19-Nortestosterone influences neural stem cell proliferation and neurogenesis in the rat brain

Developmental organophosphate flame retardant exposure disrupts adult hippocampal neurogenesis in Wistar rats

Organophosphate flame retardant (OPFR) contamination is ubiquitous and bio-monitoring studies have shown that human exposure is widespread and may be unavoidable. OPFRs bear structural similarities to known neurotoxicants such as organophosphate insecticides and have been shown to have both endocrine disrupting and developmental neurotoxic effects. The perinatal period in rodents represents a critical period in the organization of the developing nervous system and insults during this time can impart profound changes on the trajectory of neural development and function, lasting into adulthood. Adult hippocampal neurogenesis (AHN) facilitates dentate gyrus function and broader hippocampal circuit activity in adults; however, the neurogenic potential of this process in adulthood is vulnerable to disruption by exogenous factors during early life. We sought to assess the impact of OPFRs on AHN in offspring of dams exposed during gestation and lactation. Results indicate that developmental OPFR exposure has significant, sex specific impacts on multiple markers of AHN in the dentate gyrus of rats. In males, OPFR exposure significantly reduced the number of neural progenitors the number of new/immature neurons and reduced dentate gyrus volume. In females, exposure increased the number of neural progenitors, decreased the number of new/immature neurons, but had no significant effect on dentate gyrus volume. These results further elucidate the developmental neurotoxic properties of OPFRs, emphasize the long-term impact of early life OPFR exposure on neural processes, and highlight the importance of including sex as a biological variable in neurotoxicology research.

The Effects of Extrinsic and Intrinsic Factors on Neurogenesis

In the mammalian brain, neurogenesis is maintained throughout adulthood primarily in two typical niches, the subgranular zone (SGZ) of the dentate gyrus and the subventricular zone (SVZ) of the lateral ventricles and in other nonclassic neurogenic areas (e.g., the amygdala and striatum). During prenatal and early postnatal development, neural stem cells (NSCs) differentiate into neurons and migrate to appropriate areas such as the olfactory bulb where they integrate into existing neural networks; these phenomena constitute the multistep process of neurogenesis. Alterations in any of these processes impair neurogenesis and may even lead to brain dysfunction, including cognitive impairment and neurodegeneration. Here, we first summarize the main properties of mammalian neurogenic niches to describe the cellular and molecular mechanisms of neurogenesis. Accumulating evidence indicates that neurogenesis plays an integral role in neuronal plasticity in the brain and cognition in the postnatal period. Given that neurogenesis can be highly modulated by a number of extrinsic and intrinsic factors, we discuss the impact of extrinsic (e.g., alcohol) and intrinsic (e.g., hormones) modulators on neurogenesis. Additionally, we provide an overview of the contribution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection to persistent neurological sequelae such as neurodegeneration, neurogenic defects and accelerated neuronal cell death. Together, our review provides a link between extrinsic/intrinsic factors and neurogenesis and explains the possible mechanisms of abnormal neurogenesis underlying neurological disorders.

Androgen Effects on Neural Plasticity

Androgens are synthesized in the brain, gonads, and adrenal glands, in both sexes, exerting physiologically important effects on the structure and function of the central nervous system. These effects may contribute to the incidence and progression of neurological disorders such as autism spectrum disorder, schizophrenia, and Alzheimer's disease, which occur at different rates in males and females. This review briefly summarizes the current state of knowledge with respect to the neuroplastic effects of androgens, with particular emphasis on the hippocampus, which has been the focus of much of the research in this field.

Steroid hormones and hippocampal neurogenesis in the adult mammalian brain

Hippocampal neurogenesis persists across the lifespan in many species, including rodents and humans, and is associated with cognitive performance and the pathogenesis of neurodegenerative disease and psychiatric disorders. Neurogenesis is modulated by steroid hormones that change across development and differ between the sexes in rodents and humans. Here, we discuss the effects of stress and glucocorticoid exposure from gestation to adulthood as well as the effects of androgens and estrogens in adulthood on neurogenesis in the hippocampus. Throughout the review we highlight sex differences in the effects of steroid hormones on neurogenesis and how they may relate to hippocampal function and disease. These data highlight the importance of examining age and sex when evaluating the effects of steroid hormones on hippocampal neurogenesis.

Androgens and Adult Neurogenesis in the Hippocampus

Adult neurogenesis in the hippocampus is modulated by steroid hormones, including androgens, in male rodents. In this review, we summarize research showing that chronic exposure to androgens, such as testosterone and dihydrotestosterone, enhances the survival of new neurons in the dentate gyrus of male, but not female, rodents, via the androgen receptor. However, the neurogenesis promoting the effect of androgens in the dentate gyrus may be limited to younger adulthood as it is not evident in middle-aged male rodents. Although direct exposure to androgens in adult or middle age does not significantly influence neurogenesis in female rodents, the aromatase inhibitor letrozole enhances neurogenesis in the hippocampus of middle-aged female mice. Unlike other androgens, androgenic anabolic steroids reduce neurogenesis in the hippocampus of male rodents. Collectively, the research indicates that the ability of androgens to enhance hippocampal neurogenesis in adult rodents is dependent on dose, androgen type, sex, duration, and age. We discuss these findings and how androgens may be influencing neuroprotection, via neurogenesis in the hippocampus, in the context of health and disease.

Anabolic Steroids-Driven Regulation of Porcine Ovarian Putative Stem Cells Favors the Onset of Their Neoplastic Transformation

Nandrolone (Ndn) and boldenone (Bdn), the synthetic testosterone analogues with strong anabolic effects, despite being recognized as potentially carcinogenic compounds, are commonly abused by athletes and bodybuilders, which includes women, worldwide. This study tested the hypothesis that different doses of Ndn and Bdn can initiate neoplastic transformation of porcine ovarian putative stem cells (poPSCs). Immunomagnetically isolated poPSCs were expanded ex vivo in the presence of Ndn or Bdn, for 7 and 14 days. Results show that pharmacological doses of both Ndn and Bdn, already after 7 days of poPSCs culture, caused a significant increase of selected, stemness-related markers of cancer cells: CD44 and CD133. Notably, Ndn also negatively affected poPSCs growth not only by suppressing their proliferation and mitochondrial respiration but also by inducing apoptosis. This observation shows, for the first time, that chronic exposure to Ndn or Bdn represents a precondition that might enhance risk of poPSCs neoplastic transformation. These studies carried out to accomplish detailed molecular characterization of the ex vivo expanded poPSCs and their potentially cancerous derivatives (PCDs) might be helpful to determine their suitability as nuclear donor cells (NDCs) for further investigations focused on cloning by somatic cell nuclear transfer (SCNT). Such investigations might also be indispensable to estimate the capabilities of nuclear genomes inherited from poPSCs and their PCDs to be epigenetically reprogrammed (dedifferentiated) in cloned pig embryos generated by SCNT. This might open up new possibilities for biomedical research aimed at more comprehensively recognizing genetic and epigenetic mechanisms underlying not only tumorigenesis but also reversal/retardation of pro-tumorigenic intracellular events.

Association between nandrolone and behavioral alterations: A systematic review of preclinical studies

BACKGROUND AND AIM

In recent years the expanding misuse of Nandrolone among non-athletes, particularly adolescent males is a prevalent global concern due to its adverse effects. This article provides a summary of the experimental studies to clarify the relationship between Nandrolone exposure and behavioral and cognitive performances.

MATERIALS AND METHODS

The present systematic review was conducted using PubMed, Embase and ScienceDirect databases, from 2000 to 2020, using the following key terms: Nandrolone AND Cognition, Nandrolone AND Learning, Nandrolone AND Memory, Nandrolone AND (Synaptic plasticity or Hippocampal synaptic plasticity), Nandrolone AND (Aggression or Aggressive-like behavior), Nandrolone AND (Anxiety or Anxiety-like behavior), Nandrolone AND (Depression or Depressive-like behavior).

RESULTS

33 qualified papers were selected from the 2498 sources found. Of the 33 cases, 32 (96.97%) were males while only 1 (3.03%) was female and male. From 33 selected articles 8 reported studies were related to spatial memory, 2 reported studies were related to avoidance memory, 11 studies reported information on synaptic plasticity, 11 reported studies were related to aggressive behavior, 8 reported studies were related to aggressive behavior and 6 reported studies were related to depression.

CONCLUSION

Nandrolone can change spatial ability, avoidance memory and hippocampal synaptic plasticity. Also, Nandrolone exposure produces variable effects on behavioral function such as aggression, depression and anxiety. This despite the fact that the results are contradictory. These discrepancies might be due to the differences in sex, age, dosage and treatment duration, and administration route. However, the negative results are more common than the published positive ones.

