Neurotropic action of androgens: principles, mechanisms and novel targets

Gender and Neurosteroids: Implications for Brain Function, Neuroplasticity and Rehabilitation

Neurosteroids are synthesized de novo in the nervous system; they mainly moderate neuronal excitability, and reach target cells via the extracellular pathway. The synthesis of neurosteroids occurs in peripheral tissues such as gonads tissues, liver, and skin; then, because of their high lipophilia, they cross the blood-brain barrier and are stored in the brain structure. Neurosteroidogenesis occurs in brain regions such as the cortex, hippocampus, and amygdala by enzymes necessary for the in situ synthesis of progesterone from cholesterol. Neurosteroids could be considered the main players in both sexual steroid-induced hippocampal synaptic plasticity and normal transmission in the hippocampus. Moreover, they show a double function of increasing spine density and enhancing long term potentiation, and have been related to the memory-enhancing effects of sexual steroids. Estrogen and progesterone affect neuronal plasticity differently in males and females, especially regarding changes in the structure and function of neurons in different regions of the brain. Estradiol administration in postmenopausal women allowed for improving cognitive performance, and the combination with aerobic motor exercise seems to enhance this effect. The paired association between rehabilitation and neurosteroids treatment could provide a boosting effect in order to promote neuroplasticity and therefore functional recovery in neurological patients. The aim of this review is to investigate the mechanisms of action of neurosteroids as well as their sex-dependent differences in brain function and their role in neuroplasticity and rehabilitation.

Epigenetic Modifications by Estrogen and Androgen in Alzheimer's Disease

For the development and maintenance of neuron networks in the brain, epigenetic mechanisms are necessary, as indicated by recent findings. This includes some of the high-order brain processes, such as behavior and cognitive functions. Epigenetic mechanisms could influence the pathophysiology or etiology of some neuronal diseases, altering disease susceptibility and therapy responses. Recent studies support epigenetic dysfunctions in neurodegenerative and psychiatric conditions, such as Alzheimer's disease (AD). These dysfunctions in epigenetic mechanisms also play crucial roles in the transgenerational effects of the environment on the brain and subsequently in the inheritance of pathologies. The possible role of gonadal steroids in the etiology and progression of neurodegenerative diseases, including Alzheimer's disease, has become the subject of a growing body of research over the last 20 years. Recent scientific findings suggest that epigenetic changes, driven by estrogen and androgens, play a vital role in brain functioning. Therefore, exploring the role of estrogen and androgen-based epigenetic changes in the brain is critical for the deeper understanding of AD. This review highlights the epigenetic modifications caused by these two gonadal steroids and the possible therapeutic strategies for AD.

Astragaloside IV Alleviates Brain Injury Induced by Hypoxia via the Calpain-1 Signaling Pathway

Long-term hypoxia can induce oxidative stress and apoptosis in hippocampal neurons that can lead to brain injury diseases. Astragaloside IV (AS-IV) is widely used in the antiapoptotic therapy of brain injury diseases. However, its mechanism of action is still not fully understood. In this study, we investigated the effect of AS-IV on hypoxia-induced oxidative stress and apoptosis in hippocampal neurons and explored its possible mechanism. In vivo, mice were placed in a hypoxic circulatory device containing 10% O2 and gavaged with AS-IV (60 and 120 mg/kg/d) for 4 weeks. In vitro, mouse hippocampal neuronal cells (HT22) were treated with hypoxia (1% O2) for 24 hours in the presence or absence of AS-IV, MDL-28170 (calpain-1 inhibitor), or YC-1 (HIF-1α inhibitor). The protective effect of AS-IV on brain injury was further explored by examining calpain-1 knockout mice. The results showed that hypoxia induced damage to hippocampal neurons, impaired spatial learning and memory abilities, and increased oxidative stress and apoptosis. Treatment with AS-IV or calpain-1 knockout improved the damage to hippocampal neurons and spatial learning and memory, attenuated oxidative stress and inhibited cell apoptosis. These changes were verified in HT22 cells. Overexpression of calpain-1 abolished the improvement of AS-IV on apoptosis and oxidative stress. In addition, the effects of AS-IV were accompanied by decreased calpain-1 and HIF-1α expression, and YC-1 showed a similar effect as AS-IV on calpain-1 and caspase-3 expression. In conclusion, this study demonstrates that AS-IV can downregulate the calpain-1/HIF-1α/caspase-3 pathway and inhibit oxidative stress and apoptosis of hippocampal neurons induced by hypoxia, which provides new ideas for studying the antiapoptotic activity of AS-IV.

