Pituitary androgen receptor signalling regulates prolactin but not gonadotrophins in the male mouse

The Ser434Phe Androgen Receptor Gene Mutation Does Not Affect Fertility but is Associated with Increased Prolactin

Introduction

Prolactin is a hormone secreted by the anterior pituitary gland essential for lactation. Non-physiological hyperprolactinemia characterized by serum prolactin levels exceeding 20 ng/mL in men and 25 ng/mL in women, often results from medication use or pituitary gland tumors. In a minority of cases, the cause of hyperprolactinemia remains unknown despite clinical investigations. Familial idiopathic hyperprolactinemia may stem from mutations in genes encoding prolactin (PRL) and its receptor (PRLR).

Methods

This study investigated genetic polymorphisms in PRL and PRLR genes using polymerase chain reaction (PCR) and Sanger sequencing in three sisters affected by familial idiopathic hyperprolactinemia. No mutations were found in these genes, prompting whole exome sequencing (WES) of the proband to identify other potentially involved genes.

Results

WES revealed a heterozygous missense substitution c.1301C>T (p.Ser434Phe) in the androgen receptor (AR) gene. Next-generation sequencing (NGS) for the AR gene confirmed that the proband and her two affected sisters, along with three asymptomatic sisters, were all heterozygous carriers of the mutation. Their father was hemizygous, while their mother had a normal genotype.

Conclusion

The heterozygous missense mutation in the AR gene found in this family with familial idiopathic hyperprolactinemia is not yet explained. Hence, further research is warranted to elucidate the functional implications of this mutation on AR and its role in the pathogenesis of hyperprolactinemia.

Maternal transmission as a microbial symbiont sieve, and the absence of lactation in male mammals

Gut microbiomes of mammals carry a complex symbiotic assemblage of microorganisms. Feeding newborn infants milk from the mammary gland allows vertical transmission of the parental milk microbiome to the offspring's gut microbiome. This has benefits, but also has hazards for the host population. Using mathematical models, we demonstrate that biparental vertical transmission enables deleterious microbial elements to invade host populations. In contrast, uniparental vertical transmission acts as a sieve, preventing these invasions. Moreover, we show that deleterious symbionts generate selection on host modifier genes that keep uniparental transmission in place. Since microbial transmission occurs during birth in placental mammals, subsequent transmission of the milk microbiome needs to be maternal to avoid the spread of deleterious elements. This paper therefore argues that viviparity and the hazards from biparental transmission of the milk microbiome, together generate selection against male lactation in placental mammals.

Network analysis of comorbid aggressive behavior and testosterone among bipolar disorder patients: a cross-sectional study

Testosterone has complex effects on psychological traits and behavior; it is associated with social dominance and competition and is a potential human sex pheromone. This study aimed to investigate the associations between testosterone levels, aggressive behavior, and manic symptoms using a network analysis among bipolar disorder (BD) patients in psychiatric emergency departments (PED). Data from January 2021 and March 2022 BD patients in PED were analyzed. Manic symptoms were assessed using the Young Mania Rating Scale (YMRS). Aggression was assessed with subscale of the PANSS scale (PANSS-AG). The undirected network structures of testosterone levels, aggressive behavior, and manic symptoms were estimated, and centrality and bridge centrality indices were examined. Network stability was examined using the case-dropping procedure. The Network Comparison Test (NCT) was conducted to evaluate whether network characteristics differed by gender. We recruited a total of 898 BD patients, with the mean YMRS score as 13.30 ± 9.58. The prevalence of level II aggression was 35.6% (95%CI = 32.5%-38.7%), level III aggression was 29.5% (95%CI = 26.3%-32.6%), and level VI aggression was 7.0% (95%CI = 5.4%-8.8%). The male participants had a mean testosterone level of 391.71 (Standard Deviation (SD):223.39) compared to 36.90 (SD:30.50) for female participants in the whole sample. Through network analysis, "Increased motor activity-energy" emerged as the central symptom, with the highest centrality expected influence, followed by "Emotional Instability" and "Disruptive/aggression behavior". Notably, "Emotional Instability" appeared to be the bridge symptom linking manic symptoms to aggressive behavior. Within the flow network model, "Speech rate and amount" exhibited the strongest positive correlation with testosterone levels, followed closely by "Disruptive/aggression behavior". The constructed network model demonstrated robust stability, with gender showing no significant impact on the structure. In this study, "Increased motor activity-energy" stood out as the most influential symptom, and "Speech rate and amount" acted as the main bridge symptom linking testosterone levels, aggressive behavior, and manic symptoms. Targeting the central and bridge symptoms may improve the outcomes of aggression interventions implemented among BD patients in psychiatric emergency care.