Hormonal Regulation of Oligodendrogenesis I: Effects across the Lifespan

The brain’s capacity to respond to changing environments via hormonal signaling is critical to fine-tuned function. An emerging body of literature highlights a role for myelin plasticity as a prominent type of experience-dependent plasticity in the adult brain. Myelin plasticity is driven by oligodendrocytes (OLs) and their precursor cells (OPCs). OPC differentiation regulates the trajectory of myelin production throughout development, and importantly, OPCs maintain the ability to proliferate and generate new OLs throughout adulthood. The process of oligodendrogenesis, the creation of new OLs, can be dramatically influenced during early development and in adulthood by internal and environmental conditions such as hormones. Here, we review the current literature describing hormonal regulation of oligodendrogenesis within physiological conditions, focusing on several classes of hormones: steroid, peptide, and thyroid hormones. We discuss hormonal regulation at each stage of oligodendrogenesis and describe mechanisms of action, where known. Overall, the majority of hormones enhance oligodendrogenesis, increasing OPC differentiation and inducing maturation and myelin production in OLs. The mechanisms underlying these processes vary for each hormone but may ultimately converge upon common signaling pathways, mediated by specific receptors expressed across the OL lineage. However, not all of the mechanisms have been fully elucidated, and here, we note the remaining gaps in the literature, including the complex interactions between hormonal systems and with the immune system. In the companion manuscript in this issue, we discuss the implications of hormonal regulation of oligodendrogenesis for neurological and psychiatric disorders characterized by white matter loss. Ultimately, a better understanding of the fundamental mechanisms of hormonal regulation of oligodendrogenesis across the entire lifespan, especially in vivo, will progress both basic and translational research.

Sex-dependent effect of APOE on Alzheimer's disease and other age-related neurodegenerative disorders

The importance of apolipoprotein E (APOE) in late-onset Alzheimer's disease (LOAD) has been firmly established, but the mechanisms through which it exerts its pathogenic effects remain elusive. In addition, the sex-dependent effects of APOE on LOAD risk and endophenotypes have yet to be explained. In this Review, we revisit the different aspects of APOE involvement in neurodegeneration and neurological diseases, with particular attention to sex differences in the contribution of APOE to LOAD susceptibility. We discuss the role of APOE in a broader range of age-related neurodegenerative diseases, and summarize the biological factors linking APOE to sex hormones, drawing on supportive findings from rodent models to identify major mechanistic themes underlying the exacerbation of LOAD-associated neurodegeneration and pathology in the female brain. Additionally, we list sex-by-genotype interactions identified across neurodegenerative diseases, proposing APOE variants as a shared etiology for sex differences in the manifestation of these diseases. Finally, we present recent advancements in 'omics' technologies, which provide a new platform for more in-depth investigations of how dysregulation of this gene affects the development and progression of neurodegenerative diseases. Collectively, the evidence summarized in this Review highlights the interplay between APOE and sex as a key factor in the etiology of LOAD and other age-related neurodegenerative diseases. We emphasize the importance of careful examination of sex as a contributing factor in studying the underpinning genetics of neurodegenerative diseases in general, but particularly for LOAD.

Exposure to prenatal PCBs shifts the timing of neurogenesis in the hypothalamus of developing rats

The developing brain is highly sensitive to the hormonal milieu, with gonadal steroid hormones involved in neurogenesis, neural survival, and brain organization. Limited available evidence suggests that endocrine-disrupting chemicals (EDCs) may perturb these developmental processes. In this study, we tested the hypothesis that prenatal exposure to a mixture of polychlorinated biphenyls (PCBs), Aroclor 1221, would disrupt the normal timing of neurogenesis in two hypothalamic regions: the ventromedial nucleus (VMN) and the preoptic area (POA). These regions were selected because of their important roles in the control of sociosexual behaviors that are perturbed in adulthood by prenatal EDC exposure. Pregnant Sprague-Dawley rats were exposed to PCBs from Embryonic Day 8 (E8) to E18, encompassing the period of neurogenesis of all hypothalamic neurons. To determine the birth dates of neurons, bromo-2-deoxy-5-uridine (BrdU) was administered to dams on E12, E14, or E16. On the day after birth, male and female pups were perfused, brains immunolabeled for BrdU, and numbers of cells counted. In the VMN, exposure to PCBs significantly advanced the timing of neurogenesis compared to vehicle-treated pups, without changing the total number of BrdU+ cells. In the POA, PCBs did not change the timing of neurogenesis nor the total number of cells born. This is the first study to show that PCBs can shift the timing of neurogenesis in the hypothalamus, specifically in the VMN but not the POA. This result has implications for functions controlled by the VMN, especially sociosexual behaviors, as well as for sexual selection more generally.

The Role of Sex and Sex Hormones in Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are a wide class of disorders of the central nervous system (CNS) with unknown etiology. Several factors were hypothesized to be involved in the pathogenesis of these diseases, including genetic and environmental factors. Many of these diseases show a sex prevalence and sex steroids were shown to have a role in the progression of specific forms of neurodegeneration. Estrogens were reported to be neuroprotective through their action on cognate nuclear and membrane receptors, while adverse effects of male hormones have been described on neuronal cells, although some data also suggest neuroprotective activities. The response of the CNS to sex steroids is a complex and integrated process that depends on (i) the type and amount of the cognate steroid receptor and (ii) the target cell type-either neurons, glia, or microglia. Moreover, the levels of sex steroids in the CNS fluctuate due to gonadal activities and to local metabolism and synthesis. Importantly, biochemical processes involved in the pathogenesis of NDs are increasingly being recognized as different between the two sexes and as influenced by sex steroids. The aim of this review is to present current state-of-the-art understanding on the potential role of sex steroids and their receptors on the onset and progression of major neurodegenerative disorders, namely, Alzheimer's disease, Parkinson's diseases, amyotrophic lateral sclerosis, and the peculiar motoneuron disease spinal and bulbar muscular atrophy, in which hormonal therapy is potentially useful as disease modifier.

Assessment of water contamination and health risk of endocrine disrupting chemicals in outdoor and indoor swimming pools

The occurrence of endocrine disrupting chemicals (EDCs) in swimming pool waters has been scarcely investigated. In this study, the concentrations of 20 EDCs (4 phenols, 6 estrogens, 4 progestogens, 5 androgens, and 1 pharmaceutical) in 40 outdoor and indoor swimming pools in Changsha, China were investigated. Out of them, two phenols (bisphenol A and 4-tert-octylphenol), three estrogens (17β-estradiol, 17ɑ-ethinlestradiol (EE2), and hexestrol), one pharmaceutical (caffeine), and two progestogens (progesterone and levonorgestrel) were detected in the collected samples. The androgens were not detected. Bisphenol A and caffeine were the dominant EDCs at concentrations of ND-23.22 ng/L and ND-39.08 ng/L, respectively. The levels of caffeine were significantly higher in indoor swimming pools (11.15 ng/L in average) than those in outdoor pools (1.90 ng/L in average) (p < 0.05), owing to the less sun's UV radiation and less use of sunscreens containing caffeine. The progestogens (progesterone and levonorgestrel) and estrogens (17β-estradiol and hexestrol) were only detected in outdoor swimming pools. The detection frequencies and concentrations of bisphenol A and caffeine in downtown pools were significantly higher than those in outskirt pools. Besides, the correlations between the concentrations of EDCs and water quality parameters evaluated by the Spearman correlation analysis implied that residual chlorine had strong oxidant capable to bisphenol A and suggested that caffeine could be a potential indicator of organic contamination in swimming pool water. Finally, a quantitative risk assessment revealed that non-athletic child and athletic adult female were vulnerable subpopulations. The EDI_total of EE2 for athletic child, non-athletic female, non-athletic male, and non-athletic child were higher than ADI_EE2 adopted by Australia and the EDI_total of EE2 for athletic female and athletic male were higher than ADI_EE2 adopted by the United States.

Nandrolone induces a stem cell-like phenotype in human hepatocarcinoma-derived cell line inhibiting mitochondrial respiratory activity

Nandrolone is a testosterone analogue with anabolic properties commonly abused worldwide, recently utilized also as therapeutic agent in chronic diseases, cancer included. Here we investigated the impact of nandrolone on the metabolic phenotype in HepG2 cell line. The results attained show that pharmacological dosage of nandrolone, slowing cell growth, repressed mitochondrial respiration, inhibited the respiratory chain complexes I and III and enhanced mitochondrial reactive oxygen species (ROS) production. Intriguingly, nandrolone caused a significant increase of stemness-markers in both 2D and 3D cultures, which resulted to be CxIII-ROS dependent. Notably, nandrolone negatively affected differentiation both in healthy hematopoietic and mesenchymal stem cells. Finally, nandrolone administration in mice confirmed the up-regulation of stemness-markers in liver, spleen and kidney. Our observations show, for the first time, that chronic administration of nandrolone, favoring maintenance of stem cells in different tissues would represent a precondition that, in addition to multiple hits, might enhance risk of carcinogenesis raising warnings about its abuse and therapeutic utilization.

