Localisation of GPR30, a novel G protein-coupled oestrogen receptor, suggests multiple functions in rodent brain and peripheral tissues

The complex interaction between oestrogen receptor genes, oestradiol, and perinatal mood

INTRODUCTION

Genetic variations in oestrogen receptor (ER) genes are associated with inter-individual differences in the sensitivity of ER-α, ER-β and G protein-coupled oestrogen receptor (GPER). These sensitivity differences may modulate susceptibility to mood changes during phases of endogenous oestrogen fluctuations, thereby explaining individual vulnerability. This study examined the association between ER gene variations, oestradiol and perinatal mood disturbances.

METHODS

A total of 159 women were observed during the perinatal period, providing saliva samples for oestradiol assessment and completing self-report measures of depressive and anxiety symptoms at five time points. Polymorphisms in ER genes were determined from dried blood spots. The associations were analysed using linear mixed models.

RESULTS

The ER-α gene haplotypes were associated with perinatal mood disturbances. The CG haplotype was associated with perinatal depressive (p = 0.0162, F-test) and anxiety symptoms (p = 2.396e-05, F-test), whereas the TA haplotype was associated with perinatal anxiety symptoms (p = 0.004, F-test). The interaction between ER gene variations, oestradiol and perinatal mood disturbances was not significant.

CONCLUSIONS

ER-α gene variations are associated with an increased susceptibility to perinatal mood disturbances. Sensitivity differences in ER-α appear to play a more important role for emotional processes than those in ER-β and GPER, independently of oestradiol levels. This might be explained by ER-α's more dominant expression in the hypothalamus and amygdala.

Endocrine-disrupting chemicals as prostate carcinogens

Endocrine-disrupting chemicals (EDCs) are natural or synthetic compounds that are ubiquitous in the environment and in daily-usage products and interfere with the normal function of the endocrine system leading to adverse health effects in humans. Exposure to these chemicals might elevate the risk of metabolic disorders, developmental and reproductive defects, and endocrine-related cancers. Prostate cancer is the most common hormone-dependent cancer in men, and the fifth leading cause of cancer-related mortality, partly owing to a lack of knowledge about the mechanisms that lead to aggressive castration-resistant forms. In addition to the dependence of early-stage prostate cancer on androgen actions, the prostate is a target of oestrogenic regulation. This hormone dependence, along with the fact that exogenous influences are major risk factors for prostate cancer, make the prostate a likely target of harmful actions from EDCs. Various sources of EDCs and their different modes of action might explain their role in prostate carcinogenesis.

Estrogens produced within the central amygdala inhibit varicella zoster-induced orofacial pain

Varicella zoster virus (VZV) causes chicken pox, and reactivation of this virus later in life causes shingles. Previous work demonstrated that estrogens could reduce VZV-induced orofacial pain and affect gene expression in the central amygdala. It is known that the central amygdala processes pain signals from the orofacial region and that estrogens produced by the enzyme aromatase within the central amygdala regulate neuronal function. Based on the previous studies, it was hypothesized estrogens produced within the central amygdala attenuate VZV-induced orofacial pain. To address this hypothesis, male Long-Evans rats were implanted with cannulas terminating in the central amygdala. Through these cannulas, the aromatase inhibitor letrozole or estrogen receptor alpha (ERα) agonist, 4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT), was infused in the central amygdala. The whisker pad of each rat was injected with either MeWo cells or MeWo cells containing VZV. One week after VZV injection, letrozole or PPT was infused into the central amygdala, followed by measuring pain behavior, GABA release, and estradiol concentrations. Tissues in the orofacial pain pathway were isolated, and neuronal activity was quantitated by counting c-Fos-positive neurons. Letrozole significantly increased the pain response and decreased GABA release. Letrozole also decreased estradiol within the central amygdala. Infusion of PPT reduced pain and increased GABA release. Moreover, letrozole increased the number of active neurons in the lateral parabrachial nucleus and spinal trigeminal nucleus, while PPT reduced the number of active neurons in the trigeminal ganglia, lateral parabrachial nucleus, and spinal trigeminal nucleus. The results suggest aromatase-derived estradiol interacts with ERα within the central amygdala to attenuate VZV-induced pain by increasing GABA release and reducing neuronal activity in the pain pathway.

The spatial and temporal pattern of GPER/GPR30 reporter expression in the developing and mature forebrain of mice

