Estrogen actions in the brain and the basis for differential action in men and women: a case for sex-specific medicines

Addiction and the adrenal cortex

Substantial evidence shows that the hypophyseal–pituitary–adrenal (HPA) axis and corticosteroids are involved in the process of addiction to a variety of agents, and the adrenal cortex has a key role. In general, plasma concentrations of cortisol (or corticosterone in rats or mice) increase on drug withdrawal in a manner that suggests correlation with the behavioural and symptomatic sequelae both in man and in experimental animals. Corticosteroid levels fall back to normal values in resumption of drug intake. The possible interactions between brain corticotrophin releasing hormone (CRH) and proopiomelanocortin (POMC) products and the systemic HPA, and additionally with the local CRH–POMC system in the adrenal gland itself, are complex. Nevertheless, the evidence increasingly suggests that all may be interlinked and that CRH in the brain and brain POMC products interact with the blood-borne HPA directly or indirectly. Corticosteroids themselves are known to affect mood profoundly and may themselves be addictive. Additionally, there is a heightened susceptibility for addicted subjects to relapse in conditions that are associated with change in HPA activity, such as in stress, or at different times of the day. Recent studies give compelling evidence that a significant part of the array of addictive symptoms is directly attributable to the secretory activity of the adrenal cortex and the actions of corticosteroids. Additionally, sex differences in addiction may also be attributable to adrenocortical function: in humans, males may be protected through higher secretion of DHEA (and DHEAS), and in rats, females may be more susceptible because of higher corticosterone secretion.

Synergistic Action of Flavonoids, Baicalein, and Daidzein in Estrogenic and Neuroprotective Effects: A Development of Potential Health Products and Therapeutic Drugs against Alzheimer's Disease

Despite the classical hormonal effect, estrogen has been reported to mediate neuroprotection in the brain, which leads to the searching of estrogen-like substances for treating neurodegenerative diseases. Flavonoids, a group of natural compounds, are well known to possess estrogenic effects and used to substitute estrogen, that is, phytoestrogen. Flavonoid serves as one of the potential targets for the development of natural supplements and therapeutic drugs against different diseases. The neuroprotection activity of flavonoids was chosen for a possible development of anti-Alzheimer's drugs or food supplements. The estrogenic activity of two flavonoids, baicalein and daidzein, were demonstrated by their strong abilities in stimulating estrogen receptor phosphorylation and transcriptional activation of estrogen responsive element in MCF-7 breast cells. The neuroprotection effects of flavonoids against β-amyloid (Aβ) were revealed by their inhibition effects on in vitro Aβ aggregation and Aβ-induced cytotoxicity in PC12 neuronal cells. More importantly, the estrogenic and neuroprotective activities of individual flavonoid could be further enhanced by the cotreatment in the cultures. Taken together, this synergistic effect of baicalein and daidzein might serve as a method to improve the therapeutic efficacy of different flavonoids against Aβ, which might be crucial in developing those flavonoidsin treating Alzheimer's disease in the future.

Sex differences in the physiology of eating

Hypothalamic-pituitary-gonadal (HPG) axis function fundamentally affects the physiology of eating. We review sex differences in the physiological and pathophysiological controls of amounts eaten in rats, mice, monkeys, and humans. These controls result from interactions among genetic effects, organizational effects of reproductive hormones (i.e., permanent early developmental effects), and activational effects of these hormones (i.e., effects dependent on hormone levels). Male-female sex differences in the physiology of eating involve both organizational and activational effects of androgens and estrogens. An activational effect of estrogens decreases eating 1) during the periovulatory period of the ovarian cycle in rats, mice, monkeys, and women and 2) tonically between puberty and reproductive senescence or ovariectomy in rats and monkeys, sometimes in mice, and possibly in women. Estrogens acting on estrogen receptor-α (ERα) in the caudal medial nucleus of the solitary tract appear to mediate these effects in rats. Androgens, prolactin, and other reproductive hormones also affect eating in rats. Sex differences in eating are mediated by alterations in orosensory capacity and hedonics, gastric mechanoreception, ghrelin, CCK, glucagon-like peptide-1 (GLP-1), glucagon, insulin, amylin, apolipoprotein A-IV, fatty-acid oxidation, and leptin. The control of eating by central neurochemical signaling via serotonin, MSH, neuropeptide Y, Agouti-related peptide (AgRP), melanin-concentrating hormone, and dopamine is modulated by HPG function. Finally, sex differences in the physiology of eating may contribute to human obesity, anorexia nervosa, and binge eating. The variety and physiological importance of what has been learned so far warrant intensifying basic, translational, and clinical research on sex differences in eating.

Sex-related differences in epidemiological and clinic-based headache studies

This manuscript discusses sex-related differences in headache prevalence, the symptoms and natural history of migraine, associated disability, and co-morbid disorders. The role of sex hormones is discussed with reference to the effects of hormonal events across the reproductive years and the specific effects of the menstrual cycle on migraine. Differences between the sexes were identified across all parameters reviewed. Future research should ensure that data are analyzed separately for men and women to ensure that differences between the sexes are identified.

The sex-specific associations of the aromatase gene with Alzheimer's disease and its interaction with IL10 in the Epistasis Project

Epistasis between interleukin-10 (IL10) and aromatase gene polymorphisms has previously been reported to modify the risk of Alzheimer's disease (AD). However, although the main effects of aromatase variants suggest a sex-specific effect in AD, there has been insufficient power to detect sex-specific epistasis between these genes to date. Here we used the cohort of 1757 AD patients and 6294 controls in the Epistasis Project. We replicated the previously reported main effects of aromatase polymorphisms in AD risk in women, for example, adjusted odds ratio of disease for rs1065778 GG=1.22 (95% confidence interval: 1.01-1.48, P=0.03). We also confirmed a reported epistatic interaction between IL10 rs1800896 and aromatase (CYP19A1) rs1062033, again only in women: adjusted synergy factor=1.94 (1.16-3.25, 0.01). Aromatase, a rate-limiting enzyme in the synthesis of estrogens, is expressed in AD-relevant brain regions ,and is downregulated during the disease. IL-10 is an anti-inflammatory cytokine. Given that estrogens have neuroprotective and anti-inflammatory activities and regulate microglial cytokine production, epistasis is biologically plausible. Diminishing serum estrogen in postmenopausal women, coupled with suboptimal brain estrogen synthesis, may contribute to the inflammatory state, that is a pathological hallmark of AD.

