Neuroprotection and estrogen receptors

Selective estrogen receptor activation prior to global cerebral ischemia in female rats impacts microglial activation and anxiety-like behaviors without effects on CA1 neuronal injury

Estrogen receptor (ER) activation by 17-ß estradiol (E2) can attenuate neuronal injury and behavioral impairments following global cerebral ischemia (GCI) in rodents. This study sought to further examine the discrete roles of ERs through characterization of the effects of selective ER activation on post-ischemic pro-inflammatory microglial activation, hippocampal neuronal injury, and anxiety-like behaviors. Forty-six ovariectomized (OVX) adult female Wistar rats received daily s.c injections (100 μg/kg/day) of propylpyrazole triol (PPT; ERα agonist), diarylpropionitrile (DPN; ERβ agonist), G-1 (G-protein coupled ER agonist; GPER), E2 (activating all receptors), or vehicle solution (VEH) for 21 days. After final injection, rats underwent GCI via 4-vessel occlusion (n=8 per group) or sham surgery (n=6, vehicle injections). The Open Field Test (OFT), Elevated Plus Maze (EPM), and Hole Board Test (HBT) assessed anxiety-like behaviors. Microglial activation (Iba1, CD68, CD86) in the basolateral amygdala (BLA), CA1 of the hippocampus, and paraventricular nucleus of the hypothalamus (PVN) was determined 8 days post-ischemia. Compared to sham rats, Iba1 activation and CA1 neuronal injury were increased in all ischemic groups except DPN-treated rats, with PPT-treated ischemic rats also showing increased PVN Iba1-ir expression. Behaviorally, VEH ischemic rats showed slightly elevated anxiety in the EPM compared to sham counterparts, with no significant effects of agonists. While no changes were observed in the OFT, emotion regulation via grooming in the HBT was increased in G-1 rats compared to E2 rats. Our findings support selective ER activation to regulate post-ischemic microglial activation and coping strategies in the HBT, despite minimal impact on hippocampal injury.

Chronic Caffeine Consumption, Alone or Combined with Agomelatine or Quetiapine, Reduces the Maximum EEG Peak, As Linked to Cortical Neurodegeneration, Ovarian Estrogen Receptor Alpha, and Melatonin Receptor 2

RATIONALE

Evidence of the effects of chronic caffeine (CAFF)-containing beverages, alone or in combination with agomelatine (AGO) or quetiapine (QUET), on electroencephalography (EEG), which is relevant to cognition, epileptogenesis, and ovarian function, remains lacking. Estrogenic, adenosinergic, and melatonergic signaling is possibly linked to the dynamics of these substances.

OBJECTIVES

The brain and ovarian effects of CAFF were compared with those of AGO + CAFF and QUET + CAFF. The implications of estrogenic, adenosinergic, and melatonergic signaling and the brain-ovarian crosstalk were investigated.

METHODS

Adult female rats were administered AGO (10 mg/kg), QUET (10 mg/kg), CAFF, AGO + CAFF, or QUET + CAFF, once daily for 8 weeks. EEG, estrous cycle progression, and microstructure of the brain and ovaries were examined. Brain and ovarian 17β-estradiol (E2), antimullerian hormone (AMH), estrogen receptor alpha (E2Rα), adenosine receptor 2A (A2AR), and melatonin receptor 2 (MT2R) were assessed.

RESULTS

CAFF, alone or combined with AGO or QUET, reduced the maximum EEG peak, which was positively linked to ovarian E2Rα, negatively correlated to cortical neurodegeneration and ovarian MT2R, and associated with cystic ovaries. A large corpus luteum emerged with AGO + CAFF and QUET + CAFF, antagonizing the CAFF-mediated increased ovarian A2AR and reduced cortical E2Rα. AGO + CAFF provoked TTP delay and increased ovarian AMH, while QUET + CAFF slowed source EEG frequency to δ range and increased brain E2.

CONCLUSIONS

CAFF treatment triggered brain and ovarian derangements partially antagonized with concurrent AGO or QUET administration but with no overt affection of estrus cycle progression. Estrogenic, adenosinergic, and melatonergic signaling and brain-ovarian crosstalk may explain these effects.

Effect of astrocyte GPER on the optic nerve inflammatory response following optic nerve injury in mice

Activated astrocytes are a primary source of inflammatory factors following traumatic optic neuropathy (TON). Accumulation of inflammatory factors in this context leads to increased axonal damage and loss of retinal ganglion cells (RGCs). Therefore, in the present study, we explored the role of the astrocyte G protein-coupled estrogen receptor (GPER) in regulating inflammatory factors following optic nerve crush (ONC), and analyzed its potential regulatory mechanisms. Overall, our results showed that GPER was abundantly expressed in the optic nerve, and co-localized with glial fibrillary acidic proteins (GFAP). Exogenous administration of G-1 led to a significant reduction in astrocyte activation and expression of inflammation-related factors (including IL-1β, TNF-α, NFκB, and p-NFκB). Additionally, it dramatically increased the survival of RGCs. In contrast, astrocytes were activated to a greater extent by exogenous G15 administration; however, RGCs survival was significantly reduced. In vitro, GPER activation significantly reduced astrocyte activation and the release of inflammation-related factors. In conclusion, activation of astrocyte GPER significantly reduced ONC inflammation levels, and should be explored as a potential target pathway for protecting the optic nerve and RGCs after TON.

A Pilot Systematic Review and Meta-analysis of Neuroprotective Studies in Female Rodent Models of Ischemic Stroke

Most ischemic stroke (IS) patients go untreated due to limited treatment windows, restrictive eligibility criteria, and poor availability of current clinical therapies. Neuroprotective treatments targeting protracted neurodegeneration are needed yet keep failing in clinical trials. Over half of IS patients are female, and the scarcity of neuroprotective studies using female animals hinders translational success. This pilot review and meta-analysis assessed the relationship between the risk of bias and efficacy of studies testing post-ischemic neuroprotective therapies using female rodent models of IS. We carried out a systematic search of the PubMed database for studies published between 1999 and May 2022, used the CAMARADES checklist to evaluate study quality, and extracted data pertaining to lesion volume and behavioral assessment. We found that 34 studies met our inclusion criteria, with pooled effect sizes depicting a significant treatment effect. However, researchers used mostly healthy young females, administered therapies within short time windows, ignored hormonal influences, and did not assess long-term outcomes. Interestingly, studies failing to report factors impacting internal validity, such as blinding and random allocation, had inflated effect sizes or did not reach statistical significance. There was also a relationship between low study quality and larger effect sizes for functional outcome, stressing the need to follow the existing translational design, reporting, and data analysis guidelines. In this review, we cover previous recommendations and offer our own in hopes that rigorous and meticulous research using female animal models of IS will increase our chances of successful bench-to-bedside translation.

Identification of risk factors for reconstructive hip surgery after intrathecal baclofen therapy in children with cerebral palsy

OBJECTIVE

This study aimed to determine the risk factors for reconstructive hip surgery after intrathecal baclofen pump application in children with cerebral palsy.

METHODS

Inclusion criteria were children with hypertonic (spastic or mixed spastic/dystonic motor type) cerebral palsy, intrathecal baclofen implantation <8 years of age, no reconstructive osteotomies prior to or concomitant with intrathecal baclofen implantation and at least a 5-year follow-up. Exclusion criteria included reconstructive osteotomies prior to or concurrent with intrathecal baclofen implantation, lack of at least 1 hip surveillance radiograph before intrathecal baclofen, lack of a 5-year follow-up, or having selective dorsal rhizotomy. In addition, patients with bony surgery plus last follow-up migration percentage ≥50% were labeled as required reconstruction hips.