Evidence suggest that estrogens play crucial roles in the regulation of neural development and function and the G protein-coupled estrogen receptor (GPER/GPR30) appears to be the predominant estrogen receptor in the brain. However, the distribution and functions of GPER in the developing and mature brain are not fully understood. The current study aimed to characterize the expression of GPER in the forebrain, using Gper gene reporter mice combined with fluorescent in situ hybridization (FISH/RNAscope) and immunohistochemistry (IHC). Two lines of Gper reporter mice were constructed by crossing the Gper-cre mice with Ai14(RCL-tdT)-D or R26-ZsGreen mice, which showed identical spatial distributions of the reporters in adult brain. In the forebrain, neurons, protoplasmic astrocytes, mural cells and ependymal cells of third ventricle, were found to express Gper reporters. GPER-expressing neurons were particularly enriched in the olfactory system and the salience network, including posteromedial nucleus of the cortical amygdala (PmCo), entorhinal cortex, insula cortex, prefrontal cortex and dentate gyrus of the hippocampus. RNAscope and neural tracing showed GPER-expressing cortical neurons were long-range excitatory pyramidal neurons. GPER-expressing astrocytes represented a minor population (<10 %) of astrocytes and were found to be closely associated with neurovascular units. GPER-expressing mural cells were not labelled by the common pericyte marker PDGFRβ. In the critical period of neural development (P1-P10), GPER expression appeared to be intimately associated with neurogenesis, proliferation and migration in the olfactory system and the salience network. Collectively, the spatial and temporal pattern of GPER/GPR30 expression in the forebrain implied it might play important roles regulating the development and functions of the olfactory system, the salience network and the cerebral vessels.

G protein-coupled estrogen receptor deficiency exacerbates demyelination through microglial ferroptosis

Microglial activation is the initial pathological event that occurs in demyelination, a prevalent feature in various neurological diseases. G protein-coupled estrogen receptor 1 (GPER1), which is highly expressed in microglia, has been reported to reduce myelin damage. However, the precise molecular mechanisms involved remain unclear. In this study, the cuprizone (CPZ)-induced demyelination model was used to investigate the relationship between GPER1 and myelin sheath injury and its mechanism. The results demonstrated that GPER1 deficiency exacerbated cognitive impairment in mice. Along with more severe myelin damage as well as fewer oligodendrocytes. Moreover, GPER1 deficiency not only directly reduced the number of microglia in cuprizone mice but also caused iron ions overload in microglia of myelin debris induced in vitro. Transcriptomic, molecular biological, and morphological analyses revealed that microglial ferroptosis caused by GPER1 deficiency contributes to the reduction of microglia number. In summary, these findings revealed that GPER1 can regulate demyelination through ferroptosis of microglia.

From physiology to pathology: Emerging roles of GPER in cardiovascular disease

Cardiovascular diseases (CVDs) are among the leading causes of death globally and pose a significant threat to public health. Factors such as prolonged high cholesterol levels, diabetes, smoking, unhealthy diet, and genetic predisposition could contribute to the occurrence and development of CVDs. Common CVDs include hypertension (HTN), atherosclerosis (AS), myocardial infarction (MI), myocardial ischemia-reperfusion injury (MIRI), heart failure (HF) and arrhythmia. Estrogen is recognized for its cardiovascular protective effects, resulting in lower incidence and mortality rates of CVDs in premenopausal women compared to men. The G protein-coupled estrogen receptor (GPER), a G protein-coupled receptor with a seven-transmembrane structure, exhibits unique structural characteristics and widespread tissue distribution. GPER activates intracellular signaling pathways through its interaction with G proteins, mediating estrogen's biological effects and participating in the regulation of cardiovascular function, metabolic balance, and nervous system. Although recent research has highlighted the significant role of GPER in the cardiovascular system, its specific mechanisms remain unclear. Therefore, this review summarizes the latest research on GPER in CVDs, including its fundamental characteristics, physiological functions in the cardiovascular system, and its roles and potential therapeutic applications in common CVDs such as HTN, AS, MI, MIRI, HF and arrhythmia. Exploring GPER's positive effects on cardiovascular health will provide new strategies and research directions for the treatment of CVDs.

Estradiol Enhances Cerebellar Molecular Layer Interneuron-Purkinje Cell Synaptic Transmission and Improves Motor Learning Through ER-β in Vivo in Mice

In the cerebellar cortex, 17β-estradiol (E2) binds to estrogen receptors (ERs) and plays a role in regulating cerebellar synaptic plasticity and motor learning behaviors. However, the underlying mechanisms remain unclear. In this study, we investigated the effects of E2 on synaptic transmission between cerebellar molecular layer interneurons (MLIs) and Purkinje cells (PCs) in urethane-anesthetized mice. Using in vivo cell-attached and whole-cell recordings combined with immunohistochemistry, we examined MLI-PC synaptic responses elicited by facial air-puff stimulation. Cell-attached recordings from PCs demonstrated that air-puff stimulation of the ipsilateral whisker pad elicited MLI-PC synaptic currents (P1), which were significantly enhanced by local micro-application of E2 to the cerebellar molecular layer. The E2-induced potentiation of P1 amplitude exhibited dose dependency, with a 50% effective concentration (EC50) of 30 nM. The effects of E2 on amplitude of P1 and pause of simple spike firing were completely prevented by blockade of ERs or ERβ, but not by blockade of ERα or a G-protein coupled receptor (GPER). Application of a selective ERβ agonist mimicked and overwhelmed the E2-induced enhancement of the MLI-PC synaptic transmission. Whole-cell recording with biocytin staining showing that E2 does not change the spontaneous and the evoked spike firing properties of basket-type MLIs. Rotarod test indicated that microinjection of E2 onto the cerebellar surface significantly promotes initial motor learning ability, which is abolished by blockade of ERβ. ERβ immunoreactivity was expressed in the ML and PC layer, especially around the PC somata in the mouse cerebellar cortex. These results indicate that E2 binds to ERβ, resulting in an enhance in the cerebellar MLI-PC synaptic transmission and an improvement of initial motor learning ability in vivo in mice.