Seasonal variation in gonadal hormones, spatial cognition, and hippocampal attributes: More questions than answers

A large body of research has been dedicated to understanding the factors that modulate spatial cognition and attributes of the hippocampus, a highly plastic brain region that underlies spatial processing abilities. Variation in gonadal hormones impacts spatial memory and hippocampal attributes in vertebrates, although the direction of the effect has not been entirely consistent. To add complexity, individuals in the field must optimize fitness by coordinating activities with the appropriate environmental cues, and many of these behaviors are correlated tightly with seasonal variation in gonadal hormone release. As such, it remains unclear if the relationship among systemic gonadal hormones, spatial cognition, and the hippocampus also exhibits seasonal variation. This review presents an overview of the relationship among gonadal hormones, the hippocampus, and spatial cognition, and how the seasonal release of gonadal hormones correlates with seasonal variation in spatial cognition and hippocampal attributes. Additionally, this review presents other neuroendocrine mechanisms that may be involved in modulating the relationship among seasonality, gonadal hormone release, and the hippocampus and spatial cognition, including seasonal rhythms of steroid hormone binding globulins, neurosteroids, sex steroid hormone receptor expression, and hormone interactions. Here, endocrinology, ecology, and behavioral neuroscience are brought together to present an overview of the research demonstrating the mechanistic effects of systemic gonadal hormones on spatial cognition and the hippocampus, while, at a functional level, superimposing seasonal effects to examine ecologically-relevant circannual changes in gonadal hormones and spatial behaviors.

Effects and underlying cellular pathway involved in the impairment of the neurovascular unit following exposure of adult male mice to low doses of di(2-ethylhexyl) phthalate alone or in an environmental phthalate mixture

We have previously shown that adult male mice exposure to low doses of di (2-ethylhexyl)phthalate (DEHP) impacts the blood-brain barrier (BBB) integrity and surrounding parenchyma in the medial preoptic area (mPOA), a key hypothalamic area involved in the male sexual behavior. BBB leakage was associated with a decrease in the endothelial tight junction accessory protein, zona occludens-1, and caveolae protein Cav-1, added to an inflammatory profile including glial activation accompanied by enhanced expression of inducible nitric oxide synthase. As this failure of BBB functionality in the mPOA could participate, at least in part, in reported alteration of sexual behavior following DEHP exposure, we explored the cellular pathway connecting cerebral capillaries and neurons. Two-month-old C57BL/6J male mice were orally exposed for 6 weeks to DEHP alone (5 and 50 μg/kg/day) or to DEHP (5 μg/kg/day) in an environmental phthalate mixture. The presence of androgen receptor (AR) and estrogen receptor-α (ERα) were first evidenced in brain capillaries. Protein levels of AR but not of ERα were reduced in cerebral capillaries after phthalate exposure. The amounts of basement membrane and cell-matrix interaction components were decreased, while matrix metalloprotease MMP-2 and MMP-9 activities were increased. Fluorojade® labelling suggested that exposure to phthalates also lead to a neurodegenerative process in the mPOA. Altogether, the data suggest that environmental exposure to endocrine disruptors such as phthalates, could alter AR/Cav-1 interaction, impacting a Cav-1/nitric oxide/MMP pathway. This would lead to disruption of the glio-neurovascular coupling which is essential to neuronal functioning.

The influence of hormonal contraception on depression and female sexuality: a narrative review of the literature

OBJECTIVE

Over the past decades, an increasing number of women have been using hormonal contraception. The potential role of sex hormones in regulating vegetative, psychophysiological, and cognitive functions has been highlighted in several studies, and there is a need to further understand the impact of hormonal contraception on women's quality of life, especially as regards psychological health and sexuality.

METHODS

We conducted a narrative review aimed at clarifying the mechanisms involved in the interaction between sex hormones and the brain, also focusing on the association between hormonal contraception and mood and sexual function.

RESULTS

Our findings clarified that hormonal contraception may be associated with depressive symptoms, especially among adolescents, and with sexual dysfunction. However, the evidence included in this review was conflicting and did not support the hypothesis that hormonal contraception directly causes depressive symptoms, major depressive disorder, or sexual dysfunction.

CONCLUSIONS

The optimal hormonal contraception should be identified in the context of shared decision making, considering the preferences and needs of each woman, as well as her physical and psychosexual conditions.

Involvement of Testosterone Signaling in the Integrity of the Neurovascular Unit in the Male: Review of Evidence, Contradictions, and Hypothesis

Age-related central nervous system function decline and increased susceptibility of females compared to males with respect to prevalence of several neurodegenerative and neuropsychiatric diseases are both based on the principle that hormonal factors could be involved. These cerebral disorders are characterized by an alteration of blood-brain barrier (BBB) properties and chronic neuroinflammation, which lead to disease progression. Neuroinflammation, in turn, contributes to BBB dysfunction. The BBB and its environment, called the neurovascular unit (NVU), are crucial for cerebral homeostasis and neuronal function. Interestingly, sex steroids influence BBB properties and modulate neuroinflammatory responses. To date however, the majority of work reported has focused on the effects of estrogens on BBB function and neuroinflammation in female mammals. In contrast, the effects of testosterone signaling on the NVU in males are still poorly studied. The aim of this review was to summarize and discuss the literature, providing insights and contradictions to highlight hypothesis and the need for further investigations.

Low-Dose Testosterone Augmentation for Antidepressant-Resistant Major Depressive Disorder in Women: An 8-Week Randomized Placebo-Controlled Study

OBJECTIVE

Low-dose testosterone has been shown to improve depression symptom severity, fatigue, and sexual function in small studies in women not formally diagnosed with major depressive disorder. The authors sought to determine whether adjunctive low-dose transdermal testosterone improves depression symptom severity, fatigue, and sexual function in women with antidepressant-resistant major depression. A functional MRI (fMRI) substudy examined effects on activity in the anterior cingulate cortex (ACC), a brain region important in mood regulation.