Testosterone and Adult Neurogenesis

It is now well established that neurogenesis occurs throughout adulthood in select brain regions, but the functional significance of adult neurogenesis remains unclear. There is considerable evidence that steroid hormones modulate various stages of adult neurogenesis, and this review provides a focused summary of the effects of testosterone on adult neurogenesis. Initial evidence came from field studies with birds and wild rodent populations. Subsequent experiments with laboratory rodents have tested the effects of testosterone and its steroid metabolites upon adult neurogenesis, as well as the functional consequences of induced changes in neurogenesis. These experiments have provided clear evidence that testosterone increases adult neurogenesis within the dentate gyrus region of the hippocampus through an androgen-dependent pathway. Most evidence indicates that androgens selectively enhance the survival of newly generated neurons, while having little effect on cell proliferation. Whether this is a result of androgens acting directly on receptors of new neurons remains unclear, and indirect routes involving brain-derived neurotrophic factor (BDNF) and glucocorticoids may be involved. In vitro experiments suggest that testosterone has broad-ranging neuroprotective effects, which will be briefly reviewed. A better understanding of the effects of testosterone upon adult neurogenesis could shed light on neurological diseases that show sex differences.

Neurobiological mechanisms underlying sex-related differences in stress-related disorders: Effects of neuroactive steroids on the hippocampus

Men and women differ in their vulnerability to a variety of stress-related illnesses, but the underlying neurobiological mechanisms are not well understood. This is likely due to a comparative dearth of neurobiological studies that assess male and female rodents at the same time, while human neuroimaging studies often don't model sex as a variable of interest. These sex differences are often attributed to the actions of sex hormones, i.e. estrogens, progestogens and androgens. In this review, we summarize the results on sex hormone actions in the hippocampus and seek to bridge the gap between animal models and findings in humans. However, while effects of sex hormones on the hippocampus are largely consistent in animals and humans, methodological differences challenge the comparability of animal and human studies on stress effects. We summarise our current understanding of the neurobiological mechanisms that underlie sex-related differences in behavior and discuss implications for stress-related illnesses.

Androgens Enhance Adult Hippocampal Neurogenesis in Males but Not Females in an Age-Dependent Manner

Androgens (testosterone and DHT) increase adult hippocampal neurogenesis by increasing survival of new neurons in male rats and mice via an androgen receptor pathway, but it is not known whether androgens regulate neurogenesis in female rats and whether the effect is age-dependent. We investigated the effects of DHT, a potent androgen, on neurogenesis in young adult and middle-aged male and female rats. Rats were gonadectomized and injected with the DNA synthesis marker bromodeoxyuridine (BrdU). The following day, rats began receiving daily injections of oil or DHT for 30 days. We evaluated cell proliferation (Ki67) and survival of new neurons (BrdU and BrdU/NeuN) in the hippocampus of male and female rats by using immunohistochemistry. As expected, DHT increased the number of BrdU+ cells in young males but surprisingly not in middle-aged males or in young and middle-aged females. In middle age, DHT increased the proportion of BrdU/NeuN cells, an effect driven by females. Androgen receptor expression also increased with aging in both female and male rats, which may contribute to a lack of DHT neurogenic effect in middle age. Our results indicate that DHT regulates adult hippocampal neurogenesis in a sex- and age-dependent manner.

Cortisol, Testosterone, and Prospective Risk for War-zone Stress-Evoked Depression

Introduction

The major challenges of efforts to reveal biological risk factors and biomarkers of depression include the complexity of underlying systems, interactions with other systems, and contextual factors governing their expression. Altered endocrine function is believed to be a central contributor to depressive illness, but across studies, evidence for a link between endocrine markers and depression has been mixed, inconclusive, or conditional in nature. In the present study, we evaluated basal testosterone (T), cortisol (C), and CO2 inhalation-stress-reactivity measures of these hormones (TR, CR) as pre-deployment moderators of the later impact of war-zone stressors on depression symptoms in-theater.

Materials and Methods

At pre-deployment, U.S. soldiers (N = 120) completed demographic, clinical and hormone measures, and during deployment, they completed monthly, web-based assessments of war-zone stressors and depression symptoms (N = 533 observations). Mixed effects models estimated the effects of the pre-deployment hormone profiles in moderating war-zone stressors' impact on in-theater depression. Models also tested whether hormonally linked risk for later stress-evoked depression depends on pre-existing depression.

Results

Controlling for pre-deployment depression, high T was protective; whereas TR had depressogenic effects that were amplified by pre-deployment depression. Further, high C was protective, but heightened CR was depressogenic, but only among those with elevated pre-deployment depression.

Conclusions

Findings highlight the importance of examining basal and reactivity measures of endocrine function, and use of prospective, longitudinal models to test hypothesized causal pathways associated with depression vulnerability in the war-zone. Results also suggest that pre-existing depression and cortisol may work in tandem to increase vulnerability for later stress-evoked depression in the war-zone.

Sex steroid hormone modulation of neural stem cells: a critical review

While numerous in vivo experiments have sought to explore the effects of sex chromosome composition and sex steroid hormones on cellular proliferation and differentiation within the mammalian brain, far fewer studies as reviewed here, have explored these factors using a direct in vitro approach. Generally speaking, in vivo studies provide the gold standard to demonstrate applicable findings in regards to the role hormones play in development. However, in the case of neural stem cell (NSC) biology, there remain many unknown factors that likely contribute to observations made within the developed brain, specifically in regions where there are abundant sex steroid hormone receptors. For these reasons, using a NSC in vitro model may provide a more controlled and refined system to explore the direct effects of sex and hormone response, limiting the vast array of other influences on NSCs occurring during development and within adult cellular niches. These specific cellular models may have the ability to greatly improve the mechanistic understanding of changes occurring within the developing brain during the hormonal organization process, in addition to other modifications that may contribute to neuro-psychiatric sex-biased diseases.

Exercise Attenuates Anabolic Steroids-Induced Anxiety via Hippocampal NPY and MC4 Receptor in Rats

The aim of our study was to evaluate the effects of chronic administration of nandrolone-decanoate (ND) or testosterone-enanthate (TE) in supraphysiological doses and a prolonged swimming protocol, alone and in combination with ND or TE, on anxiety-like behavior in rats. We investigated the immunohistochemical alterations of the hippocampal neuropeptide Y (NPY) and melanocortin 4 receptor (MC4R) neurons, as a possible underlying mechanism in a modulation of anxiety-like behavior in rats. Both applied anabolic androgenic steroids (AASs) induced anxiogenic effect accompanied with decreased serum and hippocampal NPY. The exercise-induced anxiolytic effect was associated with increased hippocampal NPY expression. ND and TE increased the number of MC4R, while the swimming protocol was followed by the reduction of MC4R in the CA1 region of the hippocampus. However, NPY/MC4R ratio in hippocampus was lowered by AASs and elevated by exercise in all hippocampal regions. An augmentation of this ratio strongly and positively correlated to increased time in open arms of elevated plus maze, in the context that indicates anxiolytic effect. Our findings support the conclusion that alterations in both hippocampal NPY and MC4R expression are involved in anxiety level changes in rats, while their quantitative relationship (NPY/MC4R ratio) is even more valuable in the estimation of anxiety regulation than individual alterations for both NPY and MC4R expression in the hippocampus.

Nandrolone administration abolishes hippocampal fEPSP-PS potentiation and passive avoidance learning of adolescent male rats

Despite the chronic effects of nandrolone decanoate (ND), the acute effects of ND on passive avoidance learning (PAL) and memory and its mechanism have not been investigated. This research examines the acute effect of ND on PAL, CA1 synaptic plasticity, testosterone and corticosterone serum levels, and the role of androgenic receptors (ARs). Adolescent male rats were treated with ND, 30 min before training and retention and after training test. AR antagonist was applied 15 min before ND. Hippocampal slices were perfused by ND. ND administration had an inverted U-shape effect on acquisition of PAL and on testosterone and corticosterone serum levels. The consolidation was only affected by high dose of ND. ND significantly decreased the retention of PAL across all doses. The magnitude of field excitatory postsynaptic potential long term potentiation was lower than that of control slices. In addition, an attenuation of field excitatory postsynaptic potential population spike coupling was also observed. Nilutamide could nullify the ND impairment effect. We concluded although a single dose of ND could affect all stages of PAL, its effects were more potent on retrieval, possibly arising from the acute effect of ND on the alterations of CA1 synaptic plasticity. In addition, ND may induce its effects directly through ARs and indirectly through plasma testosterone and corticosterone.