Sex specific disruptions in Protein Kinase Cγ signaling in a mouse model of Spinocerebellar Ataxia Type 14

Spinocerebellar Ataxia Type 14 (SCA14) is an autosomal dominant neurodegenerative disease caused by mutations in the gene encoding protein kinase C gamma (PKCγ), a Ca 2+ /diacylglycerol (DG)-dependent serine/threonine kinase dominantly expressed in cerebellar Purkinje cells. These mutations impair autoinhibitory constraints to increase the basal activity of the kinase, resulting in deficits in the cerebellum that are not observed upon simple deletion of the gene, and severe ataxia. To better understand the phenotypic impact of aberrant PKCγ signaling in disease pathology, we developed a knock-in murine model of the SCA14 mutation ΔF48 in PKCγ. This fully penetrant mutation is severe in humans and is mechanistically informative as it has high basal activity but is unresponsive to agonist stimulation. Genetic, behavioral, and molecular testing revealed that ΔF48 PKCγ SCA14 mice have ataxia related phenotypes and an altered cerebellar phosphoproteome, effects that are more severe in male mice. Analysis of existing human data reveal that SCA14 has a significantly earlier age of onset for males compared with females. Our data from this clinically relevant mutation suggest that enhanced basal activity of PKCγ is necessary and sufficient to cause ataxia and that treatment strategies to modulate aberrant PKCγ may be particularly beneficial in males.

Summary

New mouse model of Spinocerebellar Ataxia Type 14 containing a clinically relevant mutation in PKCγ identified underlying drivers of the disease and neuroprotection in females.

The effects of estrogen depletion in female rats: differential influences on somato-motor and sensory cortices

Aging women experience a significant decline of ovarian hormones, particularly estrogen, following menopause, and become susceptible to cognitive and psychomotor deficits. Although the effects of estrogen depletion had been documented in the prefrontal and somatosensory cortices, its impact on somatomotor cortex, a region crucial for motor and cognitive functions, remains unclear. To explore this, we ovariectomized young adult female rats and fed subsequently with phytoestrogen-free diet and studied the effects of estrogen depletion on the somato-sensory and motor cortices. Low serum estrogen was confirmed prior to biochemical and morphological analyses. Results revealed that estrogen depletion differentially affected the two cortical areas: all three estrogen receptors were downregulated in the somatosensory cortex, whereas in the somatomotor cortex, G-protein-coupled estrogen receptor 30 was upregulated, estrogen receptor α decreased, and estrogen receptor β remained unaffected. Intracellular dye injections revealed decreased dendritic spines on layer III and V pyramidal neurons of the somato-sensory cortex but increased in those of the motor cortex. These were accompanied by decrease and increase of excitatory postsynaptic density protein 95 respectively. Since dendritic spines receive excitatory inputs, these findings suggest that estrogen depletion changes the excitatory connectivity of the somato-sensory and motor cortices in opposite directions. Notably, estradiol replenishment reversed the dendritic spine increase in the somatomotor cortex, confirming the estrogen dependency of this effect. The differential influence of estrogen depletion on these two cortices could have contributed to the cognitive and psychomotor abnormalities in postmenopausal females.

Cellular and molecular mechanisms of action of ovarian steroid hormones. I: Regulation of central nervous system function

The conventional way steroid hormones work through receptors inside cells is widely acknowledged. There are unanswered questions about what happens to the hormone in the end and why there isn't always a strong connection between how much tissue takes up and its biological effects through receptor binding. Steroid hormones can also have non-traditional effects that happen quickly but don't involve entering the cell. Several possible mechanisms for these non-traditional actions include (a) changes in membrane fluidity, (b) steroid hormones acting on receptors on the outer surface of cells, (c) steroid hormones regulating GABAA receptors on cell membranes, and (d) activation of steroid receptors by factors like EGF, IGF-1, and dopamine. Data also suggests that steroid hormones may be inserted into DNA through receptors, acting as transcription factors. These proposed new mechanisms of action should not be seen as challenging the conventional mechanism. Instead, they contribute to a more comprehensive understanding of how hormones work, allowing for rapid, short-term, and prolonged effects to meet the body's physiological needs.

