Localization of the glucocorticoid receptor in testis and accessory sexual organs of male rat

Differential susceptibility of male and female germ cells to glucocorticoid-mediated signaling

While physiologic stress has long been known to impair mammalian reproductive capacity through hormonal dysregulation, mounting evidence now suggests that stress experienced prior to or during gestation may also negatively impact the health of future offspring. Rodent models of gestational physiologic stress can induce neurologic and behavioral changes that persist for up to three generations, suggesting that stress signals can induce lasting epigenetic changes in the germline. Treatment with glucocorticoid stress hormones is sufficient to recapitulate the transgenerational changes seen in physiologic stress models. These hormones are known to bind and activate the glucocorticoid receptor (GR), a ligand-inducible transcription factor, thus implicating GR-mediated signaling as a potential contributor to the transgenerational inheritance of stress-induced phenotypes. Here, we demonstrate dynamic spatiotemporal regulation of GR expression in the mouse germline, showing expression in the fetal oocyte as well as the perinatal and adult spermatogonia. Functionally, we find that fetal oocytes are intrinsically buffered against changes in GR signaling, as neither genetic deletion of GR nor GR agonism with dexamethasone altered the transcriptional landscape or the progression of fetal oocytes through meiosis. In contrast, our studies revealed that the male germline is susceptible to glucocorticoid-mediated signaling, specifically by regulating RNA splicing within the spermatogonia, although this does not abrogate fertility. Together, our work suggests a sexually dimorphic function for GR in the germline, and represents an important step towards understanding the mechanisms by which stress can modulate the transmission of genetic information through the germline.

Differential susceptibility of male and female germ cells to glucocorticoid-mediated signaling

While physiologic stress has long been known to impair mammalian reproductive capacity through hormonal dysregulation, mounting evidence now suggests that stress experienced prior to or during gestation may also negatively impact the health of future offspring. Rodent models of gestational physiologic stress can induce neurologic and behavioral changes that persist for up to three generations, suggesting that stress signals can induce lasting epigenetic changes in the germline. Treatment with glucocorticoid stress hormones is sufficient to recapitulate the transgenerational changes seen in physiologic stress models. These hormones are known to bind and activate the glucocorticoid receptor (GR), a ligand-inducible transcription factor, thus implicating GR-mediated signaling as a potential contributor to the transgenerational inheritance of stress-induced phenotypes. Here we demonstrate dynamic spatiotemporal regulation of GR expression in the mouse germline, showing expression in the fetal oocyte as well as the perinatal and adult spermatogonia. Functionally, we find that fetal oocytes are intrinsically buffered against changes in GR signaling, as neither genetic deletion of GR nor GR agonism with dexamethasone altered the transcriptional landscape or the progression of fetal oocytes through meiosis. In contrast, our studies revealed that the male germline is susceptible to glucocorticoid-mediated signaling, specifically by regulating RNA splicing within the spermatogonia, although this does not abrogate fertility. Together, our work suggests a sexually dimorphic function for GR in the germline, and represents an important step towards understanding the mechanisms by which stress can modulate the transmission of genetic information through the germline.

Preconception paternal mental disorders and child health: Mechanisms and interventions

Mental illness is a significant global health issue with a steady prevalence. High heritability is suspected, but genome-wide association studies only identified a small number of risk genes associated with mental disorders. This 'missing inheritance' can be partially explained by epigenetic heredity. Evidence from numerous animal models and human studies supports the possibility that preconception paternal mental health influences their offspring's mental health via nongenetic means. Here, we review two potential pathways, including sperm epigenetics and seminal plasma components. The current review highlights the role of sperm epigenetics and explores epigenetic message origination and susceptibility to chronic stress. Meanwhile, possible spatiotemporal windows and events that induce sexually dimorphic modes and effects of paternal stress transmission are inferred in this review. Additionally, we discuss emerging interventions that could potentially block the intergenerational transmission of paternal psychiatric disorders and reduce the incidence of mental illness. Understanding the underlying mechanisms by which preconception paternal stress impacts offspring health is critical for identifying strategies supporting healthy development and successfully controlling the prevalence of mental illness.

Involvement of GLCCI1 in mouse spermatogenesis

Spermatid production is a complex regulatory process in which coordination between hormonal control and apoptosis plays a pivotal role in maintaining a balanced number of sperm cells. Apoptosis in spermatogenesis is controlled by pro-apoptotic and anti-apoptotic molecules. Hormones involved in the apoptotic process during spermatogenesis include gonadotrophins, sex hormones, and glucocorticoid (GC). GC acts broadly as an apoptosis inducer by binding to its receptor (glucocorticoid receptor: GR) during organ development processes, such as spermatogenesis. However, the downstream pathway induced in GC-GR signaling and the apoptotic process during spermatogenesis remains poorly understood. We reported previously that GC induces full-length glucocorticoid-induced transcript 1 (GLCCI1-long), which functions as an anti-apoptotic mediator in thymic T cell development. Here, we demonstrate that mature murine testis expresses a novel isoform of GLCCI1 protein (GLCCI1-short) in addition to GLCCI1-long. We demonstrate that GLCCI1-long is expressed in spermatocytes along with GR. In contrast, GLCCI1-short is primarily expressed in spermatids where GR is absent; instead, the estrogen receptor is expressed. GLCCI1-short also binds to LC8, which is a known mediator of the anti-apoptotic effect of GLCCI1-long. A luciferase reporter assay revealed that β-estradiol treatment synergistically increased Glcci1-short promotor-driven luciferase activity in Erα-overexpressing cells. Together with the evidence that the conversion of testosterone to estrogen is preceded by aromatase expression in spermatids, we hypothesize that estrogen induces GLCCI1-short, which, in turn, may function as a novel anti-apoptotic mediator in mature murine testis.

A Novel Model Using AAV9-Cre to Knockout Adult Leydig Cell Gene Expression Reveals a Physiological Role of Glucocorticoid Receptor Signalling in Leydig Cell Function

Glucocorticoids are steroids involved in key physiological processes such as development, metabolism, inflammatory and stress responses and are mostly used exogenously as medications to treat various inflammation-based conditions. They act via the glucocorticoid receptor (GR) expressed in most cells. Exogenous glucocorticoids can negatively impact the function of the Leydig cells in the testis, leading to decreased androgen production. However, endogenous glucocorticoids are produced by the adrenal and within the testis, but whether their action on GR in Leydig cells regulates steroidogenesis is unknown. This study aimed to define the role of endogenous GR signalling in adult Leydig cells. We developed and compared two models; an inducible Cre transgene driven by expression of the Cyp17a1 steroidogenic gene (Cyp17-iCre) that depletes GR during development and a viral vector-driven Cre (AAV9-Cre) to deplete GR in adulthood. The delivery of AAV9-Cre ablated GR in adult mouse Leydig cells depleted Leydig cell GR more efficiently than the Cyp17-iCre model. Importantly, adult depletion of GR in Leydig cells caused reduced expression of luteinising hormone receptor (Lhcgr) and of steroidogenic enzymes required for normal androgen production. These findings reveal that Leydig cell GR signalling plays a physiological role in the testis and highlight that a normal balance of glucocorticoid activity in the testis is important for steroidogenesis.

