Estrogen receptor-alpha gene expression in the cortex: sex differences during development and in adulthood

Treatment with brain specific estrogen prodrug ameliorates cognitive effects of surgical menopause in mice

Menopause is an endocrine shift leading to increased vulnerability for cognitive impairment and dementia risk factors, in part due to loss of neuroprotective circulating estrogens. Systemic replacement of estrogen post-menopause has limitations, including risk for estrogen-sensitive cancers. A promising therapeutic approach therefore might be to deliver estrogen only to the brain. We examined whether we could enhance cognitive performance by delivering estrogen exclusively to the brain in ovariectomized mice (a surgical menopause model). We treated mice with the prodrug 10β,17β-dihydroxyestra-1,4-dien-3-one (DHED), which can be administered systemically but is converted to 17β-estradiol only in the brain. Young and middle-aged C57BL/6 J mice received ovariectomy and subcutaneous implant containing vehicle or DHED and underwent cognitive testing to assess memory after 1-3.5 months of treatment. Low and medium doses of DHED did not alter metabolic status in middle-aged mice. In both age groups, DHED treatment improved spatial memory in ovariectomized mice. Additional testing in middle-aged mice showed that DHED treatment improved working and recognition memory in ovariectomized mice. These results lay the foundation for future studies determining if this intervention is as efficacious in models of dementia with comorbid risk factors.

Executive functioning in child victims of sexual abuse: A multi-informant comparative study

BACKGROUND

Research examining the association between child sexual abuse and executive functions is limited. Yet, exposure to traumatic situations at a young age has been associated with changes in the prefrontal cortex, which hosts executive functions (Wesarg et al., 2020). These functions are crucial for social adaptation, as they make it possible to inhibit maladaptive behavior and respond flexibly to the demands of the environment. As middle childhood is a sensitive period for the development of self-regulatory abilities, exploring executive functioning in school-age children could provide potential intervention targets (Dajani & Uddin, 2015).

OBJECTIVE

Using multiple informants, this study compared executive functioning of sexually abused children to that of non-sexually victimized children and examined whether the differences were moderated by sex.

METHODS

The sample consisted of 225, 6-to-12 years old children with a history of child sexual abuse (CSA) and 97 children without a history of CSA. Children completed two executive functioning tasks measuring cognitive flexibility and inhibition. Parents and teachers completed questionnaires evaluating children's executive functioning.

RESULTS

In comparison to non-abused children, children with a history of CSA displayed greater executive functioning difficulties as assessed by both informant-reported questionnaires and self-completed tasks. Significant interaction effects were found, such as CSA predicting lower inhibition and executive functions at school in boys but not in girls.

CONCLUSION

This study is a first step in understanding the association between CSA and executive functioning and offers a clearer picture of the differential impact of sexual trauma according to children's sex.

Comparative analysis of gonadal hormone receptor expression in the postnatal house mouse, meadow vole, and prairie vole brain

The socially monogamous prairie vole (Microtus ochrogaster) and promiscuous meadow vole (Microtus pennsylvanicus) are closely related, but only prairie voles display long-lasting pair bonds, biparental care, and selective aggression towards unfamiliar individuals after pair bonding. These social behaviors in mammals are largely mediated by steroid hormone signaling in the social behavior network (SBN) of the brain. Hormone receptors are reproducible markers of sex differences that can provide more information than anatomy alone and can even be at odds with anatomical dimorphisms. We reasoned that behaviors associated with social monogamy in prairie voles may emerge in part from unique expression patterns of steroid hormone receptors in this species, and that these expression patterns would be more similar across males and females in prairie than in meadow voles or the laboratory mouse. To obtain insight into steroid hormone signaling in the developing prairie vole brain, we assessed expression of estrogen receptor alpha (Esr1), estrogen receptor beta (Esr2), and androgen receptor (Ar) within the SBN, using in situ hybridization at postnatal day 14 in mice, meadow, and prairie voles. We found species-specific patterns of hormone receptor expression in the hippocampus and ventromedial hypothalamus, as well as species differences in the sex bias of these markers in the principal nucleus of the bed nucleus of the stria terminalis. These findings suggest the observed differences in gonadal hormone receptor expression may underlie species differences in the display of social behaviors.

Machine learning reveals common transcriptomic signatures across rat brain and placenta following developmental organophosphate ester exposure

Toxicogenomics is a critical area of inquiry for hazard identification and to identify both mechanisms of action and potential markers of exposure to toxic compounds. However, data generated by these experiments are highly dimensional and present challenges to standard statistical approaches, requiring strict correction for multiple comparisons. This stringency often fails to detect meaningful changes to low expression genes and/or eliminate genes with small but consistent changes particularly in tissues where slight changes in expression can have important functional differences, such as brain. Machine learning offers an alternative analytical approach for "omics" data that effectively sidesteps the challenges of analyzing highly dimensional data. Using 3 rat RNA transcriptome sets, we utilized an ensemble machine learning approach to predict developmental exposure to a mixture of organophosphate esters (OPEs) in brain (newborn cortex and day 10 hippocampus) and late gestation placenta of male and female rats, and identified genes that informed predictor performance. OPE exposure had sex specific effects on hippocampal transcriptome, and significantly impacted genes associated with mitochondrial transcriptional regulation and cation transport in females, including voltage-gated potassium and calcium channels and subunits. To establish if this holds for other tissues, RNAseq data from cortex and placenta, both previously published and analyzed via a more traditional pipeline, were reanalyzed with the ensemble machine learning methodology. Significant enrichment for pathways of oxidative phosphorylation and electron transport chain was found, suggesting a transcriptomic signature of OPE exposure impacting mitochondrial metabolism across tissue types and developmental epoch. Here we show how machine learning can complement more traditional analytical approaches to identify vulnerable "signature" pathways disrupted by chemical exposures and biomarkers of exposure.

Brain Specific Estrogen Ameliorates Cognitive Effects of Surgical Menopause in Mice

Menopause is a major endocrinological shift that leads to an increased vulnerability to the risk factors for cognitive impairment and dementia. This is thought to be due to the loss of circulating estrogens, which exert many potent neuroprotective effects in the brain. Systemic replacement of estrogen post-menopause has many limitations, including increased risk for estrogen-sensitive cancers. A more promising therapeutic approach therefore might be to deliver estrogen only to the brain thus limiting adverse peripheral side effects. We examined whether we could enhance cognitive performance by delivering estrogen exclusively to the brain in post-menopausal mice. We modeled surgical menopause via bilateral ovariectomy (OVX). We treated mice with the pro-drug 10β,17β-dihydroxyestra-1,4-dien-3-one (DHED), which can be administered systemically but is converted to 17β-estradiol only in the brain. Young (2.5-month) and middle-aged (11-month-old) female C57BL/6J mice received ovariectomy and a subcutaneous implant containing vehicle (cholesterol) or DHED. At 3.5 months old (young group) and 14.5 months old (middle-aged group), mice underwent behavior testing to assess memory. DHED did not significantly alter metabolic status in middle-aged, post-menopausal mice. In both young and middle-aged mice, the brain-specific estrogen DHED improved spatial memory. Additional testing in middle-aged mice also showed that DHED improved working and recognition memory. These promising results lay the foundation for future studies aimed at determining if this intervention is as efficacious in models of dementia that have comorbid risk factors.