RESULTS

We identified 34 patients (68 hips). The mean follow-up was 9.2 ± 2.8 years. The mean age for intrathecal baclofen application was 6.4 ± 1.2 years. Seven patients were Gross Motor Function Classification System IV, and 27 were V. Eighteen patients (52.9%) with 31 hips (45.6%) were requiring reconstruction at the final follow-up. In multivariate analysis, male sex (odds ratio 12.8, P=.012), pre-intrathecal baclofen migration percentage (odds ratio 1.1, P=0.003), age at intrathecal baclofen implantation (odds ratio 0.24, P=.002), and delta migration percentage (odds ratio 1.1, P=.002) were significant risk factors for requiring reconstruction. Patients with intrathecal baclofen <6.2 years of age had a significantly higher rate of requiring reconstruction. A pre-intrathecal baclofen migration percentage >31% had a greater risk of progression to requiring reconstruction (P=.001). Delta migration percentage higher than 15% was significantly associated with progression to requiring reconstruction (P=.043).

CONCLUSION

The risk of requiring reconstruction osteotomies after intrathecal baclofen was significantly increased in males, those younger (±migration percentage >31%) at the time of intrathecal baclofen implantation and those with an increased rate of migration percentage progression after intrathecal baclofen implantation.

LEVEL OF EVIDENCE

Level IV, Prognostic Study.

Estradiol and raloxifene as adjunctive treatment for women with schizophrenia: A meta-analysis of randomized, double-blind, placebo-controlled trials

OBJECTIVES

We conducted a comprehensive meta-analysis of all available trials to evaluate the efficacy and safety of estrogen and selective estrogen receptor modulators as adjunctive treatment for women with schizophrenia.

METHODS

Multiple databases were searched from the inception until March 2022. Only randomized, double-blind, placebo-controlled studies (randomized controlled trials) were included. Mean differences (MDs) and their 95% confidence intervals (CIs) were calculated using random effects models.

RESULTS

The meta-analysis included six estradiol versus placebo studies (n = 724) and seven raloxifene versus placebo studies (n = 419), covering a total of 1143 patients. Adjunctive estradiol outperformed the placebo in terms of the Positive and Negative Syndrome Scale (PANSS) total score (MD = -7.29; 95% CI = -10.67 to -3.91; I²  = 59.1%; p < 0.001; k = 9; N = 858), positive symptom score (MD = -1.54; 95% CI = -3.04 to -0.72; I²  = 45.8%; p < 0.001; k = 7; N = 624), negative symptom score (MD = -1.9; 95% CI = -1.77 to -0.34; I²  = 37.6%; p < 0.05; k = 14; N = 1042), and general psychopathology score (MD = -4.27; 95% CI = -7.14 to -1.41; I²  = 76.3%; p < 0.005; k = 7; N = 624). Adjunctive raloxifene outperformed the placebo in terms of the PANSS total score (MD = -6.83; 95% CI = -11.69 to -1.97; I²  = 67.8%; p = 0.006; k = 8; N = 432) and general psychopathology score (MD = -3.82; 95% CI = -6.36 to -1.28; I²  = 65.3%; p < 0.005; k = 8; N = 432).

CONCLUSIONS

Our meta-analysis showed that estradiol and raloxifene are effective and safe adjunctive treatments that improve schizophrenia symptoms in women. Moreover, the effects of estradiol and raloxifene differed in terms of timing and dosage. Both are promising adjunctive treatments that merit further study.

Estrogen receptor alpha signaling in dendritic cells modulates autoimmune disease phenotype in mice

Estrogen is a disease-modifying factor in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE) via estrogen receptor alpha (ERα). However, the mechanisms by which ERα signaling contributes to changes in disease pathogenesis have not been completely elucidated. Here, we demonstrate that ERα deletion in dendritic cells (DCs) of mice induces severe neurodegeneration in the central nervous system in a mouse EAE model and resistance to interferon beta (IFNβ), a first-line MS treatment. Estrogen synthesized by extragonadal sources is crucial for controlling disease phenotypes. Mechanistically, activated ERα directly interacts with TRAF3, a TLR4 downstream signaling molecule, to degrade TRAF3 via ubiquitination, resulting in reduced IRF3 nuclear translocation and transcription of membrane lymphotoxin (mLT) and IFNβ components. Diminished ERα signaling in DCs generates neurotoxic effector CD4+ T cells via mLT-lymphotoxin beta receptor (LTβR) signaling. Lymphotoxin beta receptor antagonist abolished EAE disease symptoms in the DC-specific ERα-deficient mice. These findings indicate that estrogen derived from extragonadal sources, such as lymph nodes, controls TRAF3-mediated cytokine production in DCs to modulate the EAE disease phenotype.

Targeting Estrogen Signaling in the Radiation-induced Neurodegeneration: A Possible Role of Phytoestrogens

Radiation for medical use is a well-established therapeutic method with an excellent prognosis rate for various cancer treatments. Unfortunately, a high dose of radiation therapy comes with its own share of side effects, causing radiation-induced non-specific cellular toxicity; consequently, a large percentage of treated patients suffer from chronic effects during the treatment and even after the post-treatment. Accumulating data evidenced that radiation exposure to the brain can alter the diverse cognitive-related signaling and cause progressive neurodegeneration in patients because of elevated oxidative stress, neuroinflammation, and loss of neurogenesis. Epidemiological studies suggested the beneficial effect of hormonal therapy using estrogen in slowing down the progression of various neuropathologies. Despite its primary function as a sex hormone, estrogen is also renowned for its neuroprotective activity and could manage radiation-induced side effects as it regulates many hallmarks of neurodegenerations. Thus, treatment with estrogen and estrogen-like molecules or modulators, including phytoestrogens, might be a potential approach capable of neuroprotection in radiation-induced brain degeneration. This review summarized the molecular mechanisms of radiation effects and estrogen signaling in the manifestation of neurodegeneration and highlighted the current evidence on the phytoestrogen mediated protective effect against radiationinduced brain injury. This existing knowledge points towards a new area to expand to identify the possible alternative therapy that can be taken with radiation therapy as adjuvants to improve patients' quality of life with compromised cognitive function.