Do females with juvenile ceroid lipofuscinosis (Batten disease) have a more severe disease course? The Danish experience

BACKGROUND

Juvenile neuronal ceroid lipofuscinosis (JNCL; Batten disease) is characterized by progressive visual failure starting at 4-7 years of age, followed by seizures, dementia as well as a progressive decline in motor function. The patients are typically bedridden in the late teens and death usually occurs in the third decade of life. It has been suggested, that females may have a more precipitous decline than do males.

OBJECTIVE

To compare sex differences in loss of skills and age at death in an unselected population of Danish Adolescents with Batten disease.

METHOD

Review of hospital records of all 35 Danish patients with JNCL born in the period 1971-2003. The records contain a continuously maintained history of the clinical course and first moments for different events, thus eliminating recall bias.

RESULTS

We found that females with JNCL experienced a later age at diagnosis, but showed an earlier loss of independent functions, and died at an earlier age.

CONCLUSION

Females with JNCL have a more precipitous decline than males, and die at an earlier age. Further studies are needed in order to provide possible explanations for this difference.

Neurosteroid and neurotransmitter alterations in Parkinson's disease

Parkinson's disease (PD) is associated with a massive loss of dopaminergic cells in the substantia nigra leading to dopamine hypofunction and alteration of the basal ganglia circuitry. These neurons, are under the control, among others, of the excitatory glutamatergic and inhibitory γ-aminobutyric acid (GABA) systems. An imbalance between these systems may contribute to excitotoxicity and dopaminergic cell death. Neurosteroids, a group of steroid hormones synthesized in the brain, modulate the function of several neurotransmitter systems. The substantia nigra of the human brain expresses high concentrations of allopregnanolone (3α, 5αtetrahydroprogesterone), a neurosteroid that positively modulates the action of GABA at GABAA receptors and of 5α-dihydroprogesterone, a neurosteroid acting at the genomic level. This article reviews the roles of NS acting as neuroprotectants and as GABAA receptor agonists in the physiology and pathophysiology of the basal ganglia, their impact on dopaminergic cell activity and survival, and potential therapeutic application in PD.

Sex differences in the physiology and pharmacology of the lower urinary tract

Sexual dimorphism is not only noticed in the prevalence of many diseases, but also in multiple physiological functions in the body. This review has summarized findings from published literature on the sex differences of the pathophysiology and pharmacology of the lower urinary tract (LUT) of humans and animals. Sex differences have been found in several key areas of the LUT, such as overactive bladder, expression and function of neurotransmitter receptors in the bladder and urethra, and micturition patterns in humans and animals. It is anticipated that this review will not only evoke renewed interest for further research on the mechanism of sex differences in the pathophysiology of the LUT (especially for overactive bladder), but might also open up the possibilities for gender-based drug development by pharmaceutical industries in order to find separate cures for men and women with diseases of the LUT.

Risk factors for Parkinson's disease may differ in men and women: an exploratory study

Although several environmental and genetic risk or protective factors have been associated with Parkinson's disease (PD), their interactions overall and in men and women separately remain unknown. We used the medical records-linkage system of the Rochester Epidemiology Project to identify 196 subjects who developed PD in Olmsted County, MN, from 1976 through 1995. Each incident case was matched by age (±1 year) and sex to a general population control. We considered the following 12 risk or protective factors: personal history of head trauma, pesticide use, immunologic diseases, anemia, hysterectomy (in women only), cigarette smoking, coffee consumption, and education; and family history of parkinsonism, essential tremor, dementia, or psychiatric disorders. We used recursive partitioning analyses to explore interactions overall and in men and women separately and used logistic regression analyses to test for interactions. In the overall group, we observed the independent effects of anemia, lack of coffee consumption (never vs. ever), and head trauma; however, the findings were different in men and women. In men, we observed the independent effects of lack of coffee consumption (never vs. ever), head trauma, and pesticide use, and a suggestive synergistic interaction between immunologic diseases and family history of dementia. By contrast, in women, anemia was the most important factor and we observed a suggestive synergistic interaction between anemia and higher education. Risk factors for PD and their interactions may differ in men and women.

Considerations of sex and gender differences in preclinical and clinical trials

Women continue to be underrepresented in clinical trials, particularly in Phases I and II of experimental drug studies in spite of legislative guidelines in the USA, Canada, the European Union, Australia, and Japan requiring the inclusion of women in clinical trials. As such, women remain a vulnerable population subject to the adverse effects of pharmacological therapies. Thus, women experience higher rates of adverse drug reactions than do men and for women of reproductive age or who may be pregnant, therapeutic options may be limited. This chapter provides a brief history of inclusion of sex and gender as variables in clinical trials, summarizes governmental legislation for consideration of sex and gender in clinical trials and provides specific examples of drugs which have been withdrawn from the market because of side effects in women. Additional information related to sex and gender in preclinical testing, trial design, challenges to recruitment of women for clinical trials and statistical methods for analysis of data also is considered.

Does melatonin ameliorate neurological changes associated with Alzheimer's disease in ovariectomized rat model?

This study aimed to elucidate the mechanisms of melatonin to manage neurological damage in Alzheimer's disease (AD) induced in ovariectomized rats. Forty adult female rats were enrolled in our study and were classified as; gonad intact control, ovariectomized control group, ovariectomized rats received melatonin, ovariectomized rats injected with AlCl3 to induce AD and AD-induced rats treated with melatonin. Hydrogen peroxide (H2O2), malondialdehyde (MDA), total antioxidant capacity (TAC), superoxide dismutase (SOD), catalase (CAT), B cell lymphoma 2 (Bcl-2), brain derived neurotrophic factor (BDNF), acetylcholinesterase (AchE) and acetylcholine (Ach) were estimated in the brain tissues of the different groups. Treatment of AD-induced rats with melatonin produced marked improvement in the most studied biomarkers which was confirmed by histological investigation of the brain. In Conclusion, melatonin significantly ameliorates the neurodegeneration characteristic of AD in experimental animal model due to its antioxidant, antiapoptotic, neurotrophic and anti-amyloidogenic activities.