Expression profile of the STAND protein Nwd1 in the developing and mature mouse central nervous system

The orchestrated events required during brain development, as well as the maintenance of adult neuronal plasticity, highly depend on the accurate responses of neuronal cells to various cellular stress or environmental stimuli. Recent studies have defined a previously unrecognized, broad class of multidomain proteins, designated as signal transduction ATPases with numerous domains (STAND), which comprises a large number of proteins, including the apoptotic peptidase activating factor 1 (Apaf1) and nucleotide-binding oligomerization domain-like receptors (NLRs), central players in cell death and innate immune responses, respectively. Although the involvement of STANDs in the central nervous system (CNS) has been postulated in terms of neuronal development and function, it remains largely unclear. Here, we identified Nwd1 (NACHT and WD repeat domain-containing protein 1), as a novel STAND protein, expressed in neural stem/progenitor cells (NSPCs). Structurally, Nwd1 was most analogous to the apoptosis regulator Apaf1, also involved in mitosis and axonal outgrowth regulation in the CNS. Using a specific antibody, we show that, during the embryonic and postnatal period, Nwd1 is expressed in nestin-positive NSPCs in vivo and in vitro, while postnatally it is found in terminally differentiated neurons and blood vessels. At the subcellular level, we demonstrate that Nwd1 is preferentially located in the cytosolic compartment of cultured NSPCs, partially overlapping with cytochrome c. These observations imply that Nwd1 might be involved in the neuronal lineage as a new STAND gene, including having a pro-apoptotic or nonapoptotic role, similar to Apaf1.

Neural androgen receptors affect the number of surviving new neurones in the adult dentate gyrus of male mice

Adult hippocampal neurogenesis occurs in many mammalian species. In rats, the survival of new neurones within the hippocampus is modulated by the action of androgen via the androgen receptor (AR); however, it is not known whether this holds true in mice. Furthermore, the evidence is mixed regarding whether androgens act in neural tissue or via peripheral non-neural targets to promote new neurone survival in the hippocampus. We evaluated whether the action of androgen via AR underlies the survival of new neurones in mice, and investigated whether increasing AR selectively in neural tissue would increase new neurone survival in the hippocampus. We used the cre-loxP system to overexpress AR only in neural tissues (Nestin-AR). These males were compared with wild-type males, as well as control males with 1 of the 2 mutations required for overexpression. Mice were gonadectomised and injected with the DNA synthesis marker, bromodeoxyuridine (BrdU) and for 37 days (following BrdU injection), mice were treated with oil or dihydrotestosterone (DHT). Using immunohistochemistry, proliferation (Ki67) and survival (BrdU) of new neurones were both evaluated in the dorsal and ventral dentate gyrus. Dihydrotestosterone treatment increased the survival of new neurones in the entire hippocampus in wild-type mice and control mice that only have 1 of 2 necessary mutations for transgenic expression. However, DHT treatment did not increase the survival of new neurones in mice that overexpressed AR in neural tissue. Cell proliferation (Ki67) and cell death (pyknotic cells) were not affected by DHT treatment in wild-type or transgenic males. These results suggest that androgens act via neural AR to affect hippocampal neurogenesis by promoting cell survival; however, the relationship between androgen dose and new neurone survival is nonlinear.

Steroid Transport, Local Synthesis, and Signaling within the Brain: Roles in Neurogenesis, Neuroprotection, and Sexual Behaviors

Sex steroid hormones are synthesized from cholesterol and exert pleiotropic effects notably in the central nervous system. Pioneering studies from Baulieu and colleagues have suggested that steroids are also locally-synthesized in the brain. Such steroids, called neurosteroids, can rapidly modulate neuronal excitability and functions, brain plasticity, and behavior. Accumulating data obtained on a wide variety of species demonstrate that neurosteroidogenesis is an evolutionary conserved feature across fish, birds, and mammals. In this review, we will first document neurosteroidogenesis and steroid signaling for estrogens, progestagens, and androgens in the brain of teleost fish, birds, and mammals. We will next consider the effects of sex steroids in homeostatic and regenerative neurogenesis, in neuroprotection, and in sexual behaviors. In a last part, we will discuss the transport of steroids and lipoproteins from the periphery within the brain (and vice-versa) and document their effects on the blood-brain barrier (BBB) permeability and on neuroprotection. We will emphasize the potential interaction between lipoproteins and sex steroids, addressing the beneficial effects of steroids and lipoproteins, particularly HDL-cholesterol, against the breakdown of the BBB reported to occur during brain ischemic stroke. We will consequently highlight the potential anti-inflammatory, anti-oxidant, and neuroprotective properties of sex steroid and lipoproteins, these latest improving cholesterol and steroid ester transport within the brain after insults.

Hormonal Regulation of Hippocampal Neurogenesis: Implications for Depression and Exercise

Adult hippocampal neurogenesis exists in all mammalian species, including humans, and although there has been considerable research investigating the function and regulation of neurogenesis, there remain many open questions surrounding the complexity of this phenomenon. This stems partially from the fact that neurogenesis is a multistage process that involves proliferation, differentiation, migration, survival, and eventual integration of new cells into the existing hippocampal circuitry, each of which can be independently influenced. The function of adult neurogenesis in the hippocampus is related to stress regulation, behavioral efficacy of antidepressants, long-term spatial memory, forgetting, and pattern separation. Steroid hormones influence the regulation of hippocampal neurogenesis, stress regulation, and cognition and differently in males and females. In this chapter, we will briefly tap into the complex network of steroid hormone modulation of neurogenesis in the hippocampus with specific emphasis on stress, testosterone, and estrogen. We examine the possible role of neurogenesis in the etiology of depression and influencing treatment by examining the influence of both pharmacological (selective serotonin reuptake inhibitors, tricyclic antidepressants) treatments and non-pharmacological (exercise) remedies.

The opposite effects of nandrolone decanoate and exercise on anxiety levels in rats may involve alterations in hippocampal parvalbumin-positive interneurons

The aim of this study was to evaluate the behavioral effects of chronic (six weeks) nandrolone decanoate (ND, 20 mg/kg, s.c., weekly in single dose) administration (in order to mimic heavy human abuse), and exercise (swimming protocol of 60 minutes a day, five days in a row/two days break), applied alone and simultaneously with ND, in male rats (n = 40). Also, we evaluated the effects of those protocols on hippocampal parvalbumin (PV) content and the possible connection between the alterations in certain parts of hippocampal GABAergic system and behavioral patterns. Both ND and exercise protocols induced increase in testosterone, dihydrotestosterone and estradiol blood levels. Our results confirmed anxiogenic effects of ND observed in open field (OF) test (decrease in the locomotor activity, as well as in frequency and cumulative duration in the centre zone) and in elevated plus maze (EPM) test (decrease in frequency and cumulative duration in open arms, and total exploratory activity), that were accompanied with a mild decrease in the number of PV interneurons in hippocampus. Chronic exercise protocol induced significant increase in hippocampal PV neurons (dentate gyrus and CA1 region), followed by anxiolytic-like behavioral changes, observed in both OF and EPM (increase in all estimated parameters), and in evoked beam-walking test (increase in time to cross the beam), compared to ND treated animals. The applied dose of ND was sufficient to attenuate beneficial effects of exercise in rats by means of decreased exercise-induced anxiolytic effect, as well as to reverse exercise-induced augmentation in number of PV immunoreactive neurons in hippocampus. Our results implicate the possibility that alterations in hippocampal PV interneurons (i.e. GABAergic system) may be involved in modulation of anxiety level induced by ND abuse and/or extended exercise protocols.

Changes of the brain activities after chronic restraint stress in rats: A study based on 18F-FDG PET

As a prevalent disease all over the world, changed functional activities and/or structures in many brain regions have been found in depression. In this study, 5-week chronic restraint stress (CRS) was performed to establish depression rat models, and ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) was used to detect brain functional activities. Our study found that CRS induced depressive behaviors and increased the expression of serum IL-6. After exposure to CRS, rats showed decreased glucose metabolism in the whole-brain and brain regions including left medial prefrontal and auditory cortices; right amygdala, cingulate cortex, olfactory and AcbCore/Shell; bilateral caudate putamen, dorsal hippocampi, insular and entorhinal cortices. Expression of serum IL-6 and glucose metabolism in most of the above brain regions were significantly correlated with the severity of some CRS-induced depressive behaviors. In conclusion, the increased peripheral inflammatory response and decreased brain functional activities might be the important pathogenesis of experimental depression induced by CRS, and could reflect the severity of depression to some extent.