Neuroprotective Mechanism of Icariin on Hypoxic Ischemic Brain Damage in Neonatal Mice

Objective. Our previous results showed that icariin (ICA) could inhibit apoptosis and provide neuroprotection against hypoxic-ischemic brain damage (HIBD) in neonatal mice, but the specific mechanism of its neuroprotective effect remains unknown. This study aims at exploring whether ICA plays a neuroprotective role in apoptosis inhibition by regulating autophagy through the estrogen receptor α (ERα)/estrogen receptor β (ERβ) pathway in neonatal mice with HIBD. Methods. A neonatal mouse model of HIBD was constructed in vivo, and an oxygen and glucose deprivation (OGD) model in HT22 cells from the hippocampal neuronal system was constructed in vitro. The effects of ICA pretreatment on autophagy and the expression of ERα and ERβ were detected in vitro and in vivo, respectively. ICA pretreatment was also supplemented with the autophagy inhibitor 3-methyladenine (3-MA), ERα inhibitor methylpiperidino pyrazole (MPP), and ERβ inhibitor 4-(2-phenyl-5,7-bis (trifluoromethyl) pyrazolo [1,5-a] pyramidin-3-yl) phenol (PHTPP) to further detect whether ICA pretreatment can activate the ERα/ERβ pathway to promote autophagy and reduce HIBD-induced apoptosis to play a neuroprotective role against HIBD in neonatal mice. Results. ICA pretreatment significantly promoted autophagy in HIBD mice. Treatment with 3-MA significantly inhibited the increase in autophagy induced by ICA pretreatment, reversed the neuroprotective effect of ICA pretreatment, and promoted apoptosis. Moreover, ICA pretreatment significantly increased the expression levels of the ERα and ERβ proteins in HIBD newborn mice. Both MPP and PHTPP administration significantly inhibited the expression levels of the ERα and ERβ proteins activated by ICA pretreatment, reversed the neuroprotective effects of ICA pretreatment, inhibited the increase in autophagy induced by ICA pretreatment, and promoted apoptosis. Conclusion. ICA pretreatment may promote autophagy by activating the ERα and ERβ pathways, thus reducing the apoptosis induced by HIBD and exerting a neuroprotective effect on neonatal mice with HIBD.

Exploring the role of sex differences in Alzheimer's disease pathogenesis in Down syndrome

Women are disproportionately affected by Alzheimer's disease (AD), yet little is known about sex-specific effects on the development of AD in the Down syndrome (DS) population. DS is caused by a full or partial triplication of chromosome 21, which harbors the amyloid precursor protein (APP) gene, among others. The majority of people with DS in their early- to mid-40s will accumulate sufficient amyloid-beta (Aβ) in their brains along with neurofibrillary tangles (NFT) for a neuropathological diagnosis of AD, and the triplication of the APP gene is regarded as the main cause. Studies addressing sex differences with age and impact on dementia in people with DS are inconsistent. However, women with DS experience earlier age of onset of menopause, marked by a drop in estrogen, than women without DS. This review focuses on key sex differences observed with age and AD in people with DS and a discussion of possible underlying mechanisms that could be driving or protecting from AD development in DS. Understanding how biological sex influences the brain will lead to development of dedicated therapeutics and interventions to improve the quality of life for people with DS and AD.

Necrosulfonamide Alleviates Acute Brain Injury of Intracerebral Hemorrhage via Inhibiting Inflammation and Necroptosis

Objective

Intracerebral hemorrhage (ICH) is the most lethal subtype of stroke, without effective treatment. Necrosulfonamide (NSA), a specific inhibitor for mixed lineage kinase domain-like protein, has been reported to exert neuroprotective effects in neurological diseases by ameliorating neuroinflammation and necroptosis. We hypothesized that NSA would alleviate acute brain injury and improve behavioral outcomes after ICH.

Materials and Methods

Male adult C57BL/6 mice were assigned randomly into three groups. In vehicle and treatment groups, animals were injected with collagenase VII to induce ICH. The solvent (0.25% DMSO) and NSA (5 mg/kg) were administrated intraperitoneally twice a day, respectively. The sham group was injected with saline and administrated with DMSO. The brain hematoma volume, inflammatory factors, and blood-brain barrier permeability were measured on day 3 after the operation. Fluorescent double immunostaining was performed to evaluate the neuronal death. Neurological functions were assessed.

Results

In the NSA group, the hematoma size was significantly reduced, inflammatory cells and cytokines were suppressed, and the blood-brain barrier was protected compared to vehicle controls. NSA dramatically reduced the death of neurons and improved the performance of neurological functions after ICH.

Conclusion

Necrosulfonamide has a neuroprotective role in alleviating acute brain injury in a mouse ICH model, and this is associated with reduced neuroinflammation and necroptosis.

Estrogen, Cognitive Performance, and Functional Imaging Studies: What Are We Missing About Neuroprotection?

Menopause transition can be interpreted as a vulnerable state characterized by estrogen deficiency with detrimental systemic effects as the low-grade chronic inflammation that appears with aging and partly explains age-related disorders as cancer, diabetes mellitus and increased risk of cognitive impairment. Over the course of a lifetime, estrogen produces several beneficial effects in healthy neurological tissues as well as cardioprotective effects, and anti-inflammatory effects. However, clinical evidence on the efficacy of hormone treatment in menopausal women has failed to confirm the benefit reported in observational studies. Unambiguously, enhanced verbal memory is the most robust finding from longitudinal and cross-sectional studies, what merits consideration for future studies aiming to determine estrogen neuroprotective efficacy. Estrogen related brain activity and functional connectivity remain, however, unexplored. In this context, the resting state paradigm may provide valuable information about reproductive aging and hormonal treatment effects, and their relationship with brain imaging of functional connectivity may be key to understand and anticipate estrogen cognitive protective effects. To go in-depth into the molecular and cellular mechanisms underlying rapid-to-long lasting protective effects of estrogen, we will provide a comprehensive review of cognitive tasks used in animal studies to evaluate the effect of hormone treatment on cognitive performance and discuss about the tasks best suited to the demonstration of clinically significant differences in cognitive performance to be applied in human studies. Eventually, we will focus on studies evaluating the DMN activity and responsiveness to pharmacological stimulation in humans.

Phytoestrogen genistein modulates neuron-microglia signaling in a mouse model of chronic social defeat stress

Microglia, resident immune cells in the brain, are shown to mediate the crosstalk between psychological stress and depression. Interestingly, increasing evidence indicates that sex hormones, particularly estrogen, are involved in the regulation of immune system. In this study, we aimed to understand the potential effects of chronic social defeat stress (CSDS) and genistein (GEN), an estrogenic compound of the plant origin, on neuron-microglia interactions in the mouse hippocampus. The time spent in the avoidance zone in the social interaction test was increased by CSDS 1 day after the exposure, while the avoidance behavior returned to control levels 14 days after the CSDS exposure. Similar results were obtained from the elevated plus-maze test. However, the immobility time in the forced swim test was increased by CSDS 14 days after the exposure, and the depression-related behavior was in part alleviated by GEN. The numerical densities of microglia in the hippocampus were increased by CSDS, and they were decreased by GEN. The voxel densities of synaptic structures and synaptic puncta colocalized with microglia were decreased by CSDS, and they were increased by GEN. Neither CSDS nor GEN affected the gene expressions of major pro-inflammatory cytokines. Conversely, the expression levels of genes related to neurotrophic factors were decreased by CSDS, and they were partially reversed by GEN. These findings show that GEN may in part alleviate stress-related symptoms, and the effects of GEN may be associated with the modulation of neuron-microglia signaling via chemokines and neurotrophic factors in the hippocampus.

Neuron-Derived Estrogen-A Key Neuromodulator in Synaptic Function and Memory

In addition to being a steroid hormone, 17β-estradiol (E₂) is also a neurosteroid produced in neurons in various regions of the brain of many species, including humans. Neuron-derived E₂ (NDE₂) is synthesized from androgen precursors via the action of the biosynthetic enzyme aromatase, which is located at synapses and in presynaptic terminals in neurons in both the male and female brain. In this review, we discuss evidence supporting a key role for NDE₂ as a neuromodulator that regulates synaptic plasticity and memory. Evidence supporting an important neuromodulatory role of NDE₂ in the brain has come from studies using aromatase inhibitors, aromatase overexpression in neurons, global aromatase knockout mice, and the recent development of conditional forebrain neuron-specific knockout mice. Collectively, these studies demonstrate a key role of NDE₂ in the regulation of synapse and spine density, efficacy of excitatory synaptic transmission and long-term potentiation, and regulation of hippocampal-dependent recognition memory, spatial reference memory, and contextual fear memory. NDE₂ is suggested to achieve these effects through estrogen receptor-mediated regulation of rapid kinase signaling and CREB-BDNF signaling pathways, which regulate actin remodeling, as well as transcription, translation, and transport of synaptic proteins critical for synaptic plasticity and function.