Regulation of stress response on the hypothalamic-pituitary-gonadal axis via gonadotropin-inhibitory hormone

Under stressful condition, reproductive function is impaired due to the activation of various components of the hypothalamic-pituitaryadrenal (HPA) axis, which can suppress the activity of the hypothalamic-pituitary-gonadal (HPG) axis at multiple levels. A hypothalamic neuropeptide, gonadotropin-inhibitory hormone (GnIH) is a key negative regulator of reproduction that governs the HPG axis. Converging lines of evidence have suggested that different stress types and their duration, such as physical or psychological, and acute or chronic, can modulate the GnIH system. To clarify the sensitivity and reactivity of the GnIH system in response to stress, we summarize and critically review the available studies that investigated the effects of various stressors, such as restraint, nutritional/metabolic and social stress, on GnIH expression and/or its neuronal activity leading to altered HPG action. In this review, we focus on GnIH as the potential novel mediator responsible for stress-induced reproductive dysfunction.

Male subfertility effects of sub-chronic ethanol exposure during stress in a rat model

BACKGROUND

Stressful conditions increase alcohol consumption in men. Clinical studies link disruption of the neuroendocrine stress system with alcoholism, but the effect of alcohol in a stress condition on male fertility is still relatively poorly understood. This project was undertaken to evaluate the effect of sub-chronic alcohol in a stress condition on male fertility in a rat model.

METHODS

Male Sprague-Dawley rats were randomly divided into a control group, a stress group that was exposed to restraint stress, an ethanol group that was injected with ethanol daily, and a stress + ethanol group that was injected with ethanol daily and was exposed to restraint stress, simultaneously. Furthermore, testis tissue was evaluated histomorphometrically and immunohistochemically for apoptosis using a TUNEL assay after 12 days. Epididymis sperm analysis was done. Blood cortisol and testosterone were measured and expression of hypothalamic kisspeptin (Kiss1), RFRP-3, and MC4R mRNA were evaluated.

RESULTS

Ethanol exposure during restraint stress did not alter body weight. Ethanol exposure decreased the cellular diameter and area, and stress increased the cellular diameter and area, in comparison with the control group. In the stress group, in comparison with the other groups, the number of seminiferous tubules decreased and the numerical density of seminiferous tubules increased. In addition, ethanol exposure and/or stress reduced semen analysis parameters (sperm viability and motility), but did not change serum testosterone concentrations. Apoptosis increased in spermatogonia with ethanol exposure, but spermatocytes were not affected. Our data present the novel finding that ethanol and stress reduced hypothalamic Kiss1 mRNA expression, while ethanol exposure decreased hypothalamic RFRP-3 and MC4R mRNA expression.

CONCLUSIONS

Ethanol decreased cortisol hormone level during the restraint stress condition and attenuated hypothalamic reproductive-related gene expressions. Therefore, ethanol exposure may induce reduction of sperm viability, increased sperm mortality, and increased apoptosis, with long-term effects, and may induce permanent male subfertility.

Neurophysiology of cognitive behavioural therapy, deep breathing and progressive muscle relaxation used in conjunction with ART treatments: a narrative review

BACKGROUND

Infertility is defined as the failure to achieve clinical pregnancy after 12 months of regular unprotected intercourse. It could be due to male or female factors, each requiring different treatment options. ART treatment exposes couples to numerous psychological stressors. Therefore, it has been recommended by the ESHRE Psychology and Counselling Guideline Development Group recently that psychosocial support should be offered as a complementary therapy during infertility treatments. In this context, the efficiency of different psychological interventions, such as cognitive behaviour therapy (CBT), deep breathing (DB), and progressive muscle relaxation (PMR), was evaluated in several clinical trials in terms of couples' mental health and pregnancy outcomes.

OBJECTIVE AND RATIONALE

The neurophysiology of CBT, DB and PMR, which are used in interventional studies, in both men and women undergoing ART, has not yet been fully elucidated. This review represents a comprehensive report, aiming to collate novel insights into the neurobiological processes and physiological mechanisms that occur during the practice of CBT, DB and PMR.

SEARCH METHODS

PubMed, Google Scholar and Cochrane Library were interrogated to conduct this comprehensive literature review. The search was carried out using combinations of MeSH terms and keywords: infertility, assisted reproductive techniques, IVF, ICSI, emotions, psychological stress, cognitive behavioural therapy, mind-body therapies and relaxation. Relevant information related to the mechanism of action of stress management techniques were obtained from original articles and reviews published in English without taking into consideration the time of publication. Moreover, as it was not the major focus of the review, only recent systematic reviews (2015-2019) pinpointing the effects of psychological interventions on infertility treatment outcomes were also retrieved from the above-mentioned databases.

OUTCOMES

CBT, DB and PMR may modify the activity of stress-related brain regions such as the prefrontal cortex, amygdala, hypothalamus and hippocampus, as demonstrated by functional MRI and electroencephalogram studies. Furthermore, applying these techniques was associated with mood improvements and a decline in stress biomarkers, and, hypothetically, reducing stress biomarkers attenuates the stress-induced effects on ART outcomes.

WIDER IMPLICATIONS

Increasing the knowledge of fertility staff, researchers and physicians regarding the mechanisms of action of these stress management techniques has several advantages. For instance, understanding the underlying neurophysiological pathways would assist practitioners to engage ART couples in the practice of these techniques. Also, it may enhance the quality of the support programmes and psychological research. Accordingly, this will ensure that these interventions reach their full potential and therefore improve clinical outcomes.

Sex-Specific Differences of Steroid Receptors Following Exposure to Environmentally Relevant Concentrations of Phenothiazine in Fundulus heteroclitus

Phenothiazine (PTZ) is a heterocyclic thiazine compound used for industrial and medical purposes. Through environmental surveillance studies, PTZ was found being discharged into a local river in Connecticut. Phenothiazine has been shown to act similarly to endocrine disrupting chemicals. This study sought to identify sex specific hormone receptor changes in Fundulus heteroclitus in response to PTZ exposure. Fundulus heteroclitus, also known as mummichog, are small fish native to the Atlantic coast of the United States and Canada. They reside in brackish waters and can survive harsh toxic environments. This model organism is native to the polluted waters found in Connecticut. In this study, fish were exposed to PTZ concentrations of 0.5 ppm, 1.0 ppm, and 2.0 ppm for 1 week. Following exposure, brain, liver, and gonad tissues were harvested; cDNA was synthesized; and mRNA expression was assessed for 6 different hormone receptors. Compared with vehicle control (ethanol) differences in mRNA expression, levels of hormone receptors were observed in various tissues from male and female fish. Many of the tissues assessed showed changes in expression level, while only female liver and testis showed no change. These results implicate PTZ as a potential endocrine disrupting compound to mummichog at environmentally relevant concentrations.

