediate the transport of water and small solutes across biofilms for maintaining reproductive tract water balance and germ cell water homeostasis. These aquaporins play important roles in the regulation of sperm and egg cell production, maturation, and fertilization processes. Impaired AQP function may lead to diminished male and female fertility. This review focuses on the distribution, function, and regulation of AQPs throughout the male and female reproductive organs and tracts. Their correlation with reproductive success, revealing recent advances in the physiological and pathophysiological roles of aquaporins in the reproductive system.

Tissue hydraulics in reproduction

The development of functional eggs and sperm are critical processes in mammalian development as they ensure successful reproduction and species propagation. While past studies have identified important genes that regulate these processes, the roles of luminal flow and fluid stress in reproductive biology remain less well understood. Here, we discuss recent evidence that support the diverse functions of luminal fluid in oogenesis, spermatogenesis and embryogenesis. We also review emerging techniques that allow for precise quantification and perturbation of tissue hydraulics in female and male reproductive systems, and propose new questions and approaches in this field. We hope this review will provide a useful resource to inspire future research in tissue hydraulics in reproductive biology and diseases.

The Physiological Function and Potential Role of the Ubiquitous Na+/H+ Exchanger Isoform 8 (NHE8): An Overview Data

The Na⁺/H⁺ exchanger transporters (NHE) play an important role in various biologic processes including Na⁺ absorption, intracellular pH homeostasis, cell volume regulation, proliferation, and apoptosis. The wide expression pattern and cellular localization of NHEs make these proteins pivotal players in virtually all human tissues and organs. In addition, recent studies suggest that NHEs may be one of the primeval transport protein forms in the history of life. Among the different isoforms, the most well-characterized NHEs are the Na⁺/H⁺ exchanger isoform 1 (NHE1) and Na⁺/H⁺ exchanger isoform 3 (NHE3). However, Na⁺/H⁺ exchanger isoform 8 (NHE8) has been receiving attention based on its recent discoveries in the gastrointestinal tract. In this review, we will discuss what is known about the physiological function and potential role of NHE8 in the main organ systems, including useful overviews that could inspire new studies on this multifaceted protein.

Tricresyl phosphate inhibits fertilization in Japanese medaka (Oryzias latipes): Emphasizing metabolic toxicity

As tricresyl phosphate (TCrP) is commonly found in global water sources, its potential reproductive toxicity to fish is of increasing concern. Japanese medaka larvae were exposed to TCrP at 657.9, 1,511, and 4042 ng/L for 100 days. We identified significant fertilization inhibition (6.9%-12.8%) in all exposure groups. Intersex was significantly induced at 4042 ng/L, with an incidence of 22.0%. TCrP exposure also caused dilation of the efferent duct in the testes with maximum duct widths of 83.3, 93.2, and 149.7 μm in the 657.9, 1,511, and 4042 ng/L exposure groups, respectively. These widths were all significantly larger than that observed in the control group (37.7 μm) and likely contributed substantially to fertilization inhibition. The TCrP metabolites 4-OH-MDTP and 3-OH-MDTP, were detected at high concentrations in the liver and elicited 5.8-fold and 5.3-fold greater androgen receptor antagonistic activity than that elicited by TCrP (39.8 μM), which may explain the intersex observed in low exposure groups. 4-OH-MDTP and 3-OH-MDTP elicited anti-estrogenic activities by blocking the estrogen receptor, and the concentrations at which its responses were equal to the IC₂₀ of tamoxifen were 16.1 μM and 18.9 μM, respectively, as detected using the yeast two-hybrid assay. Such anti-estrogenic activities were likely the main driver of dilation of the efferent duct. Observed adverse outcomes after exposure to TCrP all occurred under environmentally relevant concentrations, suggesting considerable ecological risk to wild fish.

Essential Roles of Efferent Duct Multicilia in Male Fertility

Cilia are microtubule-based hair-like organelles on the cell surface. Cilia have been implicated in various biological processes ranging from mechanosensation to fluid movement. Ciliary dysfunction leads to a plethora of human diseases, known as ciliopathies. Although non-motile primary cilia are ubiquitous, motile multicilia are found in restricted locations of the body, such as the respiratory tract, the oviduct, the efferent duct, and the brain ventricles. Multicilia beat in a whip-like motion to generate fluid flow over the apical surface of an epithelium. The concerted ciliary motion provides the driving force critical for clearing airway mucus and debris, transporting ova from the ovary to the uterus, maintaining sperm in suspension, and circulating cerebrospinal fluid in the brain. In the male reproductive tract, multiciliated cells (MCCs) were first described in the mid-1800s, but their importance in male fertility remained elusive until recently. MCCs exist in the efferent ducts, which are small, highly convoluted tubules that connect the testis to the epididymis and play an essential role in male fertility. In this review, we will introduce multiciliogenesis, discuss mouse models of male infertility with defective multicilia, and summarize our current knowledge on the biological function of multicilia in the male reproductive tract.

Nedd4-2-dependent Ubiquitination Potentiates the Inhibition of Human NHE3 by Cholera Toxin and Enteropathogenic Escherichia coli

BACKGROUND & AIMS

Diarrhea is one of the most common illnesses and is often caused by bacterial infection. Recently, we have shown that human Na⁺/H⁺ exchanger NHE3 (hNHE3), but not non-human NHE3s, interacts with the E3 ubiquitin ligase Nedd4-2. We hypothesize that this property of hNHE3 contributes to the increased severity of diarrhea in humans.

METHODS

We used humanized mice expressing hNHE3 in the intestine (hNHE3^int) to compare the contribution of hNHE3 and mouse NHE3 to diarrhea induced by cholera toxin (CTX) and enteropathogenic Escherichia coli (EPEC). We measured Na⁺/H⁺ exchange activity and fluid absorption. The role of Nedd4-2 on hNHE3 activity and ubiquitination was determined by knockdown in Caco-2bbe cells. The effects of protein kinase A (PKA), the primary mediator of CTX-induced diarrhea, on Nedd4-2 and hNHE3 phosphorylation and their interaction were determined.

RESULTS

The effects of CTX and EPEC were greater in hNHE3^int mice than in control wild-type (WT) mice, resulting in greater inhibition of NHE3 activity and increased fluid accumulation in the intestine, the hallmark of diarrhea. Activation of PKA increased ubiquitination of hNHE3 and enhanced interaction of Nedd4-2 with hNHE3 via phosphorylation of Nedd4-2 at S342. S342A mutation mitigated the Nedd4-2-hNHE3 interaction and blocked PKA-induced inhibition of hNHE3. Unlike non-human NHE3s, inhibition of hNHE3 by PKA is independent of NHE3 phosphorylation, suggesting a distinct mechanism of hNHE3 regulation.