Neurodegenerative Disease: Roles for Sex, Hormones, and Oxidative Stress

Neurodegenerative diseases cause severe impairments in cognitive and motor function. With an increasing aging population and the onset of these diseases between 50 and 70 years, the consequences are bound to be devastating. While age and longevity are the main risk factors for neurodegenerative diseases, sex is also an important risk factor. The characteristic of sex is multifaceted, encompassing sex chromosome complement, sex hormones (estrogens and androgens), and sex hormone receptors. Sex hormone receptors can induce various signaling cascades, ranging from genomic transcription to intracellular signaling pathways that are dependent on the health of the cell. Oxidative stress, associated with aging, can impact the health of the cell. Sex hormones can be neuroprotective under low oxidative stress conditions but not in high oxidative stress conditions. An understudied sex hormone receptor that can induce activation of oxidative stress signaling is the membrane androgen receptor (mAR). mAR can mediate nicotinamide adenine dinucleotide-phosphate (NADPH) oxidase (NOX)-generated oxidative stress that is associated with several neurodegenerative diseases, such as Alzheimer disease. Further complicating this is that aging can alter sex hormone signaling. Prior to menopause, women experience more estrogens than androgens. During menopause, this sex hormone profile switches in women due to the dramatic ovarian loss of 17β-estradiol with maintained ovarian androgen (testosterone, androstenedione) production. Indeed, aging men have higher estrogens than aging women due to aromatization of androgens to estrogens. Therefore, higher activation of mAR-NOX signaling could occur in menopausal women compared with aged men, mediating the observed sex differences. Understanding of these signaling cascades could provide therapeutic targets for neurodegenerative diseases.

Why the Hips Remain Stable When the Spine Strays: A Deeper Analysis of the Relationship Between Hip Displacement and Severe Scoliosis in Patients With Cerebral Palsy

BACKGROUND

Many patients with spastic quadriplegic cerebral palsy (CP) and severe scoliosis develop hip displacement, whereas others do not. We investigated demographic characteristics, risk factors for CP, and imaging findings associated with nondisplaced hips in patients with CP and severe scoliosis.

METHODS

We retrospectively analyzed records of 229 patients with spastic quadriplegic CP and severe scoliosis who presented for treatment at our US academic tertiary care hospital between August 2005 and September 2015. Demographic characteristics, risk factors for CP, and brain magnetic resonance imaging (MRI) findings were documented. Patients were classified as Gross Motor Function Classification System (GMFCS) level 4 or higher, with 58% at GMFCS level 5.3. Displaced hips (n=181 patients) were defined as a migration percentage of ≥30% or previous surgery for hip displacement/adductor contractures. Patients who did not meet these criteria were classified as nondisplaced (n=48 patients). We used univariate analysis and multivariate logistic regression to determine associations between patient factors and hip displacement (alpha=0.05).

RESULTS

Patients born at term (≥37 wk) had 2.5 times the odds [95% confidence interval (CI): 1.3-5.0] of having nondisplaced hips compared with patients born prematurely. Females had 2.0 times the odds (95% CI: 1.0-3.9) of having nondisplaced hips compared with males. Patients with normal brain MRI findings had 9.6 times the odds (95% CI: 2.3-41) of having nondisplaced hips compared with patients with abnormal findings. Hip displacement was not associated with race (P>0.05).

CONCLUSIONS

Gestational age 37 weeks or above, female sex, and normal brain MRI findings are independently associated with nondisplaced hips in patients with spastic quadriplegic CP and severe scoliosis. These findings direct attention to characteristics that may place patients at greater risk of displacement. Future work may influence preventative screening practices and improve patient counseling regarding the risk of hip displacement.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

Motor Function Deficits in the Estrogen Receptor Beta Knockout Mouse: Role on Excitatory Neurotransmission and Myelination in the Motor Cortex

BACKGROUND

Male estrogen receptor beta (ERβ) knockout (BERKO) mice display anxiety and aggression linked to, among others, altered serotonergic signaling in the basolateral amygdala and dorsal raphe, impaired cortical radial glia migration, and reduced GABAergic signaling. The effects on primary motor cortex (M1 cortex) and locomotor activity as a consequence of ERβ loss have not been investigated.

OBJECTIVE

The aim of this study was to determine whether locomotor activity is altered as a consequence of the changes in the M1 cortex.

METHODS

The locomotor activity of male wild-type (WT) and BERKO mice was evaluated using the open-field and rotarod tests. Molecular changes in the M1 cortex were analyzed by RNA sequencing, electron microscopy, electrophysiology, and immunohistological techniques. In addition, we established oligodendrocyte (OL) cultures from WT and BERKO mouse embryonic stem cells to evaluate OL function.

RESULTS

Locomotor profiling revealed that BERKO mice were more active than WT mice but had impaired motor coordination. Analysis of the M1 cortex pointed out differences in synapse function and myelination. There was a reduction in GABAergic signaling resulting in imbalanced excitatory and inhibitory neurotransmission as well as a defective OL differentiation accompanied by myelin defects. The effects of ERβ loss on OL differentiation were confirmed in vitro.

CONCLUSION

ERβ is an important regulator of GABAergic interneurons and OL differentiation, which impacts on adult M1 cortex function and may be linked to increased locomotor activity and decreased motor coordination in BERKO mice.

Sex and oestrogen receptor β have modest effects on gene expression in the mouse brain posterior cortex

Introduction

Sex differences in brain cortical function affect cognition, behaviour and susceptibility to neural diseases, but the molecular basis of sexual dimorphism in cortical function is still largely unknown. Oestrogen and oestrogen receptors (ERs), specifically ERβ, the most abundant ER in the cortex, may play a role in determining sex differences in gene expression, which could underlie functional sex differences. However, further investigation is needed to address brain region specificity of the effects of sex and ERβ on gene expression. The goal of this study was to investigate sex differences in gene expression in the mouse posterior cortex, where sex differences in transcription have never been examined, and to determine how genetic ablation of ERβ affects transcription.

Methods

In this study, we performed unbiased transcriptomics on RNA from the posterior cortex of adult wild-type and ERβ knockout mice (n = 4/sex/genotype). We used unbiased clustering to analyse whole-transcriptome changes between the groups. We also performed differential expression analysis on the data using DESeq2 to identify specific changes in gene expression.

Results

We found only 27 significantly differentially expressed genes (DEGs) in wild-type (WT) males vs females, of which 17 were autosomal genes. Interestingly, in ERβKO males vs females all the autosomal DEGs were lost. Gene Ontology analysis of the subset of DEGs with sex differences only in the WT cortex revealed a significant enrichment of genes annotated with the function 'cation channel activity'. Moreover, within each sex we found only a few DEGs in ERβKO vs WT mice (8 and 5 in males and females, respectively).