Cortisol Directly Stimulates Spermatogonial Differentiation, Meiosis, and Spermiogenesis in Zebrafish (Danio rerio) Testicular Explants

Cortisol is the major endocrine factor mediating the inhibitory effects of stress on vertebrate reproduction. It is well known that cortisol affects reproduction by interacting with the hypothalamic–pituitary–gonads axis, leading to downstream inhibitory and stimulatory effects on gonads. However, the mechanisms are not fully understood. In this study, we provide novel data demonstrating the stimulatory effects of cortisol on spermatogenesis using an ex vivo organ culture system. The results revealed that cortisol treatment did not modulate basal androgen production, but it influenced transcript levels of a selected number of genes involved in the zebrafish testicular function ar (androgen receptor), star (steroidogenic acute regulatory), cyp17a1 (17α-hydroxylase/17,20 lyase/17,20 desmolase), cyp11a2 (cytochrome P450, family 11, subfamily A, polypeptide 2), hsd11b2 (11-beta hydroxysteroid dehydrogenase), cyp2k22 (cytochrome P450, family 2, subfamily K, polypeptide 22), fkbp5 (FKBP prolyl isomerase 5), grα (glucocorticoid receptor alpha), and grβ (glucocorticoid receptor beta) in a short-term culture. We also showed that cortisol stimulates spermatogonial proliferation and differentiation in an androgen independent manner as well as promoting meiosis and spermiogenesis by increasing the number of spermatozoa in the testes. Moreover, we demonstrated that concomitant treatment with RU 486, a potent glucocorticoid receptor (Gr) antagonist, did not affect the cortisol effects on spermatogonial differentiation but blocked the induced effects on meiosis and spermiogenesis. Supporting the Gr-mediated effects, RU 486 nullified the cortisol-induced expression of sycp3l (synaptonemal complex protein 3), a marker for the meiotic prophase that encodes a component of the synaptonemal complex. This is consistent with in silico analysis that found 10 putative GREs (glucocorticoid response elements) upstream of the zebrafish sycp3l. Finally, we also showed that grα mRNA is expressed in Sertoli and Leydig cells, but also in several types of germ cells, including spermatogonia and spermatocytes. Altogether, this evidence indicates that cortisol exerts paracrine roles in the zebrafish testicular function and spermatogenesis, highlighting its effects on spermatogonial differentiation, meiosis, and spermiogenesis.

Chronic excessive Zn intake increases the testicular sensitivity to high ambient temperature in Bama miniature pigs

Zinc (Zn) can accumulate in the body of wild animal and human through bio-magnification effects in the food chain to pose chronic toxicity. Male spermatogenesis was sensitive to excessive Zn and elevated temperature. This study aimed to examine whether or not excessive Zn intake caused testicular toxicity and estimate the interaction between Zn and high temperature (HT) in testes of Bama miniature pigs. Six-month-old pigs were pre-fed with or without additional Zn at 1500 mg/kg diet for 30 d and afterward subjected to HT at 40 °C for 5 h daily for 8 consecutive days. Blood samples were collected on d 31 and d 38 and testes were obtained on d 38 immediately after HT exposure. Our data showed both scrotal surface temperature (T) and body surface T increased after 5-h HT exposure (p < 0.05). Pigs fed with additional Zn showed germ cell loss, the decreased testes weight (p < 0.01) and the elevated testicular H₂O₂ level (p < 0.05) as exposed to HT. In additional Zn groups, the autophagosomes or autolysosomes were more frequently observed in the Leydig cells and abnormal acrosomes increased in spermatids. Additional Zn diet increased p62 protein level (p < 0.05), decreased testicular Zn concentration (p < 0.01) and down-regulated the relative mRNA expression of heme oxygenase 1 (p < 0.05). There were significant interactions between T and Zn on testes weight, the relative weight of testes, testosterone concentration on d 31, and the relative mRNA expression of Zn transporters 1 and 2. In conclusion, chronic excessive Zn diet impacted testicular Zn concentration and made the testes more vulnerable to heat, leading to testicular toxicity in Bama miniature pigs.

Control of human testis-specific gene expression

Background

As a result of decades of effort by many investigators we now have an advanced level of understanding about several molecular systems involved in the control of gene expression. Examples include CpG islands, promoters, mRNA splicing and epigenetic signals. It is less clear, however, how such systems work together to integrate the functions of a living organism. Here I describe the results of a study to test the idea that a contribution might be made by focusing on genes specifically expressed in a particular tissue, the human testis.

Experimental design

A database of 239 testis-specific genes was accumulated and each was examined for the presence of features relevant to control of gene expression. These include: (1) the presence of a promoter, (2) the presence of a CpG island (CGI) within the promoter, (3) the presence in the promoter of a transcription factor binding site near the transcription start site, (4) the level of gene expression, and (5) the above features in genes of testis-specific cell types such as spermatocyte and spermatid that differ in their extent of differentiation.

Results

Of the 107 database genes with an annotated promoter, 56 were found to have one or more transcription factor binding sites near the transcription start site. Three of the binding sites observed, Pax-5, AP-2αA and GRα, stand out in abundance suggesting they may be involved in testis-specific gene expression. Compared to less differentiated testis-specific cells, genes of more differentiated cells were found to be (1) more likely to lack a CGI, (2) more likely to lack introns and (3) higher in expression level. The results suggest genes of more differentiated cells have a reduced need for CGI-based regulatory repression, reduced usage of gene splicing and a smaller set of expressed proteins.

Mechanisms of Stress-Induced Spermatogenesis Impairment in Male Rats Following Unpredictable Chronic Mild Stress (uCMS)

The negative association between psychological stress and male fertility has been known for many years. This study was aimed at (i) identifying spermatogenesis impairment induced by psychological stress in rats and (ii) exploring the role of glucocorticoid receptor (GR) signaling in these adverse effects (if they exist). Male Sprague Dawley rats were exposed to a six-week period of unpredictable chronic mild stress (uCMS) along with cotreatment of GR antagonist RU486 (1 mg/kg/day). Testicular damage was assessed by testicular pathological evaluation, epididymal sperm concentration, serum testosterone levels, testicular apoptotic cell measurements, and cell cycle progression analyses. Rats in the uCMS group had decreased levels of serum testosterone and decreased epididymal sperm concentration. The uCMS-treated rats also had decreased numbers of spermatids and increased levels of apoptotic seminiferous tubules; additionally, cell cycle progression of spermatogonia was arrested at the G₀/G₁ phase. Furthermore, uCMS exposure caused an increase in serum corticosterone level and activated GR signaling in the testes including upregulated GR expression. RU486 treatment suppressed GR signaling and alleviated the damaging effects of stress, resulting in an increased epididymal sperm concentration. Overall, this work demonstrated for the first time that the activation of GR signaling mediates stress-induced spermatogenesis impairment and that this outcome is related to cell apoptosis and cell cycle arrest in germ cells.

Leydig cell genes change their expression and association with polysomes in a stage-specific manner in the adult mouse testis

Spermatogenesis in mammals occurs in a very highly organized manner within the seminiferous epithelium regulated by different cell types in the testis. Testosterone produced by Leydig cells regulates blood-testis barrier formation, meiosis, spermiogenesis, and spermiation. However, it is unknown whether Leydig cell function changes with the different stages of the seminiferous epithelium. This study utilized the WIN 18,446 and retinoic acid (RA) treatment regime combined with the RiboTag mouse methodology to synchronize male germ cell development and allow for the in vivo mapping of the Leydig cell translatome across the different stages of one cycle of the seminiferous epithelium. Using microarrays analysis, we identified 11 Leydig cell-enriched genes that were expressed in stage-specific manner such as the glucocorticoid synthesis and transport genes, Cyp21a1 and Serpina6. In addition, there were nine Leydig cell transcripts that change their association with polysomes in correlation with the different stages of the spermatogenic cycle including Egr1. Interestingly, the signal intensity of EGR1 and CYP21 varied among Leydig cells in the adult asynchronous testis. However, testosterone levels across the different stages of germ cell development did not cycle. These data show, for the first time, that Leydig cell gene expression changes in a stage-specific manner during the cycle of the seminiferous epithelium and indicate that a heterogeneous Leydig cell population exists in the adult mouse testis.