17β-Estradiol reduces inhibitory synaptic currents in entorhinal cortex neurons through G protein-coupled estrogen receptor-1 activation of extracellular signal-regulated kinase

Estrogens are believed to modulate cognitive functions in part through the modulation of synaptic transmission in the cortex and hippocampus. Administration of 17β-estradiol (E2) can rapidly enhance excitatory synaptic transmission in the hippocampus and facilitate excitatory synaptic transmission in rat lateral entorhinal cortex via activation of the G protein-coupled estrogen receptor-1 (GPER1). To assess the mechanisms through which GPER1 activation facilitates synaptic transmission, we assessed the effects of acute 10 nM E2 administration on pharmacologically isolated evoked excitatory and inhibitory synaptic currents in layer II/III entorhinal neurons. Female Long-Evans rats were ovariectomized between postnatal day (PD) 63 and 74 and implanted with a subdermal E2 capsule to maintain continuous low levels of E2. Electrophysiological recordings were obtained between 7 and 20 days after ovariectomy. Application of E2 for 20 min did not significantly affect AMPA or NMDA receptor-mediated excitatory synaptic currents. However, GABA receptor-mediated inhibitory synaptic currents (IPSCs) were markedly reduced by E2 and returned towards baseline levels during the 20-min washout period. The inhibition of GABA-mediated IPSCs was blocked in the presence of the GPER1 receptor antagonist G15. GPER1 can modulate protein kinase A (PKA), but blocking PKA with intracellular KT5720 did not prevent the E2-induced reduction in IPSCs. GPER1 can also stimulate extracellular signal-regulated kinase (ERK), a negative modulator of GABAA receptors, and blocking activation of ERK with PD90859 prevented the E2-induced reduction of IPSCs. E2 can therefore result in a rapid GPER1 and ERK signaling-mediated reduction in GABA-mediated IPSCs. This provides a novel mechanism through which E2 can rapidly modulate synaptic excitability in entorhinal layer II/III neurons and may also contribute to E2 and ERK-dependent alterations in synaptic transmission in other brain areas.

Sexual dimorphic distribution of G protein-coupled receptor 30 in pain-related regions of the mouse brain

Sex differences in pain sensitivity have contributed to the fact that medications for curing chronic pain are unsatisfactory. However, the underlying mechanism remains to be elucidated. Brain-derived estrogen participates in modulation of sex differences in pain and related emotion. G protein-coupled receptor 30 (GPR30), identified as a novel estrogen receptor with a different distribution than traditional receptors, has been proved to play a vital role in regulating pain affected by estrogen. However, the contribution of its distribution to sexually dimorphic pain-related behaviors has not been fully explored. In the current study, immunofluorescence assays were applied to mark the neurons expressing GPR30 in male and female mice (in metestrus and proestrus phase) in pain-related brain regions. The neurons that express CaMKIIα or VGAT were also labeled to observe overlap with GPR30. We found that females had more GPR30-positive (GPR30+) neurons in the primary somatosensory (S1) and insular cortex (IC) than males. In the lateral habenula (LHb) and the nucleus tractus solitarius (NTS), males had more GPR30+ neurons than females. Moreover, within the LHb, the expression of GPR30 varied with estrous cycle phase; females in metestrus had fewer GPR30+ neurons than those in proestrus. In addition, females had more GPR30+ neurons, which co-expressed CaMKIIα in the medial preoptic nucleus (mPOA) than males, while males had more than females in the basolateral complex of the amygdala (BLA). These findings may partly explain the different modulatory effects of GPR30 in pain and related emotional phenotypes between sexes and provide a basis for comprehension of sexual dimorphism in pain related to estrogen and GPR30, and finally provide new targets for exploiting new treatments of sex-specific pain.

Activation of GPR30 Ameliorates Cerebral Ischemia-Reperfusion Injury by Suppressing Ferroptosis Through Nrf2/GPX4 Signaling Pathway

The newly identified estrogen receptor, G protein-coupled receptor 30 (GPR30), is prevalent in the brain and has been shown to provide significant neuroprotection. Recent studies have linked ferroptosis, a newly characterized form of programmed cell death, closely with cerebral ischemia-reperfusion injury (CIRI), highlighting it as a major contributing factor. Consequently, our research aimed to explore the potential of GPR30 targeting in controlling neuronal ferroptosis and lessening CIRI impacts. Results indicated that GPR30 activation not only improved neurological outcomes and decreased infarct size in a mouse model but also lessened iron accumulation and malondialdehyde formation post-middle cerebral artery occlusion (MCAO). This protective effect extended to increased levels of Nrf2 and GPX4 proteins. Similar protective results were replicated in PC12 cells subjected to Oxygen Glucose Deprivation and Reoxygenation (OGD/R) using the GPR30-specific agonist G1. Importantly, inhibition of Nrf2 with ML385 curtailed the neuroprotective effects of GPR30 activation, suggesting that GPR30 mitigates CIRI primarily through inhibition of neuronal ferroptosis via upregulation of Nrf2 and GPX4.