Unraveling Hypothalamus-Pituitary dysregulation: Hypergonadotropism in F1 progeny due to prenatal exposure to hexavalent chromium

The endocrine disruptor hexavalent chromium [Cr(VI)] is a proven reproductive toxicant. We recently demonstrated that prenatal Cr(VI) exposure causes testicular resistance to gonadotropins, resulting in hypergonadotropic hypoandrogenism in F1 rats. However, the mechanism driving hypergonadotropism in F1 rats exposed to Cr(VI) prenatally remains an enigma. Therefore, we hypothesized that 'Prenatal Cr(VI) exposure may disrupt steroid hormones-mediated negative feedback regulation of the hypothalamic GnRH, and its receptor in the pituitary of F1 rats, leading to hypergonadotropism.' We administered potassium dichromate (50, 100, or 200 mg/L) to pregnant rats through drinking water between days 9 and 14, and their male F1 offspring were euthanized at 60 days of age. Prenatal Cr(VI) exposure in F1 rats resulted in the accumulation of Cr in the hypothalamus and pituitary. Western blot detected decreased hypothalamic GnRH, Kisspeptin1, and its receptor GPR54, along with diminished ERα, AR, aromatase, and 5α reductase, and GnRH regulatory transcription factors Pit-1 and GATA-4 proteins. Immunohistochemical studies revealed increased immunopositivity of GnRH receptor, AR, 5α reductase, ERα, ERβ, and aromatase proteins in the pituitary, whereas decreased Kisspeptin1, GPR54, and inhibin β. Our findings imply that Cr(VI) exposure during the prenatal period disrupts the hypothalamic Kisspeptin-GPR54-Pit-1/GATA4-GnRH network, boosting the pituitary GnRH receptor. We conclude that prenatal exposure to Cr(VI) alters GnRH expression in the hypothalamus and its receptor in the pituitary of F1 progeny through interfering with the negative feedback effect of androgens and estrogens.

Sex differences in pituitary corticotroph excitability

Stress-related illness represents a major burden on health and society. Sex differences in stress-related disorders are well documented, with women having twice the lifetime rate of depression compared to men and most anxiety disorders. Anterior pituitary corticotrophs are central components of the hypothalamic-pituitary-adrenal (HPA) axis, receiving input from hypothalamic neuropeptides corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP), while regulating glucocorticoid output from the adrenal cortex. The dynamic control of electrical excitability by CRH/AVP and glucocorticoids is critical for corticotroph function; however, whether corticotrophs contribute to sexually differential responses of the HPA axis, which might underlie differences in stress-related disorders, is very poorly understood. Using perforated patch clamp electrophysiology in corticotrophs from mice expressing green fluorescent protein under the control of the Pomc promoter, we characterized basal and secretagogue-evoked excitability. Both male and female corticotrophs show predominantly single-spike action potentials under basal conditions; however, males predominantly display spikes with small-amplitude (<20 mV) afterhyperpolarizations (B-type), whereas females displayed a mixture of B-type spikes and spikes with a large-amplitude (>25 mV) afterhyperpolarization (A-type). In response to CRH, or CRH/AVP, male cells almost exclusively transition to a predominantly pseudo-plateau bursting, whereas only female B-type cells display bursting in response to CRH±AVP. Treatment of male or female corticotrophs with 1 nM estradiol (E2) for 24-72 h has no effect on the proportion of cells with A- or B-type spikes in either sex. However, E2 results in the cessation of CRH-induced bursting in both male and female corticotrophs, which can be partially reversed by adding a BK current using a dynamic clamp. RNA-seq analysis of purified corticotrophs reveals extensive differential gene expression at the transcriptional level, including more than 71 mRNAs encoding ion channel subunits. Interestingly, there is a two-fold lower level (p < 0.01) of BK channel pore-forming subunit (Kcnma1) expression in females compared to males, which may partially explain the decrease in CRH-induced bursting. This study identified sex differences at the level of the anterior pituitary corticotroph ion channel landscape and control of both spontaneous and CRH-evoked excitability. Determining the mechanisms of sex differences of corticotroph and HPA activity at the cellular level could be an important step for better understanding, diagnosing, and treating stress-related disorders.