The anti-apoptotic role of neuroglobin

The small heme-protein neuroglobin is expressed at high concentrations in certain brain neurons and in the rod cells of the retina. This paper reviews the many studies which have recently identified a protective role for neuroglobin, in a wide range of situations involving apoptotic cell death. The origins of this protective mechanism are discussed in terms of both experimental results and computational modeling of the intrinsic pathway of apoptosis, which shows that neuroglobin can intervene in this process by a reaction with released mitochondrial cytochrome c. An integrated model, based on the various molecular actions of both neuroglobin and cytochrome c, is developed, which accounts for the cellular distribution of neuroglobin.

Estrogens facilitate memory processing through membrane mediated mechanisms and alterations in spine density

Estrogens exert sustained, genomically mediated effects on memory throughout the female life cycle, but here we review new studies documenting rapid effects of estradiol on memory, which are exerted through membrane-mediated mechanisms. Use of recognition memory tasks in rats shows that estrogens enhance memory consolidation within 1h. 17α-Estradiol is more potent than 17β-estradiol, and the dose response relationship between estrogens and memory is an inverted U shape. Use of specific estrogen receptor (ER) agonists suggests mediation by an ERβ-like membrane receptor. Enhanced memory is associated with increased spine density and altered noradrenergic activity in the medial prefrontal cortex and hippocampus within 30 min of administration. The environmental chemical, bisphenol-A, rapidly antagonizes enhancements in memory in both sexes possibly through actions on spines. Thus, estradiol and related compounds exert rapid alterations in cognition through non-genomic mechanisms, a finding which may provide a basis for better understanding and treating memory impairments.

Oral contraceptive usage alters the effects of cortisol on implicit fear learning

An important feature of the human defense system comprises fear learning, which stress hormones can crucially modulate. However, stress hormones might influence men and women differently, in part because of interactions with sex hormones. In women, distinct stages of the menstrual cycle or the intake of oral contraceptives (OC) affect sex hormone levels. In this study, we used a differential fear conditioning paradigm with electrical stimulation as unconditioned stimulus (UCS) following one neutral stimulus (conditioned stimulus, CS+), but not another (CS-).To investigate implicit fear learning, participants were distracted from detecting the contingencies between CS and UCS. To address interaction effects of sex and stress hormones, 32 men, 30 women in the early follicular phase of the menstrual cycle (FO), 30 women in the luteal phase (LU), and 30 OC women received either 30 mg cortisol or a placebo. In the contrast CS+ minus CS-, an interaction between cortisol administration and sex hormone status emerged in the anterior parahippocampal gyrus and the hippocampus. Cortisol reduced fear learning in men, FO, and LU women, but enhanced it in OC women. Additionally, cortisol attenuated differential amygdala activation in the entire group. These results demonstrate that OC usage substantially modifies cortisol effects on emotional learning in women, particularly in memory-related medial temporal lobe regions. Further, a high dose of cortisol reduces amygdala differentiation pointing to a lowered learning ability of the defense system under high cortisol concentrations, irrespective of current sex hormone availability.

Gender differences in motor and non-motor symptoms among Sardinian patients with Parkinson's disease

BACKGROUND

Parkinson's disease (PD) occurs more frequently in men than in women and a higher risk for PD development in males compared with females has been hypothesized, suggesting gender may be a significant factor in the development and progression of parkinsonism. To date, gender differences in non-motor symptoms are under-reported.

OBJECTIVE

To assess gender differences in motor and non-motor symptoms among Sardinian PD patients.

METHODS

One hundred fifty-six (91 male and 65 female) consecutive Sardinian PD outpatients were included in this analysis. Modified Hoehn and Yahr scale and UPDRS were used to assess motor symptoms, while non-motor disturbances were evaluated with the non-motor symptoms scale (NMSS). Presence of depression, anxiety and other iatrogenic behavioral disorders was also investigated. In order to determine how gender differences could be specific to PD, 132 age-matched normal controls were assessed with the NMSS.

RESULTS

Women were more likely than men to present with tremor as initial symptom (p<.025) and worse UPDRS instability score (p<.02). NMSS score in females was significantly higher than that in males (p<.018). A significantly higher severity in cardiovascular (p<0.002), sleep/fatigue (p<.018) and mood/apathy (p<.001) domains was observed in female PD patients, while the sexual dysfunction domain was reported with a significantly higher score in male patients (p<.017). Fatigue (p<.03), lack of motivation (p<.015) and sadness (p<.009) were observed significantly more frequent in females, while altered interest in sex was noted as more common in males (p<.001). Frequency of depression (p<.011) and anxiety (p<.001) was significantly higher in females, while male patients had increased frequency of compulsive sexual behaviors (p<.05). There was a significantly higher frequency of non-motor symptoms in eight domains in both male and female PD patients compared with controls (p<.001, for all comparisons, with the exception of urinary disturbances in females: p<.004). Only sexual dysfunctions were not significantly higher in male and female PD patients compared with controls.

DISCUSSION

The present study highlights the role of gender differences associated with the occurrence of motor and non-motor disorders and our findings indicate that spectrum and severity of non-motor symptoms may present with different gender distribution in PD patients, suggesting a possible sex-related effect.

Estradiol acutely suppresses inhibition in the hippocampus through a sex-specific endocannabinoid and mGluR-dependent mechanism

The steroid 17β-estradiol (E2) is well known to influence hippocampal functions such as memory, affective behaviors, and epilepsy. There is growing awareness that in addition to responding to ovarian E2, the hippocampus of both males and females synthesizes E2 as a neurosteroid that could acutely modulate synaptic function. Previous work on acute E2 actions in the hippocampus has focused on excitatory synapses. Here, we show that E2 rapidly suppresses inhibitory synaptic transmission in hippocampal CA1. E2 acts through the α form of the estrogen receptor to stimulate postsynaptic mGluR1-dependent mobilization of the endocannabinoid anandamide, which retrogradely suppresses GABA release from CB1 receptor-containing inhibitory presynaptic boutons. Remarkably, this effect of E2 is sex specific, occurring in females but not in males. Acute E2 modulation of endocannabinoid tone and consequent suppression of inhibition provide a mechanism by which neurosteroid E2 could modulate hippocampus-dependent behaviors in a sex-specific manner.

Polymorphisms in the maternal sex steroid pathway are associated with behavior problems in male offspring

OBJECTIVE

Slight perturbations in maternal sex steroid production and metabolism may interfere with normal fetal neurodevelopment. The balance of maternal estrogens and androgens may have direct fetal effects, may influence the fetal hypothalamic-pituitary-gonadal axis, or may alter local hormonal activity within the fetal brain. We investigated maternal functional polymorphisms of CYP17, CYP19, and CYP1B1, which control three major enzymatic steps in sex steroid biosynthesis and metabolism, in relation to childhood behaviors.