Cortical Development Mediates Association of Prenatal Maternal Depressive Symptoms and Child Reward Sensitivity: A Longitudinal Study

OBJECTIVE

Maternal depression during pregnancy has long-term impacts on offspring. This study used neuroimaging and behavioral data from children aged 4 to 6 years and investigated whether prenatal maternal depressive symptoms (pre-MDS) associated with child cortical morphological development and subsequent reward-related behaviors in preschoolers.

METHOD

Pre-MDS was measured using the Edinburgh Postnatal Depression Scale at 26 weeks of pregnancy. Children (n = 130) underwent structural magnetic resonance imaging (MRI) at both 4 and 6 years of age. Child sensitivity to reward and punishment was reported by mothers when children were 6 years of age. Linear mixed-effect models examined pre-MDS associations with child cortical thickness and surface area. Mediation analysis examined whether cortical development mediated associations between pre-MDS and child sensitivity to reward and punishment.

RESULTS

The 3-way interactions of pre-MDS, age, and sex on cortical thickness and surface area were not statistically significant. We found a significant interaction of pre-MDS with sex on the cortical surface area but not on thickness or their growth from 4 to 6 years, adjusting for ethnicity, socioeconomic status, baseline age, and postnatal MDS as covariates. Higher pre-MDS scores were associated with larger surface areas in the prefrontal cortex, superior temporal gyrus, and superior parietal lobe (SPL) in boys, whereas the opposite pattern was seen in girls. The SPL surface area mediated the relationship between pre-MDS and sensitivity to reward in girls.

CONCLUSION

Prenatal maternal depression alters the cortical morphology of pre-schoolers in a sex-dependent manner.

Estrogen Receptor-A in Medial Preoptic Area Contributes to Sex Difference of Mice in Response to Sevoflurane Anesthesia

A growing number of studies have identified sex differences in response to general anesthesia; however, the underlying neural mechanisms are unclear. The medial preoptic area (MPA), an important sexually dimorphic structure and a critical hub for regulating consciousness transition, is enriched with estrogen receptor alpha (ERα), particularly in neuronal clusters that participate in regulating sleep. We found that male mice were more sensitive to sevoflurane. Pharmacological inhibition of ERα in the MPA abolished the sex differences in sevoflurane anesthesia, in particular by extending the induction time and facilitating emergence in males but not in females. Suppression of ERα in vitro inhibited GABAergic and glutamatergic neurons of the MPA in males but not in females. Furthermore, ERα knockdown in GABAergic neurons of the male MPA was sufficient to eliminate sex differences during sevoflurane anesthesia. Collectively, MPA ERα positively regulates the activity of MPA GABAergic neurons in males but not in females, which contributes to the sex difference of mice in sevoflurane anesthesia.

Effects of Dietary Soy Protein Isolate Versus Isoflavones Alone on Poststroke Skilled Ladder Rung Walking and Cortical mRNA Expression Differ in Adult Male Rats

Dietary soy protein isolate (SPI) and the isoflavones daidzein and genistein have been shown to provide neuroprotection from stroke. However, the mechanisms remain uncertain. We sought to determine whether the addition of isoflavones to a diet containing caseinate (CAS) as the protein source would induce behavioral neuroprotection similar to that seen previously in rats fed SPI. Furthermore, we aimed to characterize the baseline and poststroke expression of mRNAs involved in pathways previously published as perhaps mediating soy-based neuroprotection from stroke and other markers of neuronal plasticity, oxidative stress, and inflammation. Adult male rats were fed a semipurified diet containing (1) sodium caseinate (CAS), (2) CAS plus daidzein and genistein (CAS+ISO), or (3) SPI for 2 weeks. A subset of rats was euthanized, and tissue was collected for quantitative real-time PCR (qPCR). Remaining rats underwent a middle cerebral artery occlusion to induce a stroke. Samples for qPCR were collected on day 3 poststroke. Rats fed SPI made fewer errors on the skilled ladder rung walking task after stroke compared to rats fed CAS (P < .05). Rats fed CAS+ISO were not different from rats fed CAS or SPI. Significant effects of diet were found at day 0 for Syp, Pparg, and Ywhae and at day 3 for Rtn4 expression. We concluded that the benefits of SPI are not solely attributable to daidzein and genistein.

Translating the Transcriptome: Sex Differences in the Mechanisms of Depression and Stress, Revisited

The past decade has produced a plethora of studies examining sex differences in the transcriptional profiles of stress and mood disorders. As we move forward from accepting the existence of extensive molecular sex differences in the brain to exploring the purpose of these sex differences, our approach must become more systemic and less reductionist. Earlier studies have examined specific brain regions and/or cell types. To use this knowledge to develop the next generation of personalized medicine, we need to comprehend how transcriptional changes across the brain and/or the body relate to each other. We provide an overview of the relationships between baseline and depression/stress-related transcriptional sex differences and explore contributions of preclinically identified mechanisms and their impacts on behavior.

Perinatal low-dose bisphenol AF exposure impairs synaptic plasticity and cognitive function of adult offspring in a sex-dependent manner

Bisphenol AF (BPAF), a kind of the ideal substitutes of Bisphenol A (BPA), has frequently been detected in environmental media and biological samples. Numerous studies have focused on the reproductive toxicity, cardiotoxicity and endocrine disrupting toxicity of BPAF. However, little evidence is available on neurodevelopmental toxicity of BPAF. Here, our study is to evaluate the effect of perinatal BPAF exposure (0, 0.34, 3.4 and 34 mg/kg body weight/day, correspond to Ctrl, low-, medium- and high-dose groups) on the cognitive function of adult mouse offspring. This study firstly found that perinatal BPAF exposure caused cognitive impairments of mouse offspring, in which male offspring was more sensitive than female offspring in low- and medium-dose BPAF groups. Furthermore, the dendritic arborization and complexity of hippocampal CA1 and DG neurons in male offspring were impaired in all BPAF groups, and these effects were only found in high-dose BPAF group for female offspring. The damage of BPAF to dendritic spines, and the structural basis of learning and memory, was found in male offspring but not in females. Correspondingly, perinatal BPAF exposure significantly downregulated the expressions of hippocampal PSD-95 and Synapsin-1 proteins, and male offspring was more vulnerable than female offspring. Meanwhile, we explored the alteration of hippocampal estrogen receptors (ERs) to explain the sex specific impairment of cognitive function in low- and medium-dose BPAF groups. The results showed that perinatal BPAF exposure significantly decreased the expression of ERα in male offspring in a dose-dependent manner, but not in female offspring. In addition, we found that perinatal BPAF exposure can disordered the balance of oxidation and antioxidation in hippocampus of male offspring. In summary, perinatal low-dose bisphenol AF exposure impairs synaptic plasticity and cognitive function of adult offspring in a sex-dependent manner. The present results provide a pierce of potential mechanism of BPAF-caused neurodevelopmental toxicity.