The role of testosterone, the androgen receptor, and hypothalamic-pituitary-gonadal axis in depression in ageing Men

Considerable research has shown that testosterone regulates many physiological systems, modulates clinical disorders, and contributes to health outcome. However, studies on the interaction of testosterone levels with depression and the antidepressant effect of testosterone replacement therapy in hypogonadal men with depression have been inconclusive. Current findings indicate that low circulating levels of total testosterone meeting stringent clinical criteria for hypogonadism and testosterone deficiency induced by androgen deprivation therapy are associated with increased risk for depression and current depressive symptoms. The benefits of testosterone replacement therapy in men with major depressive disorder and low testosterone levels in the clinically defined hypogonadal range remain uncertain and require further investigation. Important considerations going forward are that major depressive disorder is a heterogeneous phenotype with depressed individuals differing in inherited polygenic determinants, onset and clinical course, symptom complexes, and comorbidities that contribute to potential multifactorial differences in pathophysiology. Furthermore, polygenic mechanisms are likely to be critical to the biological heterogeneity that influences testosterone-depression interactions. A genetically informed precision medicine approach using genes regulating testosterone levels and androgen receptor sensitivity will likely be essential in gaining critical insight into the role of testosterone in depression.

Postnatal developmental trajectory of sex-biased gene expression in the mouse pituitary gland

BACKGROUND

The pituitary gland regulates essential physiological processes such as growth, pubertal onset, stress response, metabolism, reproduction, and lactation. While sex biases in these functions and hormone production have been described, the underlying identity, temporal deployment, and cell-type specificity of sex-biased pituitary gene regulatory networks are not fully understood.

METHODS

To capture sex differences in pituitary gene regulation dynamics during postnatal development, we performed 3' untranslated region sequencing and small RNA sequencing to ascertain gene and microRNA expression, respectively, across five postnatal ages (postnatal days 12, 22, 27, 32, 37) that span the pubertal transition in female and male C57BL/6J mouse pituitaries (n = 5-6 biological replicates for each sex at each age).

RESULTS

We observed over 900 instances of sex-biased gene expression and 17 sex-biased microRNAs, with the majority of sex differences occurring with puberty. Using miRNA-gene target interaction databases, we identified 18 sex-biased genes that were putative targets of 5 sex-biased microRNAs. In addition, by combining our bulk RNA-seq with publicly available male and female mouse pituitary single-nuclei RNA-seq data, we obtained evidence that cell-type proportion sex differences exist prior to puberty and persist post-puberty for three major hormone-producing cell types: somatotropes, lactotropes, and gonadotropes. Finally, we identified sex-biased genes in these three pituitary cell types after accounting for cell-type proportion differences between sexes.

CONCLUSION

Our study reveals the identity and postnatal developmental trajectory of sex-biased gene expression in the mouse pituitary. This work also highlights the importance of considering sex biases in cell-type composition when understanding sex differences in the processes regulated by the pituitary gland.

Distinctive features of the hypothalamic-pituitary-gonadal axis and the level of dopamine in men of the European and Asian North

In recent years, there has been a decrease in reproductive potential, especially among residents of the Arctic territories, having the greatest stress from various body systems, including the state of the hormonal regulation of the male reproductive system. The study of the dopamine levels and the content of sex hormones in the male population of various Arctic regions is relevant due to the increased stress on the part of the dopaminergic system and the hypothalamic-pituitary-gonadal axis in residents of the Northern regions, as well as the lack of information about their interaction among the apparently healthy population. The aim of the investigation is to study the possible effect of various plasma concentrations of the dopamine on the content of sex hormones and sex-steroid-binding β-globulin (SHBG) in apparently healthy men in the Arctic zone of the Russian Federation, taking into account the territory of residence. There were examined 181 men aged 22-60 years, living in the territories of the European and Asian North. The levels of sex hormones, SHBG, and dopamine were determined by the enzyme-linked immunosorbent assay. The inhabitants of the Asian North in comparison with the men of the European North have higher levels of dopamine, luteinizing hormone, progesterone, prolactin, estradiol and SHBG with decreased serum levels of free fractions of testosterone. Reference levels of dopamine in men from the European North are combined with the stimulatory effect of dopamine on LH levels, which may indicate an increase steroidogenesis. The high levels of dopamine in men from the Asian North are combined with increased level of estradiol, which may be related to the effect of dopamine on testosterone aromatization. The separate region with its ecological differences is characterized by the presence of features of compensatory-adaptive reactions of an organism in male representatives on the part of the dopaminergic system and the hypothalamic-pituitary-gonadal axis. The identified features can help in carrying out preventive measures aimed at preserving the male reproductive potential of the inhabitants of the Arctic territories.