Conclusions

Overall, our results suggest that in the adult mouse posterior cortex there are surprisingly few sex differences in gene expression, and those that exist are mainly related to cation channel activity. Additionally, they indicate that brain region-specific functional effects of ERβ may be largely post-transcriptional.

The peri-menopause in a woman's life: a systemic inflammatory phase that enables later neurodegenerative disease

The peri-menopause or menopausal transition—the time period that surrounds the final years of a woman’s reproductive life—is associated with profound reproductive and hormonal changes in a woman’s body and exponentially increases a woman’s risk of cerebral ischemia and Alzheimer’s disease. Although our understanding of the exact timeline or definition of peri-menopause is limited, it is clear that there are two stages to the peri-menopause. These are the early menopausal transition, where menstrual cycles are mostly regular, with relatively few interruptions, and the late transition, where amenorrhea becomes more prolonged and lasts for at least 60 days, up to the final menstrual period. Emerging evidence is showing that peri-menopause is pro-inflammatory and disrupts estrogen-regulated neurological systems. Estrogen is a master regulator that functions through a network of estrogen receptors subtypes alpha (ER-α) and beta (ER-β). Estrogen receptor-beta has been shown to regulate a key component of the innate immune response known as the inflammasome, and it also is involved in regulation of neuronal mitochondrial function. This review will present an overview of the menopausal transition as an inflammatory event, with associated systemic and central nervous system inflammation, plus regulation of the innate immune response by ER-β-mediated mechanisms.

Neuron-Derived Estrogen Regulates Synaptic Plasticity and Memory

17β-estradiol (E2) is produced from androgens via the action of the enzyme aromatase. E2 is known to be made in neurons in the brain, but its precise functions in the brain are unclear. Here, we used a forebrain-neuron-specific aromatase knock-out (FBN-ARO-KO) mouse model to deplete neuron-derived E2 in the forebrain of mice and thereby elucidate its functions. FBN-ARO-KO mice showed a 70–80% decrease in aromatase and forebrain E2 levels compared with FLOX controls. Male and female FBN-ARO-KO mice exhibited significant deficits in forebrain spine and synaptic density, as well as hippocampal-dependent spatial reference memory, recognition memory, and contextual fear memory, but had normal locomotor function and anxiety levels. Reinstating forebrain E2 levels via exogenous in vivo E2 administration was able to rescue both the molecular and behavioral defects in FBN-ARO-KO mice. Furthermore, in vitro studies using FBN-ARO-KO hippocampal slices revealed that, whereas induction of long-term potentiation (LTP) was normal, the amplitude was significantly decreased. Intriguingly, the LTP defect could be fully rescued by acute E2 treatment in vitro. Mechanistic studies revealed that FBN-ARO-KO mice had compromised rapid kinase (AKT, ERK) and CREB-BDNF signaling in the hippocampus and cerebral cortex. In addition, acute E2 rescue of LTP in hippocampal FBN-ARO-KO slices could be blocked by administration of a MEK/ERK inhibitor, further suggesting a key role for rapid ERK signaling in neuronal E2 effects. In conclusion, the findings provide evidence of a critical role for neuron-derived E2 in regulating synaptic plasticity and cognitive function in the male and female brain.

SIGNIFICANCE STATEMENT The steroid hormone 17β-estradiol (E2) is well known to be produced in the ovaries in females. Intriguingly, forebrain neurons also express aromatase, the E2 biosynthetic enzyme, but the precise functions of neuron-derived E2 is unclear. Using a novel forebrain-neuron-specific aromatase knock-out mouse model to deplete neuron-derived E2, the current study provides direct genetic evidence of a critical role for neuron-derived E2 in the regulation of rapid AKT-ERK and CREB-BDNF signaling in the mouse forebrain and demonstrates that neuron-derived E2 is essential for normal expression of LTP, synaptic plasticity, and cognitive function in both the male and female brain. These findings suggest that neuron-derived E2 functions as a novel neuromodulator in the forebrain to control synaptic plasticity and cognitive function.

Neurodegenerative Diseases: Regenerative Mechanisms and Novel Therapeutic Approaches

Regeneration refers to regrowth of tissue in the central nervous system. It includes generation of new neurons, glia, myelin, and synapses, as well as the regaining of essential functions: sensory, motor, emotional and cognitive abilities. Unfortunately, regeneration within the nervous system is very slow compared to other body systems. This relative slowness is attributed to increased vulnerability to irreversible cellular insults and the loss of function due to the very long lifespan of neurons, the stretch of cells and cytoplasm over several dozens of inches throughout the body, insufficiency of the tissue-level waste removal system, and minimal neural cell proliferation/self-renewal capacity. In this context, the current review summarized the most common features of major neurodegenerative disorders; their causes and consequences and proposed novel therapeutic approaches.

Rapid non-classical effects of steroids on the membrane receptor dynamics and downstream signaling in neurons

Contribution to Special Issue on Fast effects of steroids. Although rapid effects of steroid hormones on membrane receptors and intracellular signaling molecules have been extensively studied in neurons, we are only beginning to understand the molecular mechanisms behind these non-classical steroid actions. Single molecule tracking (SMT) studies on live cells demonstrated that surface trafficking of membrane receptors determines their ligand binding properties and downstream signaling events. Recent findings suggest that one of the underlying mechanisms of non-classical steroid actions is the alteration of receptor movements on the membrane surface. In order to highlight this novel aspect of steroid effects, we first address the types of receptor movements in the plasma membrane and the role of cortical actin dynamics in receptor movement. We then discuss how single molecules and the surface movements of receptors can be detected in live cells. Next, we review the fundamental processes, which determine the effect of steroids on the plasma membrane: steroid movement through the lipid bilayer and the role of steroid membrane receptors. Using glutamate and neurotrophin receptors (NTRs) as examples, we demonstrate the features of receptor dynamics in the membrane. In addition, we survey the available data of rapid steroid actions on membrane receptor trafficking: we discuss how glucocorticoids act on the surface diffusion of glutamate receptor molecules and how estradiol acts on NTRs and gamma-aminobutyric acid type A receptors (GABA_ARs) and their related signaling events as well as on cortical actin. Finally, we address the physiological relevance of rapid steroid action on membrane receptors dynamics.

17β-Estradiol Regulates Microglia Activation and Polarization in the Hippocampus Following Global Cerebral Ischemia

17β-Estradiol (E2) is a well-known neuroprotective hormone, but its role in regulation of neuroinflammation is less understood. Recently, our lab demonstrated that E2 could regulate the NLRP3 (NOD-like receptor protein 3) inflammasome pathway in the hippocampus following global cerebral ischemia (GCI). Here, we examined the ability of E2 to regulate activation and polarization of microglia phenotype in the hippocampus after global cerebral ischemia (GCI). Our in vivo study in young adult ovariectomized rats showed that exogenous low-dose E2 profoundly suppressed microglia activation and quantitatively shifted microglia from their "activated," amoeboid morphology to a "resting," ramified morphology after GCI. Further studies using M1 "proinflammatory" and M2 "anti-inflammatory" phenotype markers showed that E2 robustly suppressed the "proinflammatory" M1 phenotype, while enhancing the "anti-inflammatory" M2 microglia phenotype in the hippocampus after GCI. These effects of E2 may be mediated directly upon microglia, as E2 suppressed the M1 while enhancing the M2 microglia phenotype in LPS- (lipopolysaccharide-) activated BV2 microglia cells in vitro. E2 also correspondingly suppressed proinflammatory while enhancing anti-inflammatory cytokine gene expression in the LPS-treated BV2 microglia cells. Finally, E2 treatment abolished the LPS-induced neurotoxic effects of BV2 microglia cells upon hippocampal HT-22 neurons. Collectively, our study findings suggest a novel E2-mediated neuroprotective effect via regulation of microglia activation and promotion of the M2 "anti-inflammatory" phenotype in the brain.