Activation of GPER-1 Attenuates Traumatic Brain Injury-Induced Neurological Impairments in Mice

This study aimed to investigate the effects of G1-activated G protein-coupled estrogen receptor 1 (GPER1) on neurological impairments and neuroinflammation in traumatic brain injury (TBI) mice. The controlled cortical impingement (CCI) method was used to establish the TBI model. The mice were subjected to ovariectomy (OVX) for two weeks prior to modeling. GPER1 agonist G1 was administered by intracerebroventricular injection. Brain tissue water content was detected by wet/dry method, and blood-brain barrier damage was detected by Evans blue extravasation. The neurological impairments in mice were evaluated by open field test, Y-maze test, nest-building test, object location memory test and novel object recognition test. Ionized calcium-binding adapter molecule 1 (Iba1) staining was used to indicate the activation of microglia. Expression of M1/M2-type microglia markers and inflammatory factors were evaluated by ELISA and qRT-PCR. The G1 administration significantly reduced cerebral edema and Evans blue extravasation at injury ipsilateral cortex and basal ganglia in TBI mice. Activation of GPER1 by G1 improved the anxiety behavior and the cognitive dysfunction of mice induced by TBI. G1 administration significantly decreased Iba1-positive staining cells and the mRNA levels of CD86, macrophage cationic peptide 1 (Mcp-1), nitric oxide synthase 2 (Nos2), interleukin 1 beta (IL-1β), and macrophage inflammatory protein-2 (MIP-2), while increased the mRNA levels of interleukin 10 (IL-10), arginase1 (Arg-1) and CD206. Activation of GPER1 through G1 administration has the potential to ameliorate cognitive dysfunction induced by TBI in mice. It may also inhibit the activation of M1 microglia in cortical tissue resulting from TBI, while promoting the activation of M2 microglia and contributing to the regulation of inflammatory responses.

Advances in immune regulation of the G protein-coupled estrogen receptor

Estrogen and related receptors have been shown to have a significant impact on human development, reproduction, metabolism and immune regulation and to play a critical role in tumor development and treatment. Traditionally, the nuclear estrogen receptors (nERs) ERα and ERβ have been thought to be involved in mediating the estrogenic effects. However, our group and others have previously demonstrated that the G protein-coupled estrogen receptor (GPER) is the third independent ER, and estrogen signaling mediated by GPER is known to play an important role in normal physiology and a variety of abnormal diseases. Interestingly, recent studies have progressively revealed GPER involvement in the maintenance of the normal immune system, abnormal immune diseases, and inflammatory lesions, which may be of significant clinical value primarily in the immunotherapy of tumors. In this article, we review current advances in GPER-related immunomodulators and provide a theoretical basis and potential clinical targets to ameliorate immune-related diseases and immunotherapy for tumors.

Activation of GPER1 by G1 prevents PTSD-like behaviors in mice: Illustrating the mechanisms from BDNF/TrkB to mitochondria and synaptic connection

BACKGROUND

G1 is a specific agonist of G protein-coupled estrogen receptor 1 (GPER1), which binds and activates GPER1 to exert various neurological functions. However, the preventive effect of G1 on post-traumatic stress disorder (PTSD) and its mechanisms are unclear.

OBJECTIVE

To evaluate the protective effect of G1 against synaptic and mitochondrial impairments and to investigate the mechanism of G1 to improve PTSD from brain-derived neurotrophic factor (BDNF)/tyrosine kinase receptor B (TrkB) signaling.

METHODS

This study initially detected GPER1 expression in the hippocampus of single prolonged stress (SPS) mice, utilizing both Western blot and immunofluorescence staining. Subsequently, the effects of G1 on PTSD-like behaviors, synaptic, and mitochondrial functions in SPS mice were investigated. Additionally, the involvement of BDNF/TrkB signaling involved in the protection was further confirmed using GPER1 antagonist and TrkB inhibitor, respectively.

RESULTS

The expression of GPER1 was reduced in the hippocampus of SPS mice, and G1 treatment given for 14 consecutive days significantly improved PTSD-like behaviors in SPS mice compared with model group. Electrophysiological local field potential (LFP) results showed that G1 administration for 14 consecutive days could reverse the abnormal changes in the gamma oscillation in the CA1 region of SPS mice. Meanwhile, G1 administration for 14 consecutive days could significantly improve the abnormal expression of synaptic proteins, increase the expression of mitochondria-related proteins, increase the number of synapses in the hippocampus, and ameliorate the damage of hippocampal mitochondrial structure in SPS mice. In addition, G15 (GPER1 inhibitor) and ANA-12 (TrkB inhibitor) blocked the ameliorative effects of G1 on PTSD-like behaviors and aberrant expression of hippocampal synaptic and mitochondrial proteins in SPS mice and inhibited the reparative effects of G1 on structural damage to hippocampal mitochondria, respectively.

CONCLUSION

G1 improved PTSD-like behaviors in SPS mice, possibly by increasing hippocampal GPER1 expression and promoting BDNF/TrkB signaling to repair synaptic and mitochondrial functional impairments. This study would provide critical mechanism for the prevention and treatment of PTSD.