CONCLUSIONS

The effects of CTX and EPEC on hNHE3 are amplified, and the unique properties of hNHE3 may contribute to diarrheal symptoms occurring in humans.

Effects of shikonin on the development of ovarian follicles and female germline stem cells

Objective

To investigate the effects and potential mechanism of action of shikonin (SHK) on the development of ovarian follicles and female germline stem cells (FGSCs).

Methods

Female Kunming adult mice were administered SHK (0, 20 and 50 mg/kg) by oral gavage. Cultures of FGSCs were treated with SHK 32 μmol/l for 24 h. The ovarian index in mouse ovaries was calculated. Numbers of primordial, primary and atretic follicles were counted. Germline stem cell markers and apoptosis were examined. Levels of glutathione (GSH), superoxide dismutase (SOD) and reactive oxygen species (ROS) were measured.

Results

Both doses of SHK significantly decreased the ovarian index, the numbers of primordial follicles, primary follicles and antral follicles in mice. SHK significantly increased the numbers of atretic follicles and atretic corpora lutea. SHK promoted apoptosis in vivo and in vitro. SHK significantly decreased the levels of the germline stem cell markers. SHK significantly lowered GSH levels and the activity of SOD in the peripheral blood from mice, whereas SHK significantly elevated cellular ROS content in FGSCs.

Conclusions

These current results suggested that follicular development and FGSCs were suppressed by SHK through the induction of apoptosis and oxidative stress might be involved in this pathological process.

Aquaporins: New markers for male (in)fertility in livestock and poultry?

Improving the methods utilized to facilitate reproduction is associated with a constant need to search for new factors that not only significantly affect reproductive processes, but also create new possibilities when assessing male reproductive potential. Aquaporins (AQPs) belong to a family of small (28-30 kDa) proteins that facilitate the transport of water and other small molecules. There have been 13 AQPs (AQP0-AQP12) discovered in mammals, and these proteins are present in a wide range of cell types. Almost all AQPs, except AQP6 and AQP12 are present in the male reproductive organs and sperm of mammals and birds. Increasing evidence suggests that these proteins are involved in a number of processes responsible for the optimal functioning of the male reproductive system. This review presents the current state of knowledge regarding the abundance and distribution of AQPs in the male reproductive organs and sperm of various livestock and poultry species, including buffalo, cattle, sheep, horses, pigs, turkeys and goose. Furthermore, the possible physiological and pathophysiological significance of AQPs in male reproduction, as well as hormonal regulation of quantities are discussed. It can be concluded from the studies analyzed in this paper that abundance patterns of AQPs may be considered in the future as specific and universal biomarkers of male fertility and infertility in animal husbandry.

Recent Update on the Molecular Mechanisms of Gonadal Steroids Action in Adipose Tissue

The gonadal steroids, including androgens, estrogens and progestogens, are involved in the control of body fat distribution in humans. Nevertheless, not only the size and localization of the fat depots depend on the sex steroids levels, but they can also highly affect the functioning of adipose tissue. Namely, the gonadocorticoids can directly influence insulin signaling, lipid metabolism, fatty acid uptake and adipokine production. They may also alter energy balance and glucose homeostasis in adipocytes in an indirect way, e.g., by changing the expression level of aquaglyceroporins. This work presents the recent advances in understanding the molecular mechanism of how the gonadal steroids influence the functioning of adipose tissue leading to a set of detrimental metabolic consequences. Special attention is given here to highlighting the sexual dimorphism of adipocyte functioning in terms of health and disease. Particularly, we discuss the molecular background of metabolic disturbances occurring in consequence of hormonal imbalance which is characteristic of some common endocrinopathies such as the polycystic ovary syndrome. From this perspective, we highlight the potential drug targets and the active substances which can be used in personalized sex-specific management of metabolic diseases, in accord with the patient's hormonal status.

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.

Aquaporins and (in)fertility: More than just water transport

Aquaporins (AQPs) are a family of channel proteins that facilitate the transport of water and small solutes across biological membranes. They are widely distributed throughout the organism, having a number of key functions, some of them unexpected, both in health and disease. Among the various diseases in which AQPs are involved, infertility has been overlooked. According to the World Health Organization (WHO) infertility is a global public health problem with one third of the couples suffering from subfertility or even infertility due to male or female factors alone or combined. Thus, there is an urgent need to unveil the molecular mechanisms that control gametes production, maturation and fertilization-related events, to more specifically determine infertility causes. In addition, as more couples seek for fertility treatment through assisted reproductive technologies (ART), it is pivotal to understand how these techniques can be improved. AQPs are heterogeneously expressed throughout the male and female reproductive tracts, highlighting a possible regulatory role for these proteins in conception. In fact, their function, far beyond water transport, highlights potential intervention points to enhance ART. In this review we discuss AQPs distribution and structural organization, functions, and modulation throughout the male and female reproductive tracts and their relevance to the reproductive success. We also highlight the most recent advances and research trends regarding how the different AQPs are involved and regulated in specific mechanisms underlying (in)fertility. Finally, we discuss the involvement of AQPs in ART-related processes and how their handling can lead to improvement of infertility treatment.

Function and therapeutic potential of G protein-coupled receptors in epididymis

Infertility rates for both females and males have increased continuously in recent years. Currently, effective treatments for male infertility with defined mechanisms or targets are still lacking. G protein-coupled receptors (GPCRs) are the largest class of drug targets, but their functions and the implications for the therapeutic development for male infertility largely remain elusive. Nevertheless, recent studies have shown that several members of the GPCR superfamily play crucial roles in the maintenance of ion-water homeostasis of the epididymis, development of the efferent ductules, formation of the blood-epididymal barrier and maturation of sperm. Knowledge of the functions, genetic variations and working mechanisms of such GPCRs, along with the drugs and ligands relevant to their specific functions, provide future directions and a great arsenal for new developments in the treatment of male infertility.

The Fundamental Role of Bicarbonate Transporters and Associated Carbonic Anhydrase Enzymes in Maintaining Ion and pH Homeostasis in Non-Secretory Organs

The bicarbonate ion has a fundamental role in vital systems. Impaired bicarbonate transport leads to various diseases, including immune disorders, cystic fibrosis, tumorigenesis, kidney diseases, brain dysfunction, tooth fracture, ischemic reperfusion injury, hypertension, impaired reproductive system, and systemic acidosis. Carbonic anhydrases are involved in the mechanism of bicarbonate movement and consist of complex of bicarbonate transport systems including bicarbonate transporters. This review focused on the convergent regulation of ion homeostasis through various ion transporters including bicarbonate transporters, their regulatory enzymes, such as carbonic anhydrases, pH regulatory role, and the expression pattern of ion transporters in non-secretory systems throughout the body. Understanding the correlation between these systems will be helpful in order to obtain new insights and design potential therapeutic strategies for the treatment of pH-related disorders. In this review, we have discussed the broad prospects and challenges that remain in elucidation of bicarbonate-transport-related biological and developmental systems.