METHODS

The Mount Sinai Children's Environmental Health Study enrolled a multiethnic urban pregnancy cohort from 1998 to 2002 (n=404). DNA was obtained from maternal blood (n=149) and from neonatal cord blood (n=53). At each visit, mothers completed the Behavior Assessment System for Children, a parent-reported questionnaire used to evaluate children for behavior problems. We focused on problem behaviors more commonly associated with attention deficit-hyperactivity disorder (Hyperactivity, Attention Problems, Externalizing Behaviors, Conduct Disorder, Poor Adaptability) to determine whether maternal genetic variants in sex steroid production and metabolism influence sexually dimorphic behaviors in offspring.

RESULTS

The more active gene variants were significantly associated with Attention Problems and poorer Adaptive Skills in male compared with female offspring. The CYP19 variant allele was also significantly associated with worse scores for boys on the Hyperactivity, Externalizing Problems Composite, and Adaptive Skills Composite scales (P<0.05).

CONCLUSION

We observed maladaptive behaviors in the male offspring of mothers who carried functional polymorphisms in the sex steroid pathway. The strongest associations were in domains commonly affected in attention deficit-hyperactivity disorder.

Expression of aromatase P450(AROM) in the human fetal and early postnatal cerebral cortex

Aromatase (P450(AROM)), the enzyme responsible for the conversion of testosterone (T) into 17-β estradiol (E(2)), plays a crucial role in the sexual differentiation of specific hypothalamic nuclei. Moreover, recent findings indicate that local E(2) synthesis has an impact on other brain areas including hippocampus, temporal cortex and cerebellum, and may thus influence also cognitive functions. Numerous studies have described the expression and the distribution of P450(AROM) throughout ontogenesis and postnatal development of the central nervous system in several mammals, but data referring to humans are scarce. In the adult human brain, P450(AROM) has been detected in the hypothalamus, limbic areas, and in the basal forebrain, and described in glial cells of the cerebral cortex and hippocampus. In this study we report the expression, distribution and cellular localization of P450(AROM) in the human fetal and early postnatal cerebral cortex. In our series of fetal brains of the second trimester, P450(AROM) expression appeared at gestational week (GW) 17 and resulted limited to groups of cells localized close to the growing neuroepithelium in the ventricular and subventricular zones. At GWs 20-24, scattered P450(AROM) immunoreactive (-ir) neural cells were identified in the intermediate plate and subplate, and in the parietal cortical plate. In perinatal and early postnatal individuals the quantity of P450(AROM)-ir elements increased, and revealed the morphology typical of glial cells. Double labeling immunostaining with anti-GFAP and anti-P450(AROM) antisera, and subsequent confocal analysis, confirmed this observation. Our data show that the expression of P450(AROM) in the fetal cortex starts approx at the end of the fourth gestational month, but increases steadily only in the last trimester or in the early postnatal period. This temporal trend may suggest that P450(AROM) could act as a differentiation-promoting factor, based on timing of the steroid actions.

Estrogen deficiency accelerates aging of the optic nerve

The aim of this study was to provide a comprehensive review on hormone-based pathophysiology of aging of the optic nerve and glaucoma, including a literature review and expert opinions. Glaucoma, a group of intraocular pressure-related optic neuropathies, is characterized by the slow progressive neurodegeneration of retinal ganglion cells and their axons, resulting in irreversible visual sensitivity loss and blindness. Increasing evidence suggests that glaucoma represents the accelerated aging of the optic nerve and is a neurodegenerative disease of the central nervous system. This review highlights the high burden of glaucoma in older women and the importance of understanding the hormone-related pathophysiology of optic nerve aging and glaucoma in women. Strong epidemiological, clinical, and experimental evidence supports the proposed hypothesis that early loss of estrogen leads to premature aging and increased susceptibility of the optic nerve to glaucomatous damage. Future investigations into the hormone-related mechanisms of aging and glaucoma will support the development of novel sex-specific preventive and therapeutic strategies in glaucoma.

Cell surface estrogen receptor alpha is upregulated during subchronic metabolic stress and inhibits neuronal cell degeneration

In addition to the classical nuclear estrogen receptor, the expression of non-nuclear estrogen receptors localized to the cell surface membrane (mER) has recently been demonstrated. Estrogen and its receptors have been implicated in the development or progression of numerous neurodegenerative disorders. Furthermore, the pathogenesis of these diseases has been associated with disturbances of two key cellular programs: apoptosis and autophagy. An excess of apoptosis or a defect in autophagy has been implicated in neurodegeneration. The aim of this study was to clarify the role of ER in determining neuronal cell fate and the possible implication of these receptors in regulating either apoptosis or autophagy. The human neuronal cell line SH-SY5Y and mouse neuronal cells in primary culture were thus exposed to chronic minimal peroxide treatment (CMP), a form of subcytotoxic minimal chronic stress previously that mimics multiple aspects of long-term cell stress and represents a limited molecular proxy for neurodegenerative processes. We actually found that either E2 or E2-bovine serum albumin construct (E2BSA, i.e. a non-permeant form of E2) was capable of modulating intracellular cell signals and regulating cell survival and death. In particular, under CMP, the up-regulation of mERα, but not mERβ, was associated with functional signals (ERK phosphorylation and p38 dephosphorylation) compatible with autophagic cytoprotection triggering and leading to cell survival. The mERα trafficking appeared to be independent of the microfilament system cytoskeletal network but was seemingly associated with microtubular apparatus network, i.e., to MAP2 molecular chaperone. Importantly, antioxidant treatments, administration of siRNA to ERα, or the presence of antagonist of ERα hindered these events. These results support that the surface expression of mERα plays a pivotal role in determining cell fate, and that ligand-induced activation of mER signalling exerts a powerful cell-survival signal. These results shed new light on the pathogenetic mechanisms leading to neuronal cell degeneration.