Flutamide treatment reveals a relationship between steroidogenic activity of Leydig cells and ultrastructure of their mitochondria

Our present knowledge on interrelation between morphology/ultrastructure of mitochondria of the Leydig cell and its steroidogenic function is far from satisfactory and needs additional studies. Here, we analyzed the effects of blockade of androgen receptor, triggered by exposure to flutamide, on the expression of steroidogenic proteins (1) and ultrastructure of Leydig cells' constituents (2). We demonstrated that increase in the expression level of steroidogenic (StAR, CYP11A1, 3β-HSD, and CYP19A1) proteins (and respective mRNAs) in rat testicular tissue as well as elevation of intratesticular sex steroid hormone (testosterone and estradiol) levels observed in treated animals correspond well to morphological alterations of the Leydig cell ultrastructure. Most importantly, up-regulation of steroidogenic proteins' expression apparently correlates with considerable multiplication of Leydig cell mitochondria and subsequent formation of local mitochondrial networks. Interestingly, we showed also that the above-mentioned processes were associated with elevated transcription of Drp1 and Mfn2 genes, encoding proteins implicated in mitochondrial dynamics. Collectively, our studies emphasize the importance of mitochondrial homeostasis to the steroidogenic function of Leydig cells.

Androgen receptor positively regulates gonadotropin-releasing hormone receptor in pituitary gonadotropes

Within pituitary gonadotropes, the gonadotropin-releasing hormone receptor (GnRHR) receives hypothalamic input from GnRH neurons that is critical for reproduction. Previous studies have suggested that androgens may regulate GnRHR, although the mechanisms remain unknown. In this study, we demonstrated that androgens positively regulate Gnrhr mRNA in mice. We then investigated the effects of androgens and androgen receptor (AR) on Gnrhr promoter activity in immortalized mouse LβT2 cells, which represent mature gonadotropes. We found that AR positively regulates the Gnrhr proximal promoter, and that this effect requires a hormone response element (HRE) half site at -159/-153 relative to the transcription start site. We also identified nonconsensus, full-length HREs at -499/-484 and -159/-144, which are both positively regulated by androgens on a heterologous promoter. Furthermore, AR associates with the Gnrhr promoter in ChIP. Altogether, we report that GnRHR is positively regulated by androgens through recruitment of AR to the Gnrhr proximal promoter.

Hyperprolactinemia in a male pituitary androgen receptor knockout mouse is associated with female-like lactotroph development

BACKGROUND

Circulating prolactin concentration in rodents and humans is sexually dimorphic. Oestrogens are a well-characterised stimulator of prolactin release. Circulating prolactin fluctuates throughout the menstrual/oestrous cycle of females in response to oestrogen levels, but remains continually low in males. We have previously identified androgens as an inhibitor of prolactin release through characterisation of males of a mouse line with a conditional pituitary androgen receptor knockout (PARKO) which have an increase in circulating prolactin, but unchanged lactotroph number.

OBJECTIVES

In the present study, we aimed to specify the cell type that androgens act on to repress prolactin release.

MATERIALS AND METHODS

PARKO, lactotroph-specific, Pit1 lineage-specific and neural-specific conditional androgen receptor knockout male mice were investigated using prolactin ELISA, pituitary electron microscopy, immunohistochemistry and qRT-PCR.

RESULTS

Lactotroph-specific, Pit1 lineage-specific and neural-specific conditional AR knockouts did not duplicate the high circulating prolactin seen in the PARKO line. Using electron microscopy to examine ultrastructure, we showed that pituitary androgen receptor knockout male mice develop lactotrophs that resemble those seen in female mice. Castrated PARKO males have significantly reduced circulating prolactin compared to intact males. When expression of selected oestrogen-regulated anterior pituitary genes was examined, there were no differences in expression level between controls and knockouts.

DISCUSSION

The cell type that androgens act on to repress prolactin release is not the lactotroph, cells in the Pit1-lineage, or the dopaminergic neurons in the hypothalamus. PARKO males develop a female-specific lactotroph ultrastructure that this is likely to contribute to the increase in circulating prolactin. Castrated PARKO males have significantly reduced circulating prolactin compared to intact males, which suggests that removal of both circulating oestrogens and androgens reduces the stimulation of pituitary prolactin release.

CONCLUSION

Further investigation is needed into prolactin regulation by changes in androgen-oestrogen balance, which is involved sexual dimorphism of development and diseases including hyperprolactinemia.