Low dose of propyl-pyrazole-triol, an agonist of estrogen receptor alpha, administration stimulates the Coolidge effect in fadrozole-treated male rats

Estrogen receptor (ER) α is involved in male sexual function. Here, we aim to investigate how ERα activation influences sexual satiety and the Coolidge effect (i.e., when a rat, that has reached sexual satiety, experiences an increased arousal after exposure to a novel sexual partner) in estrogen-deprived male rats. Male rats (8 per group) were treated daily for 29 days with either saline (Control group) or fadrozole dissolved in saline (1 mg/kg/day) 1 h before mating. On Days 13 and 29, rats treated with fadrozole received either no additional treatment (fadrozole group) or a single injection of propyl-pyrazole-triol (ERα-agonist group, dissolved in sesame oil, 1 mg/kg). Rats mated until reaching sexual satiety on Days 13 and 29. In these sessions, the Control group displayed higher frequency of intromission and ejaculation than the other groups. The ERα-agonist group mounted more frequently but reached sexual satiety sooner than the Control group. On Day 29, when exposed to a new sexual partner, the fadrozole-treated rats were less likely to display intromission than the other groups, or ejaculation than the Control group, or mounting than the ERα-agonist group. The Control group showed more ejaculatory behavior and shorter ejaculation latency than the other groups. Body weights, testosterone levels, estradiol levels, and ERα-immunoreactive cell counts in brain regions for sexual behavior were comparable between groups after 29 days of treatments. Our data suggest that estrogen helps regulate sexual satiety and the Coolidge effect in male rats.

Estrogen receptor GPR30 in the anterior cingulate cortex mediates exacerbated neuropathic pain in ovariectomized mice

Menopausal women experience neuropathic pain 63% more frequently than men do, which may attribute to the estrogen withdrawal. However, the underlying mechanisms remain unclear. Here, the role of estrogen receptors (ERs) in ovariectomized (OVX) female mice following chronic constriction injury (CCI) was investigated. With 17β-estradiol (E2) supplemented, aggravated mechanical allodynia in OVX mice could be significantly alleviated, particularly after intra-anterior cingulate cortex (ACC) E2 delivery. Pharmacological interventions further demonstrated that the agonist of G-protein-coupled estrogen receptor 30 (GPR30), rather than ERα or ERβ in the ACC, exhibited the similar analgesic effect as E2, whereas antagonist of GPR30 exacerbated allodynia. Furthermore, OVX surgery reduced GPR30 expression in the ACC, which could be restored with estrogen supplementation. Selective downregulation of GPR30 in the ACC of naïve female mice induces mechanical allodynia, whereas GPR30 overexpression in the ACC remarkedly alleviated OVX-exacerbated allodynia. Collectively, estrogen withdrawal could downregulate the ACC GPR30 expression, resulting in exacerbated neuropathic pain. Our findings highlight the importance of GPR30 in the ACC in aggravated neuropathic pain during menopause, and offer a potential therapeutic candidate for neuropathic pain management in menopausal women.

Endocrine Disruptors and Metabolic Changes: Impact on Puberty Control

OBJECTIVE

This study aims to explore the significant impact of environmental chemicals on disease development, focusing on their role in developing metabolic and endocrine diseases. The objective is to understand how these chemicals contribute to the increasing prevalence of precocious puberty, considering various factors, including epigenetic changes, lifestyle, and emotional disturbances.

METHODS

The study employs a comprehensive review of descriptive observational studies in both human and animal models to identify a degree of causality between exposure to environmental chemicals and disease development, specifically focusing on endocrine disruption. Due to ethical constraints, direct causation studies in human subjects are not feasible; therefore, the research relies on accumulated observational data.

RESULTS

Puberty is a crucial life period with marked physiological and psychological changes. The age at which sexual characteristics develop is changing in many regions. The findings indicate a correlation between exposure to endocrine-disrupting chemicals and the early onset of puberty. These chemicals have been shown to interfere with normal hormonal processes, particularly during critical developmental stages such as adolescence. The research also highlights the interaction of these chemical exposures with other factors, including nutritional history, social and lifestyle changes, and emotional stress, which together contribute to the prevalence of precocious puberty.

CONCLUSION

Environmental chemicals significantly contribute to the development of certain metabolic and endocrine diseases, particularly in the rising incidence of precocious puberty. Although the evidence is mainly observational, it adequately justifies regulatory actions to reduce exposure risks. Furthermore, these findings highlight the urgent need for more research on the epigenetic effects of these chemicals and their wider impact on human health, especially during vital developmental periods.

The impact of estradiol on serotonin, glutamate, and dopamine systems

Estradiol, the most potent and prevalent member of the estrogen class of steroid hormones and is expressed in both sexes. Functioning as a neuroactive steroid, it plays a crucial role in modulating neurotransmitter systems affecting neuronal circuits and brain functions including learning and memory, reward and sexual behaviors. These neurotransmitter systems encompass the serotonergic, dopaminergic, and glutamatergic signaling pathways. Consequently, this review examines the pivotal role of estradiol and its receptors in the regulation of these neurotransmitter systems in the brain. Through a comprehensive analysis of current literature, we investigate the multifaceted effects of estradiol on key neurotransmitter signaling systems, namely serotonin, dopamine, and glutamate. Findings from rodent models illuminate the impact of hormone manipulations, such as gonadectomy, on the regulation of neuronal brain circuits, providing valuable insights into the connection between hormonal fluctuations and neurotransmitter regulation. Estradiol exerts its effects by binding to three estrogen receptors: estrogen receptor alpha (ERα), estrogen receptor beta (ERβ), and G protein-coupled receptor (GPER). Thus, this review explores the promising outcomes observed with estradiol and estrogen receptor agonists administration in both gonadectomized and/or genetically knockout rodents, suggesting potential therapeutic avenues. Despite limited human studies on this topic, the findings underscore the significance of translational research in bridging the gap between preclinical findings and clinical applications. This approach offers valuable insights into the complex relationship between estradiol and neurotransmitter systems. The integration of evidence from neurotransmitter systems and receptor-specific effects not only enhances our understanding of the neurobiological basis of physiological brain functioning but also provides a comprehensive framework for the understanding of possible pathophysiological mechanisms resulting to disease states. By unraveling the complexities of estradiol's impact on neurotransmitter regulation, this review contributes to advancing the field and lays the groundwork for future research aimed at refining understanding of the relationship between estradiol and neuronal circuits as well as their involvement in brain disorders.