Progression from amnesic mild cognitive impairment to Alzheimer's disease: ESR1 and ESR2 polymorphisms and APOE gene

BACKGROUND

Many genes have been studied to determine how they might be involved in Alzheimer's disease (AD). Estrogens have a protective effect in the central nervous system. The mechanisms of action of estrogens are mediated by two estrogen receptors (ERs), ERα and ERβ. Thus, these genes could also play a role in the progression of amnesic mild cognitive impairment (MCIa) to AD. The aim of this study was to examine the role of ER single nucleotide polymorphisms (SNPs) as a risk factor for MCIa, as well as the interaction with apolipoprotein E (APOE) ε4 in the progression to AD.

METHODS

79 MCIa patients and 138 healthy controls were analyzed. SNPs were genotyped via restriction fragment length polymorphisms and real-time PCR, RT-PCR or RT-PCR (TaqMan) assays.

RESULTS

There is a lack of association between MCIa patients who converted to AD and ER SNPs. APOE ε4 allele is an independent risk factor of MCIa (OR=1.86; 95% CI=1.02-3.38, p=0.042) with a high prevalence in converted subjects. APOE ε4 is able to predict the progression from MCIa patients to AD (OR=2.55; 95% CI=1.20-5.42, p=0.015).

CONCLUSIONS

The presence of the APOE ε4 allele, and not the alleles of ER SNPs, is a risk factor for MCIa. Furthermore, APOE genotype seems to predict the conversion from MCIa to AD.

A comparative, developmental, and clinical perspective of neurobehavioral sexual dimorphisms

Women and men differ in a wide variety of behavioral traits and in their vulnerability to developing certain mental disorders. This review endeavors to explore how recent preclinical and clinical research findings have enhanced our understanding of the factors that underlie these disparities. We start with a brief overview of some of the important genetic, molecular, and hormonal determinants that contribute to the process of sexual differentiation. We then discuss the importance of animal models in studying the mechanisms responsible for sex differences in neuropsychiatric disorders (e.g., drug dependence) - with a special emphasis on experimental models based on the neurodevelopmental and "three hits" hypotheses. Next, we describe the most common brain phenotypes observed in vivo with magnetic resonance imaging. We discuss the challenges in interpreting these phenotypes vis-à-vis the underlying neurobiology and revisit the known sex differences in brain structure from birth, through adolescence, and into adulthood. This is followed by a presentation of pertinent clinical and epidemiological data that point to important sex differences in the prevalence, course, and expression of psychopathologies such as schizophrenia, and mood disorders including major depression and posttraumatic stress disorder. Recent evidence implies that mood disorders and psychosis share some common genetic predispositions and neurobiological bases. Therefore, modern research is emphasizing dimensional representation of mental disorders and conceptualization of schizophrenia and major depression as a continuum of cognitive deficits and neurobiological abnormalities. Herein, we examine available evidence on cerebral sexual dimorphism to verify if sex differences vary quantitatively and/or qualitatively along the psychoses-depression continuum. Finally, sex differences in the prevalence of posttraumatic disorder and drug abuse have been described, and we consider the genomic and molecular data supporting these differences.

The human testis-determining factor SRY localizes in midbrain dopamine neurons and regulates multiple components of catecholamine synthesis and metabolism

The male gender is determined by the sex-determining region on the Y chromosome (SRY) transcription factor. The unexpected action of SRY in the control of voluntary movement in male rodents suggests a role in the regulation of dopamine transmission and dopamine-related disorders with gender bias, such as Parkinson's disease. We investigated SRY expression in the human brain and function in vitro. SRY immunoreactivity was detected in the human male, but not female substantia nigra pars compacta, within a sub-population of tyrosine hydroxylase (TH) positive neurons. SRY protein also co-localized with TH positive neurons in the ventral tegmental area, and with GAD-positive neurons in the substantia nigra pars reticulata. Retinoic acid-induced differentiation of human precursor NT2 cells into dopaminergic cells increased expression of TH, NURR1, D2 R and SRY. In the human neuroblastoma cell line, M17, SRY knockdown resulted in a reduction in TH, DDC, DBH and MAO-A expression; enzymes which control dopamine synthesis and metabolism. Conversely, SRY over-expression increased TH, DDC, DBH, D2 R and MAO-A levels, accompanied by increased extracellular dopamine levels. A luciferase assay demonstrated that SRY activated a 4.6 kb 5' upstream regulatory region of the human TH promoter/nigral enhancer. Combined, these results suggest that SRY plays a role as a positive regulator of catecholamine synthesis and metabolism in the human male midbrain. This ancillary genetic mechanism might contribute to gender bias in fight-flight behaviours in men or their increased susceptibility to dopamine disorders, such as Parkinson's disease and schizophrenia.

Neuroglobin, a novel target for endogenous neuroprotection against stroke and neurodegenerative disorders

Brain neurons and tissues respond to sublethal injury by activating endogenous protective pathways. Recently, following the failure of a large number of clinical trials for protective strategies against stroke that aim to inhibit a specific ischemia response pathway, endogenous neuroprotection has emerged as a more promising and hopeful strategy for development of therapeutics against stroke and neurodegenerative disorders. Neuroglobin (Ngb) is an oxygen-binding globin protein that is highly and specifically expressed in brain neurons. Accumulating evidence have clearly demonstrated that Ngb is an endogenous neuroprotective molecule against hypoxic/ischemic and oxidative stress-related insults in cultured neurons and animals, as well as neurodegenerative disorders such as Alzheimer’s disease, thus any pharmacological strategy that can up-regulate endogenous Ngb expression may lead to novel therapeutics against these brain disorders. In this review, we summarize recent studies about the biological function, regulation of gene expression, and neuroprotective mechanisms of Ngb. Furthermore, strategies for identification of chemical compounds that can up-regulate endogenous Ngb expression for neuroprotection against stroke and neurodegenerative disorders are discussed.