Intergenerational Effects of Alcohol: A Review of Paternal Preconception Ethanol Exposure Studies and Epigenetic Mechanisms in the Male Germline

While alcohol use disorder (AUD) is a highly heritable psychiatric disease, efforts to elucidate that heritability by examining genetic variation (e.g., single nucleotide polymorphisms) have been insufficient to fully account for familial AUD risk. Perhaps not coincidently, there has been a burgeoning interest in novel nongenomic mechanisms of inheritance (i.e., epigenetics) that are shaped in the male or female germ cells by significant lifetime experiences such as exposure to chronic stress, malnutrition, or drugs of abuse. While many epidemiological and preclinical studies have long pointed to a role for the parental preconception environment in offspring behavior, over the last decade many studies have implicated a causal relationship between the environmentally sensitive sperm epigenome and intergenerational phenotypes. This critical review will detail the heritable effects of alcohol and the potential role for epigenetics.

Pubertal abnormalities in adolescents with chronic disease

Pubertal disorders in the context of chronic disease especially in those with chronic inflammatory disorders or those requiring prolonged periods of treatment with glucocorticoid are common reasons for referral to the paediatric endocrine clinic. Disorders of puberty are also common in adolescents with disability requiring management by paediatric endocrinologists. In these adolescents, impaired skeletal development is also observed and this can be associated with fragility fractures. Chronic inflammation, glucocorticoid and sub-optimal nutrition all impact on the hypothalamic-pituitary gonadal axis, and can also impact on skeletal development locally by their effects on the growth plate and bone. Addressing pubertal disorders is important to ensure adolescents with chronic disease are matched with their peers, promote adequate bone mass accrual and linear growth. Careful discussion with primary clinicians, the young person and the family is needed when instituting endocrine therapies to address puberty and manage bone health.

Dexamethasone suppresses the differentiation of stem Leydig cells in rats in vitro

BACKGROUND

It is an established fact that excess of glucocorticoids could cause the harmful effects, such as suppression on the male reproduction. Although glucocorticoids pharmacologically inhibit the Leydig cell function, their roles in Leydig cell development are unclear. Therefore, the present study was designed to investigate effects of synthetic glucocorticoid dexamethasone (DEX) on rat stem Leydig cell proliferation and differentiation.

METHODS

Male Sprague-Dawley rats received a single intraperitoneal injection of 75 mg/kg EDS to eliminate Leydig cells and an in vitro culture system of the seminiferous tubules was established from Leydig cell-depleted testis. Using basal medium and Leydig cell differentiation-inducing medium (LIM) in the culture system, we examined the effects of DEX (0-100 nM) on the proliferation and differentiation of the stem Leydig cells in vitro, respectively.

RESULTS

Results showed that LIM is a good agent to induce stem Leydig cell differentiation into Leydig cells that produce testosterone in vitro. DEX inhibited the differentiation of stem Leydig cells by reducing the expression levels of Cyp17a1 and Scarb1 and that NR3C1 antagonist RU38486 reversed the DEX-mediated effects. However, DEX are not involved with the proliferation of stem Leydig cells.

CONCLUSIONS

DEX suppressed the differentiation of rat Leydig cells in vitro and glucocorticoid-induced effects acted through NR3C1. This suppression partially targets on Cyp17a1 and Scarb1 gene expression.

Corticosterone rather than ethanol epigenetic programmed testicular dysplasia caused by prenatal ethanol exposure in male offspring rats

Prenatal ethanol exposure (PEE) could affect offspring's testicular development. This study aimed to illuminate its intrauterine origin and the programming mechanism caused by PEE. Pregnant Wistar rats were given ethanol (4 g/kg.d) by gavage administration during gestational days (GD) 9-20. Serum samples and testes of male offspring rats were collected on GD20, postnatal week (PW) 6, and PW12. We found that PEE induced testicular morphological abnormality, low serum testosterone levels, expressive suppression of 3β-hydroxysteroid dehydrogenase (3β-HSD), and low acetylation levels of histone 3 lysine 14 (H3K14ac) of 3β-HSD before and after birth. In utero, when fetal rats were overexposed to corticosterone by PEE, the expression levels of testicular glucocorticoid receptor (GR) and histone deacetylase 2 (HDAC2) were increased, while that of steroidogenic factor 1 (SF1) was decreased. In vitro, corticosterone (rather than ethanol) at 500 to 2,000 nM concentration decreased testosterone production and 3β-HSD expression in a concentration-dependent manner. Moreover, corticosterone downregulated SF1 and upregulated HDAC2 via activating GR, accompanied by a low H3K14ac level of 3β-HSD; SF1 overexpression could reverse the increased HDAC2 expression, and knockdown of HDAC2 could partially reverse the inhibitory effects of corticosterone on H3K14ac level and 3β-HSD expression but not on SF1 expression. Taken together, PEE caused testicular dysplasia in male offspring rats, which was associated with corticosterone-induced low-functional programming of 3β-HSD through the GR/SF1/HDAC2/H3K14ac pathway. This study provides new academic perspectives to illuminate the theory of 'Developmental Origins of Health and Disease.'

Safety of important dermatological drugs (retinoids, immune suppressants, anti androgens and thalidomide) in reproductively active males with respect to pregnancy outcome: A brief review of literature

Paternally transmitted damage to offspring is recognized as a complex issue. Each parent contributes 23 chromosomes to a child; hence, it is necessary to know the effects of both maternal and paternal pre-and peri-conceptional exposure to drugs on pregnancy outcome. While there are many studies on the effects of maternal drug exposure on pregnancy outcome, literature on paternal exposure is scarce. Of late however, paternal exposure has been receiving increasing attention. We present a brief review on the safety of commonly used drugs in dermatology, focused on retinoids, immune suppressants, anti androgens and thalidomide.

The possible effects of anthropogenic acoustic pollution on marine mammals' reproduction: an emerging threat to animal extinction

For about 119 species of cetaceans and other aquatic animals, sound is the key source of learning about the environment, navigation, communication, foraging, and avoiding predators. However, in the recent era, the introduction of large quantities of anthropogenic noise into the ocean has significantly altered the ocean's acoustic environment. The anthropogenic noises travel very long distances, blanketing enormous areas. This can affect cetaceans, either by direct killing or compromising hearing, navigation, communication, predation, as well as normal behaviors. It has been suggested that acoustic pollution could possibly negatively affect cetacean reproduction, which is harmful for endangered and threatened species. However, it is still unknown how acoustic pollution can suppress cetacean reproduction. This is the first comprehensive review article, which focuses on the possible consequences affecting the reproduction of marine mammals resulting from acoustic pollution.

Dehydroepiandrosterone Antagonizes Pain Stress-Induced Suppression of Testosterone Production in Male Rats

Background: Leydig cells secrete the steroid hormone, testosterone, which is essential for male fertility and reproductive health. Stress increases the secretion of glucocorticoid [corticosterone, (CORT) in rats] that decreases circulating testosterone levels in part through a direct action on its receptors in Leydig cells. Intratesticular CORT level is dependent on oxidative inactivation of CORT by 11β-hydroxysteroid dehydrogenase 1 (HSD11B1) in rat Leydig cells. Pain may cause the stress, thus affecting testosterone production in Leydig cells.

Methods: Adult male Sprague–Dawley rats orally received vehicle control or 5 or 10 mg/kg dehydroepiandrosterone (DHEA) 0.5 h before being subjected to pain stimulation for 1, 3, and 6 h. In the present study, we investigated the time-course changes of steroidogenic gene expression levels after acute pain-induced stress in rats and the possible mechanism of DHEA that prevented it. Plasma CORT, luteinizing hormone (LH), and testosterone (T) levels were measured, and Leydig cell gene expression levels were determined. The direct regulation of HSD11B1 catalytic direction by DHEA was detected in purified rat Leydig, liver, and rat Hsd11b1-transfected COS1 cells.