Transcriptional role of androgen receptor in the expression of long non-coding RNA Sox2OT in neurogenesis

The complex architecture of adult brain derives from tightly regulated migration and differentiation of precursor cells generated during embryonic neurogenesis. Changes at transcriptional level of genes that regulate migration and differentiation may lead to neurodevelopmental disorders. Androgen receptor (AR) is a transcription factor that is already expressed during early embryonic days. However, AR role in the regulation of gene expression at early embryonic stage is yet to be determinate. Long non-coding RNA (lncRNA) Sox2 overlapping transcript (Sox2OT) plays a crucial role in gene expression control during development but its transcriptional regulation is still to be clearly defined. Here, using Bicalutamide in order to pharmacologically inactivated AR, we investigated whether AR participates in the regulation of the transcription of the lncRNASox2OTat early embryonic stage. We identified a new DNA binding region upstream of Sox2 locus containing three androgen response elements (ARE), and found that AR binds such a sequence in embryonic neural stem cells and in mouse embryonic brain. Our data suggest that through this binding, AR can promote the RNA polymerase II dependent transcription of Sox2OT. Our findings also suggest that AR participates in embryonic neurogenesis through transcriptional control of the long non-coding RNA Sox2OT.

The role of neuropeptide-Y in nandrolone decanoate-induced attenuation of antidepressant effect of exercise

Since the increased prevalence of anabolic androgenic steroids abuse in last few decades is usually accompanied by various exercise protocols, the scope of our study was to evaluate the effects of chronic nandrolone decanoate administration in supraphysiological dose and a prolonged swimming protocol (alone and simultaneously with nandrolone decanoate) on depressive state in male rats. Simultaneously, we investigated the possible alterations in neuropeptide Y (NPY) content in blood and the hippocampus, in order to determine the role of NPY in the modulation of depressive-like behavior.Exercise induced antidepressant effects in tail suspension test (decrease of the total duration of immobility), as well as significant increase in the number of hippocampal NPY-interneurons in CA1 region. Chronic nandrolone decanoate treatment attenuated the beneficial antidepressant effects of exercise as measured by the tail suspension test parameters. Simultaneously, nandrolone decanoate treatment resulted in diminution of NPY content both in blood (decreased serum levels) and in hippocampus (the significant decrease in NPY expression in all three investigated hippocampal regions-CA1, CA2/3 and DG). Our findings indicate that alterations in serum and hippocampal NPY contents may underlie the changes in depressive state in rats. The exercise was beneficial as it exerted antidepressant effect, while chronic nandrolone decanoate treatment resulted in depressive-like behavior. Furthermore, the behavioral indicators of depression showed strong correlations with the serum levels and the hippocampal content of NPY.

Increased Testosterone Decreases Medial Cortical Volume and Neurogenesis in Territorial Side-Blotched Lizards (Uta stansburiana)

Variation in an animal's spatial environment can induce variation in the hippocampus, an area of the brain involved in spatial cognitive processing. Specifically, increased spatial area use is correlated with increased hippocampal attributes, such as volume and neurogenesis. In the side-blotched lizard (Uta stansburiana), males demonstrate alternative reproductive tactics and are either territorial—defending large, clearly defined spatial boundaries—or non-territorial—traversing home ranges that are smaller than the territorial males' territories. Our previous work demonstrated cortical volume (reptilian hippocampal homolog) correlates with these spatial niches. We found that territorial holders have larger medial cortices than non-territory holders, yet these differences in the neural architecture demonstrated some degree of plasticity as well. Although we have demonstrated a link among territoriality, spatial use, and brain plasticity, the mechanisms that underlie this relationship are unclear. Previous studies found that higher testosterone levels can induce increased use of the spatial area and can cause an upregulation in hippocampal attributes. Thus, testosterone may be the mechanistic link between spatial area use and the brain. What remains unclear, however, is if testosterone can affect the cortices independent of spatial experiences and whether testosterone differentially interacts with territorial status to produce the resultant cortical phenotype. In this study, we compared neurogenesis as measured by the total number of doublecortin-positive cells and cortical volume between territorial and non-territorial males supplemented with testosterone. We found no significant differences in the number of doublecortin-positive cells or cortical volume among control territorial, control non-territorial, and testosterone-supplemented non-territorial males, while testosterone-supplemented territorial males had smaller medial cortices containing fewer doublecortin-positive cells. These results demonstrate that testosterone can modulate medial cortical attributes outside of differential spatial processing experiences but that territorial males appear to be more sensitive to alterations in testosterone levels compared with non-territorial males.

Ameliorative Effects of Endurance Exercise with Two Different Intensities on Nandrolone Decanoate-Induced Neurodegeneration in Rats: Involving Redox and Apoptotic Systems

Despite the importance of this issue, less has been paid to the influence of exercise on the neural side effects of anabolic androgenic steroids and mechanisms. We investigated the effects of two levels of endurance exercise on neurodegeneration side effects of nandrolone. The study period was 8 weeks. Wistar rats were divided into nine groups including the control (CTL) group, mild exercise (mEx) group, and vehicle (Arach) group which received arachis oil intramuscularly, nandrolone (Nan) group which received nandrolone decanoate 5 mg/kg two times weekly, mEx+Arach group which treated with arachis oil along with mild exercise, mEx+Nan group which treated with nandrolone along with mild exercise, severe exercise (sEx) group, sEx+Arach, and sEx+Nan groups. Finally, brain samples were taken for histopathological, biochemical, and western blot analysis. Nandrolone significantly decreased the intact cells of the hippocampus, total antioxidant capacity (TAC) (P < 0.05 versus CTL and Arach groups), TAC to malondialdehyde ratio (TAC/MDA), and Bcl-2. Nandrolone increased the Bax/Bcl-2 ratio of the brain tissue (P < 0.01 versus CTL and Arach groups). Combination of mild exercise and nandrolone rescued the intact cells to some extent, and this effect was associated with the improvement of Bcl-2 level and Bax/Bcl-2 ratio of brain tissue. Combination of severe exercise and nandrolone rescued the intact cells and improved the TAC, TAC/MDA, and Bax/Bcl-2 ratios. The findings suggest that low- and high-intensity endurance exercise decreased the risk of neurodegeneration effect of nandrolone in the hippocampus of rats. This effect can be explained by the regulation of the redox system and cell homeostasis.

Sex-Specific Effects of Testosterone on the Sexually Dimorphic Transcriptome and Epigenome of Embryonic Neural Stem/Progenitor Cells

The mechanisms by which sex differences in the mammalian brain arise are poorly understood, but are influenced by a combination of underlying genetic differences and gonadal hormone exposure. Using a mouse embryonic neural stem cell (eNSC) model to understand early events contributing to sexually dimorphic brain development, we identified novel interactions between chromosomal sex and hormonal exposure that are instrumental to early brain sex differences. RNA-sequencing identified 103 transcripts that were differentially expressed between XX and XY eNSCs at baseline (FDR = 0.10). Treatment with testosterone-propionate (TP) reveals sex-specific gene expression changes, causing 2854 and 792 transcripts to become differentially expressed on XX and XY genetic backgrounds respectively. Within the TP responsive transcripts, there was enrichment for genes which function as epigenetic regulators that affect both histone modifications and DNA methylation patterning. We observed that TP caused a global decrease in 5-methylcytosine abundance in both sexes, a transmissible effect that was maintained in cellular progeny. Additionally, we determined that TP was associated with residue-specific alterations in acetylation of histone tails. These findings highlight an unknown component of androgen action on cells within the developmental CNS, and contribute to a novel mechanism of action by which early hormonal organization is initiated and maintained.

Co-activator candidate interactions for orphan nuclear receptor NR2E1

Background

NR2E1 (Tlx) is an orphan nuclear receptor that regulates the maintenance and self-renewal of neural stem cells, and promotes tumourigenesis. Nr2e1-null mice exhibit reduced cortical and limbic structures and pronounced retinal dystrophy. NR2E1 functions mainly as a repressor of gene transcription in association with the co-repressors atrophin-1, LSD1, HDAC and BCL11A. Recent evidence suggests that NR2E1 also acts as an activator of gene transcription. However, co-activator complexes that interact with NR2E1 have not yet been identified. In order to find potential novel co-regulators for NR2E1, we used a microarray assay for real-time analysis of co-regulator–nuclear receptor interaction (MARCoNI) that contains peptides representing interaction motifs from potential co-regulatory proteins, including known co-activator nuclear receptor box sequences (LxxLL motif).