Lack of AR in LepRb Cells Disrupts Ambulatory Activity and Neuroendocrine Axes in a Sex-Specific Manner in Mice

Disorders of androgen imbalance, such as hyperandrogenism in females or hypoandrogenism in males, increase risk of visceral adiposity, type 2 diabetes, and infertility. Androgens act upon androgen receptors (AR) which are expressed in many tissues. In the brain, AR are abundant in hypothalamic nuclei involved in regulation of reproduction and energy homeostasis, yet the role of androgens acting via AR in specific neuronal populations has not been fully elucidated. Leptin receptor (LepRb)-expressing neurons coexpress AR predominantly in hypothalamic arcuate and ventral premammillary nuclei (ARH and PMv, respectively), with low colocalization in other LepRb neuronal populations, and very low colocalization in the pituitary gland and gonads. Deletion of AR from LepRb-expressing cells (LepRbΔAR) has no effect on body weight, energy expenditure, and glucose homeostasis in male and female mice. However, LepRbΔAR female mice show increased body length later in life, whereas male LepRbΔAR mice show an increase in spontaneous ambulatory activity. LepRbΔAR mice display typical pubertal timing, estrous cycles, and fertility, but increased testosterone levels in males. Removal of sex steroid negative feedback action induced an exaggerated rise in luteinizing hormone in LepRbΔAR males and follicle-stimulating hormone in LepRbΔAR females. Our findings show that AR can directly affect a subset of ARH and PMv neurons in a sex-specific manner and demonstrate specific androgenic actions in the neuroendocrine hypothalamus.

Pituitary Hyperplasia, Hormonal Changes and Prolactinoma Development in Males Exposed to Estrogens-An Insight From Translational Studies

Estrogen signaling plays an important role in pituitary development and function. In sensitive rat or mice strains of both sexes, estrogen treatments promote lactotropic cell proliferation and induce the formation of pituitary adenomas (dominantly prolactin or growth-hormone-secreting ones). In male patients receiving estrogen, treatment does not necessarily result in pituitary hyperplasia, hyperprolactinemia or adenoma development. In this review, we comprehensively analyze the mechanisms of estrogen action upon their application in male animal models comparing it with available data in human subjects. Sex-specific molecular targets of estrogen action in lactotropic (PRL) cells are highlighted in the context of their proliferative and secretory activity. In addition, putative effects of estradiol on the cellular/tumor microenvironment and the contribution of postnatal pituitary progenitor/stem cells and transdifferentiation processes to prolactinoma development have been analyzed. Finally, estrogen-induced morphological and hormone-secreting changes in pituitary thyrotropic (TSH) and adrenocorticotropic (ACTH) cells are discussed, as well as the putative role of the thyroid and/or glucocorticoid hormones in prolactinoma development, based on the current scarce literature.

Male hypogonadism: a review

This article contains a systematic review of the main developments that have occurred in the area of male hypogonadism between the publication of the Endocrine Society Guidelines of 2010 and 2018 and after 2018.

The maternal hormone in the male brain: Sexually dimorphic distribution of prolactin signalling in the mouse brain

Research of the central actions of prolactin is highly focused on females, but this hormone has also documented roles in male physiology and behaviour. Here, we provide the first description of the pattern of prolactin-derived signalling in the male mouse brain, employing the immunostaining of phosphorylated signal transducer and activator of transcription 5 (pSTAT5) after exogenous prolactin administration. Next, we explore possible sexually dimorphic differences by comparing pSTAT5 immunoreactivity in prolactin-supplemented males and females. We also assess the role of testosterone in the regulation of central prolactin signalling in males by comparing intact with castrated prolactin-supplemented males. Prolactin-supplemented males displayed a widespread pattern of pSTAT5 immunoreactivity, restricted to brain centres showing expression of the prolactin receptor. Immunoreactivity for pSTAT5 was present in several nuclei of the preoptic, anterior and tuberal hypothalamus, as well as in the septofimbrial nucleus or posterodorsal medial amygdala of the telencephalon. Conversely, non-supplemented control males were virtually devoid of pSTAT5-immunoreactivity, suggesting that central prolactin actions in males are limited to situations concurrent with substantial hypophyseal prolactin release (e.g. stress or mating). Furthermore, comparison of prolactin-supplemented males and females revealed a significant, female-biased sexual dimorphism, supporting the view that prolactin has a preeminent role in female physiology and behaviour. Finally, in males, castration significantly reduced pSTAT5 immunoreactivity in some structures, including the paraventricular and ventromedial hypothalamic nuclei and the septofimbrial region, thus indicating a region-specific regulatory role of testosterone over central prolactin signalling.