Importance of SLC26 Transmembrane Anion Exchangers in Sperm Post-testicular Maturation and Fertilization Potential

In mammals, sperm cells produced within the testis are structurally differentiated but remain immotile and are unable to fertilize the oocyte unless they undergo a series of maturation events during their transit in the male and female genital tracts. This post-testicular functional maturation is known to rely on the micro-environment of both male and female genital tracts, and is tightly controlled by the pH of their luminal milieus. In particular, within the epididymis, the establishment of a low bicarbonate (HCO₃^–) concentration contributes to luminal acidification, which is necessary for sperm maturation and subsequent storage in a quiescent state. Following ejaculation, sperm is exposed to the basic pH of the female genital tract and bicarbonate (HCO₃^–), calcium (Ca²⁺), and chloride (Cl^–) influxes induce biochemical and electrophysiological changes to the sperm cells (cytoplasmic alkalinization, increased cAMP concentration, and protein phosphorylation cascades), which are indispensable for the acquisition of fertilization potential, a process called capacitation. Solute carrier 26 (SLC26) members are conserved membranous proteins that mediate the transport of various anions across the plasma membrane of epithelial cells and constitute important regulators of pH and HCO₃^– concentration. Most SLC26 members were shown to physically interact and cooperate with the cystic fibrosis transmembrane conductance regulator channel (CFTR) in various epithelia, mainly by stimulating its Cl^– channel activity. Among SLC26 members, the function of SLC26A3, A6, and A8 were particularly investigated in the male genital tract and the sperm cells. In this review, we will focus on SLC26s contributions to ionic- and pH-dependent processes during sperm post-testicular maturation. We will specify the current knowledge regarding their functions, based on data from the literature generated by means of in vitro and in vivo studies in knock-out mouse models together with genetic studies of infertile patients. We will also discuss the limits of those studies, the current research gaps and identify some key points for potential developments in this field.

pH and male fertility: making sense on pH homeodynamics throughout the male reproductive tract

In the male reproductive tract, ionic equilibrium is essential to maintain normal spermatozoa production and, hence, the reproductive potential. Among the several ions, HCO3- and H+ have a central role, mainly due to their role on pH homeostasis. In the male reproductive tract, the major players in pH regulation and homeodynamics are carbonic anhydrases (CAs), HCO3- membrane transporters (solute carrier 4-SLC4 and solute carrier 26-SLC26 family transporters), Na+-H+ exchangers (NHEs), monocarboxylate transporters (MCTs) and voltage-gated proton channels (Hv1). CAs and these membrane transporters are widely distributed throughout the male reproductive tract, where they play essential roles in the ionic balance of tubular fluids. CAs are the enzymes responsible for the production of HCO3- which is then transported by membrane transporters to ensure the maturation, storage, and capacitation of the spermatozoa. The transport of H+ is carried out by NHEs, Hv1, and MCTs and is essential for the electrochemical balance and for the maintenance of the pH within the physiological limits along the male reproductive tract. Alterations in HCO3- production and transport of ions have been associated with some male reproductive dysfunctions. Herein, we present an up-to-date review on the distribution and role of the main intervenient on pH homeodynamics in the fluids throughout the male reproductive tract. In addition, we discuss their relevance for the establishment of the male reproductive potential.

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.

Genetic defects in human azoospermia

As with many other diseases, genetic testing in human azoospermia was initially restricted to karyotype analyses (leading to diagnostic chromosome rearrangement tests for Klinefelter and other syndromes). With the advent of molecular biology in the 1980s, genetic screening was broadened to analyses of Y chromosome microdeletions and the gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR). Decades later, the emergence of whole-genome techniques has led to the identification of other genetic defects associated with human azoospermia. Although TEX11 and ADGRG2 defects are frequently described in men with azoospermia, most of the causal gene defects found to date are private (i.e. identified in a small number of consanguineous families).

Here, we provide an up-to-date overview of all the types of genetic defects known to be linked to human azoospermia and try to give clinical practice guidelines according to azoospermia phenotype. Along with homozygous mutations, polymorphisms and epigenetic defects are also briefly discussed. However, as these variations predispose to azoospermia, a specific review will be needed to compile data on all the particular genetic variations reported in the literature.

SLC9A3 Affects Vas Deferens Development and Associates with Taiwanese Congenital Bilateral Absence of the Vas Deferens

Background

The pathophysiology of Taiwanese congenital bilateral absence of the vas deferens (CBAVD) is different from that in Caucasians. In particular, major cystic fibrosis transmembrane conductance regulator (CFTR) mutations and cystic fibrosis are absent in the former. Instead, deficiency in solute carrier family 9 sodium/hydrogen exchanger isoform 3 (SLC9A3) may play a role by generating obstructive azoospermia and degraded epithelial structure in the reproductive tract.

Objectives

The objective of the study was to test whether SLC9A3 variants cause Taiwanese CBAVD.

Materials and Methods

Six-month-old Slc9a3 ^-/-male mice were used to evaluate the effect of long-term SLC9A3 loss on the reproductive system. A case-control cohort of 29 men with CBAVD and 32 fertile men were genotyped for SLC9A3 variants.

Results

SLC9A3 was expressed and localized in the apical border of the epithelium of human vas deferens and glandular epithelium of the seminal vesicle. SLC9A3 deficiency specifically induces atrophy of vas deferens and unfolding of seminal vesicle mucosa in mice. Loss of SLC9A3 increased the incidence of CBAVD in humans from 3.1% to 37.9% (p < 0.001). Up to 75.9% of CBAVD patients carry at least one variant in either SLC9A3 or CFTR.

Discussion

Our findings build upon previous data associated with CBAVD pathogenesis. Here, we now report for the first time an association between CBAVD and loss of SLC9A3 and propose that specific defects in the reproductive duct due to SLC9A3 variants drive CBAVD development.

Conclusion

The data implicate loss of SLC9A3 as a basis of Taiwanese CBAVD and highlight SLC9A3 function in reproduction.