Results: Plasma CORT levels were significantly increased at hour 1, 3, and 6 during the pain stimulation, while plasma T levels were significantly decreased starting at hour 3 and 6. Pain-induced stress also decreased Star, Hsd3b1, and Cyp17a1 expression levels at hour 3. When 5 and 10 mg/kg DHEA were orally administered to rats 0.5 h before starting pain stimulation, DHEA prevented pain-mediated decrease in plasma T levels and the expression of Star, Hsd3b1, and Cyp17a1 without affecting plasma CORT levels. DHEA was found to modulate HSD11B1 activities by increasing its oxidative activity and decreasing its reductive activity, thus decreasing the intracellular CORT levels in Leydig cells.

Conclusion: Stress induced by acute pain can inhibit Leydig cell T production by upregulation of corticosterone. DHEA can prevent the negative effects of excessive corticosterone by modulating HSD11B1 activity.

Gradual decrease in spermatogenesis caused by chronic stress

Chronic stress induces decreased sperm motility, viability and concentration in stressed males. Also, stress modifies oxidative status and causes apoptosis in testes, as well as a decrease in the epithelial area of seminiferous tubules. However, there are no studies that analyze the alterations caused by stress in testicular cells. Thus, in this study, alterations in the morphology of testicular germ cells caused by different days of chronic stress were assessed. Adult male rats were exposed to stress by immersion in cold water (ICW) daily for 3, 8, 20 or 50 consecutive days. Plasma testosterone and corticosterone were also assessed. Results showed that chronic stress causes loss of germ cells, and alteration of spermatogenesis. Seminiferous tubules from stressed males showed several degenerative signs, such as vacuoles in the basal epithelium, with picnotic indicia; moderate to severe exfoliation of degenerative germinal cells in the tubule lumen was also observed. These alterations were observed in all days of stress in a gradual way, from day 3-50. Testosterone levels were decreased at all those times, and corticosterone concentrations were increased on the same days. These results show that chronic stress causes severe damage to germ cells, which can account for infertility problems in males. These alterations are related to a decrease in testosterone as well as an increase in corticosterone caused by stress.

The role of the hypothalamus-pituitary-adrenal/interrenal axis in mediating predator-avoidance trade-offs

Maintaining energy balance and reproducing are important for fitness, yet animals have evolved mechanisms by which the hypothalamus-pituitary-adrenal/interrenal (HPA/HPI) axis can shut these activities off. While HPA/HPI axis inhibition of feeding and reproduction may have evolved as a predator defense, to date there has been no review across taxa of the causal evidence for such a relationship. Here we review the literature on this topic by addressing evidence for three predictions: that exposure to predators decreases reproduction and feeding, that exposure to predators activates the HPA/HPI axis, and that predator-induced activation of the HPA/HPI axis inhibits foraging and reproduction. Weight of evidence indicates that exposure to predator cues inhibits several aspects of foraging and reproduction. While the evidence from fish and mammals supports the hypothesis that predator cues activate the HPA/HPI axis, the existing data in other vertebrate taxa are equivocal. A causal role for the HPA axis in predator-induced suppression of feeding and reproduction has not been demonstrated to date, although many studies report correlative relationships between HPA activity and reproduction and/or feeding. Manipulation of HPA/HPI axis signaling will be required in future studies to demonstrate direct mediation of predator-induced inhibition of feeding and reproduction. Understanding the circuitry linking sensory pathways to their control of the HPA/HPI axis also is needed. Finally, the role that fear and anxiety pathways play in the response of the HPA axis to predator cues is needed to better understand the role that predators have played in shaping anxiety related behaviors in all species, including humans.

Glucocorticoid Receptor as a Potential Target to Decrease Aromatase Expression and Inhibit Leydig Tumor Growth

Leydig cell tumors are the most frequent interstitial neoplasms of the testis with increased incidence in recent years. They are hormonally active and are considered one of the steroid-secreting tumors. Although usually benign, the malignant phenotype responds poorly to conventional chemotherapy or radiation, highlighting the need to identify new therapeutic targets for treatment. Here, we identified a novel glucocorticoid-mediated mechanism that controls cell growth in Leydig cell tumors. We found that a synthetic glucocorticoid receptor agonist, dexamethasone, reduces cell proliferation in rat Leydig tumor cells by decreasing the expression and the enzymatic activity of the estrogen-producing enzyme aromatase. This inhibitory effect relies on the ability of activated glucocorticoid receptor to regulate the aromatase gene transcriptional activity through the recruitment of nuclear receptor corepressor protein and silencing mediator of retinoid and thyroid hormone receptors to a newly identified putative glucocorticoid responsive element within the aromatase promoter II. Our in vivo studies reveal a reduction of tumor growth, after dexamethasone treatment, in animal xenografts. Tumors from dexamethasone-treated mice exhibit a decrease in the expression of the proliferation marker Ki-67 and the aromatase enzyme. Our data demonstrate that activated glucocorticoid receptor, decreasing aromatase expression, induces Leydig tumor regression both in vitro and in vivo, suggesting that glucocorticoid receptor might be a potential target for the therapy of Leydig cell tumors.

Glucocorticoid Regulation of Reproduction

It is well accepted that stress, measured by increased glucocorticoid secretion, leads to profound reproductive dysfunction. In times of stress, glucocorticoids activate many parts of the fight or flight response, mobilizing energy and enhancing survival, while inhibiting metabolic processes that are not necessary for survival in the moment. This includes reproduction, an energetically costly procedure that is very finely regulated. In the short term, this is meant to be beneficial, so that the organism does not waste precious energy needed for survival. However, long-term inhibition can lead to persistent reproductive dysfunction, even if no longer stressed. This response is mediated by the increased levels of circulating glucocorticoids, which orchestrate complex inhibition of the entire reproductive axis. Stress and glucocorticoids exhibits both central and peripheral inhibition of the reproductive hormonal axis. While this has long been recognized as an issue, understanding the complex signaling mechanism behind this inhibition remains somewhat of a mystery. What makes this especially difficult is attempting to differentiate the many parts of both of these hormonal axes, and new neuropeptide discoveries in the last decade in the reproductive field have added even more complexity to an already complicated system. Glucocorticoids (GCs) and other hormones within the hypothalamic-pituitary-adrenal (HPA) axis (as well as contributors in the sympathetic system) can modulate the hypothalamic-pituitary-gonadal (HPG) axis at all levels-GCs can inhibit release of GnRH from the hypothalamus, inhibit gonadotropin synthesis and release in the pituitary, and inhibit testosterone synthesis and release from the gonads, while also influencing gametogenesis and sexual behavior. This chapter is not an exhaustive review of all the known literature, however is aimed at giving a brief look at both the central and peripheral effects of glucocorticoids on the reproductive function.

Nongenetic inheritance and transgenerational epigenetics

The idea that inherited genotypes define phenotypes has been paramount in modern biology. The question remains, however, whether stable phenotypes could be also inherited from parents independently of the genetic sequence per se. Recent data suggest that parental experiences can be transmitted behaviorally, through in utero exposure of the developing fetus to the maternal environment, or through either the male or female germline. The challenge is to delineate a plausible mechanism. In the past decade it has been proposed that epigenetic mechanisms are involved in multigenerational transmission of phenotypes and transgenerational inheritance. The prospect that ancestral experiences are written in our epigenome has immense implications for our understanding of human behavior, health, and disease.