METHODS

The authors conducted an 8-week randomized double-blind placebo-controlled trial of adjunctive testosterone cream in 101 women, ages 21-70, with antidepressant-resistant major depression. The primary outcome measure was depression symptom severity as assessed by the Montgomery-Åsberg Depression Rating Scale (MADRS). Secondary endpoints included fatigue, sexual function, and safety measures. The primary outcome of the fMRI substudy (N=20) was change in ACC activity.

RESULTS

The participants' mean age was 47 years (SD=14) and their mean baseline MADRS score was 26.6 (SD=5.9). Eighty-seven (86%) participants completed 8 weeks of treatment. MADRS scores decreased in both study arms from baseline to week 8 (testosterone arm: from 26.8 [SD=6.3] to 15.3 [SD=9.6]; placebo arm: from 26.3 [SD=5.4] to 14.4 [SD=9.3]), with no significant difference between groups. Improvement in fatigue and sexual function did not differ between groups, nor did side effects. fMRI results showed a relationship between ACC activation and androgen levels before treatment but no difference in ACC activation with testosterone compared with placebo.

CONCLUSIONS

Adjunctive transdermal testosterone, although well tolerated, was not more effective than placebo in improving symptoms of depression, fatigue, or sexual dysfunction. Imaging in a subset of participants demonstrated that testosterone did not result in greater activation of the ACC.

Self-repair behaviour of the neuronal cell membrane by conductive atomic force indentation

Conductive atomic force indentation (CAFI) was proposed to study the self-repair behaviour of the neuronal cell membrane here. CAFI was used to detect the changes of membrane potentials by performing the mechanical indentation on neurons with a conductive atomic force microscope. In the experiment, a special insulation treatment was made on the conductive probe, which turned out to be a conductive nanoelectrode, to implement the CAFI function. The mechanical properties of the neuronal cell membrane surface were tested and the membrane potential changes of neurons cultured in vitro were detected. The self-repair behaviour of the neuronal cell membrane after being punctured was investigated. The experiment results show that CAFI provides a new way for the study of self-repair behaviours of neuronal cell membranes and mechanical and electrical properties of living cells.

Neuroanatomical and molecular correlates of cognitive and behavioural outcomes in hypogonadal males

Robust epidemiological, clinical and laboratory evidence supports emerging roles for the sex steroids in such domains as neurodevelopment, behaviour, learning and cognition. Regions of the mammalian brain that are involved in cognitive development and memory do not only express the classical nuclear androgen receptor, but also the non-genomic membrane receptor, which is a G protein-coupled receptor that mediates some rapid effects of the androgens on neurogenesis and synaptic plasticity. Under physiological conditions, hippocampal neurons do express the enzyme aromatase, and therefore actively aromatize testosterone to oestradiol. Although glial expression of the aromatase enzyme is minimal, increased expression following injury suggests a role for sex steroids in neuroprotection. It is therefore plausible to deduce that low levels of circulating androgens in males would perturb neuronal functions in relation to cognition and memory, as well as neural repair following injury. The present review is an overview of some roles of the sex steroids on cognitive function in males, and the neuroanatomical and molecular underpinnings of some behavioural and cognitive deficits characteristic of such genetic disorders noted for low androgen levels, including Klinefelter syndrome, Bardet-Biedl syndrome, Kallman syndrome and Prader-Willi syndrome. Recent literature in relation to some behavioural and cognitive changes secondary to surgical and pharmacological castration are also appraised.

Effects of testosterone dose on spatial memory among castrated adult male rats

Previous research on the activational effects of testosterone on spatial memory has produced mixed results, possibly because such effects are dose-dependent. We tested a wide range of testosterone doses using two spatial memory tasks: a working-reference memory version of the radial-arm maze (RAM) and an object location memory task (OLMT). Adult male Sprague-Dawley rats were castrated or sham-castrated and given daily injections of drug vehicle (Oil Sham and Oil GDX) or one of four doses of testosterone propionate (0.125, 0.250, 0.500, and 1.000 mg T) beginning seven days before the first day of behavioral tests and continuing throughout testing. For the RAM, four arms of the maze were consistently baited on each day of testing. Testosterone had a significant effect on working memory on the RAM, with the Oil Sham, 0.125 mg T, and 0.500 mg T groups performing better than the Oil GDX group. In contrast, there was no significant effect of testosterone on spatial reference memory on the RAM. For the OLMT, we tested long-term memory using a 2 h inter-trial interval between first exposure to two identical objects and re-exposure after one object had been moved. Only the 0.125 and 0.500 mg T groups showed a significant increase in exploration of the moved object during the testing trials, indicating better memory than all other groups. Testosterone replacement restored spatial memory among castrated male rats on both behavioral tasks, but there was a complex dose-response relationship; therefore, the therapeutic value of testosterone is likely sensitive to dose.

Finasteride inhibited brain dopaminergic system and open-field behaviors in adolescent male rats

AIMS

Finasteride inhibits the conversion of testosterone to dihydrotestosterone. Because androgen regulates dopaminergic system in the brain, it could be hypothesized that finasteride may inhibit dopaminergic system. The present study therefore investigates the effects of finasteride in adolescent and early developmental rats on dopaminergic system, including contents of dopamine and its metabolites (dihydroxy phenyl acetic acid and homovanillic acid) and tyrosine hydroxylase expressions both at gene and protein levels. Meanwhile, open-field behaviors of the rats are examined because of the regulatory effect of dopaminergic system on the behaviors.