An Adolescent Sensitive Period for Threat Responding: Impacts of Stress and Sex

Anxiety and fear-related disorders peak in prevalence during adolescence, a window of rapid behavioral development and neural remodeling. However, understanding of the development of threat responding and the underlying neural circuits remains limited. Preclinical models of threat conditioning and extinction have provided an unparalleled glimpse into the developing brain. In this review we discuss mouse and rat studies on the development of threat response regulation, with a focus on the adolescent period. Evidence of nonlinear patterns of threat responding during adolescence and the continued development of the underlying circuitry is highly indicative of an adolescent sensitive period for threat response regulation. While we highlight literature in support of this unique developmental window, we also emphasize the need for causal studies to clarify the parameters defining such a sensitive period. In doing so, we explore how stress and biological sex affect the development and expression of threat response regulation during adolescence and beyond. Ultimately, a deeper understanding of how these factors interact with and affect developmental trajectories of learning and memory will inform treatment and prevention strategies for pediatric anxiety disorders.

Assessment of conditioned fear extinction in male and female adolescent rats

Pavlovian fear conditioning and extinction have been widely studied across many species to understand emotional learning and memory. Importantly, it is becoming clear that these processes are affected by sex and age. In adult rodents and humans, sex differences are evident in extinction, with estradiol playing a significant role. In adolescence, an extinction deficit has been reported in rodents and humans. However, the influence of sex on extinction during adolescence is unknown. This is surprising, since adolescence coincides with the onset of hormone cycling, and therefore it might be expected that hormones fluctuations exert a more profound effect at this time. Therefore, we examined Pavlovian fear conditioning and extinction in adolescent male and female rats. In experiment 1, 35-day-old male and female rats were exposed to 6 pairings of a conditioned stimulus (CS, a tone) with an aversive unconditioned stimulus (US, a footshock). The next day they were extinguished in a contextually distinct chamber, via 60 presentations of the CS without the US. Extinction recall was tested 24 hours later in the extinction context. Estrous phase was monitored by cytology on vaginal smears taken 1 hour after each behavioral session. In experiment 2, male and female rats were given sham surgery or gonadectomy at 21 days of age. They were then trained and tested as for experiment 1. We observed that females in proestrus or met/diestrus during extinction showed delayed extinction and impaired extinction recall the next day compared to males. Ovariectomy enhanced extinction for female rats, but orchidectomy delayed extinction for males. Plasma analyses showed that met/di/proestrus phases were associated with high estradiol levels. These findings suggest that high plasma estradiol levels impair extinction for adolescent females. These results contradict what is reported in adult animals, suggesting that hormonal influences on extinction are dependent on age. Given that impaired extinction is widely used as a model to understand resistance to exposure-based therapies, our findings have important implications for understanding mental health treatments in adolescents.

Oestradiol, threat conditioning and extinction, post-traumatic stress disorder, and prolonged exposure therapy: A common link

The accumulating evidence regarding the impact of estradiol on learning and memory synergized studies to examine its influence on enhancing animal's ability to quell fear and anxiety. In this review, we first provide a foundational platform regarding the impact of oestradiol on cellular mechanisms of learning and memory and we review recent advances from rodent and human data showing that oestrogen enhances extinction learning across species. We then propose clinical application to these data. We discuss the potential role of oestradiol variance on the aetiology, maintenance and treatment for post-traumatic stress disorder. Specifically, we argue that the use of oestradiol as an adjunct to prolonged exposure (PE) therapy for PTSD may provide a new treatment approach for enhancing the efficacy of PE in women with PTSD. This could advance our understanding of the mechanisms of PTSD and help tailor sex-specific treatments for this disorder.

Blocking of Estradiol Receptors ERα, ERβ and GPER During Development, Differentially Alters Energy Metabolism in Male and Female Rats

Estradiol not only participates in the regulation of energy metabolism in adulthood, but also during the first stages of life as it modulates the alterations induced by under- and over-nutrition. The objectives of the present study were to determine: 1) If estradiol is involved in the normal programming of energy metabolism in rats; 2) If there is a specific window of time for this programming and 3) If males and females are differentially vulnerable to the action of this hormone. Estrogen receptors (ER) α, ERβ and GPER were blocked by their specific antagonists MPP, PHTPP and G15, respectively, from postnatal day (P) 1 (the day of birth) to P5 or from P5 to P13. Physiological parameters such as body weight, fat depots and caloric intake were then analysed at P90. Hypothalamic AgRP, POMC, MC4R, ERα, ERβ and GPER mRNA levels and plasma levels of estradiol, were also studied. We found that blocking ER receptors from P5 to P13 significantly decreases long-term body weight in males and hypothalamic POMC mRNA levels in females. The blocking of ERs from P1 to P5 only affected plasma estradiol levels in females. The present results indicate programming actions of estradiol from P5 to P13 on body weight in male and POMC expression in female rats and emphasize the importance of including both sexes in metabolic studies. It is necessary to unravel the mechanisms that underlie the actions of estradiol on food intake, both during development and in adulthood, and to determine how this programming differentially takes place in males and females.

Gender differences in tolerance to the hyperthermia mediated by the synthetic cathinone methylone

The toxidrome associated with death from the synthetic cathinones includes hyperthermia as part of the sympathomimetic syndrome. Here, we examine the gender differences in the development of tolerance to the hyperthermia mediated by the synthetic cathinone methylone. In addition to temperature changes, expression differences in genes encoding the uncoupling proteins (UCP) 1 & 3, and TGR5 in skeletal muscle (SKM) and brown adipose tissue (BAT) were examined. Male and female rats were treated weekly with methylone (10 mg/kg). The females developed a tolerance to the methylone-induced hyperthermia by week two of drug exposure. By the third week, females displayed a hypothermic response to methylone. Conversely, males continued to display a hyperthermic response up to and including week four. At week four, the males demonstrated a significantly lower hyperthermia and a complete tolerance seen at week five with no significant hyperthermia. Tissue samples collected after treatment on the sixth week indicate that chronic exposure to methylone reduced UCP1 expression in SKM and BAT of the female rats. Only the females displayed increased TGR5 expression in BAT. UCP3 expression increased in both the SKM and BAT of the males and females. The differences between responses in male and female subjects further demonstrate the need for gender studies in the toxicology associated with drugs with abuse potential.

Sex Differences in the Epigenome: A Cause or Consequence of Sexual Differentiation of the Brain?

Females and males display differences in neural activity patterns, behavioral responses, and incidence of psychiatric and neurological diseases. Sex differences in the brain appear throughout the animal kingdom and are largely a consequence of the physiological requirements necessary for the distinct roles of the two sexes in reproduction. As with the rest of the body, gonadal steroid hormones act to specify and regulate many of these differences. It is thought that transient hormonal signaling during brain development gives rise to persistent sex differences in gene expression via an epigenetic mechanism, leading to divergent neurodevelopmental trajectories that may underlie sex differences in disease susceptibility. However, few genes with a persistent sex difference in expression have been identified, and only a handful of studies have employed genome-wide approaches to assess sex differences in epigenomic modifications. To date, there are no confirmed examples of gene regulatory elements that direct sex differences in gene expression in the brain. Here, we review foundational studies in this field, describe transcriptional mechanisms that could act downstream of hormone receptors in the brain, and suggest future approaches for identification and validation of sex-typical gene programs. We propose that sexual differentiation of the brain involves self-perpetuating transcriptional states that canalize sex-specific development.