Estradiol Activates PI3K/Akt/GSK3 Pathway Under Chronic Neurodegenerative Conditions Triggered by Perinatal Asphyxia

Perinatal asphyxia (PA) remains as one of the most important causes of short-term mortality, psychiatric and neurological disorders in children, without an effective treatment. In previous studies we have observed that the expression of different neurodegenerative markers increases in CA1 hippocampal area of 4-months-old male rats born by cesarean section and exposed for 19 min to PA. We have also shown that a late treatment with 17β estradiol (daily dose of 250 μg/kg for 3 days) was able to revert the brain alterations observed in those animals. Based on these previous results, the main aim of the present study was to explore the mechanism by which the estrogenic treatment is involved in the reversion of the chronic neurodegenerative conditions induced by PA. We demonstrated that estradiol treatment of adult PA exposed animals induced an increase in estrogen receptor (ER) α and insulin-like growth factor receptor (IGF-1R) protein levels, an activation of the phosphatidylinositol 3-kinase/Akt/glycogen synthase kinase 3 beta/β-catenin signaling pathway and an increase in Bcl-2/Bax ratio in the hippocampus in comparison to PA exposed animals treated with vehicle. Taking together, our data suggest that the interaction between ERα and IGF-IR, with the subsequent downstream activation, underlies the beneficial effects of estradiol observed in late treatment of PA.

Estrogen-induced neuroimmunomodulation as facilitator of and barrier to reproductive aging in brain and lymphoid organs

Reproductive aging in females is marked by alterations in gonadal hormones, estrogen and progesterone, that facilitate cessation of reproductive cycles and onset of female-specific diseases such as autoimmune and neurodegenerative diseases, hormone-dependent cancers, and osteoporosis. Bidirectional communication between the three homeostatic systems, nervous system, endocrine system, and immune system, is essential for the maintenance of health and any dysfunction in the cross-talk promotes the development of diseases and cancer. The pleiotropic effects of estrogen on neural-immune interactions may promote either neuroprotection or inflammatory conditions depending on the site of action, dose and duration of treatment, type of estrogen receptors and its influence on intracellular signaling pathways, etc. Our studies involving treatment of early middle-aged female rats with low and high doses of estrogen and examining the brain areas, thymus, spleen, and lymph nodes revealed that estrogen-induced changes in neural-immune interactions are markedly affected in thymus followed by spleen and lymph nodes while it confers neuroprotection in the brain areas. These alterations are determined by antioxidant enzyme status, growth factors, intracellular signaling pathways involved in cell survival and inflammation, and metabolic enzymes and thus, may regulate the various stages in female reproductive aging. It is imperative that detailed longitudinal studies are carried out to understand the mechanisms of neuroendocrine-immune interactions in reproductive aging to facilitate healthy aging and for the development of better treatment strategies for female-specific diseases.

Role of estrogen receptor beta in neural differentiation of mouse embryonic stem cells

The ability to propagate mature cells and tissue from pluripotent stem cells offers enormous promise for treating many diseases, including neurodegenerative diseases. Before such cells can be used successfully in neurodegenerative diseases without causing unwanted cell growth and migration, genes regulating growth and migration of neural stem cells need to be well characterized. Estrogen receptor beta (ERβ) is essential for migration of neurons and glial cells in the developing mouse brain. To examine whether ERβ influences differentiation of mouse embryonic stem cells (mESC) into neural lineages, we compared control and ERβ knockout (BERKO) mESCs at defined stages of neural development and examined the effects of an ERβ-selective ligand (LY3201) with a combination of global and targeted gene-expression profiling and the expression of key pluripotency markers. We found that ERβ was induced in embryoid bodies (EBs) and neural precursor cells (NPCs) during development. Proliferation was higher in BERKO NPCs and was inhibited by LY3201. Neurogenesis was reduced in BERKO ES cells, and oligodendrogliogenesis was enhanced. BERKO EBs expressed higher levels of key ectodermal and neural progenitor markers and lower levels of markers for mesoderm and endoderm lineages. ERβ-regulated factors are involved in cell adhesion, axon guidance, and signaling of Notch and GABA receptor pathways, as well as factors important for the differentiation of neuronal precursors into dopaminergic neurons (Engrailed 1) and for the oligodendrocyte fate acquisition (Olig2). Our data suggest that ERβ is an important component for differentiation into midbrain neurons as well as for preventing precocious oligodendrogliogenesis.

Sex and the development of Alzheimer's disease

Men and women exhibit differences in the development and progression of Alzheimer's disease (AD). The factors underlying the sex differences in AD are not well understood. This Review emphasizes the contributions of sex steroid hormones to the relationship between sex and AD. In women, events that decrease lifetime exposure to estrogens are generally associated with increased AD risk, whereas estrogen-based hormone therapy administered near the time of menopause may reduce AD risk. In men, estrogens do not exhibit age-related reduction and are not significantly associated with AD risk. Rather, normal age-related depletions of testosterone in plasma and brain predict enhanced vulnerability to AD. Both estrogens and androgens exert numerous protective actions in the adult brain that increase neural functioning and resilience as well as specifically attenuating multiple aspects of AD-related neuropathology. Aging diminishes the activational effects of sex hormones in sex-specific manners, which is hypothesized to contribute to the relationship between aging and AD. Sex steroid hormones may also drive sex differences in AD through their organizational effects during developmental sexual differentiation of the brain. Specifically, sex hormone actions during early development may confer inherent vulnerability of the female brain to development of AD in advanced age. The combined effects of organizational and activational effects of sex steroids yield distinct sex differences in AD pathogenesis, a significant variable that must be more rigorously considered in future research. © 2016 Wiley Periodicals, Inc.

GPER Agonist G1 Attenuates Neuroinflammation and Dopaminergic Neurodegeneration in Parkinson Disease

OBJECTIVE

Epidemiological studies have shown that women of reproductive age have much less possibility of developing Parkinson disease (PD) than men. The beneficial effect of estrogen also has been well-described in both culture and animal models of PD. G protein-coupled estrogen receptor (GPER) is a membrane-associated estrogen receptor, and displayed a neuroprotective role in a mouse model of PD. Since GPER is highly expressed in microglia, we speculate that GPER mediates the neuroprotective function of estradiol through suppressing the neuroinflammation of PD.

METHODS

We investigated the effects of GPER agonist G1 and GPER antagonist G15 on the neurodegeneration of dopaminergic neuron, the activation of microglia, and the production of IL-1β, TNF-α, and IL-6 in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced animal model of parkinsonism. Furthermore, we confirmed the effects of GPER activation on the production of IL-1β, TNF-α, and IL-6 in an in vitro MPP+ model in BV2 microglial cells.

RESULTS

After 12-day treatment with G1, mice showed an increase in the number of tyrosine hydroxylase-immunoreactive cells, reduced activation of microglia, and the abatement of proinflammatory cytokines, and the anti-inflammatory effect of G1 was abolished by G15. Meanwhile, in vitro studies demonstrated that GPER activation also reduced the release of proinflammatory cytokines from BV2 microglial cells after MPP+ stimulation.