METHODS

Open-field behaviors were evaluated by exploratory and motor behaviors. Dopamine and its metabolites were assayed by liquid chromatography-mass spectrometry. Tyrosine hydroxylase mRNA and protein expressions were determined by real-time qRT-PCR and western blot, respectively.

RESULTS

It was found that in adolescent male rats, administration of finasteride at doses of 25 and 50 mg/kg for 14 days dose dependently inhibited open-field behaviors, reduced contents of dopamine and its metabolites in frontal cortex, hippocampus, caudate putamen, nucleus accumbens, and down-regulated tyrosine hydroxylase mRNA and protein expressions in substantia nigra and ventral tegmental area. However, there was no significant change of these parameters in early developmental rats after finasteride treatment.

CONCLUSION

These results suggest that finasteride inhibits dopaminergic system and open-field behaviors in adolescent male rats by inhibiting the conversion of testosterone to dihydrotestosterone, and imply finasteride as a potential therapeutic option for neuropsychiatric disorders associated with hyperactivities of dopaminergic system and androgen.

Seasonal changes of androgen receptor, estrogen receptors and aromatase expression in the hippocampus of the wild male ground squirrels (Citellus dauricus Brandt)

The wild ground squirrel is a typical seasonal breeder whose annual life cycle can be roughly divided into the breeding season, the post-breeding season and hibernation. Our previous study has reported the seasonal changes in the expressions of androgen receptor (AR), estrogen receptors α and β (ERα and ERβ), and aromatase cytochrome P450 (P450arom) in the hypothalamus of male wild ground squirrels. To further seek evidence of seasonal expression of steroid hormone receptors and steroid hormone synthases in other brain regions, we investigated the protein and mRNA expressions of AR, ERα, ERβ and P450arom in the hippocampus of the male wild ground squirrels during these different reproductive periods. Histological observation showed that the number of pyramidal cells in Cornu Ammonis 1 (CA1) increased in the breeding season. Both protein and mRNA of AR, ERα, ERβ and P450arom were present in CA1 and CA3 of all seasons. There was significant increment in the immune-signal intensity and mRNA level of AR and ERα during the pre-hibernation, whereas those of ERβ and P450arom were higher during the post-breeding season. In addition, the profile of plasma testosterone concentration showed the nadir in the post-breeding season, a marked elevation in the pre-hibernation, and the summit in the breeding season. These findings suggested that the hippocampus may be a direct target of androgen and estrogen; androgen may play important regulatory roles through its receptor and/or the aromatized estrogen in the hippocampus of the wild male ground squirrels.

The role of morphine on rat neural stem cells viability, neuro-angiogenesis and neuro-steroidgenesis properties

A lack of comprehensive data exists on the effect of morphine on neural stem cell neuro-steroidogenesis and neuro-angiogenesis properties. We, herein, investigated the effects of morphine (100μM), naloxone (100μM) and their combination on rat neural stem cells viability, clonogenicity and Ki-67 expression over a period of 72h. Any alterations in the total fatty acids profile under treatment protocols were elucidated by direct transesterification method. We also monitored the expression of p53, aromatase and 5-alpha reductase by real-time PCR assay. To examine angiogenic capacity, in vitro tubulogenesis and the level of VE-cadherin transcript were investigated during neural to endothelial differentiation under the experimental procedure. Cells supplemented with morphine displayed reduced survival (p<0.01) and clonogenicity (p<0.001). Flow cytometric analysis showed a decrease in Ki-67 during 72h. Naloxone potentially blunted morphine-induced all effects. The normal levels of fatty acids, including saturated and unsaturated were altered by naloxone and morphine supplements. Following 48h, the up-regulation of p53, aromatase and 5-alpha reductase genes occurred in morphine-primed cells. Using three-dimensional culture models of angiogenesis and real time PCR assay, we showed morphine impaired the tubulogenesis properties of neural stem cells (p<0.001) by the inhibition of trans-differentiation into vascular cells and led to decrease of in VE-cadherin expression. Collectively, morphine strongly impaired the healthy status of neural stem cells by inducing p53 and concurrent elevation of aromatase and 5-alpha reductase activities especially during early 48h. Also, neural stem cells-being exposed to morphine lost their potency to elicit angiogenesis.

Effects of methomyl on steroidogenic gene transcription of the hypothalamic-pituitary-gonad-liver axis in male tilapia

Male tilapia were exposed to sub-lethal methomyl concentrations of 0, 0.2, 2, 20 or 200 μg/L for 30 d, and were subsequently cultured in methomyl-free water for 18 d. Relative transcript abundance of steroidogenic genes involved in the HPGL axis of male tilapia was examined at 30 d in the exposure test and at 18 d in the recovery test. The results revealed that low concentrations of methomyl (0.2 and 2 μg/L) did not cause significant changes in gene mRNA levels in the HPGL axis of male tilapia; thus, we considered 2 μg/L concentrations as the level that showed no apparent adverse endocrine disruption effects. However, higher concentrations of methomyl (20 and 200 μg/L) disrupted the endocrine system and caused significant increase in the levels of GnRH2, GnRH3, ERα, and ERβ genes in the hypothalamus, GnRHR and FSHβ genes in the pituitary, CYP19a, FSHR, and ERα genes in the testis, and VTG and ERα genes in the liver, and significantly decreased the levels of LHR, StAR, 3β-HSD, and ARα genes in the testis and LHβ gene in the pituitary, leading to changes in sex steroid hormone and vitellogenin levels in the serum and ultimately resulting in reproductive dysfunction in male tilapia. The recovery tests showed that the toxicity effect caused by 20 μg/L methomyl was reversible; however, the toxicity effect at 200 μg/L of methomyl was irreversible after 18 d. Therefore, we concluded that 200 μg/L was the threshold concentration for methomyl-induced irreversible endocrine disruption in male tilapia.