Perinatal High-Fat Diet and Bisphenol A: Effects on Behavior and Gene Expression in the Medial Prefrontal Cortex

Both high-fat diets (HFD) and bisphenol A (BPA), an environmental endocrine disruptor, are prevalent in industrialized societies. Previous studies have detected separate effects of BPA and HFD; however, none have assessed possible interactive effects. Here, pregnant dams consumed 0, 40, or 400 µg BPA/kg/day and were fed either a control (CON; 15.8% kcal fat) or HFD (45% kcal fat) from gestational day 2 through parturition. The pups were individually dosed with BPA from postnatal days (P) 1-10, while the dams continued to consume one of the two diets. Maternal behavior increased with the HFD while the offspring's periadolescent social play decreased with BPA, but no interactive effects were observed. Neither HFD nor BPA exposure changed performance on a social recognition task, and only BPA had an effect on the elevated plus maze. BPA increased several cytokines in the medial prefrontal cortex (mPFC) of P10 males but not females. Expression of several genes related to hormone synthesis and receptors, inflammation, oxidative stress, and apoptosis in the mPFC on P10 and P90 were altered due to BPA and/or HFD exposure with rare interactive effects. BPA resulted in an increase in the gene expression of Esr1 in the mPFC of females on both P10 and P90. Epigenetic analysis on P90 did not show a change in methylation or in the levels of pre-mRNA or microRNA. Thus, perinatal BPA and HFD have separate effects but rarely interact.

Ischemic stroke across sexes: What is the status quo?

Stroke prevalence is expected to increase in the next decades due to the aging of the Western population. Ischemic stroke (IS) shows an age- and sex-dependent distribution in which men represent the most affected population within 65 years of age, being passed by post-menopausal women in older age groups. Furthermore, a sexual dimorphism concerning risk factors, presentation and treatment of IS has been widely recognized. In order to address these phenomena, a number of issue have been raised involving both socio-economical and biological factors. The latter can be either dependent on sex hormones or due to intrinsic factors. Although women have poorer outcomes and are more likely to die after a cerebrovascular event, they are still underrepresented in clinical trials and this is mirrored by the lack of sex-tailored therapies. A greater effort is needed in the future to ensure improved treatment and quality of life to both sexes.

Longitudinal effects of developmental bisphenol A, variable diet, and physical activity on age-related methylation in blood

Research indicates that environmental factors can alter DNA methylation, but the specific effects of environmental exposures on epigenetic aging remain unclear. Here, using a mouse model of human-relevant exposures, we tested the hypothesis that early-life exposure to bisphenol A (BPA), variable diet, and/or changes in physical activity would modify rates of age-related methylation at several target regions, as measured from longitudinal blood samples (2, 4, and 10 months old). DNA methylation was quantified at two repetitive elements (LINE-1, IAP), two imprinted genes (Igf2, H19), and one non-imprinted gene (Esr1) in isogenic mice developmentally exposed to Control, Control + BPA (50 µg/kg diet), Western high-fat diet (WHFD), or Western + BPA diets. In blood samples, Esr1 DNA methylation increased significantly with age, but no other investigated loci showed significant age-related methylation. LINE-1 and IAP both showed significant negative environmental deflection by WHFD exposure (P < 0.05). Esr1also showed significant negative environmental deflection by WHFD exposure in female mice (P = 0.02), but not male mice. Physical activity had a non-significant positive effect on age-related Esr1 methylation in female blood, suggesting that it may partially abrogate the effects of WHFD on the aging epigenome. These results suggest that developmental nutritional exposures can modify age-related DNA methylation patterns at a gene related to growth and development. As such, environmental deflection of the aging epigenome may help to explain the growing prevalence of chronic diseases in human populations.

Ischemic stroke across sexes: what is the status quo?

Stroke prevalence is expected to increase in the next decades due to the aging of the Western population. Ischemic stroke (IS) shows an age- and sex-dependent distribution in which men represent the most affected population within 65 years of age, being passed by post-menopausal women in older age groups. Furthermore, a sexual dimorphism concerning risk factors, presentation and treatment of IS has been widely recognized. In order to address these phenomena, a number of issue have been raised involving both socio-economical and biological factors. The latter can be either dependent on sex hormones or due to intrinsic factors. Although women have poorer outcomes and are more likely to die after a cerebrovascular event, they are still underrepresented in clinical trials and this is mirrored by the lack of sex-tailored therapies. A greater effort is needed in the future to ensure improved treatment and quality of life to both sexes.

An examination of sex differences on neurocognitive functioning and behavior problems in maltreated youth

OBJECTIVE

In the developmental traumatology model, the biological construct of sex is considered a moderator that may negatively influence child maltreatment sequelae including those pertaining to neurocognitive function.

METHOD

This study examined sex-differences in neurocognitive function and behavior problems in maltreated boys (n = 42), maltreated girls (n = 56) versus nonmaltreated boys (n = 45) and girls (n = 59). Maltreated boys were hypothesized to have poorer neurocognitive functioning than maltreated girls, and nonmaltreated boys and girls, in all neurocognitive domains, particularly pertaining to executive function and attention. We also examined correlations between cognitive function and parent report of child behavior problems for maltreated and nonmaltreated children.

RESULTS

Maltreated boys performed more poorly on measures of intelligence, attention, language, memory, executive function, and academic achievement in both reading and math than nonmaltreated boys. Maltreated boys did not perform more poorly on these cognitive measures or behavioral measures than maltreated girls, except for one memory measure. Maltreated girls performed more poorly on measures of intelligence, language, memory, executive function, and academic achievement than nonmaltreated girls. Maltreated girls with better visual-spatial skills had more internalizing and externalizing problems. Effect sizes for these sex differences ranged from small to large.

CONCLUSIONS

Both maltreated boys and girls showed poorer cognitive function than their nonmaltreated sex-matched controls. Maltreated girls had subtle sparing of attention and short-term memory (STM). Understanding sex differences in neurocognitive functioning may have implications for designing large population studies of maltreated youth. (PsycINFO Database Record

Genetic and epigenetic factors underlying sex differences in the regulation of gene expression in the brain

There are inherent biological differences between males and females that contribute to sex differences in brain function and to many sex-specific illnesses and disorders. Traditionally, it has been thought that such differences are due largely to hormonal regulation; however, there are also genetic and epigenetic effects caused by the inheritance and unequal dosage of genes located on the X and Y chromosomes. Here we discuss the evidence in favor of a genetic and epigenetic basis for sexually dimorphic behavior, as a consequence of underlying differences in the regulation of genes that drive brain function. A better understanding of sex-specific molecular processes in the brain will provide further insight for the development of novel therapeutic approaches for the treatment of neuropsychiatric disorders characterized by sex differences. © 2016 Wiley Periodicals, Inc.

Phytochemicals Targeting Estrogen Receptors: Beneficial Rather Than Adverse Effects?