Ethylene dimethane sulfonate (EDS) ablation of Leydig cells in adult rat depletes testosterone resulting in epididymal sperm granuloma: Testosterone replacement prevents granuloma formation

Sperm granuloma may develop in the epididymis following vasectomy or chemical insults. Inflammation due to sperm granuloma causes abdominal and scrotal pain. Prolonged and persistent inflammation in the epididymis due to sperm granuloma may lead to infertility. Extravasation of germ cells into the interstitium of epididymis following damage of the epididymal epithelium is one of the primary reasons for sperm granuloma-associated pathology. Since testosterone is vital for the maintenance of epididymal epithelium, we investigated the pathology of sperm granuloma and its relationship with testosterone. Adult rats were treated with a Leydig cell-specific toxicant ethylene dimethane sulfonate (EDS) to eliminate testosterone. At 7 days post-EDS, disrupted epididymal epithelium and sperm granuloma were observed in the caput epididymis. Sperm granuloma and caput were collagen-filled indicating fibrosis. Numerous round apoptotic cells were localized inside the caput lumen and dispersed through the sperm granuloma. Tnp1 (round spermatid marker) was significantly higher in the epididymis of the EDS-treated group compared to controls suggesting the apoptotic cells were round spermatids. Increases in CD68⁺ macrophages and T cells (CD4 and CD8) support an inflammatory immune infiltration in post-EDS epididymis. However, testosterone replacement following EDS prevented the sperm granuloma-associated pathology. We suggest that the immune response in the sperm granuloma may be due to the increased numbers of apoptotic round spermatids or other testicular tissue components that may be released, in addition to the regression of epididymal epithelium due to testosterone loss. Thus, testosterone replacement prevents EDS-induced sperm granuloma and ameliorates sperm granuloma-associated pathology.

Targeting newly identified ERβ/TGF-β1/SMAD3 signals with the FDA-approved anti-estrogen Faslodex or an ERβ selective antagonist in renal cell carcinoma

Renal cell carcinoma (RCC) has the third highest mortality rate among urological tumors, and 20–30% of RCC patients present with metastatic RCC at the time of diagnosis. Although recent studies have indicated that estrogen receptor β (ERβ) could play promoting roles in RCC progression, the detailed mechanisms remain to be clarified. In the present study, we found that expression of ERβ, but not ERα, increases with tumor stage and grade, and also observed that modification of ERβ signals using estrogens/anti‐estrogens, shRNA knockdown of ERβ and overexpression of ERβ using ectopic cDNA affects RCC cell proliferation, migration and invasion. Mechanism analysis revealed that ERβ can promote RCC cell invasion via an increase in transforming growth factor β1 (TGF‐β1)/SMAD3 signals, and interrupting TGF‐β1/SMAD3 signals with a TGFβR1 inhibitor can reverse/block ERβ‐increased RCC cell migration. Importantly, preclinical analyses using in vivo mouse models of RCC revealed that targeting of this newly identified ERβ/TGF‐β1/SMAD3 pathway with either the FDA‐approved anti‐estrogen ICI182,780 (Faslodex) or a selective ERβ antagonist 4‐[2‐phenyl‐5,7 bis(trifluoromethyl)pyrazolo[1,5‐a]pyrimidin‐3‐yl]phenol can significantly reduce RCC tumor growth and invasion, which may be suitable as the basis for novel therapies to more effectively suppress metastatic RCC.

Estrogen Receptors: New Directions in the New Millennium

Nineteen years have passed since our previous review in this journal in 1999 regarding estrogen receptors. At that time, we described the current assessments of the physiological activities of estrogen and estrogen receptors. Since that time there has been an explosion of progress in our understanding of details of estrogen receptor-mediated processes from the molecular and cellular level to the whole organism. In this review we discuss the basic understanding of estrogen signaling and then elaborate on the progress and current understanding of estrogen receptor actions that have developed using new models and continuing clinical studies.

Localization of epithelial sodium channel (ENaC) and CFTR in the germinal epithelium of the testis, Sertoli cells, and spermatozoa

Spermatogenesis starts within the seminiferous tubules of the testis by mitotic division of spermatogonia that produces spermatocytes. Meiotic division of these spermatocytes produces haploid spermatids that differentiate into spermatozoa. In this study, we examined the expression of ENaC and CFTR (a Cl^- channel) in rat testicular sections using confocal microscopic immunofluorescence. The structural integrity of the seminiferous tubule sections was verified by precise phalloidin staining of the actin fibers located abundantly at both basal and adluminal tight junctions. The acrosome forming regions in the round spermatids were stained using an FITC coupled lectin (wheat germ agglutinin). In all phases of the germ cells (spermatogonia, spermatocytes, and spermatids) ENaC was localized in cytoplasmic pools. Prior to spermiation, ENaC immunofluorescence appeared along the tails of the spermatids. In spermatozoa isolated from the epididymis, ENaC was localized at the acrosome and a central region of the sperm flagellum. The mature sperm are transcriptionally silent. Hence, we suggest that ENaC subunits in cytoplasmic pools in germ cells serve as the source of ENaC subunits located along the tail of spermatozoa. The locations of ENaC is compatible with a possible role in the acrosomal reaction and sperm mobility. In contrast to ENaC, CFTR immunofluorescence was most strongly observed specifically within the Sertoli cell nuclei. Based on the nuclear localization of CFTR we suggest that, in addition to its role as an ion channel, CFTR may have an independent role in gene regulation within the nuclei.

Gq activity- and β-arrestin-1 scaffolding-mediated ADGRG2/CFTR coupling are required for male fertility

Luminal fluid reabsorption plays a fundamental role in male fertility. We demonstrated that the ubiquitous GPCR signaling proteins Gq and β-arrestin-1 are essential for fluid reabsorption because they mediate coupling between an orphan receptor ADGRG2 (GPR64) and the ion channel CFTR. A reduction in protein level or deficiency of ADGRG2, Gq or β-arrestin-1 in a mouse model led to an imbalance in pH homeostasis in the efferent ductules due to decreased constitutive CFTR currents. Efferent ductule dysfunction was rescued by the specific activation of another GPCR, AGTR2. Further mechanistic analysis revealed that β-arrestin-1 acts as a scaffold for ADGRG2/CFTR complex formation in apical membranes, whereas specific residues of ADGRG2 confer coupling specificity for different G protein subtypes, this specificity is critical for male fertility. Therefore, manipulation of the signaling components of the ADGRG2-Gq/β-arrestin-1/CFTR complex by small molecules may be an effective therapeutic strategy for male infertility.