A synopsis on the role of tyrosine hydroxylase in Parkinson's disease

Parkinson's disease (PD) is a common chronic progressive neurodegenerative disorder in elderly people. A consistent neurochemical abnormality in PD is degeneration of dopaminergic neurons in substantia nigra pars compacta, leading to a reduction of striatal dopamine (DA) levels. As tyrosine hydroxylase (TH) catalyses the formation of L-dihydroxyphenylalanine (L-DOPA), the rate-limiting step in the biosynthesis of DA, the disease can be considered as a TH-deficiency syndrome of the striatum. Problems related to PD usually build up when vesicular storage of DA is altered by the presence of either α-synuclein protofibrils or oxidative stress. Phosphorylation of three physiologically-regulated specific sites of N-terminal domain of TH is vital in regulating its kinetic and protein interaction. The concept of physiological significance of TH isoforms is another interesting aspect to be explored further for a comprehensive understanding of its role in PD. Thus, a logical and efficient strategy for PD treatment is based on correcting or bypassing the enzyme deficiency by the treatment with L-DOPA, DA agonists, inhibitors of DA metabolism or brain grafts with cells expressing a high level of TH. Neurotrophic factors are also attracting the attention of neuroscientists because they provide the essential neuroprotective and neurorestorative properties to the nigrostriatal DA system. PPAR-γ, a key regulator of immune responses, is likewise a promising target for the treatment of PD, which can be achieved by the use of agonists with the potential to impact the expression of pro- and anti-inflammatory cytokines at the transcriptional level in immune cells via expression of TH. Herein, we review the primary biochemical and pathological features of PD, and describe both classical and developing approaches aimed to ameliorate disease symptoms and its progression.

Altered expression of Alzheimer's disease-related proteins in male hypogonadal mice

Age-related depletion of estrogens and androgens is associated with an increase in Alzheimer's disease (AD) brain pathology and diminished cognitive function. Here we investigated AD-associated molecular and cellular changes in brains of aged hypogonadal (hpg) male and female mice. hpg Mice have a spontaneous, inactivating genetic mutation in the GnRH gene resulting in life-long deficiency of gonadotropins and gonadal sex hormones. Western blot analysis revealed low levels of amyloid precursor protein and high levels of presenilin 1, amyloid precursor protein C-terminal fragment, and β-amyloid 42 in brains of aged male, but not female, hpg mice. Changes were confined to the hippocampus and were not evident in the cerebellum or other brain tissues. Male hpg mice tended to have lower levels of IL-1β protein than male littermate controls. Immunohistochemical staining of the basal forebrain revealed that male hpg mice had lower choline acetyltransferase levels per neuron compared with controls. These AD-like changes specific to male hpg mice supports a link between androgen depletion and the development of AD pathology.

Females experience a more severe disease course in Batten disease

Juvenile neuronal ceroid lipofuscinosis (JNCL; CLN3 disease; Batten disease) is an autosomal recessive neurodegenerative disease of childhood. Symptoms typically present at school age with vision loss followed by progressive cognitive decline, motor dysfunction, seizures, and behavior problems. Studies on sex differences in JNCL have yielded mixed results, but parent anecdotes suggest that females experience a more precipitous disease course. Therefore, we sought to determine if sex-based differences exist in JNCL. We used data from the Unified Batten Disease Rating Scale (UBDRS), the Batten Disease Support and Research Association (BDSRA) database, and the PedsQL quality of life (QoL) survey to evaluate sex-based differences in functional independence and time from symptom onset to death. On average, females had JNCL symptom onset one year later and death one year earlier than did males. Despite a later age at onset, females had lower functional capability, earlier loss of independent function, and lower physical QoL. Future research in sex differences in JNCL may help to further understand the biological mechanisms underpinning the disease course and may point to targeted therapies.

Sex differences in brain epigenetics

Sexual differentiation of the brain takes place during a perinatal-sensitive time window as a result of gonadal hormone-induced activational and organizational effects on neuronal substrates. Increasing evidence suggests that epigenetic mechanisms can contribute to the establishment and maintenance of some aspects of these processes, and that these epigenetic mechanisms may themselves be under the control of sex hormones. Epigenetic programming of neuroendocrine and behavioral phenotypes frequently occurs sex specifically, pointing to sex differences in brain epigenetics as a possible determinant. Understanding how sex-specific epigenomes and sex-biased responses to environmental cues contribute to the development of brain diseases might provide new insights for epigenetic therapy.

Fear extinction as a model for translational neuroscience: ten years of progress

The psychology of extinction has been studied for decades. Approximately 10 years ago, however, there began a concerted effort to understand the neural circuits of extinction of fear conditioning, in both animals and humans. Progress during this period has been facilitated by a high degree of coordination between rodent and human researchers examining fear extinction. Here we review the major advances and highlight new approaches to understanding and exploiting fear extinction. Research in fear extinction could serve as a model for translational research in other areas of behavioral neuroscience.

Neuroprotective effects of 17β-estradiol rely on estrogen receptor membrane initiated signals

Besides its crucial role in many physiological events, 17β-estradiol (E2) exerts protective effects in the central nervous system. The E2 effects are not restricted to the brain areas related with the control of reproductive function, but rather are widespread throughout the developing and the adult brain. E2 actions are mediated through estrogen receptors (i.e., ERα and ERβ) belonging to the nuclear receptor super-family. As members of the ligand-regulated transcription factor family, classically, the actions of ERs in the brain were thought to mediate only the E2 long-term transcriptional effects. However, a growing body of evidence highlighted rapid, membrane initiated E2 effects in the brain that are independent of ER transcriptional activities and are involved in E2-induced neuroprotection. The aim of this review is to focus on the rapid effects of E2 in the brain highlighting the specific role of the signaling pathway(s) of the ERβ subtype in the neuroprotective actions of E2.

Ontogeny of cytochrome p450 aromatase mRNA expression in the developing sheep brain

The intraneuronal conversion of testosterone to oestradiol constitutes a critical step in the development and sexual differentiation of the brain of many short gestation mammalian species and has been inferred to play a similar role in long gestation sheep. This conversion is catalysed by cytochrome P450 aromatase (CYP19), which is expressed in specific brain structures during foetal development. The present study was undertaken to examine the specific neuroanatomical distribution and relative expression of aromatase mRNA in the developing sheep hypothalamus. The foetal sheep is a highly tractable model system for localising the region-specific expression of aromatase in the brain during prenatal development that can help predict regions where oestrogen acts to shape neural development. Our results, obtained using real time quantitative reverse transcriptase-polymerase chain reaction, revealed that aromatase mRNA was expressed throughout mid to late gestation in the foetal preoptic area and amygdala. In the preoptic area, aromatase expression declined with advancing gestation, whereas, it increased in the amygdala. No sex differences were observed in either brain area. We next investigated the anatomical distribution of aromatase using in situ hybridisation histochemistry and found that the pattern of mRNA expression was largely established by midgestation. High expression was observed in the medial preoptic nucleus, bed nucleus of the stria terminalis and corticomedial amygdala. We also observed substantial expression in the dorsal striatum. These results extend our understanding of the developmental expression of aromatase in the foetal sheep brain and lend support to the view that it plays an essential role in sexual differentiation and maturation of the neuroendocrine, motor and reward control systems.