In mammals, the effects of estrogen are mainly mediated by two different estrogen receptors, ERα and ERβ. These proteins are members of the nuclear receptor family, characterized by distinct structural and functional domains, and participate in the regulation of different biological processes, including cell growth, survival and differentiation. The two estrogen receptor (ER) subtypes are generated from two distinct genes and have partially distinct expression patterns. Their activities are modulated differently by a range of natural and synthetic ligands. Some of these ligands show agonistic or antagonistic effects depending on ER subtype and are described as selective ER modulators (SERMs). Accordingly, a few phytochemicals, called phytoestrogens, which are synthesized from plants and vegetables, show low estrogenic activity or anti-estrogenic activity with potentially anti-proliferative effects that offer nutraceutical or pharmacological advantages. These compounds may be used as hormonal substitutes or as complements in breast cancer treatments. In this review, we discuss and summarize the in vitro and in vivo effects of certain phytoestrogens and their potential roles in the interaction with estrogen receptors.

Does puberty mark a transition in sensitive periods for plasticity in the associative neocortex?

Postnatal brain development is studded with sensitive periods during which experience dependent plasticity is enhanced. This enables rapid learning from environmental inputs and reorganization of cortical circuits that matches behavior with environmental contingencies. Significant headway has been achieved in characterizing and understanding sensitive period biology in primary sensory cortices, but relatively little is known about sensitive period biology in associative neocortex. One possible mediator is the onset of puberty, which marks the transition to adolescence, when animals shift their behavior toward gaining independence and exploring their social world. Puberty onset correlates with reduced behavioral plasticity in some domains and enhanced plasticity in others, and therefore may drive the transition from juvenile to adolescent brain function. Pubertal onset is also occurring earlier in developed nations, particularly in unserved populations, and earlier puberty is associated with vulnerability for substance use, depression and anxiety. In the present article we review the evidence that supports a causal role for puberty in developmental changes in the function and neurobiology of the associative neocortex. We also propose a model for how pubertal hormones may regulate sensitive period plasticity in associative neocortex. We conclude that the evidence suggests puberty onset may play a causal role in some aspects of associative neocortical development, but that further research that manipulates puberty and measures gonadal hormones is required. We argue that further work of this kind is urgently needed to determine how earlier puberty may negatively impact human health and learning potential. This article is part of a Special Issue entitled SI: Adolescent plasticity.

Sex differences in the brain–an interplay of sex steroid hormones and sex chromosomes

Although considerable progress has been made in our understanding of brain function, many questions remain unanswered. The ultimate goal of studying the brain is to understand the connection between brain structure and function and behavioural outcomes. Since sex differences in brain morphology were first observed, subsequent studies suggest different functional organization of the male and female brains in humans. Sex and gender have been identified as being a significant factor in understanding human physiology, health and disease, and the biological differences between the sexes is not limited to the gonads and secondary sexual characteristics, but also affects the structure and, more crucially, the function of the brain and other organs. Significant variability in brain structures between individuals, in addition to between the sexes, is factor that complicates the study of sex differences in the brain. In this review, we explore the current understanding of sex differences in the brain, mostly focusing on preclinical animal studies.

Neuroprotective effects of a chromatin modifier on ischemia/reperfusion neurons: implication of its regulation of BCL2 transactivation by ERα signaling

An understanding of the molecular mechanisms involved in the regulation of estrogen receptor alpha (ERα)-mediated neuroprotective effects is valuable for the development of therapeutic strategy against neuronal ischemic injury. Here, we report the upregulated expression of metastasis-associated protein 1 (MTA1), a master chromatin modifier and transcriptional regulator, in the murine middle cerebral artery occlusion (MCAO) model. Inhibition of MTA1 expression by in vivo short interfering RNA treatment potentiated neuronal apoptosis in a caspase-3-dependent manner and thereafter aggravated MCAO-induced neuronal damage. Mechanistically, the pro-survival effects of MTA1 required the participation of ERα signaling. We also provide in vitro evidence that MTA1 enhances the binding of ERα with the BCL2 promoter upon ischemic insults via recruitment of HDAC2 together with other unidentified coregulators, thus promoting the ERα-mediated transactivation of the BCL2 gene. Collectively, our results suggest that the augmentation of endogenous MTA1 expression during neuronal ischemic injury acts additionally to an endocrinous cascade orchestrating intimate interactions between ERα and BCL2 pathways and operates as an indispensable defensive mechanism in response to neuronal ischemia/reperfusion stress. Future studies in this field will shed light on the modulation of the complicated neuroprotective effects by estrogen signaling.

Baby babbling at five months linked to sex hormone levels in early infancy

Gender-dependent differentiation of the brain at morphological, neurochemical and functional levels of organization have been shown to be primarily controlled by sex differences in gonadal hormone concentrations during pre- and early postnatal development. Indeed, previous studies have reported that pre- and perinatal hormonal environments influence brain development and, consequently, affect sex specific long-term language outcomes. Herein, we investigated whether postnatal surges of estrogen (estradiol) and androgen (testosterone) may predict properties of pre-speech babbling at five months. This study is the first attempt to investigate a possible correlation between sex hormones and infants' articulatory skills during the typical postnatal period of extended hormonal activity known as 'mini-puberty.' A hierarchical, multiple regression approach revealed a significant, robust positive relationship between 4-week concentrations of estradiol and individual articulatory skills. In contrast, testosterone concentrations at five months negatively correlated with articulatory skills at the same age in both boys and girls. Our findings reinforce the assumption of the importance of sex hormones for auditory-vocal development towards language in human infants.

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

The wild ground squirrel is a typical seasonal breeder. In this study, using RT-PCR, western blot and immunohistochemistry, we investigated the mRNA and protein expressions of androgen receptor (AR), estrogen receptors a and β (ERα and ERβ) and aromatase cytochrome P450 (P450arom) in the medial preoptic area (MPOA) of hypothalamus of the wild male ground squirrel during the breeding season (April), the non-breeding season (June) and pre-hibernation (September). AR, ERα, ERβ and P450arom protein/mRNA were present in the MPOA of all seasons detected. The immunostaining of AR and ERα showed no significant changes in different periods, whereas ERβ and P450arom had higher immunoreactivities during the breeding season and pre-hibernation when compared to those of the non-breeding season. Consistently, both the protein and mRNA levels of P450arom and ERβ were higher in the MPOA of pre-hibernation and the breeding season than in the non-breeding season, whereas no significant difference amongst the three periods was observed for AR and ERα levels. These findings suggested that the MPOA of hypothalamus 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 MPOA of hypothalamus of the wild male ground squirrels.