Echinacoside Increases Sperm Quantity in Rats by Targeting the Hypothalamic Androgen Receptor

Male infertility is a major health issue with an estimated prevalence of 4.2% of male infertility worldwide. Our early work demonstrated that Cistanche extracts protect against sperm damage in mice and that echinacoside (ECH) is one of the major active components. Here we report an essential role for ECH, a natural product that reverses or protects against oligoasthenospermia in rats. ECH was assayed by HPLC, the quantity and quality of sperm was evaluated and hormone levels were determined by radioimmunosorbent assay. ECH reduced levels of androgen receptor (AR) and key steroidogenic-related genes as determined by Western blot and qPCR analysis. The interaction between ECH and AR were evaluated by indirect ELISA and molecular docking. The results show that ECH combined with hypothalamic AR in the pocket of Met-894 and Val-713 to inhibit transfer of AR from the cytoplasm to nuclei in the hypothalamus. While negative feedback of sex hormone regulation was inhibited, positive feedback was stimulated to increase the secretion of luteinizing hormone and testosterone subsequently enhancing the quantity of sperm. Taken together, these data demonstrate that ECH blocks AR activity in the hypothalamus to increase the quantity of sperm and protect against oligoasthenospermia in rats.

Effects of active immunization against GnRH versus surgical castration on hypothalamic-pituitary function in boars

The objective was to compare effects of anti-GnRH immunization (immunocastration) versus surgical castration on hypothalamic-pituitary function in boars. Thirty-six boars were randomly divided into three groups (n = 12/group): control, surgically castrated, or immunized against GnRH at 10 wk of age (boostered 8 wk later). Compared to intact boars, immunocastration reduced (P < 0.05) serum concentrations of LH, FSH, testosterone and inhibin B and caused severe testicular atrophy, whereas surgical castration increased (P < 0.05) serum concentrations of LH and FSH. Both immunocastration and surgical castration consistently reduced hypothalamic GnRH synthesis, with decreased (P < 0.05) mRNA expressions of GnRH, GnRH up-stream gatekeeper genes kiss1 and its receptor (GPR54), and androgen receptor in the hypothalamic arcuate nucleus (ARC) and anteroventral periventricular nucleus (AVPV), as well as GnRH content in the median eminence. Inconsistently, mRNA expressions of gonadotropin-inhibitory hormone (GnIH) in ARC and AVPV as well as its receptor (GPR147) in pituitary were selectively reduced (P < 0.05), but mRNA expressions of estrogen receptor alpha and aromatase (CPY17A1) in pituitary were selectively increased (P < 0.05) in surgical castrates. In response to selectively attenuated suppressive signaling from GnIH and testosterone, mRNA expressions of GnRH receptor (GnRHR), LH-β and FSH-β in pituitary were increased (P < 0.05) in surgical castrates, whereas these pituitary gene expressions were decreased (P < 0.05) in immunocastrates, due to loss of hypothalamic GnRH signaling. We concluded that immunocastration and surgical castration consistently reduced hypothalamic GnRH synthesis due to a testosterone deficiency disrupting testosterone-Kisspeptin-GPR54-GnRH signaling pathways. Furthermore, selectively attenuated GnIH and testosterone signaling in the pituitary increased gonadotropin production in surgical castrates.

Delayed onset of puberty in male offspring from bisphenol A-treated dams is followed by the modulation of gene expression in the hypothalamic–pituitary–testis axis in adulthood

Bisphenol A (BPA) is a synthetic endocrine-disrupting chemical of high prevalence in the environment, which may affect the function of the hypothalamic–pituitary–testis (HPT) axis in adult rats. The aim of the present study was to evaluate whether exposure to BPA during hypothalamic sexual differentiation at doses below the reproductive no observable adverse effect level of the World Health Organization causes changes in the regulation of the HPT axis. For this, 0.5 or 5 mg kg−1 BPA was injected subcutaneously to the mothers from gestational day 18 to postnatal day (PND) 5. In adulthood (PND90), the mRNA expression of genes related to HPT axis was evaluated in hypothalamus, pituitary and testis. Hypothalamic expression of gonadotrophin-releasing hormone (Gnrh) and estrogen receptor 2 (Esr2) mRNA was increased in both BPA-treated groups compared to control group. In the pituitary, follicle stimulating hormone beta subunit (Fshb) and androgen receptor (Ar) mRNA expression was increased compared to control group in rats treated with 0.5 mg kg−1 of BPA, whereas estrogen receptor 1 (Esr1) mRNA expression was only increased in the group treated with 5 mg kg−1 of BPA, compared to control group. In the testis, there was increased expression of FSH receptor (Fshr) and inhibin beta B subunit (Inhbb) transcripts only in rats treated with 0.5 mg kg−1 of BPA. Serum testosterone and LH concentrations were increased in the group treated with 5 mg kg−1 of BPA. The results of the present study demonstrate for the first time that perinatal exposure to low doses of BPA during the critical period of hypothalamic sexual differentiation modifies the activity of the HPT axis in the offspring, with consequences for later life in adult rats.