Atrazine affects the morphophysiology, tissue homeostasis and aromatase expression in the efferent ductules of adult rats with mild alterations in the ventral prostate

The widely used herbicide atrazine is a potent endocrine disruptor known to cause increased aromatase expression and transient increase in testicular weight followed by remarkable testis atrophy. However, whether the effects of atrazine on the testes are primary or secondary to dysfunctions in other components of male reproductive tract remains unknown. Given the high sensitivity of the efferent ductules to estrogen imbalance and the similarity to alterations previously described for other disruptors of these ductules function, and the testicular alterations observed after atrazine exposure, we hypothesized that the efferent ductules could be a target for atrazine. Herein we characterized the efferent ductules and the ventral prostate of adult Wistar rats treated with 200 mg/kg/day of atrazine for 7, 15, and 40 days. Additionally, we evaluated if the effects of atrazine in these organs could be reduced after discontinuation of the treatment. Atrazine exposure resulted in mild effects on the ventral prostate, but remarkable alterations on the efferent ductules, including luminal dilation, reduced epithelial height, and disruption of the epithelial homeostasis, which coincides with increased aromatase expression. Together with our previous data, these results suggest that at least part of the testicular effects of atrazine may be secondary to the alterations in the efferent ductules.

SLC9A3 Protein Is Critical for Acrosomal Formation in Postmeiotic Male Germ Cells

Solute carrier family 9 isoform 3 (SLC9A3), a Na⁺/H⁺ exchanger, regulates the transepithelial absorption of Na⁺ and water and is primarily expressed on the apical membranes of the intestinal epithelium, renal proximal tubule, epididymis, and vas deferens. Loss of the Slc9a3 allele in mice enhances intestinal fluid and causes diarrhoea as a consequence of diminished Na⁺ and HCO₃⁻ absorption. Hence, the loss also causes male infertility and reveals the abnormal dilated lumen of the rete testis and calcification in efferent ductules. However, whether loss of Slc9a3 alleles also disrupts mammalian spermatogenesis remains unknown. First, through immunoblotting, we determined that SLC9A3 is highly expressed in the murine testis compared with the small intestine, epididymis, and vas deferens. During murine spermatogenesis, SLC9A3 is specifically expressed in the acrosome region of round, elongating, and elongated spermatids through immunostaining. Furthermore, SLC9A3 signals are enriched in the acrosome of mature sperm isolated from the vas deferens. In Slc9a3 knockout (KO) mice, compared with the same-aged controls, the number of spermatids on the testicular section of the mice progressively worsened in mice aged 20, 35, and 60 days. Sperm isolated from the epididymis of Slc9a3 KO mice revealed severe acrosomal defects. Our data indicated that SLC9A3 has a vital role in acrosomal formation during spermiogenesis.

Genome-Wide Mapping of In Vivo ERα-Binding Sites in Male Mouse Efferent Ductules

As an important nuclear hormone receptor, estrogen receptor α (ERα), which is encoded by the Esr1 gene, regulates the expression of hundreds of genes in a stimulus-specific, temporal, and tissue-specific fashion, mainly by binding to specific DNA sequences called estrogen response elements (EREs). As an important estrogen target tissue in males, the function of the efferent ductules relies on the presence of the ERα protein, but the underlying regulatory mechanisms are poorly illustrated. In this study, genome-wide ERα-binding sites in mouse efferent ductules were mapped by chromatin immunoprecipitation sequencing. In total, 12,105 peaks were identified, and a majority of them were located far from the annotated gene transcription start site. Motif analysis revealed that ∼80% of the ERα-binding peaks harbored at least one ERE, whereas androgen response element-like sequences were the most overrepresented motif in the peaks without any EREs. A number of candidate transcription factor motifs adjacent to the EREs were significantly enriched, including AP2 and GRE, implying the involvement of these putative adjacent factors in the global regulation of ERα target genes. Unexpectedly, more than 50% of the ERα-binding peaks in mouse efferent ductules overlapped with those binding peaks previously identified in mouse uterus, suggesting the conserved mechanism of ERα action in these two tissues. Cobinding of ERα target genes by androgen receptor was further confirmed for Slc9a3 gene, which was responsible for fluid resorption in the efferent ductules. Taken together, our study provides a useful reference set for future work aimed at exploring the mechanism of ERα action in physiological conditions.

A missense mutation in SLC26A3 is associated with human male subfertility and impaired activation of CFTR

Chloride absorption and bicarbonate excretion through exchange by the solute carrier family 26 member 3 (SLC26A3) and cystic fibrosis transmembrane conductance regulator (CFTR) are crucial for many tissues including sperm and epithelia of the male reproductive tract. Homozygous SLC26A3 mutations cause congenital chloride diarrhea with male subfertility, while homozygous CFTR mutations cause cystic fibrosis with male infertility. Some homozygous or heterozygous CFTR mutations only manifest as male infertility. Accordingly, we studied the influence of SLC26A3 on idiopathic infertility by sequencing exons of SLC26A3 in 283 infertile and 211 control men. A heterozygous mutation c.2062 G > C (p.Asp688His) appeared in nine (3.2%) infertile men, and additionally, in two (0.9%) control men, whose samples revealed a sperm motility defect. The p.Asp688His mutation is localized in the CFTR-interacting STAS domain of SLC26A3 and enriched in Finland, showing a significant association with male infertility in comparison with 6,572 Finnish (P < 0.05) and over 120,000 global alleles (P < 0.0001) (ExAC database). Functional studies showed that while SLC26A3 is a strong activator of CFTR-dependent anion transport, SLC26A3-p.Asp688His mutant retains normal Cl⁻/HCO₃⁻ exchange activity but suppresses CFTR, despite unaffected domain binding and expression. These results suggest a novel mechanism for human male infertility─impaired anion transport by the coupled SLC26A3 and CFTR.

Persistent testicular structural and functional alterations after exposure of adult rats to atrazine

Atrazine is an endocrine disruptor affecting testicular steroidogenesis, and promoting testicular atrophy and 3β-HSD reduction. However, it remains unknown whether these effects are reversible or permanent. To address this issue was the aim of this study. Exposition of rats to 200mg/kg of atrazine resulted in transient increase in testicular weight, seminiferous tubules dilation and atrophy, and reduction in Leydig cell 3β-HSD. Testicular atrophy and 3β-HSD reduction were more pronounced after the recovery period of 75days. There was increase in aromatase expression after long-term exposure but it returned to control level after recovery. Moreover, there was increase in ED1^-/ED2⁺, ED1⁺/ED2⁺ and ED1⁺/ED2^- macrophages, in the recovery group. These macrophages were positive for 3β-HSD, thereby raising possibility of their involvement in steroidogenesis. These findings further emphasize the adverse effects of atrazine on male reproduction, highlighting that testicular damages may be irreversible even after a recovery period longer than the spermatogenic cycle.