Calbindin Knockout Alters Sex-Specific Regulation of Behavior and Gene Expression in Amygdala and Prefrontal Cortex

Calbindin-D(28K) (Calb1), a high-affinity calcium buffer/sensor, shows abundant expression in neurons and has been associated with a number of neurobehavioral diseases, many of which are sexually dimorphic in incidence. Behavioral and physiological end points are affected by experimental manipulations of calbindin levels, including disruption of spatial learning, hippocampal long-term potentiation, and circadian rhythms. In this study, we investigated novel aspects of calbindin function on social behavior, anxiety-like behavior, and fear conditioning in adult mice of both sexes by comparing wild-type to littermate Calb1 KO mice. Because Calb1 mRNA and protein are sexually dimorphic in some areas of the brain, we hypothesized that sex differences in behavioral responses of these behaviors would be eliminated or revealed in Calb1 KO mice. We also examined gene expression in the amygdala and prefrontal cortex, two areas of the brain intimately connected with limbic system control of the behaviors tested, in response to sex and genotype. Our results demonstrate that fear memory and social behavior are altered in male knockout mice, and Calb1 KO mice of both sexes show less anxiety. Moreover, gene expression studies of the amygdala and prefrontal cortex revealed several significant genotype and sex effects in genes related to brain-derived neurotrophic factor signaling, hormone receptors, histone deacetylases, and γ-aminobutyric acid signaling. Our findings are the first to directly link calbindin with affective and social behaviors in rodents; moreover, the results suggest that sex differences in calbindin protein influence behavior.

ERα Signaling Is Required for TrkB-Mediated Hippocampal Neuroprotection in Female Neonatal Mice after Hypoxic Ischemic Encephalopathy(1,2,3)

Male neonate brains are more susceptible to the effects of perinatal asphyxia resulting in hypoxia and ischemia (HI)-related brain injury. The relative resistance of female neonatal brains to adverse consequences of HI suggests that there are sex-specific mechanisms that afford females greater neuroprotection and/or facilitates recovery post-HI. We hypothesized that HI preferentially induces estrogen receptor α (ERα) expression in female neonatal hippocampi and that ERα is coupled to Src family kinase (SFK) activation that in turn augments phosphorylation of the TrkB and thereby results in decreased apoptosis. After inducing the Vannucci’s HI model on P9 (C57BL/6J) mice, female and male ERα wild-type (ERα^+/+) or ERα null mutant (ERα^−/−) mice received vehicle control or the selective TrkB agonist 7,8-dihydroxyflavone (7,8-DHF). Hippocampi were collected for analysis of mRNA of ERα and BDNF, protein levels of ERα, p-TrkB, p-src, and cleaved caspase 3 (c-caspase-3) post-HI. Our results demonstrate that: (1) HI differentially induces ERα expression in the hippocampus of the female versus male neonate, (2) src and TrkB phosphorylation post-HI is greater in females than in males after 7,8-DHF therapy, (3) src and TrkB phosphorylation post-HI depend on the presence of ERα, and (4) TrkB agonist therapy decreases the c-caspase-3 only in ERα^+/+ female mice hippocampus. Together, these observations provide evidence that female-specific induction of ERα expression confers neuroprotection with TrkB agonist therapy via SFK activation and account for improved functional outcomes in female neonates post-HI.

Estrogen Effects on Cognitive and Synaptic Health Over the Lifecourse

Estrogen facilitates higher cognitive functions by exerting effects on brain regions such as the prefrontal cortex and hippocampus. Estrogen induces spinogenesis and synaptogenesis in these two brain regions and also initiates a complex set of signal transduction pathways via estrogen receptors (ERs). Along with the classical genomic effects mediated by activation of ER α and ER β, there are membrane-bound ER α, ER β, and G protein-coupled estrogen receptor 1 (GPER1) that can mediate rapid nongenomic effects. All key ERs present throughout the body are also present in synapses of the hippocampus and prefrontal cortex. This review summarizes estrogen actions in the brain from the standpoint of their effects on synapse structure and function, noting also the synergistic role of progesterone. We first begin with a review of ER subtypes in the brain and how their abundance and distributions are altered with aging and estrogen loss (e.g., ovariectomy or menopause) in the rodent, monkey, and human brain. As there is much evidence that estrogen loss induced by menopause can exacerbate the effects of aging on cognitive functions, we then review the clinical trials of hormone replacement therapies and their effectiveness on cognitive symptoms experienced by women. Finally, we summarize studies carried out in nonhuman primate models of age- and menopause-related cognitive decline that are highly relevant for developing effective interventions for menopausal women. Together, we highlight a new understanding of how estrogen affects higher cognitive functions and synaptic health that go well beyond its effects on reproduction.

The timing of neuronal loss across adolescence in the medial prefrontal cortex of male and female rats

Adolescence is a critical period of brain maturation characterized by the reorganization of interacting neural networks. In particular the prefrontal cortex (PFC), a region involved in executive function, undergoes synaptic and neuronal pruning during this time in both humans and rats. Our laboratory has previously shown that rats lose neurons in the medial prefrontal cortex (mPFC) and there is an increase in white matter under the frontal cortex between adolescence and adulthood. Female rats lose more neurons during this period, and ovarian hormones may play a role as ovariectomy before adolescence prevents neuronal loss. However, little is known regarding the timing of neuroanatomical changes that occur between early adolescence and adulthood. In the present study, we quantified the number of neurons and glia in the male and female mPFC at multiple time points from preadolescence through adulthood (postnatal days 25, 35, 45, 60 and 90). Females, but not males, lost a significant number of neurons in the mPFC between days 35 and 45, coinciding with the onset of puberty. Counts of GABA immunoreactive cell bodies indicated that the neurons lost were not primarily GABAergic. These results suggest that in females, pubertal hormones may exert temporally specific changes in PFC anatomy. As expected, both males and females gained white matter under the PFC throughout adolescence, though these gains in females were diminished after day 35, but not in males. The differences in cell loss in males and females may lead to differential vulnerability to external influences and dysfunctions of the PFC that manifest in adolescence.

Expression of estrogen receptor α in the mouse cerebral cortex

Although estrogen receptor alpha (ERα) and 17β-estradiol play critical roles in protecting the cerebral cortex from ischemia-induced damage, there has been some controversy about the expression of ERα in this region of the brain. We have examined ERα mRNA and protein levels in the cerebral cortices of female mice at postnatal days 5 and 17 and at 4, 13, and 18 months of age. We found that although ERα transcript levels declined from postnatal day 5 through 18 months of age, ERα protein levels remained stable. Importantly, expression of the E2-regulated progesterone receptor gene was sustained in younger and in older females suggesting that age-related changes in estrogen responsiveness in the cerebral cortex are not due to the absence of ERα protein.

Estrogen receptors regulate innate immune cells and signaling pathways

Humans show strong sex differences in immunity to infection and autoimmunity, suggesting sex hormones modulate immune responses. Indeed, receptors for estrogens (ER) regulate cells and pathways in the innate and adaptive immune system, as well as immune cell development. ERs are ligand-dependent transcription factors that mediate long-range chromatin interactions and form complexes at gene regulatory elements, thus promoting epigenetic changes and transcription. ERs also participate in membrane-initiated steroid signaling to generate rapid responses. Estradiol and ER activity show profound dose- and context-dependent effects on innate immune signaling pathways and myeloid cell development. While estradiol most often promotes the production of type I interferon, innate pathways leading to pro-inflammatory cytokine production may be enhanced or dampened by ER activity. Regulation of innate immune cells and signaling by ERs may contribute to the reported sex differences in innate immune pathways. Here we review the recent literature and highlight several molecular mechanisms by which ERs regulate the development or functional responses of innate immune cells.