Echinacoside and Cistanche tubulosa (Schenk) R. wight ameliorate bisphenol A-induced testicular and sperm damage in rats through gonad axis regulated steroidogenic enzymes

ETHNOPHARMACOLOGICAL RELEVANCE

Male infertility has been increasing over the last decades and being a pressing health problem nowadays. Cistanche tubulosa (CT) is a traditional Chinese medicine used to boost male sexual function. Echinacoside (ECH) is one of the major compounds exist in CT and might be a potential agent to protect testis and sperm injury.

AIM OF THE STUDY

To investigate the mechanisms behind the possible protective effects of CT and ECH against testicular and sperm toxicity.

MATERIALS AND METHODS

CT was identified by 5.8s gene sequencing. The major compositions (echinacoside and acteoside) of CT were quantified by HPLC method. The adult male Sprague-Dawley rats were exposed to BPA, CT or ECH for 42 consecutive days. The sperm parameters were observed by dark-field microscope; serum hormone levels (FSH, LH and testosterone) were tested by radio immunosorbent; LDH-x activity were evaluated using commercial kits; the expressions of the key steroidogenic enzymes were evaluated by qRT-PCR, heat map, immunofluorescence and western blot.

RESULTS

The CT and ECH treatments against BPA-induced testicular and sperm toxicity showed that CT and ECH have reversed BPA-induced abnormality in sperm characteristics, testicular structure and normalized serum testosterone. This was concomitant with the increased expression of LDH-x as well as the key steroidogenic enzymes including StAR, CYP11A1, 3β-HSD, 17β-HSD and CYP17A1, suggesting that CT and ECH enhanced testosterone biosynthesis.

CONCLUSIONS

CT and ECH attenuated poor sperm quality and testicular toxicity in rats through up-regulation steroidogenesis enzymes and ECH is the active compound of CT as a potential natural reproductive agent.

Sex-Specific Metabolic Outcomes in Offspring of Female Rats Born Small or Exposed to Stress During Pregnancy

Low birth weight increases adult metabolic disease risk in both the first (F1) and second (F2) generation. Physiological stress during pregnancy in F1 females that were born small induces F2 fetal growth restriction, but the long-term metabolic health of these F2 offspring is unknown. Uteroplacental insufficiency (restricted) or sham (control) surgery was performed in F0 rats. F1 females (control, restricted) were allocated to unstressed or stressed pregnancies. F2 offspring exposed to maternal stress in utero had reduced birth weight. At 6 months, F2 stressed males had elevated fasting glucose. In contrast, F2 restricted males had reduced pancreatic β-cell mass. Interestingly, these metabolic deficits were not present at 12 month. F2 males had increased adrenal mRNA expression of steroidogenic acute regulatory protein and IGF-1 receptor when their mothers were born small or exposed to stress during pregnancy. Stressed control F2 males had increased expression of adrenal genes that regulate androgen signaling at 6 months, whereas expression increased in restricted male and female offspring at 12 months. F2 females from stressed mothers had lower area under the glucose curve during glucose tolerance testing at 12 months compared with unstressed females but were otherwise unaffected. If F1 mothers were either born small or exposed to stress during her pregnancy, F2 offspring had impaired physiological outcomes in a sex- and age-specific manner. Importantly, stress during pregnancy did not exacerbate disease risk in F2 offspring of mothers born small, suggesting that they independently program disease in offspring through different mechanisms.

Excess Testosterone Exposure Alters Hypothalamic-Pituitary-Testicular Axis Dynamics and Gene Expression in Sheep Fetuses

Prenatal exposure to excess androgen may result in impaired adult fertility in a variety of mammalian species. However, little is known about what feedback mechanisms regulate gonadotropin secretion during early gestation and how they respond to excess T exposure. The objective of this study was to determine the effect of exogenous exposure to T on key genes that regulate gonadotropin and GnRH secretion in fetal male lambs as compared with female cohorts. We found that biweekly maternal testosterone propionate (100 mg) treatment administered from day 30 to day 58 of gestation acutely decreased (P < .05) serum LH concentrations and reduced the expression of gonadotropin subunit mRNA in both sexes and the levels of GnRH receptor mRNA in males. These results are consistent with enhanced negative feedback at the level of the pituitary and were accompanied by reduced mRNA levels for testicular steroidogenic enzymes, suggesting that Leydig cell function was also suppressed. The expression of kisspeptin 1 mRNA, a key regulator of GnRH neurons, was significantly greater (P < .01) in control females than in males and reduced (P < .001) in females by T exposure, indicating that hypothalamic regulation of gonadotropin secretion was also affected by androgen exposure. Although endocrine homeostasis was reestablished 2 weeks after maternal testosterone propionate treatment ceased, additional differences in the gene expression of GnRH, estrogen receptor-β, and kisspeptin receptor (G protein coupled receptor 54) emerged between the treatment cohorts. These changes suggest the normal trajectory of hypothalamic-pituitary axis development was disrupted, which may, in turn, contribute to negative effects on fertility later in life.