G protein-coupled estrogen receptor expression in postnatal developing mouse retina

Introduction

Estrogen has emerged as a multifaceted signaling molecule in the retina, playing an important role in neural development and providing neuroprotection in adults. It interacts with two receptor types: classical estrogen receptors (ERs) alpha and beta, and G protein-coupled estrogen receptor (Gper). Gper differs from classical ERs in structure, localization, and signaling. Here we provide the first report of the temporal and spatial properties of Gper transcript and protein expression in the developing and mature mouse retina.

Methods

We applied qRT-PCR to determine Gper transcript expression in wild type mouse retina from P0-P21. Immunohistochemistry and Western blot were used to determine Gper protein expression and localization at the same time points.

Results

Gper expression showed a 6-fold increase during postnatal development, peaking at P14. Relative total Gper expression exhibited a significant decrease during retinal development, although variations emerged in the timing of changes among different forms of the protein. Gper immunoreactivity was seen in retinal ganglion cells (RGCs) throughout development and also in somas in the position of horizontal cells at early time points. Immunoreactivity was observed in the cytoplasm and Golgi at all time points, in the nucleus at early time points, and in RGC axons as the retina matured.

Discussion

In conclusion, our study illuminates the spatial and temporal expression patterns of Gper in the developing mouse retina and provides a vital foundation for further investigations into the role of Gper in retinal development and degeneration.

Role of estrogen in treatment of female depression

Depression is a neurological disorder that profoundly affects human physical and mental health, resulting in various changes in the central nervous system. Despite several prominent hypotheses, such as the monoaminergic theory, hypothalamic-pituitary-adrenal (HPA) axis theory, neuroinflammation, and neuroplasticity, the current understanding of depression's pathogenesis remains incomplete. Importantly, depression is a gender-dimorphic disorder, with women exhibiting higher incidence rates than men. Given estrogen's pivotal role in the menstrual cycle, it is reasonable to postulate that its fluctuating levels could contribute to the pathogenesis of depression. Estrogen acts by binding to a diversity of receptors, which are widely distributed in the central nervous system. An abundance of research has established that estrogen and its receptors play a crucial role in depression, spanning pathogenesis and treatment. In this comprehensive review, we provide an in-depth analysis of the fundamental role of estrogen and its receptors in depression, with a focus on neuroinflammation, neuroendocrinology, and neuroplasticity. Furthermore, we discuss potential mechanisms underlying the therapeutic effects of estrogen in the treatment of depression, which may pave the way for new antidepressant drug development and alternative treatment options.

The G protein-coupled estrogen receptor of the trigeminal ganglion regulates acute and chronic itch in mice

AIMS

Itch is an unpleasant sensation that severely impacts the patient's quality of life. Recent studies revealed that the G protein-coupled estrogen receptor (GPER) may play a crucial role in the regulation of pain and itch perception. However, the contribution of the GPER in primary sensory neurons to the regulation of itch perception remains elusive. This study aimed to investigate whether and how the GPER participates in the regulation of itch perception in the trigeminal ganglion (TG).

METHODS AND RESULTS

Immunofluorescence staining results showed that GPER-positive (GPER+ ) neurons of the TG were activated in both acute and chronic itch. Behavioral data indicated that the chemogenetic activation of GPER+ neurons of the TG of Gper-Cre mice abrogated scratching behaviors evoked by acute and chronic itch. Conversely, the chemogenetic inhibition of GPER+ neurons resulted in increased itch responses. Furthermore, the GPER expression and function were both upregulated in the TG of the dry skin-induced chronic itch mouse model. Pharmacological inhibition of GPER (or Gper deficiency) markedly increased acute and chronic itch-related scratching behaviors in mouse. Calcium imaging assays further revealed that Gper deficiency in TG neurons led to a marked increase in the calcium responses evoked by agonists of the transient receptor potential ankyrin A1 (TRPA1) and transient receptor potential vanilloid V1 (TRPV1).

CONCLUSION

Our findings demonstrated that the GPER of TG neurons is involved in the regulation of acute and chronic itch perception, by modulating the function of TRPA1 and TRPV1. This study provides new insights into peripheral itch sensory signal processing mechanisms and offers new targets for future clinical antipruritic therapy.