Estrogen receptor-mediated resveratrol actions on blood-brain barrier of ovariectomized mice

To test whether resveratrol provides benefits via estrogen receptors (ERs) in the blood-brain barrier of estrogen-deficient females, ovariectomized mice were treated with resveratrol then were subjected to transient middle cerebral artery occlusion (MCAO). Compared with vehicle treatment, resveratrol reduced infarct volume and neurologic deficits after MCAO. Basal tight junction (TJ) protein levels in the brain were increased by resveratrol. After MCAO, blood-brain barrier breakdown reduced levels of TJ proteins, and induction of HIF-1α and VEGF were attenuated by resveratrol. These effects were reversed by the ERs antagonist, ICI182,780. In mouse brain, endothelial cells (bEnd.3) exposed to hypoxia, resveratrol treatment protected the cells against cytotoxicity, increases of paracellular permeability and changes in levels of TJ protein and HIF-1α/VEGF proteins. These effects were reversed by ICI182,780 but not by specific ERα or ERβ antagonists, indicating nonspecific ER mediated effects. Altogether, these results showed that neuroprotective effects of resveratrol in ovariectomized mice were mediated by ERs and associated with tightening of blood-brain barrier, suggesting that resveratrol can be an alternative to estrogens to protect the brains of estrogen-deficient females against ischemic insult.

The role of genetics in estrogen responses: a critical piece of an intricate puzzle

The estrogens are female sex hormones that are involved in a variety of physiological processes, including reproductive development and function, wound healing, and bone growth. They are mainly known for their roles in reproductive tissues--specifically, 17β-estradiol (E2), the primary estrogen, which is secreted by the ovaries and induces cellular proliferation and growth of the uterus and mammary glands. In addition to the role of estrogens in promoting tissue growth and development during normal physiological states, they have a well-established role in determining susceptibility to disease, particularly cancer, in reproductive tissues. The responsiveness of various tissues to estrogen is genetically controlled, with marked quantitative variation observed across multiple species, including humans. This variation presents both researchers and clinicians with a veritable physiological puzzle, the pieces of which--many of them unknown--are complex and difficult to fit together. Although genetics is known to play a major role in determining sensitivity to estrogens, there are other factors, including parent of origin and the maternal environment, that are intimately linked to heritable phenotypes but do not represent genotype, per se. The objectives of this review article were to summarize the current knowledge of the role of genotype, and uterine and neonatal environments, in phenotypic variation in the response to estrogens; to discuss recent findings and the potential mechanisms involved; and to highlight exciting research opportunities for the future.

Programming of metabolic effects in C57BL/6JxFVB mice by exposure to bisphenol A during gestation and lactation

The global rise in prevalence of obesity is not fully explained by genetics or life style factors. The developmental origins of health and disease paradigm suggests that environmental factors during early life could play a role. In this perspective, perinatal exposure to bisphenol A (BPA) has been indicated as a programming factor for obesity and related metabolic disorders later in life. Here we study early life programming by BPA using an experimental design that is relevant for human exposure. C57BL/6JxFVB hybrid mice were exposed during gestation and lactation via maternal feed to 8 non-toxic doses (0-3000 μg/kg body weight/day (μg/kg bw/d)) of BPA. After weaning, offspring were followed for 20 weeks without further exposure. Adult male offspring showed dose-dependent increases of body and liver weights, no effects on fat pad weights and a dose-dependent decrease in circulating glucagon. Female offspring showed a dose-dependent decrease in body weight, liver, muscle and fat pad weights, adipocyte size, serum lipids, serum leptin and adiponectin. Physical activity was decreased in exposed males and suggested to be increased in exposed females. Brown adipose tissue showed slightly increased lipid accumulation in males and lipid depletion in females, and ucp1 expression was dose-dependently increased in females. The effects in females were more reliable and robust than in males due to wide confidence intervals and potential confounding by litter size for male data. The lowest derived BMDL (lower bound of the (two-sided) 90%-confidence interval for the benchmark dose) of 233 μg/kg bw/d (for interscapular weight in females) was below the proposed BMDL of 3633 μg/kg bw/d as a basis for tolerable daily intake. Although these results suggest that BPA can program for an altered metabolic phenotype, the sexual dimorphism of effects and diversity of outcomes among studies similar in design as the present study do not mark BPA as a specific obesogen. The consistency within the complex of observed metabolic effects suggests that upstream key element(s) in energy homeostasis are modified. Sex-dependent factors contribute to the final phenotypic outcome.

Neural correlates of cognitive and affective processing in maltreated youth with posttraumatic stress symptoms: does gender matter?

We investigated the relationship of gender to cognitive and affective processing in maltreated youth with posttraumatic stress disorder symptoms using functional magnetic resonance imaging. Maltreated (N = 29, 13 females, 16 males) and nonmaltreated participants (N = 45, 26 females, 19 males) performed an emotional oddball task that involved detection of targets with fear or scrambled face distractors. Results were moderated by gender. During the executive component of this task, left precuneus/posterior middle cingulate hypoactivation to fear versus calm or scrambled face targets were seen in maltreated versus control males and may represent dysfunction and less resilience in attentional networks. Maltreated males also showed decreased activation in the inferior frontal gyrus compared to control males. No differences were found in females. Posterior cingulate activations positively correlated with posttraumatic stress disorder symptoms. While viewing fear faces, maltreated females exhibited decreased activity in the dorsomedial prefrontal cortex and cerebellum I-VI, whereas maltreated males exhibited increased activity in the left hippocampus, fusiform cortex, right cerebellar crus I, and visual cortex compared to their same-gender controls. Gender by maltreatment effects were not attributable to demographic, clinical, or maltreatment parameters. Maltreated girls and boys exhibited distinct patterns of neural activations during executive and affective processing, a new finding in the maltreatment literature.

Vitamin D hormone regulates serotonin synthesis. Part 1: relevance for autism

Serotonin and vitamin D have been proposed to play a role in autism; however, no causal mechanism has been established. Here, we present evidence that vitamin D hormone (calcitriol) activates the transcription of the serotonin-synthesizing gene tryptophan hydroxylase 2 (TPH2) in the brain at a vitamin D response element (VDRE) and represses the transcription of TPH1 in tissues outside the blood-brain barrier at a distinct VDRE. The proposed mechanism explains 4 major characteristics associated with autism: the low concentrations of serotonin in the brain and its elevated concentrations in tissues outside the blood-brain barrier; the low concentrations of the vitamin D hormone precursor 25-hydroxyvitamin D [25(OH)D3]; the high male prevalence of autism; and the presence of maternal antibodies against fetal brain tissue. Two peptide hormones, oxytocin and vasopressin, are also associated with autism and genes encoding the oxytocin-neurophysin I preproprotein, the oxytocin receptor, and the arginine vasopressin receptor contain VDREs for activation. Supplementation with vitamin D and tryptophan is a practical and affordable solution to help prevent autism and possibly ameliorate some symptoms of the disorder.