The expression of several reproductive hormone receptors can be modified by perfluorooctane sulfonate (PFOS) in adult male rats

This study was undertaken to evaluate the possible role of several reproductive hormone receptors on the disruption of the hypothalamic-pituitary-testis (HPT) axis activity induced by perfluorooctane sulfonate (PFOS). The studied receptors are the gonadotropin-releasing hormone receptor (GnRHr), luteinizing hormone receptor (LHr), follicle-stimulating hormone receptor (FSHr), and the androgen receptor (Ar). Adult male rats were orally treated with 1.0; 3.0 and 6.0 mg of PFOS kg(-1) d(-1) for 28 days. In general terms, PFOS can modify the relative gene and protein expressions of these receptors in several tissues of the reproductive axis. At the testicular level, apart from the expected inhibition of both gene and protein expressions of FSHr and Ar, PFOS also stimulates the GnRHr protein and the LHr gene expression. The receptors of the main hormones involved in the HPT axis may have an important role in the disruption exerted by PFOS on this axis.

Pituitary Aromatase P450 May Be Involved in Maintenance of the Population of Luteinizing Hormone-Positive Pituitary Cells in Mice

As aromatase P450 is located in several pituitary cells, testosterone can be transformed into 17β-estradiol in the gland by the enzyme. The possible role of this transformation in pituitary function remains to be elucidated, but some evidence suggests a physiological and pathophysiological role for pituitary aromatase. To determine its relevance in the modulation of pituitary function, mainly associated with reproduction, luteinizing hormone (LH)-positive cells in the hypophysis of female and male aromatase knockout (ArKO) mice were studied. In all LH-positive cells, significant increases in the cellular (p < 0.01) and nuclear (p < 0.05) areas were found in the ArKO mice compared to the wild-type mice. In the ArKO mice, LH-positive cells were more abundant (p < 0.01); they were characterized by a stronger cytoplasmic reaction and the cells were more polygonal and exhibited more short, thick cytoplasmic prolongations than those in the wild-type mice. Moreover, LH-positive cells showed a greater proliferation rate in the ArKO mice compared to the wild-type mice (p < 0.01). These findings suggest that the local production of estradiol mediated by pituitary aromatase is necessary for the regulation of LH-positive gonadotropic cells, exerting an autoparacrine inhibitory regulation. These results could underlie the higher pituitary aromatase expression observed in male versus female mice. Similar effects were found in ArKO male and female mice, suggesting that in both sexes the effects of estrogens on maintenance of the LH-positive pituitary cell population could be related to the local aromatization of testosterone to estradiol inside the hypophysis. Therefore, aromatase could modulate pituitary LH-positive cells in males through local estradiol synthesis.

Opposite effects of dihydrotestosterone and estradiol on apoptosis in the anterior pituitary gland from male rats

Hormones locally synthesized in the anterior pituitary gland are involved in regulation of pituitary cell renewal. In the pituitary, testosterone (T) may exert its actions per se or by conversion to dihydrotestosterone (DHT) or 17β-estradiol (E2) by 5α-reductase and aromatase activity, which are expressed in this gland. Previous reports from our laboratory showed that estrogens modulate apoptosis of lactotropes and somatotropes from female rats. Now, we examined the in vitro and in vivo effects of gonadal steroids on apoptosis of anterior pituitary cells from adult male rats. T in vitro did not modify apoptosis in anterior pituitary cells from gonadectomized (GNX) male rats. DHT, a non-aromatizable androgen, exerted direct antiapoptotic action on total anterior pituitary cells and folliculo-stellate cells, but not on lactotropes, somatotropes, or gonadotropes. On the contrary, E2 exerted a rapid apoptotic effect on total cells as well as on lactotropes and somatotropes. Incubation of anterior pituitary cells with T in presence of Finasteride, an inhibitor of 5α-reductase, increased the percentage of TUNEL-positive cells. In vivo administration of DHT to GNX rats reduced apoptosis in the anterior pituitary whereas E2 exerted proapoptotic action and reduced cells in G2/M-phase of the cell cycle. In summary, our results indicate that DHT and E2 have opposite effects on apoptosis in the anterior pituitary gland suggesting that local metabolization of T to these steroids could be involved in pituitary cell turnover in males. Changes in expression and/or activity of 5α-reductase and aromatase may play a role in the development of anterior pituitary tumors.