Colocalization of metastasis-associated proteins 1/2 and estrogen receptor alpha in rat epididymis

It has been suggested that metastasis-associated proteins 1 and 2 (MTA1 and MTA2) are capable of suppressing estrogen receptor alpha (ERα) transactivation activity in breast cancer cells. ERα, which is present in the epididymis, is a crucial mediator of maintaining the luminal environment necessary for proper sperm maturation and function. The present study was undertaken to analyze the expression profile of both MTA1 and MTA2 in the epididymis of rats and to ascertain whether MTA1/2 colocalizes with ERα in the epididymis and primary cultured epididymal epithelial cells. Reverse transcription polymerase chain reaction (RT-PCR), Western blotting and immunohistochemistry analyses were utilized to demonstrate that MTA1 and MTA2 are expressed in the epididymis. Furthermore, these analyses revealed that MTA1 and MTA2 are predominantly localized in the nuclei of almost all epididymal epithelial cells. Immunofluorescence staining revealed that MTA1/2 colocalizes with ERα in epididymal epithelial cells. In conclusion, MTA1 and MTA2 are expressed in the epididymis of rats; these proteins colocalize with ERα in epididymal epithelial cells, suggesting that MTA1 and MTA2 may be involved in the regulation of ERα transactivation activity in the epididymis of rats to facilitate a stable environment in the lumen.

Estrogens in Male Physiology

Estrogens have historically been associated with female reproduction, but work over the last two decades established that estrogens and their main nuclear receptors (ESR1 and ESR2) and G protein-coupled estrogen receptor (GPER) also regulate male reproductive and nonreproductive organs. 17β-Estradiol (E2) is measureable in blood of men and males of other species, but in rete testis fluids, E2 reaches concentrations normally found only in females and in some species nanomolar concentrations of estrone sulfate are found in semen. Aromatase, which converts androgens to estrogens, is expressed in Leydig cells, seminiferous epithelium, and other male organs. Early studies showed E2 binding in numerous male tissues, and ESR1 and ESR2 each show unique distributions and actions in males. Exogenous estrogen treatment produced male reproductive pathologies in laboratory animals and men, especially during development, and studies with transgenic mice with compromised estrogen signaling demonstrated an E2 role in normal male physiology. Efferent ductules and epididymal functions are dependent on estrogen signaling through ESR1, whose loss impaired ion transport and water reabsorption, resulting in abnormal sperm. Loss of ESR1 or aromatase also produces effects on nonreproductive targets such as brain, adipose, skeletal muscle, bone, cardiovascular, and immune tissues. Expression of GPER is extensive in male tracts, suggesting a possible role for E2 signaling through this receptor in male reproduction. Recent evidence also indicates that membrane ESR1 has critical roles in male reproduction. Thus estrogens are important physiological regulators in males, and future studies may reveal additional roles for estrogen signaling in various target tissues.

The expressions in oxytocin and sex steroid receptors in the reproductive tissues of normal and unilateral cryptorchid dogs

In males, oxytocin is involved with various physiological functions, such as reproductive tract contractility and testicular steroidogenesis. Due to the relationship between sex steroid hormones, oxytocin receptor (OTR) expression and cryptorchidism pathogenesis, this study aimed to investigate the mRNA expression and the localization of OTR in relation to sex steroid receptors in the male reproductive tract of both normal and unilateral abdominal cryptorchid dogs using quantitative PCR and immunohistochemistry. Male dogs were divided into two groups of normal and cryptorchid dogs. Samples from each cryptorchid dog were separated into two subgroups: scrotal and abdominal subgroups. The results showed that a lower percentage of positive OTR immunostaining in the testis and epididymis was observed in the cryptorchid group compared to the normal group. Within the cryptorchid group, the mRNA expression and the localization of OTR in the testis and epididymis of the abdominal subgroup was less than that of the scrotal subgroup. Moreover, the localization of OTR and estrogen receptor beta (ERβ) in reproductive tissues was positively correlated only in the normal group and not in the cryptorchid group. In conclusion, this study proposed that OTR expression, as well as the correlation between the OTR and ERβ in reproductive tissues of male dogs, can be disturbed by cryptorchidism. Furthermore, the OTR, ERβ and their correlation may be involved with the pathogenesis of cryptorchidism. Therefore, the study of gene knockout models to confirm the effect of OTR and sex steroid receptors on canine cryptorchidism should be of interest for further investigation.

Membrane estrogen receptor 1 is required for normal reproduction in male and female mice

Steroid hormones, acting through their cognate nuclear receptors, are critical for many reproductive and non-reproductive functions. Over the past two decades, it has become increasingly clear that in addition to cytoplasmic/nuclear steroid receptors that alter gene transcription when liganded, a small fraction of cellular steroid receptors are localized to the cell membranes, where they mediate rapid steroid hormone effects. 17β-Estradiol (E2), a key steroid hormone for both male and female reproduction, acts predominately through its main receptor, estrogen receptor 1 (ESR1). Most ESR1 is nuclear; however, 5-10% of ESR1 is localized to the cell membrane after being palmitoylated at cysteine 451 in mice. This review discusses reproductive phenotypes of a newly-developed mouse model with a C451A point mutation that precludes membrane targeting of ESR1. This transgenic mouse, termed the nuclear-only ESR1 (NOER) mouse, shows extensive male and female reproductive abnormalities and infertility despite normally functional nuclear ESR1 (nESR1). These results provide the first in vivo evidence that membrane-initiated E2/ESR1 signaling is required for normal male and female reproductive functions and fertility. Signaling mechanisms for membrane ESR1 (mESR1), as well as how mESR1 works with nESR1 to mediate estrogen effects, are still being established. We discuss some possible mechanisms by which mESR1 might facilitate nESR1 signaling, as well as the emerging evidence that mESR1 might be a major mediator of epigenetic effects of estrogens, which are potentially linked to various adult-onset pathologies.