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.

Emergence of sex differences in the development of substance use and abuse during adolescence

Substance use and abuse begin during adolescence. Male and female adolescent humans initiate use at comparable rates, but males increase use faster. In adulthood, more men than women use and abuse addictive drugs. However, some women progress more rapidly from initiation of use to entry into treatment. In animal models, adolescent males and females consume addictive drugs similarly. However, reproductively mature females acquire self-administration faster, and in some models, escalate use more. Sex/gender differences exist in neurobiologic factors mediating both reinforcement (dopamine, opioids) and aversiveness (CRF, dynorphin), as well as intrinsic factors (personality, psychiatric co-morbidities) and extrinsic factors (history of abuse, environment especially peers and family) which influence the progression from initial use to abuse. Many of these important differences emerge during adolescence, and are moderated by sexual differentiation of the brain. Estradiol effects which enhance both dopaminergic and CRF-mediated processes contribute to the female vulnerability to substance use and abuse. Testosterone enhances impulsivity and sensation seeking in both males and females. Several protective factors in females also influence initiation and progression of substance use including hormonal changes of pregnancy as well as greater capacity for self-regulation and lower peak levels of impulsivity/sensation seeking. Same sex peers represent a risk factor more for males than females during adolescence, while romantic partners increase risk for women during this developmental epoch. In summary, biologic factors, psychiatric co-morbidities as well as personality and environment present sex/gender-specific risks as adolescents begin to initiate substance use.

The effect of acute exercise and psychosocial stress on fine motor skills and testosterone concentration in the saliva of high school students

Little is known about the influence of different stressors on fine motor skills, the concentration of testosterone (T), and their interaction in adolescents. Therefore, 62 high school students aged 14–15 years were randomly assigned to two experimental groups (exercise, psychosocial stress) and a control group. Exercise stress was induced at 65–75% of the maximum heart rate by running for 15 minutes (n = 24). Psychosocial stress was generated by an intelligence test (HAWIK-IV), which was uncontrollable and characterized by social-evaluative-threat to the students (n = 21). The control group followed was part of a regular school lesson with the same duration (n = 28). Saliva was collected after a normal school lesson (pre-test) as well as after the intervention/control period (post-test) and was analyzed for testosterone. Fine motor skills were assessed pre- and post-intervention using a manual dexterity test (Flower Trail) from the Movement Assessment Battery for Children-2. A repeated measure ANCOVA including gender as a covariate revealed a significant group by test interaction, indicating an increase in manual dexterity only for the psychosocial stress group. Correlation analysis of all students shows that the change of testosterone from pre- to post-test was directly linked (r = −.31, p = .01) to the changes in manual dexterity performance. Participants showing high increases in testosterone from pre- to post-test made fewer mistakes in the fine motor skills task. Findings suggest that manual dexterity increases when psychosocial stress is induced and that improvement of manual dexterity performance corresponds with the increase of testosterone.

Cerebral involvement in spinal and bulbar muscular atrophy (Kennedy's disease): a pilot study of PET

OBJECTIVE

To investigate possible cerebral involvement in patients with spinal and bulbar muscular atrophy (SBMA) by (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET).

DESIGN

Ten patients with molecularly-confirmed SBMA and 5 age- and gender-matched healthy controls were recruited for brain FDG-PET studies. The data were analyzed and compared using the statistical parametric mapping (SPM) method.

RESULTS

Glucose hypometabolism in frontal areas of the cerebrum was found in patients with SBMA. However, no significant correlation with clinical variables, such as CAG repeat length, age at onset, or serum testosterone levels, was noted.

CONCLUSIONS

The perturbation of cerebral glucose metabolism in patients with SBMA argues against SBMA being a pure lower motor and sensory neuron syndrome. Mutations in the androgen receptor gene might have a more widespread effect in the cerebrum than previously recognized.

Sexual dimorphism in cerebral ischemia injury

Stroke is a leading cause of permanent disability and death. A complex series of biochemical and molecular mechanisms (e.g. the release of ROS/NOS, proapoptotic proteins and proinflammatory cytokine; neuronal depolarization, Ca2+ accumulation and so on) impair the neurologic functions of cerebral ischemia and stroke. We have known for some time that the epidemiology of human stroke is sexually dimorphic until late in life, well beyond the years of reproductive senescence and menopause. The principal mammalian estrogen (17β estradiol or E2) is neuroprotective in many types of brain injury and has been the major focus of investigation over the past several decades. However the incidence of stroke in women is lower than in men until decades past menopause, suggesting that factors beyond sex hormone contribute to these epidemiological sex differences. So a new concept is emerging: both sex steroids and biologic sex are important factors in clinical and experimental strokes. In this review, we will address sex steroids and gender differences in influencing the mechanisms and outcomes of brain ischemia stroke. These sex differences need to be identified which could help future translation to human neuroprotection.