Time-course changes of steroidogenic gene expression and steroidogenesis of rat Leydig cells after acute immobilization stress

Leydig cells secrete testosterone, which is essential for male fertility and reproductive health. Stress increases the secretion of glucocorticoid (corticosterone, CORT; in rats), which decreases circulating testosterone levels in part through a direct action by binding to the glucocorticoid receptors (NR3C1) in Leydig cells. The intratesticular CORT level is dependent on oxidative inactivation of glucocorticoid by 11β-hydroxysteroid dehydrogenase 1 (HSD11B1) in Leydig cells. In the present study, we investigated the time-course changes of steroidogenic gene expression levels after acute immobilization stress in rats. The plasma CORT levels were significantly increased 0.5, 1, 3 and 6 h after immobilization stress, while plasma testosterone levels were significantly reduced 3 and 6 h, after stress and luteinizing hormone (LH) did not change. Immobilization stress caused the down-regulation of Scarb1, Star and Cyp17a1 expression levels in the rat testis starting at the first hour of stress, ahead of the significant decreases of plasma testosterone levels. Other mRNA levels, including Cyp11a1, Hsd3b1 and Hsd17b3, began to decline after 3 h. Hsd11b1 and Nos2 mRNA levels did not change during the course of stress. Administration of glucocorticoid antagonist RU486 significantly restored plasma testosterone levels. In conclusion, Scarb1, Star and Cyp17a1 expression levels are more sensitive to acute stress, and acute immobilization stress causes the decline of the steroidogenic pathway via elevating the levels of glucocorticoid, which binds to NR3C1 in Leydig cells to inhibit steroidogenic gene expression.

Impact of adrenalectomy and dexamethasone treatment on testicular morphology and sperm parameters in rats: insights into the adrenal control of male reproduction

Here we investigated the hypothesis that normal levels of glucocorticoids, a class of adrenal steroid hormones, are required for normal testicular and epididymal functions. We examined the effects of the manipulation of glucocorticoid plasma levels by bilateral adrenalectomy (1, 2, 7 and 15 days) alone or in combination with daily treatment with the synthetic glucocorticoid dexamethasone (DEX; 5 μg/kg, i.p., 6 days) on the morphology of the testis and sperm parameters in rats. We showed that adrenalectomy led to a reduction in testicular sperm count and daily sperm production starting 2 days after surgery and a differential decrease in sperm count in the epididymis, according to the region and time post-adrenalectomy analysed. In parallel, testes from 7-day adrenalectomized (ADX) rats displayed a higher frequency of damaged seminiferous tubules and the presence of elongated spermatids retained in the basal epithelial compartment in stages IX-XVII, which is indicative of defective spermiation. The alkaline comet assay revealed a late effect of adrenalectomy on epididymal sperm DNA fragmentation, which was increased only 15 days after surgery. DEX treatment prevented the changes in testicular and epididymal sperm count observed in 7-day ADX rats, but failed to protect the testis from ADX-induced morphological abnormalities. Thus, our results indicated that glucocorticoids may be involved in events related to the maintenance of spermatogenesis and sperm maturation during adulthood. These findings provide new insights into the importance of adrenal steroids to male fertility.

A role for glucocorticoids in stress-impaired reproduction: beyond the hypothalamus and pituitary

In addition to the well-characterized role of the sex steroid receptors in regulating fertility and reproduction, reproductive events are also mediated by the hypothalamic-pituitary-adrenal axis in response to an individual's environment. Glucocorticoid secretion in response to stress contributes to the well-characterized suppression of the hypothalamic-pituitary-gonadal axis through central actions in the hypothalamus and pituitary. However, both animal and in vitro studies indicate that other components of the reproductive system are also regulated by glucocorticoids. Furthermore, in the absence of stress, it appears that homeostatic glucocorticoid signaling plays a significant role in reproduction and fertility in all tissues comprising the hypothalamic-pituitary-gonadal axis. Indeed, as central regulators of the immune response, glucocorticoids are uniquely poised to integrate an individual's infectious, inflammatory, stress, nutritional, and metabolic status through glucocorticoid receptor signaling in target tissues. Endocrine signaling between tissues regulating the immune and stress response and those determining reproductive status provides an evolutionary advantage, facilitating the trade-off between reproductive investment and offspring fitness. This review focuses on the actions of glucocorticoids in tissues important for fertility and reproduction, highlighting recent studies that show glucocorticoid signaling plays a significant role throughout the hypothalamic-pituitary-gonadal axis and characterizing these effects as permissive or inhibitory in terms of facilitating reproductive success.

The influence of aging and estradiol to progesterone ratio on rat macrophage phenotypic profile and NO and TNF-α production

The phenotype and function of tissue macrophages substantially depend on the cellular milieu and biological effector molecules, such as steroid hormones, to which they are exposed. Furthermore, in female rats, aging is associated with the altered macrophage functioning and the increased estrogen level is followed by a decrease in that of progesterone. Therefore, the present study aimed to investigate the influence of estradiol/progesterone balance on rat macrophage function and phenotype throughout whole adult lifespan. We ovariectomized rats at the late prepubertal age or at the very end of reproductive lifespan, and examined the expression of ED2 (CD163, a marker of mature resident macrophages related to secretion of inflammatory mediators) on peritoneal macrophages and their ability to produce TNF-α and NO upon LPS-stimulation at different age points. In addition, to delineate direct and indirect effects of estrogen, we assessed the in vitro influence of different concentrations of 17β-estradiol on LPS-induced macrophage TNF-α and NO production. Results showed that: (a) the low frequency of ED2(high) cells amongst peritoneal macrophages of aged rats was accompanied with the reduced TNF-α, but not NO production; (b) estradiol level gradually increased following ovariectomy; (c) macrophage ED2 expression and TNF-α production were dependent on estradiol/progesterone balance and they changed in the same direction; (d) changes in estradiol/progesterone balance differentially affected macrophages TNF-α and NO production; and (e) estradiol exerted pro-inflammatory and anti-inflammatory effects on macrophages in vivo and in vitro, respectively. Overall, our study discloses that estradiol/progesterone balance contributes to the fine-tuning of rat macrophage secretory capacity, and adds to a better understanding of the ovarian steroid hormone role in the regulation of macrophage function, and its significance for the age-associated changes in innate immunity.

Toxicological assessment of drugs that affect the endocrine system in puberty-related disorders

INTRODUCTION

Toxicologists must ensure that clinical risk-to-benefit analysis should be made both for genders and age groups, with any treatment. Puberty concerns physiological changes leading to organism's maturation. Pubertal growth disorders are increasing in last decades: besides causing physical and psychological distress, they may signal underlying endocrine-metabolic abnormalities with serious health consequences later on. Therapeutic approaches for some health conditions in childhood and adolescence are considered.

AREAS COVERED

The authors discuss how some diseases and treatments can impact pubertal growth. The authors look at particular immunological disorders such as asthma and how both the disease and treatment affects pubertal growth. They also discuss how the provision of available data can help to assess the dose-response of the drug, in these cases, and minimize the chance of side effects. The authors also discuss pediatric inflammatory bowel disease and how both the disease and treatment can mitigate the growth delay. Last, but not least, the authors discuss how the effects of the drugs used in the treatment of psychiatric disorders may accentuate endocrine issues in juvenile patients. Hyperprolactinemia induction by some antipsychotics is highlighted as an example.