Results

We found that NR2E1 binds strongly to an atrophin-1 peptide (Atro box) used as positive control and to 19 other peptides that constitute candidate NR2E1 partners. Two of these proteins, p300 and androgen receptor (AR), were further validated by reciprocal pull-down assays. The specificity of NR2E1 binding to peptides in the array was evaluated using two single amino acid variants, R274G and R276Q, which disrupted the majority of the binding interactions observed with wild-type NR2E1. The decreased binding affinity of these variants to co-regulators was further validated by pull-down assays using atrophin1 as bait. Despite the high conservation of arginine 274 in vertebrates, its reduced interactions with co-regulators were not significant in vivo as determined by retinal phenotype analysis in single-copy Nr2e1-null mice carrying the variant R274G.

Conclusions

We showed that MARCoNI is a specific assay to test interactions of NR2E1 with candidate co-regulators. In this way, we unveiled 19 potential co-regulator partners for NR2E1, including eight co-activators. All the candidates here identified need to be further validated using in vitro and in vivo models. This assay was sensitive to point mutations in NR2E1 ligand binding domain making it useful to identify mutations and/or small molecules that alter binding of NR2E1 to protein partners.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3173-5) contains supplementary material, which is available to authorized users.

Social behavior, hormones and adult neurogenesis

A variety of experiences have been shown to affect the production of neurons in the adult hippocampus. These effects may be mediated by experience-driven hormonal changes, which, in turn, interact with factors such as sex, age and life history to alter brain plasticity. Although the effects of physical experience and stress have been extensively characterized, various types of social experience across the lifespan trigger profound neuroendocrine changes in parallel with changes in adult neurogenesis. This review article focuses on the influence of specific social experiences on adult neurogenesis in the dentate gyrus and the potential role of hormones in these effects.

Association between CYP17A1 rs3824755 and rs743572 gene polymorphisms and Alzheimer's disease in the Chinese Han population

The CYP17A1 gene encodes cytochrome P450c17α, an enzyme that catalyzes the formation of sex hormones, which have been linked to the pathogenesis of Alzheimer's disease (AD). An association between the CYP17A1 rs743572 single nucleotide polymorphism (SNP) and AD has been reported; however, the findings are controversial. In the present study, we investigated the association between rs743572 and another SNP, rs3824755, and AD risk in a Chinese Han population (n=207 patients and 239 controls), and their interaction with the apolipoprotein E (APOE) e4 allele. We found that the C allele and GC+CC genotypes of rs3824755 conferred protection against AD only in APOE e4 carriers. Both rs3824755 and rs743572 polymorphisms showed interactions with APOE e4. The C allele and GC+CC genotypes of rs3824755 acted as protective factors that decreased the risk of APOE e4 in AD. The CYP17A1 rs743572G allele and AG+GG genotypes were found to be potential risk factors that act synergetically with APOE e4. Moreover, the CA and GG haplotypes were protective and conferred a slight risk, respectively, in APOE e4 carriers. These results indicate that CYP17A1 rs3824755 and rs743572 are associated with AD in the Chinese Han population and act in combination with APOE e4.

Gonadectomy reduces the density of androgen receptor-immunoreactive neurons in male rat's hippocampus: testosterone replacement compensates it

BACKGROUND

In the present study, the role of gonadectomy on memory impairment and the density of androgen receptor-immunoreactive neurons in rats' hippocampus as well as the ability of testosterone to compensate of memory and the density of androgen receptors in the hippocampus was evaluated.

METHODS

Adult male rats (except intact-no testosterone group) were bilaterally castrated, and behavioral tests performed 2 weeks later. Animals bilaterally cannulated into lateral ventricles and then received testosterone (10, 40 and 120 µg/0.5 µl DMSO) or vehicle (DMSO; 0.5 µl) for gonadectomized-vehicle group, 30 min before training in water maze test. The androgen receptor-immunoreactive neurons were detected by immunohistochemical technique in the hippocampal areas.

RESULTS

In the gonadectomized male rats, a memory deficit was found in Morris water maze test on test day (5th day) after DMSO administration. Gonadectomy decreased density of androgen receptor-immunoreactive neurons in the rats' hippocampus. The treatment with testosterone daily for 5 days attenuated memory deficits induced by gonadectomy. Testosterone also significantly increased the density of androgen receptor-immunoreactive neurons in the hippocampal areas. The intermediate dose of this hormone (40 µg) appeared to have a significant effect on spatial memory and the density of androgen receptor-immunoreactive neurons in gonadectomized rats' hippocampus.

CONCLUSIONS

The present study suggests that testosterone can compensate memory failure in gonadectomized rats. Also testosterone replacement can compensate the reduction of androgen receptor-immunoreactive neurons density in the rats' hippocampus after gonadectomy.

The Androgen Receptor Bridges Stem Cell-Associated Signaling Nodes in Prostate Stem Cells

The therapeutic potential of stem cells relies on dissecting the complex signaling networks that are thought to regulate their pluripotency and self-renewal. Until recently, attention has focused almost exclusively on a small set of "core" transcription factors for maintaining the stem cell state. It is now clear that stem cell regulatory networks are far more complex. In this review, we examine the role of the androgen receptor (AR) in coordinating interactions between signaling nodes that govern the balance of cell fate decisions in prostate stem cells.

Testosterone-induced adult neurosphere growth is mediated by sexually-dimorphic aromatase expression

We derived adult neural stem/progenitor cells (NSPCs) from the sub-ventricular zone of male and female mice to examine direct responses to principal sex hormones. In the presence of epidermal growth factor (EGF) and fibroblast growth factor-2 (FGF2) NSPCs of both sexes expressed nestin and sox2, and could be maintained as neurospheres without addition of any sex hormones. The reverse was not observed; neither testosterone (T), 17β-estradiol (E₂) nor progesterone (P₄) was able to support neurosphere growth in the absence of EGF and FGF2. Ten nanomolar T, E₂ or P₄ induced nestin(+) cell proliferation within 20 min and enhanced neurosphere growth over 7 days irrespective of sex, which was abolished by Erk inhibition with 20 μM U0126. Maintaining neurospheres with each sex hormone did not affect subsequent neuronal differentiation. However, 10 nM T, E₂ or P₄ added during differentiation increased βIII tubulin(+) neuron production with E₂ being more potent compared to T and P₄ in both sexes. Androgen receptor (AR) inhibition with 20 μM flutamide but not aromatase inhibition with 10 μM letrozole reduced basal and T-induced neurosphere growth in females, while only concurrent inhibition of AR and aromatase produced the same effect in males. This sex-specific effect was supported by higher aromatase expression in male neurospheres compared to females measured by Western blot and green fluorescent protein (GFP) reporter. Ten micromolar menadione induced oxidative stress, impaired neurosphere growth and up-regulated aromatase expression in both sexes. However, under oxidative stress letrozole significantly exacerbated impaired neurosphere growth in males only. While both E₂ and T could prevent oxidative stress-induced growth reduction in both sexes, the effects of T were dependent on innate aromatase activity. We show for the first time that intrinsic androgen and estrogen signaling may impact the capacity of NSPCs to produce neural progenitors under pathological conditions of oxidative stress.

Brain and cognition abnormalities in long-term anabolic-androgenic steroid users

BACKGROUND

Anabolic-androgenic steroid (AAS) use is associated with psychiatric symptoms including increased aggression as well as with cognitive dysfunction. The brain effects of long-term AAS use have not been assessed in humans.

METHODS

This multimodal magnetic resonance imaging study of the brain compared 10 male weightlifters reporting long-term AAS use with 10 age-matched weightlifters reporting no AAS exposure. Participants were administered visuospatial memory tests and underwent neuroimaging. Brain volumetric analyses were performed; resting-state fMRI functional connectivity (rsFC) was evaluated using a region-of-interest analysis focused on the amygdala; and dorsal anterior cingulate cortex (dACC) metabolites were quantified by proton magnetic resonance spectroscopy (MRS).

RESULTS

AAS users had larger right amygdala volumes than nonusers (P=0.002) and reduced rsFC between right amygdala and frontal, striatal, limbic, hippocampal, and visual cortical areas. Left amygdala volumes were slightly larger in AAS users (P=0.061) but few group differences were detected in left amygdala rsFC. AAS users also had lower dACC scyllo-inositol levels (P=0.004) and higher glutamine/glutamate ratios (P=0.028), possibly reflecting increased glutamate turnover. On a visuospatial cognitive task, AAS users performed more poorly than nonusers, with the difference approaching significance (P=0.053).