The rs3743205 SNP is important for the regulation of the dyslexia candidate gene DYX1C1 by estrogen receptor β and DNA methylation

Estrogen is involved in numerous physiological processes such as growth, differentiation, and function of the male and female reproductive tissues. In the developing brain, estrogen signaling has been linked to cognitive functions, such as learning and memory; however, the molecular mechanisms underlying this phenomenon are poorly understood. We have previously shown a link between developmental dyslexia and estrogen signaling, when we studied the functional interactions between the dyslexia candidate protein DYX1C1 and the estrogen receptors α (ERα) and β (ERβ). Here, we investigate the 17β-estradiol (E2)-dependent regulation of dyslexia susceptibility 1 candidate 1 (DYX1C1) expression. We demonstrate that ERβ, not ERα, binds to a transcriptionally active cis-regulatory region upstream of DYX1C1 transcriptional start site and that DYX1C1 expression is enhanced by E2 in a neuroblastoma cell line. This regulation is dependent on transcription factor II-I and liganded ERβ recruitment to this region. In addition, we describe that a single nucleotide polymorphism previously shown to be associated with dyslexia and located in the cis-regulatory region of DYX1C1 may alter the epigenetic and endocrine regulation of this gene. Our data provide important molecular insights into the relationship between developmental dyslexia susceptibility and estrogen signaling.

Ovariectomy in the developing rat decelerates cortical spreading depression in adult brain

The brain of mammals is one important target organ for the action of gonadal steroids and, when occurring during development, this hormonal influence may result in important repercussion on the brain electrophysiological properties at adulthood, some of which depending on the brain excitability. Here we have characterized in early-ovariectomized adult rats the brain ability to propagate the excitability-related phenomenon known as cortical spreading depression (CSD), as an index of the cerebral electrophysiological effects of the early-induced absence of the ovarian hormones. Wistar female rat pups (7-day old) underwent bilateral ovariectomy (Ovx group; n=21) or Sham surgery (Sham group; n=22), or no surgery (Naive group; n=22). When the pups became adult (90-130 days), they were submitted to the recording of CSD (electrocorticogram and slow DC-voltage variation) in two points of the cortical surface during 4h. Compared with both Naïve and Sham controls, bilateral ovariectomy early in life resulted in significantly higher body weights (from days 50-65 onwards) and severely reduced uterus weights at adulthood. Furthermore, in the Ovx animals the amplitudes and durations of the DC-potential changes of CSD were higher, and the CSD propagation velocities were reduced. Another group of rats ovariectomized in adulthood did not present such CSD alterations. It is concluded that ovariectomy during brain development is causally associated with the CSD changes in the adult brain, indicating a long-lasting effect, which we suggest as being related to the long-term suppression of the action of the ovarian hormones on brain excitability.

Sex differences, gonadal hormones and the fear extinction network: implications for anxiety disorders

Convergent data from rodents and human studies have led to the development of models describing the neural mechanisms of fear extinction. Key components of the now well-characterized fear extinction network include the amygdala, hippocampus, and medial prefrontal cortical regions. These models are fueling novel hypotheses that are currently being tested with much refined experimental tools to examine the interactions within this network. Lagging far behind, however, is the examination of sex differences in this network and how sex hormones influence the functional activity and reactivity of these brain regions in the context of fear inhibition. Indeed, there is a large body of literature suggesting that sex hormones, such as estrogen, do modulate neural plasticity within the fear extinction network, especially in the hippocampus.After a brief overview of the fear extinction network, we summarize what is currently known about sex differences in fear extinction and the influence of gonadal hormones on the fear extinction network. We then go on to propose possible mechanisms by which sex hormones, such as estrogen, may influence neural plasticity within the fear extinction network. We end with a discussion of how knowledge to be gained from developing this line of research may have significant ramifications towards the etiology, epidemiology and treatment of anxiety disorders.

Sex differences and sex steroids in lung health and disease

Sex differences in the biology of different organ systems and the influence of sex hormones in modulating health and disease are increasingly relevant in clinical and research areas. Although work has focused on sex differences and sex hormones in cardiovascular, musculoskeletal, and neuronal systems, there is now increasing clinical evidence for sex differences in incidence, morbidity, and mortality of lung diseases including allergic diseases (such as asthma), chronic obstructive pulmonary disease, pulmonary fibrosis, lung cancer, as well as pulmonary hypertension. Whether such differences are inherent and/or whether sex steroids play a role in modulating these differences is currently under investigation. The purpose of this review is to define sex differences in lung structure/function under normal and specific disease states, with exploration of whether and how sex hormone signaling mechanisms may explain these clinical observations. Focusing on adult age groups, the review addresses the following: 1) inherent sex differences in lung anatomy and physiology; 2) the importance of certain time points in life such as puberty, pregnancy, menopause, and aging; 3) expression and signaling of sex steroid receptors under normal vs. disease states; 4) potential interplay between different sex steroids; 5) the question of whether sex steroids are beneficial or detrimental to the lung; and 6) the potential use of sex steroid signaling as biomarkers and therapeutic avenues in lung diseases. The importance of focusing on sex differences and sex steroids in the lung lies in the increasing incidence of lung diseases in women and the need to address lung diseases across the life span.

Changes in oestrogen receptor-β mRNA expression in male rat brain with age

Oestrogen has important roles not only in the regulation of reproductive function, but also with respect to other functions, such as cognition, emotion and cardiovascular regulation. Oestrogen acts mainly via its oestrogen receptor (ER), namely, ERα and ERβ in target tissues, including the brain. During ageing, the actions of oestrogen are altered in both females and males, raising the possibility that the expression level of ER may be altered with age. Age-related changes in ER expression in female rat brain have been well demonstrated with regard to reproductive ageing, whereas very little is known about the effects of age on the expression of ERs, especially ERβ, in males. In the present study, which aimed to elucidate the effects of ageing on ERβ expression in the male brain at the transcriptional level, we performed in situ hybridisation using young (10weeks), middle-aged (12months) and old (24 months) gonadally-intact male rats. We revealed a wide distribution of ERβ mRNA-positive cells throughout the brain, and found that the number of ERβ mRNA-positive cells was reduced in several brain regions in males with ageing. ERβ mRNA-positive cells were decreased with age in layer 6 of the cerebral cortex, hippocampal CA1/CA3 regions, the dorsal endopiriform nucleus, the medial septal nucleus, various subregions of the amygdala (central, lateral, anterior cortical and posterolateral cortical subnuclei), the anteroventral periventricular nucleus, the substantia nigra pars compacta, the raphe magnus nucleus and the locus coeruleus. These results suggest that ERβ expression in male rat brain decreases with age at the transcriptional level and that these ageing effects are region-specific.