Loss of the Na+/H+ exchanger NHE8 causes male infertility in mice by disrupting acrosome formation

Mammalian sperm feature a specialized secretory organelle on the anterior part of the sperm nucleus, the acrosome, which is essential for male fertility. It is formed by a fusion of Golgi-derived vesicles. We show here that the predominantly Golgi-resident Na⁺/H⁺ exchanger NHE8 localizes to the developing acrosome of spermatids. Similar to wild-type mice, Nhe8^-/- mice generated Golgi-derived vesicles positive for acrosomal markers and attached to nuclei, but these vesicles failed to form large acrosomal granules and the acrosomal cap. Spermatozoa from Nhe8^-/- mice completely lacked acrosomes, were round-headed, exhibited abnormal mitochondrial distribution, and displayed decreased motility, resulting in selective male infertility. Of note, similar features are also found in globozoospermia, one of the causes of male infertility in humans. Germ cell-specific, but not Sertoli cell-specific Nhe8 disruption recapitulated the globozoospermia phenotype, demonstrating that NHE8's role in spermiogenesis is germ cell-intrinsic. Our work has uncovered a crucial role of NHE8 in acrosome biogenesis and suggests that some forms of human globozoospermia might be caused by a loss of function of this Na⁺/H⁺ exchanger. It points to NHE8 as a candidate gene for human globozoospermia and a possible drug target for male contraception.

Loss of SLC9A3 decreases CFTR protein and causes obstructed azoospermia in mice

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause cystic fibrosis (CF) and are associated with congenital bilateral absence of the vas deferens (CBAVD), which is the major cause of infertility in male patients with CF. However, most Taiwanese patients with CBAVD do not carry major CFTR mutations. Some patients have a single copy deletion of the solute carrier family 9 isoform 3 (SLC9A3) gene. SLC9A3 is a Na⁺/H⁺ exchanger, and depleted Slc9a3 in male mice causes infertility due to the abnormal dilated lumen of the rete testis and efferent ductules. Furthermore, SLC9A3 interacts with CFTR in the pancreatic duct and functions as a genetic modifier of CF. However, SLC9A3 function and its relation to CFTR expression in the male reproductive tract in vivo remain elusive. In the present study, we found that CFTR expression was dramatically decreased in the epididymis and vas deferens of Slc9a3 knockout mice. Adult Slc9a3^-/- mice showed not only significantly decreased epididymis and vas deferens weight but also increased testis weight. Furthermore, Slc9a3^-/- mice developed obstructive azoospermia because of abnormal abundant secretions and calcification in the lumen of the reproductive tract. Ultrastructural analysis of the epithelium in Slc9a3^–/–epididymis and vas deferens displayed disorganized and reduced number of stereocilia and numerous secretory apparatuses. Our data revealed that interdependence between SLC9A3 and CFTR is critical for maintaining a precise microenvironment in the epithelial cytoarchitecture of the male reproductive tract. The Slc9a3-deficient mice with impaired male excurrent ducts in this study provide proof for our clinical findings that some Taiwanese of CBAVD carry SLC9A3 deletion but without major CFTR mutations.

Cystic fibrosis (CF) is the most common inherited life-threatening disease in Caucasians. The most well-known cause of CF is a genetic defect in CFTR, an apical membrane chloride and bicarbonate channel. The symptoms of CF include defects in the respiratory, digestive, and male reproductive systems. Most male patients with CF are infertile due to congenital bilateral absence of the vas deferens (CBAVD), which leads to obstructive azoospermia. Nevertheless, Taiwanese patients with CBAVD do not carry the common mutations of CFTR found in Caucasians. We have identified a potential candidate, SLC9A3, of which a single copy is lost in Taiwanese patients with CBAVD. In addition to the previously reported role of SLC9A3 in the digestive system and efferent ductules, we now report that the SLC9A3 deficiency causes obstructive azoospermia and impairs the epithelial structure of the reproductive tract. Loss of SLC9A3 also leads to dramatic reduced expression of CFTR in the reproductive tract. We suggest that the interplay between SLC9A3 and CFTR is responsible for CF-related infertility. Thus, we have characterized a potential critical player in the pathogenesis of CBAVD and provide a new diagnostic candidate for Asian patients with CBAVD.

Functional expression of G protein-coupled receptor 30 in immature rat epididymal epithelium

The aim of this study is to investigate the functional role of G protein-coupled receptor 30 (GPR30) in the epididymis. We found that GPR30 is expressed in the epithelium of the immature rat epididymis and is involved in chloride secretion into the caudal epididymis lumen. The short-circuit current (Isc) experiments showed that in primary cultured caudal epididymis epithelium, activation of GPR30 by its specific agonist G1 induced a mono-phasic current increase, and G15, the specific antagonist of GPR30, could completely inhibit the current induced by G1. The G1-induced Isc was largely blocked by application of the non-specific chloride channel inhibitor diphenylamine-dicarboxylic acid (DPC), or by the cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor CFTR_inh-172 , suggesting that the current was mainly mediated through CFTR. In addition, after stimulating GPR30 by G1, the intracellular concentration of cAMP in the epithelium was significantly increased, indicating that the cAMP signal pathway is involved and could be responsible for the CFTR activation. Finally, to further investigate the function of GPR30 in vivo, G15 was administrated into rats subcutaneously. The osmotic pressure of the micro perfusion solution from epididymis was measured and the sperms were collected. Results showed that there was an osmotic pressure increase of the perfusion solution from G15 treated rats. When the GPR30 was inhibited by G15 endogenously, the motility of sperms decreased. Our data demonstrated that GPR30 is involved in the formation of caudal epididymis fluid micro-environment thus affecting sperm motility.

E2f4 and E2f5 are essential for the development of the male reproductive system

The E2F transcription factors are primarily implicated in the regulation of entry and exit from the cell cycle. However, in vivo studies have established additional roles for E2Fs during organ development and homeostasis. With the goal of addressing the intestinal requirements of E2f4 and E2f5, we crossed mice carrying Vil-cre, E2f4 conditional and E2f5 germline alleles. E2f4 deletion had no detectable effect on intestinal development. However, E2f4f/f;E2f5+/-;Vil-cre males, but not E2f4f/f;Vil-cre littermates, were unexpectedly sterile. This defect was not due to defective spermatogenesis. Instead, the seminiferous tubules and rete testes showed significant dilation, and spermatozoa accumulated aberrantly in the rete testis and efferent ducts. Our data show that these problems result from defective efferent ducts, a tissue whose primary function is to concentrate sperm through fluid absorption. First, Vil-cre expression, and consequent E2F4 loss, was specific to the efferent ducts and not other reproductive tract tissues. Second, the E2f4f/f;E2f5+/-;Vil-cre efferent ducts had completely lost multiciliated cells and greatly reduced levels of critical absorptive cell proteins: aquaporin1, a water channel protein, and clusterin, an endocytic marker. Collectively, the observed testis phenotypes suggest a fluid flux defect. Remarkably, we observed rete testis dilation prior to the normal time of seminiferous fluid production, arguing that the efferent duct defects promote excessive secretory activity within the reproductive tract. Finally, we also detect key aspects of these testis defects in E2f5-/- mice. Thus, we conclude that E2f4 and E2f5 display overlapping roles in controlling the normal development of the male reproductive system.