CONCLUSIONS

Long-term AAS use is associated with right amygdala enlargement and reduced right amygdala rsFC with brain areas involved in cognitive control and spatial memory, which could contribute to the psychiatric effects and cognitive dysfunction associated with AAS use. The MRS abnormalities we detected could reflect enhanced glutamate turnover and increased vulnerability to neurotoxic or neurodegenerative processes, which could contribute to AAS-associated cognitive dysfunction.

The effect of adolescent testosterone on hippocampal BDNF and TrkB mRNA expression: relationship with cell proliferation

BACKGROUND

Testosterone attenuates postnatal hippocampal neurogenesis in adolescent male rhesus macaques through altering neuronal survival. While brain-derived neurotropic factor (BDNF)/ tyrosine kinase receptor B (TrkB) are critical in regulating neuronal survival, it is not known if the molecular mechanism underlying testosterone's action on postnatal neurogenesis involves changes in BDNF/TrkB levels. First, (1) we sought to localize the site of synthesis of the full length and truncated TrkB receptor in the neurogenic regions of the adolescent rhesus macaque hippocampus. Next, (2) we asked if gonadectomy or sex hormone replacement altered hippocampal BDNF and TrkB expression level in mammalian hippocampus (rhesus macaque and Sprague Dawley rat), and (3) if the relationship between BDNF/TrkB expression was altered depending on the sex steroid environment.

RESULTS

We find that truncated TrkB mRNA+ cells are highly abundant in the proliferative subgranular zone (SGZ) of the primate hippocampus; in addition, there are scant and scattered full length TrkB mRNA+ cells in this region. Gonadectomy or sex steroid replacement did not alter BDNF or TrkB mRNA levels in young adult male rat or rhesus macaque hippocampus. In the monkey and rat, we find a positive correlation with cell proliferation and TrkB-TK+ mRNA expression, and this positive relationship was found only when sex steroids were present.

CONCLUSIONS

We suggest that testosterone does not down-regulate neurogenesis at adolescence via overall changes in BDNF or TrkB expression. However, BDNF/TrkB mRNA appears to have a greater link to cell proliferation in the presence of circulating testosterone.

Could androgens maintain specific domains of mental health in aging men by preserving hippocampal neurogenesis?

Interest surrounds the role of sex-hormones in regulating brain function outside of reproductive behaviour. Declining androgen production in aging males has been associated with cognitive impairment, depression and increased risk of developing Alzheimer's disease. Indication for testosterone replacement therapy is based on biochemically determined low circulating testosterone combined with manifest symptoms. However, which aspects of age-related cognitive decline are attributable to low circulating testosterone remain ambiguous. Studies examining cognition in aging men receiving testosterone replacement therapy have yielded equivocal results. The exact role of testosterone in maintaining cognitive function and the underlying neural mechanisms are largely unknown, though it would appear to be domain specific. Clarity in this area will provide clinical direction toward addressing an increasing healthcare burden of mental health decline coincident with increasing longevity. The premise that androgens contribute to maintaining aspects of mental health in aging men by preserving hippocampal neurogenesis will be used as a forum in this review to discuss current knowledge and the need for further studies to better define testosterone replacement strategies for aging male health.

Testosterone and estradiol differentially affect cell proliferation in the subventricular zone of young adult gonadectomized male and female rats

Steroid hormones are important players to regulate adult neurogenesis in the dentate gyrus of the hippocampus, but their involvement in the regulation of the same phenomenon in the subventricular zone (SVZ) of the lateral ventricles is not completely understood. Here, in male rats, we tested the existence of activational effects of testosterone (T) on cell proliferation in the adult SVZ. To this aim, three groups of male rats: castrated, castrated and treated with T, and controls were treated with 5-bromo-2'-deoxyuridine (BrdU) and killed after 24h. The density of BrdU-labeled cells was significantly lower in castrated animals in comparison to the other two groups, thus supporting a direct correlation between SVZ proliferation and levels of circulating T. To clarify whether this effect is purely androgen-dependent, or mediated by the T metabolites, estradiol (E2) and dihydrotestosterone (DHT), we evaluated SVZ proliferation in castrated males treated with E2, DHT and E2+DHT, in comparison to T- and vehicle-treated animals, and sham-operated controls. The stereological analysis demonstrated that E2 and T, but not DHT, increase proliferation in the SVZ of adult male rats. Quantitative evaluation of cells expressing the endogenous marker of cell proliferation phosphorylated form of Histone H3 (PHH3), or the marker of highly dividing SVZ progenitors Mash1, indicated the effect of T/E2 is mostly restricted to SVZ proliferating progenitors. The same experimental protocol was repeated on ovariectomized female rats treated with E2 or T. In this case, no statistically significant difference was found among groups. Overall, our results clearly show that the gonadal hormones T and E2 represent important mediators of cell proliferation in the adult SVZ. Moreover, we show that such an effect is restricted to males, supporting adult neurogenesis in rats is a process differentially modulated in the two sexes.

The beneficial effects of strength exercise on hippocampal cell proliferation and apoptotic signaling is impaired by anabolic androgenic steroids

Previous studies have shown that strength exercise improves memory and increases expression of a myriad of proteins involved on neuronal survival and synaptic plasticity in the hippocampus. Conversely, chronic exposure to supraphysiological levels of anabolic androgenic steroids (AAS) can induce psychiatric abnormalities, cognitive deficits, impair neurotransmission, alter the levels of neurotrophic factors, decrease cell proliferation and neurogenesis, and enhance neuronal cell death. In the present study, we investigated the effects of the AAS nandrolone decanoate (ND) administration during a strength exercise program on cell proliferation, apoptotic status and brain-derived neurotrophic factor (BDNF) expression in the rat hippocampus. Adult male Wistar rats were subjected to 4 weeks of progressive strength exercise in a vertical ladder apparatus with or without daily doses (5.0 mg/kg, SC) of ND. Immunohistochemistry analysis revealed that strength exercise increased significantly the number of Ki-67-positive cells (a cell proliferation marker) in dentate gyrus (DG) of hippocampus. However, this effect was abrogated when strength exercise was combined with ND. Although western blot analysis of whole hippocampus showed no significant differences in Bax and Bcl-2 protein expression among groups, the immunoreactivity of the pro-apoptotic protein Bax was significantly increased in DG, CA1 and CA3 hippocampal subfields of sedentary rats treated with ND. Moreover, the increase in the immunoreactivity of anti-apoptotic protein Bcl-2 (DG and CA3) induced by strength exercise was diminished by ND. There were no significant differences in BDNF expression among experimental groups. Therefore, the present findings suggest that the beneficial effects of strength exercise on hippocampal cell proliferation and apoptotic signaling are impaired by ND.

Maternal administration of flutamide during late gestation affects the brain and reproductive organs development in the rat male offspring

We have previously demonstrated that male rats exposed to stress during the last week of gestation present age-specific impairments of brain development. Since the organization of the fetal developing brain is subject to androgen exposure and prenatal stress was reported to disrupt perinatal testosterone surges, the aim of this research was to explore whether abnormal androgen concentrations during late gestation affects the morphology of the prefrontal cortex (PFC), hippocampus (HPC) and ventral tegmental area (VTA), three major areas that were shown to be affected by prenatal stress in our previous studies. We administered 10-mg/kg/day of the androgen receptor antagonist flutamide (4'nitro-3'-trifluoromethylsobutyranilide) or vehicle injections to pregnant rats from days 15-21 of gestation. The antiandrogenic effects of flutamide were confirmed by the analysis of androgen-dependent developmental markers: flutamide-exposed rats showed reduced anogenital distance, delay in the completion of testis descent, hypospadias, cryptorchidism and atrophied seminal vesicles. Brain morphological studies revealed that prenatal flutamide decreased the number of MAP2 (a microtubule-associated protein type 2, present almost exclusively in dendrites) immunoreactive neuronal processes in all evaluated brain areas, both in prepubertal and adult offspring, suggesting that prenatal androgen disruption induces long-term reductions of the dendritic arborization of several brain structures, affecting the normal connectivity between areas. Moreover, the number of tyrosine hydroxylase (TH)-immunopositive neurons in the VTA of prepubertal offspring was reduced in flutamide rats but reach normal values at adulthood. Our results demonstrate that the effects of prenatal flutamide on the offspring brain morphology resemble several prenatal stress effects suggesting that the mechanism of action of prenatal stress might be related to the impairment of the organizational role of androgens on brain development.