Gender-related differences in the burden of non-motor symptoms in Parkinson's disease

Differences in the expression of non-motor symptoms (NMS) by Parkinson's disease (PD) patients may have important implications for their management and prognosis. Gender is a basic epidemiological variable that could influence such expression. The present study evaluated the prevalence and severity of NMS by gender in an international sample of 951 PD patients, 62.63% males, using the non-motor symptoms scale (NMSS). Assessments for motor impairment and complications, global severity, and health state were also applied. All disease stages were included. No significant gender differences were found for demographic and clinical characteristics. For the entire sample, the most prevalent symptoms were Nocturia (64.88%) and Fatigue (62.78%) and the most prevalent affected domains were Sleep/Fatigue (84.02%) and Miscellaneous (82.44%). Fatigue, feelings of nervousness, feelings of sadness, constipation, restless legs, and pain were more common and severe in women. On the contrary, daytime sleepiness, dribbling saliva, interest in sex, and problems having sex were more prevalent and severe in men. Regarding the NMSS domains, Mood/Apathy and Miscellaneous problems (pain, loss of taste or smell, weight change, and excessive sweating) were predominantly affected in women and Sexual dysfunction in men. No other significant differences by gender were observed. To conclude, in this study significant differences between men and women in prevalence and severity of fatigue, mood, sexual and digestive problems, pain, restless legs, and daytime sleepiness were found. Gender-related patterns of NMS involvement may be relevant for clinical trials in PD.

Estrogen receptor-α expression in neuronal cells affects bone mass

It has generally been assumed that bone mass is controlled by endocrine mechanisms and the local bone environment. Recent findings demonstrate that central pathways are involved in the regulation of bone mass. Estrogen is involved in the regulation of bone homeostasis and the CNS is also a target for estrogen actions. The aim of this study was to investigate in vivo the role of central estrogen receptor-α (ERα) expression for bone mass. Nestin-Cre mice were crossed with ERα(flox) mice to generate mice lacking ERα expression specifically in nervous tissue (nestin-ERα(-/-)). Bone mineral density was increased in both the trabecular and cortical bone compartments in nestin-ERα(-/-) mice compared with controls. Femoral bone strength was increased in nestin-ERα(-/-) mice, as demonstrated by increased stiffness and maximal load of failure. The high bone mass phenotype in nestin-ERα(-/-) mice was mainly caused by increased bone formation. Serum leptin levels were elevated as a result of increased leptin expression in white adipose tissue (WAT) and slightly increased amount of WAT in nestin-ERα(-/-) mice. Leptin receptor mRNA levels were reduced in the hypothalamus but not in bone. In conclusion, inactivation of central ERα signaling results in increased bone mass, demonstrating that the balance between peripheral stimulatory and central inhibitory ERα actions is important for the regulation of bone mass. We propose that the increased bone mass in nestin-ERα(-/-) mice is mediated via decreased central leptin sensitivity and thereby increased secretion of leptin from WAT, which, in turn, results in increased peripheral leptin-induced bone formation.

Strategies and methods to study sex differences in cardiovascular structure and function: a guide for basic scientists

Background

Cardiovascular disease remains the primary cause of death worldwide. In the US, deaths due to cardiovascular disease for women exceed those of men. While cultural and psychosocial factors such as education, economic status, marital status and access to healthcare contribute to sex differences in adverse outcomes, physiological and molecular bases of differences between women and men that contribute to development of cardiovascular disease and response to therapy remain underexplored.

Methods

This article describes concepts, methods and procedures to assist in the design of animal and tissue/cell based studies of sex differences in cardiovascular structure, function and models of disease.

Results

To address knowledge gaps, study designs must incorporate appropriate experimental material including species/strain characteristics, sex and hormonal status. Determining whether a sex difference exists in a trait must take into account the reproductive status and history of the animal including those used for tissue (cell) harvest, such as the presence of gonadal steroids at the time of testing, during development or number of pregnancies. When selecting the type of experimental animal, additional consideration should be given to diet requirements (soy or plant based influencing consumption of phytoestrogen), lifespan, frequency of estrous cycle in females, and ability to investigate developmental or environmental components of disease modulation. Stress imposed by disruption of sleep/wake cycles, patterns of social interaction (or degree of social isolation), or handling may influence adrenal hormones that interact with pathways activated by the sex steroid hormones. Care must be given to selection of hormonal treatment and route of administration.

Conclusions

Accounting for sex in the design and interpretation of studies including pharmacological effects of drugs is essential to increase the foundation of basic knowledge upon which to build translational approaches to prevent, diagnose and treat cardiovascular diseases in humans.

Neuronal correlates of extinction learning are modulated by sex hormones

In emotional learning tasks, sex differences, stress effects and an interaction of these two moderators have often been observed. The sex hormones estradiol (E2) and progesterone (P4) vary over the menstrual cycle. We tested groups with different sex hormone status: 39 men, 30 women in the luteal phase (LU, high E2+P4) and 29 women taking oral contraceptives (OC, low E2+P4). They received either 30 mg cortisol or placebo prior to instructed differential fear conditioning consisting of neutral conditioned stimuli (CS) and an electrical stimulation (unconditioned stimulus; UCS). One figure (CS+) was paired with the UCS, the other figure (CS-) never. During extinction, no electrical stimulation was administered. Regarding fear acquisition, results showed higher skin conductance and higher brain responses to the CS+ compared to the CS- in several structures that were not modulated by cortisol or sex hormones. However, OC women exhibited higher CS+/CS- differentiations than men and LU women in the amygdala, thalamus, anterior cingulate and ventromedial prefrontal cortex during extinction. The suppression of endogenous sex hormones by OC seems to alter neuronal correlates of extinction. The observation that extinction is influenced by the current sex hormone availability is relevant for future studies and might also be clinically important.