Role of testosterone in memory impairment of Alzheimer disease induced by Streptozotocin in male rats

BACKGROUND AND PURPOSE OF THE STUDY

Recent studies demonstrate that androgens, beyond regulating sexual behavior, exert several neuroprotective functions in the brain. The present study was designed to explore effect of testosterone in memory impairment induced by intra- cerebroventricular (icv) injection of streptozotocin (STZ) as a model of sporadic AD.

METHODS

Study was carried out on male Wistar rats. Animals were randomly divided into 11 equal groups. Experimental model of AD was induced by bilateral icv injection of STZ at the dose of 750 μg/Rat/10 μl ACSF at days 1 and 3. STZ-induced memory impairment was assessed two weeks after the last dose of STZ by using a passive avoidance task (1 mA). The interval between the placement of animals in the illuminated chamber and the entry into the dark chamber was measured as a step-through latency (STL). Castration was performed by surgical removing of testis and behavioral study of memory impairment was done after 4 weeks.

RESULTS

Results of this study showed that icv injection of STZ could induce marked (p < 0.05) memory impairment at the dose of 750 μg/Rat/dissolve10 μl CSF/bilateral/days 1 and 3. Therefore, we used this dose of STZ for induction of experimental model of AD. Memory was worsened in castrated rats (P < 0.05) when compared with normal and sham-operated animals. Testosterone replacement therapy (1 mg/kg, sc, for 6 days) in 4 week castrated rats restored memory up to the level of control groups. Testosterone had not any significant effect on memory impairments of non-castrated rats.

MAJOR CONCLUSION

According to the obtained results it can be concluded that testosterone improves cognitive and memory impairment of AD. We suggest that testosterone replacement therapy may have beneficial effect in ameliorating memory impairments of senile patients suffering from AD. Further clinical studies should be carried out to prove possible useful effect of testosterone as an adjuvant therapy in AD.

Factor structure and psychometric properties of the trier inventory for chronic stress (TICS) in a representative German sample

Background

Chronic stress results from an imbalance of personal traits, resources and the demands placed upon an individual by social and occupational situations. This chronic stress can be measured using the Trier Inventory for Chronic Stress (TICS). Aims of the present study are to test the factorial structure of the TICS, report its psychometric properties, and evaluate the influence of gender and age on chronic stress.

Methods

The TICS was answered by N = 2,339 healthy participants aged 14 to 99. The sample was selected by random-route sampling. Exploratory factor analyses with Oblimin-rotated Principal Axis extraction were calculated. Confirmatory factor analyses applying Robust Maximum Likelihood estimations (MLM) tested model fit and configural invariance as well as the measurement invariance for gender and age. Reliability estimations and effect sizes are reported.

Results

In the exploratory factor analyses, both a two-factor and a nine-factor model emerged. Confirmatory factor analyses resulted in acceptable model fit (RMSEA), with model comparison fit statistics corroborating the superiority of the nine-factor model. Most factors were moderately to highly intercorrelated. Reliabilities were good to very good. Measurement invariance tests gave evidence for differential effects of gender and age on the factor structure. Furthermore, women and younger individuals, especially those aged 35 to 44, tended to report more chronic stress than men and older individuals.

Conclusions

The proposed nine-factor structure could be factorially validated, results in good scale reliability, and heuristically can be grouped by two higher-order factors: "High Demands" and "Lack of Satisfaction". Age and gender represent differentiable and meaningful contributors to the perception of chronic stress.

Introduction to the interaction between gonadal steroids and the central nervous system

The sex steroids are frequently referred to as the gonadal steroids and are erroneously assumed to be exclusively linked to the ovaries in women or the testes in men and the functions of the reproductive tract. This chapter will provide an overview of some of the extragonadal effects of these hormones, focusing on the central nervous system, and the mechanisms of hormone action. Hormone synthesis and metabolism within the CNS will be discussed with particular focus on the role of aromatase. Sex steroids exert many of their effects via intracellular receptors and these genomic responses tend to be slow in onset, however, some responses to steroids occur more quickly and are mediated via membrane receptors and involve interactions with many different transduction pathways to produce a diverse array of responses. These complexities do pose challenges but also offer opportunity for novel approaches for therapeutic exploitation as the pharmacological tools with which to modulate systems become increasingly available.

Pax6 represses androgen receptor-mediated transactivation by inhibiting recruitment of the coactivator SPBP

The androgen receptor (AR) has a central role in development and maintenance of the male reproductive system and in the etiology of prostate cancer. The transcription factor Pax6 has recently been reported to act as a repressor of AR and to be hypermethylated in prostate cancer cells. SPBP is a transcriptional regulator that previously has been shown to enhance the activity of Pax6. In this study we have identified SPBP to act as a transcriptional coactivator of AR. We also show that Pax6 inhibits SPBP-mediated enhancement of AR activity on the AR target gene probasin promoter, a repression that was partly reversed by increased expression of SPBP. Enhanced expression of Pax6 reduced the amount of SPBP associated with the probasin promoter when assayed by ChIP in HeLa cells. We mapped the interaction between both AR and SPBP, and AR and Pax6 to the DNA-binding domains of the involved proteins. Further binding studies revealed that Pax6 and SPBP compete for binding to AR. These results suggest that Pax6 represses AR activity by displacing and/or inhibiting recruitment of coactivators to AR target promoters. Understanding the mechanism for inhibition of AR coactivators can give rise to molecular targeted drugs for treatment of prostate cancer.