Chronic nandrolone decanoate exposure during adolescence affects emotional behavior and monoaminergic neurotransmission in adulthood

Nandrolone decanoate, an anabolic androgen steroid (AAS) illicitly used by adult and adolescent athletes to enhance physical performance and body image, induces psychiatric side effects, such as aggression, depression as well as a spectrum of adverse physiological impairments. Since adolescence represents a neurodevelopmental window that is extremely sensitive to the detrimental effects of drug abuse, we investigated the long-term behavioral and neurophysiological consequences of nandrolone abuse during adolescence. Adolescent rats received daily injections of nandrolone decanoate (15 mg/kg, i.m.) for 14 days (PND 40-53). At early adulthood (PND 68), forced swim, sucrose preference, open field and elevated plus maze tests were performed to assess behavioral changes. In vivo electrophysiological recordings were carried out to monitor changes in electrical activity of serotonergic neurons of the dorsal raphe nucleus (DRN) and noradrenergic neurons of the locus coeruleus (LC). Our results show that after early exposure to nandrolone, rats display depression-related behavior, characterized by increased immobility in the forced swim test and reduced sucrose intake in the sucrose preference test. In addition, adult rats presented anxiety-like behavior characterized by decreased time and number of entries in the central zone of the open field and decreased time spent in the open arms of the elevated plus maze. Nandrolone decreased the firing rate of spontaneously active serotonergic neurons in the DRN while increasing the firing rate of noradrenergic neurons in the LC. These results provide evidence that nandrolone decanoate exposure during adolescence alters the emotional profile of animals in adulthood and significantly modifies both serotonergic and noradrenergic neurotransmission.

Gonadectomy increases neurogenesis in the male adolescent rhesus macaque hippocampus

New neurons are continuously produced in the subgranular zone of the adult hippocampus and can modulate hippocampal plasticity across life. Adolescence is characterized by dramatic changes in sex hormone levels, and social and emotional behaviors. It is also an age for increased risk of psychiatric disorders, including schizophrenia, which may involve altered hippocampal neurogenesis. The extent to which testosterone and other testicular hormones modulate hippocampal neurogenesis and adolescent behavioral development is unclear. This study aimed to determine if removal of testicular hormones during adolescence alters neurogenesis in the male rhesus macaque hippocampus. We used stereology to examine levels of cell proliferation, cell survival and neuronal differentiation in late adolescent male rhesus macaques (4.6-yrs old) that had previously been gonadectomized or sham operated prior to puberty (2.4-yrs old). While the absence of adolescent testicular hormones had no effect on cell proliferation, cell survival was increased by 65% and indices of immature neuronal differentiation were increased by 56% in gonadectomized monkeys compared to intact monkeys. We show for the first time that presence of circulating testicular hormones, including testosterone, may decrease neuronal survival in the primate hippocampus during adolescence. Our findings are in contrast to existing studies in adults where testosterone tends to be a pro-survival factor and demonstrate that testicular hormones may reduce hippocampal neurogenesis during the age typical of schizophrenia onset.

Effects of androgens on early post-ischemic neurogenesis in mice

Although androgens are reported to affect stroke outcomes by altering ischemic tissue damage, their effect on post-injury repair is unknown. Since neurogenesis has recently been recognized as contributing to stroke outcomes, we investigated the role of androgens on stroke-induced neurogenesis. Adult male mice were subjected to transient middle cerebral artery occlusion (MCAO) and neurogenesis was examined 1 week later by quantifying BrdU/doublecortin-positive and BrdU/NeuN-positive neurons in brain germinal regions as well as the injured striatum. To elucidate the role of endogenous androgens, post-MCAO neurogenesis was examined in gonadally intact males, intact males implanted with the androgen receptor antagonist flutamide, and surgically castrated males. Surgical castration or pharmacologic androgen receptor blockade had no effects on post-ischemic neurogenesis, except that continuous androgen receptor blockade unexpectedly suppressed maturation of newborn neurons (BrdU/NeuN-positive cells) in the dentate gyrus. Post-MCAO neurogenesis was also examined in surgically castrated mice treated with continuous release implants containing testosterone or dihydrotestosterone (DHT). Testosterone and DHT robustly inhibited post-ischemic neurogenesis in the dentate gyrus, and the more potent androgen DHT virtually abolished the presence of immature newborn neurons (BrdU/doublecortin-positive cells) in the injured striatum. Our data suggest that endogenous androgens do not alter post-stroke neurogenesis quantitatively, but the presence of supra-physiological androgen stimulation profoundly suppresses early neurogenesis in germinal brain areas and reduces cellular repair in injured tissue after cerebral ischemia. These results advance the understanding of the role that androgens play in stroke outcomes.

Sex, hormones and neurogenesis in the hippocampus: hormonal modulation of neurogenesis and potential functional implications

The hippocampus is an area of the brain that undergoes dramatic plasticity in response to experience and hormone exposure. The hippocampus retains the ability to produce new neurones in most mammalian species and is a structure that is targeted in a number of neurodegenerative and neuropsychiatric diseases, many of which are influenced by both sex and sex hormone exposure. Intriguingly, gonadal and adrenal hormones affect the structure and function of the hippocampus differently in males and females. Adult neurogenesis in the hippocampus is regulated by both gonadal and adrenal hormones in a sex- and experience-dependent way. Sex differences in the effects of steroid hormones to modulate hippocampal plasticity should not be completely unexpected because the physiology of males and females is different, with the most notable difference being that females gestate and nurse the offspring. Furthermore, reproductive experience (i.e. pregnancy and mothering) results in permanent changes to the maternal brain, including the hippocampus. This review outlines the ability of gonadal and stress hormones to modulate multiple aspects of neurogenesis (cell proliferation and cell survival) in both male and female rodents. The function of adult neurogenesis in the hippocampus is linked to spatial memory and depression, and the present review provides early evidence of the functional links between the hormonal modulation of neurogenesis that may contribute to the regulation of cognition and stress.

Androgens increase survival of adult-born neurons in the dentate gyrus by an androgen receptor-dependent mechanism in male rats

Gonadal steroids are potent regulators of adult neurogenesis. We previously reported that androgens, such as testosterone (T) and dihydrotestosterone (DHT), but not estradiol, increased the survival of new neurons in the dentate gyrus of the male rat. These results suggest androgens regulate hippocampal neurogenesis via the androgen receptor (AR). To test this supposition, we examined the role of ARs in hippocampal neurogenesis using 2 different approaches. In experiment 1, we examined neurogenesis in male rats insensitive to androgens due to a naturally occurring mutation in the gene encoding the AR (termed testicular feminization mutation) compared with wild-type males. In experiment 2, we injected the AR antagonist, flutamide, into castrated male rats and compared neurogenesis levels in the dentate gyrus of DHT and oil-treated controls. In experiment 1, chronic T increased hippocampal neurogenesis in wild-type males but not in androgen-insensitive testicular feminization mutation males. In experiment 2, DHT increased hippocampal neurogenesis via cell survival, an effect that was blocked by concurrent treatment with flutamide. DHT, however, did not affect cell proliferation. Interestingly, cells expressing doublecortin, a marker of immature neurons, did not colabel with ARs in the dentate gyrus, but ARs were robustly expressed in other regions of the hippocampus. Together these studies provide complementary evidence that androgens regulate adult neurogenesis in the hippocampus via the AR but at a site other than the dentate gyrus. Understanding where in the brain androgens act to increase the survival of new neurons in the adult brain may have implications for neurodegenerative disorders.

Androgen receptor increases CD133 expression and progenitor-like population that associate with cisplatin resistance in endometrial cancer cell line

Endometrial cancer (EMC) is a sex steroid hormone-related female malignancy. Androgen and androgen receptor (androgen/AR) signals have been implicated in EMC progression. Cancer stem/progenitor cells (CSPCs) are suspected to link to chemoresistance in patients with EMC. In this study, we examined the androgen/AR roles in cisplatin resistance and CSPC population. We found AR expression increased naive EMC side population, CSPC population, cell migration, and epithelial-mesenchymal transition. Meanwhile, it decreased cisplatin cytotoxic effect on EMC cells. Collaterally, endogenous AR expressions in EMC cells were upregulated in the cisplatin-resisting state. Moreover, AR expression could further enhance CD133 expression, CSPC-related markers, and drug-resistance gene messenger RNA expression in EMC cells. Finally, the AR-associated gene expression might go through indirect regulation. This is the first report revealing AR function on EMC cells' CSPC and cisplatin resistance.