Effects of bilateral vasectomy on the interleukin 1 system in mouse epididymis

PROBLEM

Regional difference in the inflammatory response in vasectomized (VAX) epididymis remains unraveled.

METHOD OF STUDY

Epididymal expression of interleukin 1α (IL1α), IL1β, IL1 receptor antagonist (IL1ra), IL1 receptor 1 (IL1R1), IL6, IL10, tumor necrosis factor α (TNF-α), and transforming growth factor-β1 (TGF-β1) was examined in bilateral VAX mice by real-time RT-PCR and immunohistochemistry.

RESULTS

IL1α, IL1β, IL1ra, and IL1R1 were expressed in the epididymal epithelia of normal mice. Following VAX, IL1R1 mRNA was not changed, but TNF-α, IL10, IL1α, IL1β, and IL1ra mRNA were significantly upregulated in whole epididymis, whereas IL6 and TGF-β1 mRNA were significantly increased in corpus and cauda but not in caput epididymis. Consistently, IL1α, IL1β, and IL1ra immunoreactivities were visibly increased in epididymis following VAX.

CONCLUSION

Following VAX, IL1α, IL1β, IL1ra, IL10, and TNF-α may mediate immune reaction in whole epididymis, whereas IL6 and TGF-β1 may mediate regionally different immune response primarily in the lower part of epididymis.

HNF1 regulates critical processes in the human epididymis epithelium

The luminal environment of the epididymis participates in sperm maturation and impacts male fertility. It is dependent on the coordinated expression of many genes encoding proteins with a role in epithelial transport. We identified cis-regulatory elements for critical genes in epididymis function, by mapping open chromatin genome-wide in human epididymis epithelial (HEE) cells. Bioinformatic predictions of transcription factors binding to the regulatory elements suggested an important role for hepatocyte nuclear factor 1 (HNF1) in the transcriptional program of these cells. Chromatin immunoprecipitation and deep sequencing (ChIP-seq) revealed HNF1 target genes in HEE cells. In parallel, the contribution of HNF1 to the transcriptome of HEE cells was determined by RNA-seq, following siRNA-mediated depletion of both HNF1α and HNF1β transcription factors. Repression of these factors caused differential expression of 1892 transcripts (902 were downregulated and 990 upregulated) in comparison to non-targeting siRNAs. Differentially expressed genes with HNF1 ChIP-seq peaks within 20 kb were subject to gene ontology process enrichment analysis. Among the most significant processes associated with down-regulated genes were epithelial transport of water, phosphate and bicarbonate, all critical processes in epididymis epithelial function. Measurements of intracellular pH (pHi) confirmed a role for HNF1 in regulating the epididymis luminal environment.

Estradiol modulates Na(+) -dependent HCO3 (-) transporters altering intracellular pH and ion transport in human Sertoli cells: A role on male fertility?

BACKGROUND INFORMATION

Infertile men often present deregulation of serum estrogen levels. Notably, high levels of estradiol (E2) are associated with low sperm production and quality. Sertoli cells (SCs) are responsible for spermatogenesis maintenance and are major targets for the hormonal signalling that regulates this complex process.

RESULTS

In this study, we used primary cultures of human SCs and studied the localisation, expression and functionality of the Na(+) -dependent HCO3 (-) transporters by confocal microscopy, immunoblot, epifluorescence and voltage clamp after 24 h of exposure to E2 (100 nM). All studied transporters were identified in human SCs. In E2-treated human SCs, there was an increase in NBCn1, NBCe1 and NDCBE protein levels, as well as an increase in intracellular pH and a decrease in transcellular transport.

CONCLUSIONS

We report an association between increased levels of E2 and the expression/function of Na(+) -dependent HCO3 (-) transporters in human SCs. Our results provide new evidence on the mechanisms by which E2 can regulate SCs physiology and consequently spermatogenesis. These mechanisms may have an influence on male reproductive potential and help to explain male infertility conditions associated with estrogen deregulation.

SIGNIFICANCE

Exposure to E2 increased human SCs intracellular pH. E2 is a modulator of ionic transcellular transport in human SCs.

Normal Fertility Requires the Expression of Carbonic Anhydrases II and IV in Sperm

HCO3 (-) is a key factor in the regulation of sperm motility. High concentrations of HCO3 (-) in the female genital tract induce an increase in sperm beat frequency, which speeds progress of the sperm through the female reproductive tract. Carbonic anhydrases (CA), which catalyze the reversible hydration of CO2 to HCO3 (-), represent potential candidates in the regulation of the HCO3 (-) homeostasis in sperm and the composition of the male and female genital tract fluids. We show that two CA isoforms, CAII and CAIV, are distributed along the epididymal epithelium and appear with the onset of puberty. Expression analyses reveal an up-regulation of CAII and CAIV in the different epididymal sections of the knockout lines. In sperm, we find that CAII is located in the principal piece, whereas CAIV is present in the plasma membrane of the entire sperm tail. CAII and CAIV single knockout animals display an imbalanced HCO3 (-) homeostasis, resulting in substantially reduced sperm motility, swimming speed, and HCO3 (-)-enhanced beat frequency. The CA activity remaining in the sperm of CAII- and CAIV-null mutants is 35% and 68% of that found in WT mice. Sperm of the double knockout mutant mice show responses to stimulus by HCO3 (-) or CO2 that were delayed in onset and reduced in magnitude. In comparison with sperm from CAII and CAIV double knockout animals, pharmacological loss of CAIV in sperm from CAII knockout animals, show an even lower response to HCO3 (-). These results suggest that CAII and CAIV are required for optimal fertilization.

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.

Small tubules, surprising discoveries: from efferent ductules in the turkey to the discovery that estrogen receptor alpha is essential for fertility in the male

Efferent ductules are small, delicate tubules that connect rete testis with the head of the epididymis, first identified by de Graaf in 1668. Although difficult to find in routine dissection, the ductules are an essential component of the male reproductive tract and in larger mammals occupy up more than 50% of the caput epididymidis. My introduction to research began with the study of efferent ductules in the domestic turkey, and to my surprise these small structures with kidney-like function become the core for numerous discoveries throughout my scientific career. In this review, only two discoveries that I found interesting will be discussed: cilia that line the efferent ductule lumen and estrogen receptors that play an essential role in regulating fluid reabsorption. A potential link between these two discoveries was uncovered in the study of efferent ductule effects observed in the estrogen receptor knockout mouse and following toxic exposure to the fungicide benomyl.

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.