Testostérone et contrôle central de l’érection

La testostérone orchestre l’organisation périnatale et l’activation adulte des structures nerveuses cérébrales et spinales impliquées dans l’expression du comportement sexuel mâle. Cette revue décrit brièvement les différents effets de la testostérone dans la régulation de la motivation sexuelle et de l’érection, et les modèles génétiques générés, jusqu’à présent, dans le but d’élucider ses mécanismes d’action centraux.

Sex shapes experimental ischemic brain injury

Biologic sex and sex steroids are important factors in clinical and experimental stroke. This review evaluates key evidence that biological sex strongly alters mechanisms and outcomes from cerebral ischemia. The role of androgens in male stroke is understudied and important to pursue given that male sex is a well known risk factor for human stroke. To date, male sex steroids remain largely evaluated at the bench rather than the bedside. We review recent advances in our understanding of androgens in the context of ischemic cell death and neuroprotection. We also highlight some possible molecular mechanisms by which androgens impact ischemic outcomes.

Spatiotemporal expression of androgen receptors in the female rat brain during the oestrous cycle and the impact of exogenous androgen administration: a comparison with gonadally intact males

Little is known about the regulation and cellular distribution of androgen receptors (ARs) in female rodent brains at various stages of the oestrous cycle. This information is critical for further studies of androgen signalling in the regulation of brain function under physiological and pathophysiological conditions. In this report, we show that the distribution of AR immunoreactivity in the female rat brain is consistent with reported AR mRNA hybridisation signals in the male brain, except for the dentate gyrus of the hippocampus. Immunohistochemical and Western blot analyses performed herein revealed that the onset of region-specific changes in AR proteins was strongly correlated with circulating and ovarian levels of estradiol and testosterone across the oestrous cycle. During the metestrus and diestrus stages, however, the highest levels of AR expression were abolished by chronic dihydrotestosterone (DHT) treatment. This demonstrates that fluctuations in endogenous androgens are required for the regulation of AR expression in the female rat brain. Colocalisation studies revealed that: (1) anatomical variations in AR protein localisation existed between female and male brains, (2) AR immunoreactivity was both neuronal and non-neuronal, and (3) AR protein expression was lower in female rat brains at all stages of the oestrous cycle compared to age-matched males. Our results indicate the presence of regional sex differences in AR expression and changes in the proportion of AR between different subcellular compartments. Furthermore, DHT was found to down-regulate the level of AR in the subcellular compartment in females in a region-specific manner. As a whole, the present study provides the first step toward understanding the dynamics of AR expression and regulation in the brain during normal physiological conditions and for differences in neuronal androgen effects based on sex.

Sexual dimorphism of oligodendrocytes is mediated by differential regulation of signaling pathways

Sexual dimorphism of white matter has not been considered important, the assumption being that sex hormones are not essential for glial development. We recently showed exogenous hormones in vivo differentially regulate in male and female rodents the life span of oligodendrocytes (Olgs) and amount of myelin (Cerghet et al. [2006] J. Neurosci. 26:1439-1447). To determine which hormones regulate male and female Olg development, we prepared enriched Olg cultures grown in serum-free medium with estrogen (E2), progesterone (P2), and dihydrotestosterone (DHT) or their combinations. P2 significantly increased the number of Olgs in both sexes, but more so in females; E2 had minor effects on Olg numbers; and DHT reduced Olgs numbers in both sexes, but more so in females. Combinations of hormones affected Olg numbers differently from single hormones. The change in Olg numbers was due to changes not in proliferation but rather in survival. P2 increased pAKT by many-fold, but MAPK levels were unchanged, indicating that activation of the Akt pathway by P2 is sufficient to regulate Olg differentiation. DHT reduced pAkt in both sexes but differentially increased pMAPK in males and decreased it in females. Stressing Olgs reveals that both sexes are protected by P2, but females are slightly better protected than males. Females always showed greater differences than males regarding changes in Olg numbers and in signaling molecules. Given the greater fluctuation of neurosteroids in women than in men and the higher incidence of multiple sclerosis (MS) in women, these sexually dimorphic differences may contribute to differences in male and female MS lesions.