EXPERT OPINION

Appropriate risk-benefit analysis of drugs prescribed during childhood and adolescence and intended to be used in the long term is required. Furthermore, future treatment strategies and safer compounds development should be supported by the knowledge of mechanisms underlying adverse side effects in pubertal growth and development.

Immunolocalisation of 11β-HSD-1 and -2, glucocorticoid receptor, mineralocorticoid receptor and Na+ K+-ATPase during the postnatal development of the rat epididymis

Glucocorticoids have been implicated in male reproductive function and 11β-HSD-1 and -2, the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR), all of which are known to modulate glucocorticoid action, have been localised in the adult rat epididymis, but their developmental expression has not been investigated. Na(+)K(+)-ATPase activity, responsible for sodium transport, is induced by both mineralocorticoids and glucocorticoids in the kidney and colon, and has been localised in epididymal epithelium. This study examined the immunolocalisation of 11β-HSD-1 and -2, GR, MR and Na(+)K(+)-ATPase in rat epididymal epithelium (n = 5) at postnatal days (pnd) 1, 7, 15, 28, 40, 60, 75 and 104, and relative mRNA expression of 11β-HSD-1 and -2, and GR at pre-puberty (pnd 28) and post-puberty (pnd 75). 11β-HSD-1, GR and MR were localised in the epididymal epithelium from pnd 1, and 11β-HSD-2 and Na(+)K(+)-ATPase reactivity from pnd 15. At pnd 28 there was maximal immunoreactivity for both the GR and MR and 11β-HSD-1 and -2. 11β-HSD-1 mRNA expression in the caput increased from pre- to post-puberty, whereas 11β-HSD-2 mRNA expression fell over the same period (P < 0.01). GR mRNA expression was similar at pre- and post-puberty in both caput and cauda. Developmental changes in expression of 11β-HSD-1 and -2 suggest that overall exposure of the epididymis to glucocorticoids increases post-puberty, but cell-specific expression of the 11β-HSD enzymes still provides a capacity for intricate local control of glucocorticoid exposure.

Acute stress rapidly decreases plasma testosterone in a free-ranging male songbird: potential site of action and mechanism

We used a free-ranging, seasonally breeding adult male songbird, the rufous-winged sparrow, Aimophila carpalis, to investigate the effects of acute stress-induced by capture followed by restraint, on the hypothalamo-pituitary-testicular axis. Intra- and interindividual comparisons revealed that males decreased their plasma testosterone (T) by 37-52% in response to acute stress. The decrease occurred within 15 min of capture and persisted for at least another 15 min. Within 15 min, the decrease in plasma T was not associated with a reduction in plasma luteinizing hormone (LH). Thirty minutes after capture and restraint, the decrease in plasma T either was likewise not associated with decreased plasma LH (intraindividual comparison) or concurred with a reduction in plasma LH (interindividual comparison). These observations indicate that effects of stress may have been mediated at the pituitary gland and also directly at the testicular levels. To address this question, we measured the hormonal response to an injection of the glutamate receptor agonist N-methyl-d,l-aspartate (NMA) to stimulate to stimulate the release of gonadotropin-releasing hormone (GnRH) or of GnRH to stimulate the release of LH. Treatment with NMA did not change plasma LH, presumably because the birds were in breeding condition and already secreting GnRH at a maximum rate. Administration of GnRH increased plasma LH equally in birds that were or were not stressed before the treatment. An injection of purified ovine LH (oLH) increased plasma T equally in birds that were or were not acutely stressed before the hormone injection. Thus, the observed acute stress-induced decrease in plasma T was apparently not mediated by decreased responsiveness of the pituitary gland to GnRH or of the testes to LH. Decreased plasma T following stress may involve a direct impairment of the testicular endocrine function.

Glucocorticoid receptor in the rat epididymis: expression, cellular distribution and regulation by steroid hormones

Glucocorticoids regulate several physiological functions, including reproduction, in mammals. Curiously, little is known about glucocorticoid-induced effects on the epididymis, an androgen-dependent tissue with vital role on sperm maturation. Here, RT-PCR, Western blot and immunohistochemical studies were performed to evaluate expression, cellular distribution and hormonal regulation of glucocorticoid receptor (GR) along rat epididymis. The rat orthologue of human GRalpha (mRNA and protein) was detected in caput, corpus and cauda epididymis and immunolocalized in the nucleus and cytoplasm of different epididymal cells (epithelial, smooth muscle and interstitial cells) and nerve fibers. Changes in plasma glucocorticoid and androgen levels differentially regulated GR expression in caput and cauda epididymis by homologous and heterologous mechanisms. In vivo treatment with dexamethasone significantly changed the expression of glucocorticoid-responsive genes and induced ligand-dependent GR nuclear translocation in epithelial cells from epididymis, indicating that GR is fully active in this tissue. Heterologous regulation of androgen receptor expression by glucocorticoids was also demonstrated in cauda epididymis. Our results demonstrate that the epididymis is under glucocorticoid regulation, opening new insights into the roles of this hormone in male fertility.

Age-related changes in the expression of 11beta-hydroxysteroid dehydrogenase type 2 in rat Leydig cells

Previous studies in rats have shown that the ability of Leydig cells (LCs) to produce testosterone significantly declines with age. To address the possible mechanisms by which aging LCs lose their steroidogenic function, we determined the effect of aging on the expression of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) type 2. The enzyme plays a protective role in blunting the suppressive effects of glucocorticoids on LCs steroidogenesis. Our immunohistochemical analysis revealed progressive decline in 11beta-HDS type 2 expression in LCs of the 18 months of age rats and the most significant reduction in 11beta-HSD2 immunoreactivity was evident in the testicular interstitium of 24- month-old rats. The decrease in the 11beta-HDS type 2 immunostaining in LCs during aging coincided with decline in insulin-like 3/relaxin-like factor (INSL3/RLF) expression, an independent marker for LCs differentiation status. Concomitant with the age-related decrease of 11beta-HDS type 2 immunoreactivity in the LCs population, the immunoexpression of 3beta-hydroxysteroid dehydrogenase (3beta-HSD), marker for LCs steroidogenic activity, was greatly reduced at 24 months compared to 3-month-old control. Similar pattern of expression exhibited also androgen receptor (AR) which is localized in the nuclei of Sertoli cells (SCs), LCs, and peritubular cells. During ages we observed progressive decrease in the immunoreactivity for AR in the testicular types and there was a loss of stage specificity in SCs at age of 24 months. It now seems evident that a variety of factors are likely to be involved in age-related decreases in LCs steroidogenesis, including 11beta-HSD type 2. The observed reduction in 11beta-HSD type 2 expression in aging LCs reflects the decline in their protection ability, opposing the suppressive effect of glucocorticoids on testosterone production.