CONCLUSION

Our data suggest that GPER mediates the anti-neuroinflammatory effect of estrogen in experimental PD progression.

Neuroprotection by Estrogen and Progesterone in Traumatic Brain Injury and Spinal Cord Injury

In recent years there has been a growing body of clinical and laboratory evidence demonstrating the neuroprotective effects of estrogen and progesterone after traumatic brain injury (TBI) and spinal cord injury (SCI). In humans, women have been shown to have a lower incidence of morbidity and mortality after TBI compared with age-matched men. Similarly, numerous laboratory studies have demonstrated that estrogen and progesterone administration is associated with a mortality reduction, improvement in neurological outcomes, and a reduction in neuronal apoptosis after TBI and SCI. Here, we review the evidence that supports hormone-related neuroprotection and discuss possible underlying mechanisms. Estrogen and progesterone-mediated neuroprotection are thought to be related to their effects on hormone receptors, signaling systems, direct antioxidant effects, effects on astrocytes and microglia, modulation of the inflammatory response, effects on cerebral blood flow and metabolism, and effects on mediating glutamate excitotoxicity. Future laboratory research is needed to better determine the mechanisms underlying the hormones' neuroprotective effects, which will allow for more clinical studies. Furthermore, large randomized clinical control trials are needed to better assess their role in human neurodegenerative conditions.

In Vitro Neuroprotective and Anti-Inflammatory Activities of Natural and Semi-Synthetic Spirosteroid Analogues

Two spirosteroid analogues were synthesized and evaluated for their in vitro neuroprotective activities in PC12 cells, against glutamate-induced excitotoxicity and mitochondrial damage in glucose deprivation conditions, as well as their anti-inflammatory potential in LPS/IFNγ-stimulated microglia primary cultures. We also evaluated the in vitro anti-excitotoxic and anti-inflammatory activities of natural and endogenous steroids. Our results show that the plant-derived steroid solasodine decreased PC12 glutamate-induced excitotoxicity, but not the cell death induced by mitochondrial damage and glucose deprivation. Among the two synthetic spirosteroid analogues, only the (25R)-5α-spirostan-3,6-one (S15) protected PC12 against ischemia-related in vitro models and inhibited NO production, as well as the release of IL-1β by stimulated primary microglia. These findings provide further insights into the role of specific modifications of the A and B rings of sapogenins for their neuroprotective potential.

Roles of PTEN with DNA Repair in Parkinson's Disease

Oxidative stress is considered to play key roles in aging and pathogenesis of many neurodegenerative diseases such as Parkinson’s disease, which could bring DNA damage by cells. The DNA damage may lead to the cell apoptosis, which could contribute to the degeneration of neuronal tissues. Recent evidence suggests that PTEN (phosphatase and tensin homolog on chromosome 10) may be involved in the pathophysiology of the neurodegenerative disorders. Since PTEN expression appears to be one dominant determinant of the neuronal cell death, PTEN should be a potential molecular target of novel therapeutic strategies against Parkinson’s disease. In addition, defects in DNA damage response and DNA repair are often associated with modulation of hormone signaling pathways. Especially, many observations imply a role for estrogen in a regulation of the DNA repair action. In the present review, we have attempted to summarize the function of DNA repair molecules at a viewpoint of the PTEN signaling pathway and the hormone related functional modulation of cells, providing a broad interpretation on the molecular mechanisms for treatment of Parkinson’s disease. Particular attention will be paid to the mechanisms proposed to explain the health effects of food ingredients against Parkinson’s disease related to reduce oxidative stress for an efficient therapeutic intervention.

Transcriptional Regulation of Glutamate Transporters: From Extracellular Signals to Transcription Factors

Glutamate is the predominant excitatory neurotransmitter in the mammalian CNS. It mediates essentially all rapid excitatory signaling. Dysfunction of glutamatergic signaling contributes to developmental, neurologic, and psychiatric diseases. Extracellular glutamate is cleared by a family of five Na(+)-dependent glutamate transporters. Two of these transporters (GLAST and GLT-1) are relatively selectively expressed in astrocytes. Other of these transporters (EAAC1) is expressed by neurons throughout the nervous system. Expression of the last two members of this family (EAAT4 and EAAT5) is almost exclusively restricted to specific populations of neurons in cerebellum and retina, respectively. In this review, we will discuss our current understanding of the mechanisms that control transcriptional regulation of the different members of this family. Over the last two decades, our understanding of the mechanisms that regulate expression of GLT-1 and GLAST has advanced considerably; several specific transcription factors, cis-elements, and epigenetic mechanisms have been identified. For the other members of the family, little or nothing is known about the mechanisms that control their transcription. It is assumed that by defining the mechanisms involved, we will advance our understanding of the events that result in cell-specific expression of these transporters and perhaps begin to define the mechanisms by which neurologic diseases are changing the biology of the cells that express these transporters. This approach might provide a pathway for developing new therapies for a wide range of essentially untreatable and devastating diseases that kill neurons by an excitotoxic mechanism.

Proline-, glutamic acid-, and leucine-rich protein 1 mediates estrogen rapid signaling and neuroprotection in the brain

17-β estradiol (E2) has been implicated as neuroprotective in a variety of neurodegenerative disorders. However, the underlying mechanism remains unknown. Here, we provide genetic evidence, using forebrain-specific knockout (FBKO) mice, that proline-, glutamic acid-, and leucine-rich protein 1 (PELP1), an estrogen receptor coregulator protein, is essential for the extranuclear signaling and neuroprotective actions of E2 in the hippocampal CA1 region after global cerebral ischemia (GCI). E2-mediated extranuclear signaling (including activation of extracellular signal-regulated kinase and Akt) and antiapoptotic effects [such as attenuation of JNK signaling and increase in phosphorylation of glycogen synthase kinase-3β (GSK3β)] after GCI were compromised in PELP1 FBKO mice. Mechanistic studies revealed that PELP1 interacts with GSK3β, E2 modulates interaction of PELP1 with GSK3β, and PELP1 is a novel substrate for GSK3β. RNA-seq analysis of control and PELP1 FBKO mice after ischemia demonstrated alterations in several genes related to inflammation, metabolism, and survival in PELP1 FBKO mice, as well as a significant reduction in the activation of the Wnt/β-catenin signaling pathway. In addition, PELP1 FBKO studies revealed that PELP1 is required for E2-mediated neuroprotection and for E2-mediated preservation of cognitive function after GCI. Collectively, our data provide the first direct in vivo evidence, to our knowledge, of an essential role for PELP1 in E2-mediated rapid extranuclear signaling, neuroprotection, and cognitive function in the brain.

Estrogen receptor variant ER-α36 is involved in estrogen neuroprotection against oxidative toxicity

It is well known that estrogen exerts neuroprotective effect against various neuronal damages. However, the estrogen receptor (ER) that mediates estrogen neuroprotection has not been well established. In this study, we investigated the potential receptor that mediates estrogen neuroprotection and the underlying molecular mechanisms. Hydrogen peroxide (H2O2) was chosen as an agent in our study to mimic free radicals that are often involved in the pathogenesis of many degenerative diseases. We found that in human SY5Y and IMR-32 cells, the estrogen neuroprotection against H2O2 toxicity was abrogated by knockdown of a variant of estrogen receptor-α, ER-α36. We also studied the rapid estrogen signaling mediated by ER-α36 in neuroprotective effect and found the PI3K/AKT and MAPK/ERK1/2 signaling mediated by ER-α36 is involved in estrogen neuroprotection. We also found that GPER, an orphan G protein-coupled receptor, is not involved in ER-α36-mediated rapid estrogen response. Our study thus demonstrates that ER-α36-mediated rapid estrogen signaling is involved in the neuroprotection activity of estrogen against oxidative toxicity.