Dihydrotestosterone activates CREB signaling in cultured hippocampal neurons

Although androgens induce numerous actions in brain, relatively little is known about which cell signaling pathways androgens activate in neurons. Recent work in our laboratory showed that the androgens testosterone and dihydrotestosterone (DHT) activate androgen receptor (AR)-dependent mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling. Since the transcription factor cyclic AMP response element binding protein (CREB) is a downstream effector of MAPK/ERK and androgens activate CREB in non-neuronal cells, we investigated whether androgens activate CREB signaling in neurons. First, we observed that DHT rapidly activates CREB in cultured hippocampal neurons, as evidenced by CREB phosphorylation. Further, we observed that DHT-induced CREB phosphorylation is AR-dependent, as it occurs in PC12 cells stably transfected with AR but in neither wild-type nor empty vector-transfected cells. Next, we sought to identify the signal transduction pathways upstream of CREB phosphorylation using pharmacological inhibitors. DHT-induced CREB phosphorylation in neurons was found to be dependent upon protein kinase C (PKC) signaling but independent of MAPK/ERK, phosphatidylinositol 3-kinase, protein kinase A, and Ca(2+)/calmodulin-dependent protein kinase IV. These results demonstrate that DHT induces PKC-dependent CREB signaling, which may contribute to androgen-mediated neural functions.

Testosterone and dihydrotestosterone differentially improve cognition in aged female mice

Compared with age-matched male mice, female mice experience a more severe age-related cognitive decline (ACD). Since androgens are less abundant in aged female mice compared with aged male mice, androgen supplementation may enhance cognition in aged female mice. To test this, we assessed behavioral performance on a variety of tasks in 22- to 24-mo-old gonadally intact female mice treated for 6 wk with silastic capsules containing either testosterone (T) or dihydrotestosterone (DHT) or empty capsules (placebo). Compared with placebo-treated mice, spatial memory retention in the water maze was enhanced by testosterone treatment, but not DHT treatment. In contrast, DHT treatment improved passive avoidance (PA) retention, while T treatment only did so marginally. These data support that androgen supplementation in old female mice improves cognitive performance differentially depending upon the type of hormone treatment and cognitive task.

Androgens and the brain

Steroids arriving from the gonads via the circulation modulate brain function, affecting gender differentiation and sexually differentiated behavioral responses, but also the ability of the brain to process, store and retrieve sensory information. Androgens play a pivotal neuroactive role during the "organizational/developmental" phase, mainly in the fetal-neonatal period, when participated to the formation of neuronal circuits, as well as during the aging process when it has been demonstrated to directly affect hippocampal spine synapse density, suggesting a physiopathological role for androgen in the modulation cognitive function and development of neurodegenerative disease. The present short review will focus on the neuroactive effect of androgen with particular regard to the Delta4 and Delta5 androgen replacement therapy.

A novel variant of the putative demethylase gene, s-JMJD1C, is a coactivator of the AR

Evidence is accumulating in support of the view that tissue-specific effects of steroid hormones depend on the recruitment of nuclear receptor comodulator proteins. The latter interact directly with the hormone receptors and modify their transcriptional effects on specific target genes. The mechanisms of comodulator influence on nuclear receptor-controlled gene transcription is only partially understood. Here, we describe the discovery of a new AR coactivator which belongs to the JmjC containing enzyme family as a novel variant of JMJD1C (jumonji domain-containing 1C). By using a fragment of the human AR (aa 325-919) as bait in a yeast two-hybrid screen, a region of the human JMJD1C gene was identified as interacting with AR. A novel splice variant s-JMJD1C was amplified by RACE, and the binding to AR was analysed by GST-pull-down and mammalian one-hybrid experiments. As a nuclear-localized protein, the s-JMJD1C gene is expressed in a variety of human tissues. In the brain, this protein is present in several, but not confined to, AR-expressing neuronal populations and its abundance varies with the hormonal status in a region-specific fashion. Interestingly, the expression of s-JMJD1C is reduced in breast cancer tumors and significantly higher in normal breast tissues indicating a putative role in tumor suppression. As s-JMJD1C has putative demethylase activity, removal of methylation seems to be important for nuclear receptor-based gene regulation.

Single opioid administration modifies gonadal steroids in both the CNS and plasma of male rats

While morphine remains one of the most widely used opioids for the treatment of painful conditions, other opioids are also commonly employed. Because of the interactions between opioids and gonadal hormones, in particular opioid-induced hypogonadism, this study investigated the effects of widely used opioids on plasma testosterone and estradiol levels and brain testosterone levels in male rats. Animals were s.c. injected with two concentrations of morphine (5 or 10 mg/kg), fentanyl (0.05 or 0.1 mg/kg), tramadol (10 or 40 mg/kg), buprenorphine (0.05 or 0.1 mg/kg) or saline (0.7 ml/kg). Four or 24 h after treatment, the rats were deeply anesthetized to collect blood samples from the abdominal aorta and to perfuse the brains with saline. Plasma and brain hormone levels were measured by radioimmunoassay. In rats studied 4 h after treatment, all the opioids except tramadol 10 mg/kg decreased plasma testosterone in comparison with saline administration. At the same time, plasma estradiol levels were lower than control in the groups treated with the low doses of morphine, tramadol and buprenorphine, while estradiol remained at control levels in the other groups. Twenty-four hours after treatment, plasma testosterone levels were different (higher) than control in the animals treated with the low doses of morphine, fentanyl and buprenorphine. Estradiol was lower than control in the low dose groups, while the high doses did not produce any changes with respect to control. Four hours after treatment, brain testosterone was drastically decreased in all groups except buprenorphine, in which it remained at control levels. All groups returned to control levels at 24 h after treatment. In conclusion, opioids exert important effects on plasma and CNS sex hormone levels. The different magnitude and time-course of the effects of the different opiates on testosterone and estradiol levels are likely due to their different mechanism of action.