Rapid mechanisms of glucocorticoid signaling in the Leydig cell

Stress-mediated elevations in circulating glucocorticoid levels lead to corresponding rapid declines in testosterone production by Leydig cells in the testis. In previous studies we have established that glucocorticoids act on Leydig cells directly, through the classic glucocorticoid receptor (GR), and that access to the GR is controlled prior to the GR by a metabolizing pathway mediated by the type 1 isoform of 11beta-hydroxysteroid dehydrogenase (11betaHSD1). This enzyme is bidirectional (with both oxidase and reductase activities) and in the rat testis is exclusively localized in Leydig cells where it is abundantly expressed and may catalyze the oxidative inactivation of glucocorticoids. The predominant reductase direction of 11betaHSD1 activity in liver cells is determined by an enzyme, hexose-6-phosphate dehydrogenase (H6PDH), on the luminal side of the smooth endoplasmic reticulum (SER). Generation of the pyridine nucleotide cofactor NADPH by H6PDH stimulates the reductase direction of 11betaHSD1 resulting in increased levels of active glucocorticoids in liver cells. Unlike liver cells, steroidogenic enzymes including 17beta-hydroxysteroid dehydrogenase 3 (17betaHSD3) forms the coupling with 11betaHSD1. Thus the physiological concentrations of androstenedione serve as a substrate for 17betaHSD3 utilizing NADPH to generate NADP+, which drives 11betaHSD1 in Leydig cells primarily as an oxidase; thus eliminating the adverse effects of glucocorticoids on testosterone production. At the same time 11betaHSD1 generates NADPH which promotes testosterone biosynthesis by stimulating 17betaHSD3 in a cooperative cycle. This enzymatic coupling constitutes a rapid mechanism for modulating glucocorticoid control of testosterone biosynthesis. Under stress conditions, glucocorticoids also have rapid actions to suppress cAMP formation thus to lower testosterone production.

In vivo inhibition of steroidogenic acute regulatory protein expression by dexamethasone parallels induction of the negative transcription factor DAX-1

In this study, we investigated the effect of dexamethasone on the synthesis of steroidogenic acute regulatory protein (StAR) and the expression of DAX-1 (dosage sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome, gene 1) and SF-1 (steroidogenic factor-1) in vivo. Male rats were treated with dexamethasone (0.4 and 4 mg/kg body wt per day) by intraperitoneal injections using phosphate-buffered saline as the vehicle for 7 d. At the end of 7 d, serum testosterone levels were decreased. Response to luteinizing hormone (LH) and 8-bromo-cyclic-AMP (8-Br-cAMP) in vitro was reduced in testicular cells isolated from dexamethasone-treated rat testes. Dexamethasone decreased LH-stimulated cAMP production. The conversion of 22(R)-hydroxycholesterol, pregnenolone, 17-hydroxypregnenolone, dehydroepiandrosterone, and androstenedione to testosterone was not affected by dexamethasone. Dexamethasone increased DAX-1 expression and concordantly decreased StAR protein and mRNA in testicular cells. The increase in DAX-1 protein corresponded to a 57% reduction in StAR mRNA levels concomitant with a 79% reduction in serum testosterone levels. Dexamethasone had no effect on the level of SF-1, but increased the amount of complexed DAX-1-SF-1. Dexamethasone in vitro suppressed StAR promoter activity when an increasing amount of DAX-1 cDNA was transfected. These results demonstrate that dexamethasone increases expression of DAX-1, which results in increased amounts of complexed DAX-1-SF-1, in the absence of any change in the expression of SF-1. These observations strongly support the concept that dexamethasone suppresses rat testicular testosterone production, at least in part, by increasing the amount of complexed DAX-1-SF-1 in these cells, which leads directly to decreased availability of free SF-1 and, therefore, decreased activation of transcription of the rat StAR gene.

Transfection with steroid-responsive reporter constructs shows glucocorticoid rather than androgen responsiveness in cultured Sertoli cells

It remains unclear why it has proven so difficult to identify androgen target genes in cultured Sertoli cells. Given the lack of useful endogenous reporter genes, we studied the androgen and glucocorticoid responsiveness of these cells by transfection with three different steroid-responsive reporter constructs. The constructs were driven by the tyrosine aminotransferase steroid-responsive region (TAT-GRE4x-Luc), the mouse mammary tumor virus promoter (MMTV-Luc) and the Pem homeobox gene proximal promoter respectively (Pem-Luc). These constructs can be activated either by both the glucocorticoid receptor (GR) and the androgen receptor (AR) (TAT-GRE4x-Luc and MMTV-Luc) or selectively by the AR (Pem-Luc). Despite high transfection efficiency (30-40%) none of the constructs could be activated by treatment of the Sertoli cells with testosterone, 5alpha-dihydrotestosterone or synthetic androgens. Even pretreatment with follicle-stimulating hormone to raise AR levels (from 31 up to 82fmol/mg protein) did not result in androgen responsiveness. In contrast, treatment with dexamethasone markedly stimulated TAT-GRE4x-Luc and MMTV-Luc activity. GR levels reached a value of 172fmol/mg protein in the cultured cells and both AR and GR displayed homogeneous distribution by immunocytochemical evaluation. Androgen responsiveness was restored and glucocorticoid responsiveness was increased by cotransfection with AR or GR expression constructs. Under cotransfection conditions, 1nM of testosterone (a concentration that is some 100 times lower than that estimated to be present in the testis) was sufficient to stimulate the TAT-GRE4x-Luc maximally. Our data indicate that cultured Sertoli cells respond better to glucocorticoids than to androgens and that one of the factors limiting androgen responsiveness is the availability of AR. Other factors limiting the transactivation capacity of the (endogenous) AR, however, cannot be excluded.

Involvement of glucocorticoids in testicular involution after active immunization of boars against GnRH

Active GnRH immunization of boars inhibits LH and testicular steroids but the consequences for spermatogenesis are unknown. Six boars were immunized three times against GnRH at 20, 24 and 28 weeks. Another six boars served as controls. Plasma LH and FSH were determined at 28 and 31 weeks. Testosterone and cortisol were determined before killing the pigs at 32 weeks. Tissue samples were taken for histology and fluid from the seminiferous tubuli for steroid determination. Individual germ cells were counted in histological sections. The glucocorticoid receptor (GCR), mitosis of spermatogonia and apoptosis were characterized by immunocytochemistry. Immunization reduced LH and testosterone to base levels whereas FSH was not changed. Testis weight was reduced by 64% due to a loss of Leydig cell cytoplasm (90.3%) and a decrease of tubule diameters (60.6%). Except for A-spermatogonia, all other spermatogenic cells were reduced by about 60%. Mitosis was reduced in immunized boars. Expression of GCRs was limited to spermatogonia and differed between immunized boars (8% of spermatogonia) and controls (2%). In the controls, androgen concentrations in tubular fluid were tenfold higher compared with immunized boars. Cortisol concentrations were of the order of 40 nmol/l both in the tubular fluid and blood plasma. These concentrations did not differ between groups. Apoptosis occurred only in spermatogonia and pachytene spermatocytes and was twofold higher in immunized boars compared with controls. Thus the availability of glucocorticoids in the tubuli and the expression of GCRs initiate apoptosis, which in turn reduces sperm yield. Testosterone is known to be an inhibitor of GCR expression, thus increasing the efficiency of spermatogenesis.

The functional roles of 11 beta-HSD1: vascular tissue, testis and brain

Glucocorticoid hormones bind both glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) exerting a broad spectrum of actions in various tissues. The concentrations of glucocorticoid hormones in the target cells are regulated by 11 beta-hydroxysteroid dehydrogenases, type 1 (11 beta-HSD1) and type 2 (11 beta-HSD2). 11 beta-HSD2 is a unidirectional dehydrogenase, which inactivates biologically active glucocorticoid into inert metabolite, while 11 beta-HSD1 is a bi-directional oxidoreductase, which either inactivates biologically active glucocorticoid or activates inert metabolite into active forms. GRs and MRs are present in various tissues and mediate a broad spectrum of physiological actions. The co-existence of 11 beta-HSD1 with these two types of receptors plays an important role in regulation of glucocorticoid actions. This review examines the roles of 11 beta-HSD1 in vascular tissues, testis, brain and other tissues such as placental, retinal and adipose tissues.