HIV-1 Tat and cocaine mediated synaptopathy in cortical and midbrain neurons is prevented by the isoflavone Equol

Illicit drugs, such as cocaine, are known to increase the likelihood and severity of HIV-1 associated neurocognitive disorders (HAND). In the current studies synaptic integrity was assessed following exposure to low concentrations of the HIV-1 viral protein Tat 1-86B, with or without cocaine, by quantifying filamentous actin (F-actin) rich structures (i.e., puncta and dendritic spines) on neuronal dendrites in vitro. In addition, the synapse-protective effects of either R-Equol (RE) or S-Equol (SE; derivatives of the soy isoflavone, daidzein) were determined. Individually, neither low concentrations of HIV-1 Tat (10 nM) nor low concentrations of cocaine (1.6 μM) had any significant effect on F-actin puncta number; however, the same low concentrations of HIV-1 Tat + cocaine in combination significantly reduced dendritic synapses. This synaptic reduction was prevented by pre-treatment with either RE or SE, in an estrogen receptor beta dependent manner. In sum, targeted therapeutic intervention with SE may prevent HIV-1 + drug abuse synaptopathy, and thereby potentially influence the development of HAND.

Selective estrogen receptor modulators (SERMs) enhance neurogenesis and spine density following focal cerebral ischemia

Selective estrogen receptor modulators (SERMs) have been reported to enhance synaptic plasticity and improve cognitive performance in adult rats. SERMs have also been shown to induce neuroprotection against cerebral ischemia and other CNS insults. In this study, we sought to determine whether acute regulation of neurogenesis and spine remodeling could be a novel mechanism associated with neuroprotection induced by SERMs following cerebral ischemia. Toward this end, ovariectomized adult female rats were either implanted with pellets of 17β-estradiol (estrogen) or tamoxifen, or injected with raloxifene. After one week, cerebral ischemia was induced by the transient middle-cerebral artery occlusion (MCAO) method. Bromodeoxyuridine (BrdU) was injected to label dividing cells in brain. We analyzed neurogenesis and spine density at day-1 and day-5 post MCAO. In agreement with earlier findings, we observed a robust induction of neurogenesis in the ipsilateral subventricular zone (SVZ) of both the intact as well as ovariectomized female rats following MCAO. Interestingly, neurogenesis in the ipsilateral SVZ following ischemia was significantly higher in estrogen and raloxifene-treated animals compared to placebo-treated rats. In contrast, this enhancing effect on neurogenesis was not observed in tamoxifen-treated rats. Finally, both SERMs, as well as estrogen significantly reversed the spine density loss observed in the ischemic cortex at day-5 post ischemia. Taken, together these results reveal a profound structural remodeling potential of SERMs in the brain following cerebral ischemia. This article is part of a Special Issue entitled "Sex steroids and brain disorders".

Regulation of brain microglia by female gonadal steroids

Microglial cells are the primary mediators of the CNS immune defense system and crucial for shaping inflammatory responses. They represent a highly dynamic cell population which is constantly moving and surveying their environment. Acute brain damage causes a local attraction and activation of this immune cell type which involves neuron-to-glia and glia-to-glia interactions. The prevailing view attributes microglia a "negative" role such as defense and debris elimination. More topical studies also suggest a protective and "positive" regulatory function. Estrogens and progestins exert anti-inflammatory and neuroprotective effects in the CNS in acute and chronic brain diseases. Recent work revealed that microglial cells express subsets of classical and non-classical estrogen and progesterone receptors in a highly dynamic way. In this review article, we would like to stress the importance of microglia for the spreading of neural damage during hypoxia, their susceptibility to functional modulation by sex steroids, the potency of sex hormones to switch microglia from a pro-inflammatory M1 to neuroprotective M2 phenotype, and the regulation of pro- and anti-inflammatory properties including the inflammasome. We will further discuss the possibility that the neuroprotective action of sex steroids in the brain involves an early and direct modulation of local microglia cell function. This article is part of a Special Issue entitled 'Sex steroids and brain disorders'.

Pterostilbene mediates neuroprotection against oxidative toxicity via oestrogen receptor α signalling pathways

Objectives

Accumulating evidence indicated protective role of phytoestrogens against neuronal damage induced by various insults, such as amyloid beta, oxygen deprivation and mitochondrial toxins. Hydrogen peroxide (H2O2) influences the mitochondrial membrane potential, which eventually results in cell apoptosis. In this study, we investigated the effects and possible mechanisms of a phytoestrogen, pterostilbene (PTER), in cell apoptosis induced by H2O2 in human neuronal SH-SY5Y cells. We also analysed the involvement of oestrogen receptors, oestrogen receptor-α and -β (ER-α and ER-β) in the protective role of PTER.

Methods

The effects of PTER on H2O2-stimulated cell were examined using MTT and FACS analysis. The signal pathways and estrogen receptors involved in PTER's effects were investigated using MTT and Western blot analysis.

Key findings

The results showed that H2O2 treatment significantly reduced cell viability in SY5Y cells, which was protected by PTER treatment. We also found that H2O2 inhibited the PI3K/AKT and MAPK/ERK signalling pathways, whereas PTER treatment restored these signalling pathways. We also found that the PTER effect could be largely blocked by an ER-α antagonist, 3-Bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1H-pyrazole dihydrochloride (MPP), but not by an ER-β antagonist, 4-[2-Phenyl-5,7-bis(trifluoromethyl)pyrazolo[1,5-a] pyrimidin-3-yl]phenol (PHTPP), suggesting that ER-α is a major player in the neuroprotective activity of PTER.

Conclusion

Our study thus demonstrates that PTER is an effective neuroprotective agent presumably through ER-α-mediated signalling pathways.

The neuroprotective actions of oestradiol and oestrogen receptors

Hormones regulate homeostasis by communicating through the bloodstream to the body's organs, including the brain. As homeostatic regulators of brain function, some hormones exert neuroprotective actions. This is the case for the ovarian hormone 17β-oestradiol, which signals through oestrogen receptors (ERs) that are widely distributed in the male and female brain. Recent discoveries have shown that oestradiol is not only a reproductive hormone but also a brain-derived neuroprotective factor in males and females and that ERs coordinate multiple signalling mechanisms that protect the brain from neurodegenerative diseases, affective disorders and cognitive decline.

Tibolone protects T98G cells from glucose deprivation

The steroidal drug Tibolone is used for the treatment of climacteric symptoms and osteoporosis in post-menopausal women. Although Tibolone has been shown to exert neuroprotective actions after middle cerebral artery occlusion, its specific actions on glial cells have received very little attention. In the present study we have assessed whether Tibolone exerts protective actions in a human astrocyte cell model, the T98G cells, subjected to glucose deprivation. Our findings indicate that Tibolone decreases the effects of glucose deprivation on cell death, nuclear fragmentation, superoxide ion production, mitochondrial membrane potential, cytoplasmic calcium concentration and morphological parameters. These findings suggest that glial cells may participate in the neuroprotective actions of Tibolone in the brain.