Sexually selected traits: a fundamental framework for studies on behavioral epigenetics

Emerging evidence suggests that epigenetic-based mechanisms contribute to various aspects of sex differences in brain and behavior. The major obstacle in establishing and fully understanding this linkage is identifying the traits that are most susceptible to epigenetic modification. We have proposed that sexual selection provides a conceptual framework for identifying such traits. These are traits involved in intrasexual competition for mates and intersexual choice of mating partners and generally entail a combination of male-male competition and female choice. These behaviors are programmed during early embryonic and postnatal development, particularly during the transition from the juvenile to adult periods, by exposure of the brain to steroid hormones, including estradiol and testosterone. We evaluate the evidence that endocrine-disrupting compounds, including bisphenol A, can interfere with the vital epigenetic and gene expression pathways and with the elaboration of sexually selected traits with epigenetic mechanisms presumably governing the expression of these traits. Finally, we review the evidence to suggest that these steroid hormones can induce a variety of epigenetic changes in the brain, including the extent of DNA methylation, histone protein alterations, and even alterations of noncoding RNA, and that many of the changes differ between males and females. Although much previous attention has focused on primary sex differences in reproductive behaviors, such as male mounting and female lordosis, we outline why secondary sex differences related to competition and mate choice might also trace their origins back to steroid-induced epigenetic programming in disparate regions of the brain.

Expression profile of the aromatase enzyme in the Xenopus brain and localization of estradiol and estrogen receptors in each tissue

Estradiol (E2) with the strongest bioactivity of the estrogens, is synthesized by the cytochrome p450 aromatase enzyme and plays a key role in sex differentiation of the vertebrate's gonads. In Xenopus, aromatase mRNA is highly expressed in the brain rather than in the gonad during sex differentiation. In this study, we analyzed the stage change, tissue specificity, and localization of the aromatase expression in the Xenopus brain. Regardless of the sex difference, expression level of aromatase was remarkably higher in the brain than in other tissues during the early stages of brain morphogenesis and was observed in the formation regions of the choroid plexus of cerebral ventricle and the paleocortex and olfactory bulb of the prosencephalon. However, E2 concentrations in each tissue indicated a different localization of aromatase and were seen in the heart at almost double the level as seen in the brain. In addition, while aromatase expression level in the brain was increasing, E2 in the whole body began to increase at the same stage. Since the expression level of estrogen receptor α also corresponded to localization of E2, these results may imply that the E2 synthesized by the high aromatase expression in the choroid plexus, which generates cerebrospinal fluid, circulates to the heart and acts through ERα.

Biochemical evaluation of the neurotoxicity of MPTP and MPP⁺ in embryonic and newborn mice

One of the toxicities caused by 1-Methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) is damage to dopaminergic neurons. When injected into C57BL/6J mice, MPTP penetrates into the brain and is converted to 1-methyl-4-phenylpyridinium (MPP⁺) by monoamine oxidase (MAO)-B in astrocytes. MPP⁺ has high affinity for the dopamine transporter (DAT) on dopaminergic neurons, and is taken up into the cell to cause cell death. There have been relatively few researches on the acute MPTP toxicity to embryonic or newborn mice. In the present study, we attempted to evaluate the influence of MPTP and MPP⁺ on embryonic and newborn mice by measuring sequential changes in major indexes of MPTP toxicity and MPTP metabolism; levels of Tyrosine Hydroxylase (TH), DAT, MAO-A and MAO-B. In addition, we measured the levels of dopamine and its metabolites, 3,4-dihydroxy-phenylacetic acid (DOPAC) and homovanillic acid (HVA), in the brain of newborn mice. A single injection of MPTP and MPP⁺ reduced the levels of dopamine and its metabolites, DOPAC and HVA, in the brain of newborn mice about 6-12 hr after the injection. Similarly the levels of mRNAs and proteins of DAT and TH were lowered in the brain of embryonic and newborn mice as well. The levels of these indexes were generally recovered at 24 hr after injection, indicating that the neurotoxicity induced by a single injection of MPTP or MPP⁺ is temporary and recoverable in embryonic and newborn mice. By contrast, no significant changes in the expression levels of MAO-A and MAO-B were observed in either MPTP- or MPP⁺-treated mice.

Estradiol activates epithelial sodium channels in rat alveolar cells through the G protein-coupled estrogen receptor

Female sex predisposes individuals to poorer outcomes during respiratory disorders like cystic fibrosis and influenza-associated pneumonia. A common link between these disorders is dysregulation of alveolar fluid clearance via disruption of epithelial sodium channel (ENaC) activity. Recent evidence suggests that female sex hormones directly regulate expression and activity of alveolar ENaC. In our study, we identified the mechanism by which estradiol (E2) or progesterone (P4) independently regulates alveolar ENaC. Using cell-attached patch clamp, we measured ENaC single-channel activity in a rat alveolar cell line (L2) in response to overnight exposure to either E2 or P4. In contrast to P4, E2 increased ENaC channel activity (NPo) through an increase in channel open probability (Po) and an increased number of patches with observable channel activity. Apical plasma membrane abundance of the ENaC α-subunit (αENaC) more than doubled in response to E2 as determined by cell surface biotinylation. αENaC membrane abundance was approximately threefold greater in lungs from female rats in proestrus, when serum E2 is greatest, compared with diestrus, when it is lowest. Our results also revealed a significant role for the G protein-coupled estrogen receptor (Gper) to mediate E2's effects on ENaC. Overall, our results demonstrate that E2 signaling through Gper selectively activates alveolar ENaC through an effect on channel gating and channel density, the latter via greater trafficking of channels to the plasma membrane. The results presented herein implicate E2-mediated regulation of alveolar sodium channels in the sex differences observed in the pathogenesis of several pulmonary diseases.

Impact of pubertal and adult estradiol treatments on cocaine self-administration

Estradiol is thought to play a critical role in the increased vulnerability to psychostimulant abuse in women. Sex differences in the ability of estradiol to influence cocaine self-administration in adult rats have been hypothesized to depend upon pubertal estradiol exposure. The current study investigated whether the presence of gonadal hormones during puberty affected cocaine self-administration behavior and its sensitivity to adult estradiol treatment in male and female Sprague-Dawley rats. Subjects were gonadectomized or SHAM-operated at postnatal day (PD) 22, and received either OIL or estradiol benzoate (EB) during the approximate time of puberty (PD27 to PD37). Adult rats were subsequently treated with either EB or OIL 30 min before cocaine self-administration (0.3 mg/kg/inf) in order to examine the effects of pubertal manipulations on the estradiol sensitivity of acquisition on a fixed ratio (FR) 1 schedule, total intake on a FR5 schedule and motivation on a progressive ratio schedule. Adult EB treatment only affected cocaine self-administration in females, which is consistent with previous research. Adult EB treatment enhanced acquisition in all females irrespective of puberty manipulations. All females, except those treated with EB during puberty, displayed increased cocaine intake following adult EB treatment. Adult EB treatment only enhanced motivation in females that were intact during puberty, whereas those treated with EB during puberty showed reduced motivation. Therefore, the sensitivities of different self-administration behaviors to adult estradiol treatment are organized independently in females, with pubertal estradiol exerting a greater influence over motivational processes, and negligible effects on learning/acquisition.