Learning exceptions to category rules varies across the menstrual cycle

Ways in which ovarian hormones affect cognition have been long overlooked despite strong evidence of their effects on the brain. To address this gap, we study performance on a rule-plus-exception category learning task, a complex task that requires careful coordination of core cognitive mechanisms, across the menstrual cycle (N = 171). Results show that the menstrual cycle distinctly affects exception learning in a manner that parallels the typical rise and fall of estradiol across the cycle. Participants in their high estradiol phase outperform participants in their low estradiol phase and demonstrate more rapid learning of exceptions than a male comparison group. A likely mechanism underlying this effect is estradiol's impact on pattern separation and completion pathways in the hippocampus. These results provide novel evidence for the effects of the menstrual cycle on category learning, and underscore the importance of considering female sex-related variables in cognitive neuroscience research.

GPER involvement in inflammatory pain

Chronic pain is a worldwide refractory health disease that causes major financial and emotional burdens and that is devastating for individuals and society. One primary source of pain is inflammation. Current treatments for inflammatory pain are weakly effective, although they usually replace analgesics, such as opioids and non-steroidal anti-inflammatory drugs, which display serious side effects. Emerging evidence indicates that the membrane G protein-coupled estrogen receptor (GPER) may play an important role in the regulation of inflammation and pain. Herein, we focus on the consequences of pharmacological and genetic GPER modulation in different animal models of inflammatory pain. We also provide a brief overview of the putative mechanisms including the direct action of GPER on pain transmission and inflammation.

Aromatase enzyme: Paving the way for exploring aromatization for cardio-renal protection

Documented male-female differences in the risk of cardiovascular and chronic kidney diseases have been largely attributed to estrogens. The cardiovascular and renal protective effects of estrogens are mediated via the activation of estrogen receptors (ERα and ERβ) and G protein-coupled estrogen receptor, and involve interactions with the renin-angiotensin-aldosterone system. Aromatase, also called estrogen synthase, is a cytochrome P-450 enzyme that plays a pivotal role in the conversion of androgens into estrogens. Estrogens are biosynthesized in gonadal and extra-gonadal sites by the action of aromatase. Evidence suggests that aromatase inhibitors, which are used to treat high estrogen-related pathologies, are associated with the development of cardiovascular events. We review the potential role of aromatization in providing cardio-renal protection and highlight several meta-analysis studies on cardiovascular events associated with aromatase inhibitors. Overall, we present the potential of aromatase enzyme as a fundamental contributor to cardio-renal protection.

Steroid hormone-mediated regulation of sexual and aggressive behaviour by non-genomic signalling

Sex and aggression are well studied examples of social behaviours that are common to most animals and are mediated by an evolutionary conserved group of interconnected nuclei in the brain called the social behaviour network. Though glucocorticoids and in particular estrogen regulate these social behaviours, their effects in the brain are generally thought to be mediated by genomic signalling, a slow transcriptional regulation mediated by nuclear hormone receptors. In the last decade or so, there has been renewed interest in understanding the physiological significance of rapid, non-genomic signalling mediated by steroids. Though the identity of the membrane hormone receptors that mediate this signalling is not clearly understood and appears to be different in different cell types, such signalling contributes to physiologically relevant behaviours such as sex and aggression. In this short review, we summarise the evidence for this phenomenon in the rodent, by focusing on estrogen and to some extent, glucocorticoid signalling. The use of these signals, in relation to genomic signalling is manifold and ranges from potentiation of transcription to the possible transduction of environmental signals.

Estrogen signaling in healthy and tumor brain

Sex-specific differences in brain organization and function are widely explored in multidisciplinary studies, ranging from sociology and biology to digital modelling. In addition, there is growing evidence that natural or disturbed hormonal environments play a crucial role in the onset of brain disorders and pathogenesis. For example, steroid hormones, but also enzymes involved in steroidogenesis and receptors triggering hormone signaling are key players of gliomagenesis. In the present review we summarize the current knowledge about steroid hormone, particularly estrogens synthesis and signaling, in normal brain compared to the tumor brain. We will focus on two key molecular players, aromatase and the G Protein-Coupled Estrogen Receptor, GPER.

Corticosterone rapidly reduces glutamatergic but not GABAergic transmission in the infralimbic prefrontal cortex of male mice

Rapid non-genomic effects of corticosteroid hormones, affecting glutamatergic and GABAergic transmission, have been described for many limbic structures in the rodent brain. These rapid effects appear to be region specific. It is not always clear which (or even whether) corticosteroid receptor -the glucocorticoid receptor (GR) or mineralocorticoid receptor (MR)- initiate these rapid effects. In the hippocampus and amygdala membrane-associated MR, but also membrane-associated GR (in amygdala), are involved. Other studies indicate that the rapid modulation may be induced by transactivation of kinases, or other receptors, like the G-protein coupled estrogen receptor (GPER) which was recently found to bind the mineralocorticoid aldosterone. In the current study we explored, in young adult male C57Bl6 mice, possible rapid effects of corticosterone on layer 2/3 infralimbic-prefrontal cortex (IL-PFC) neurons. We show that corticosterone, via non-genomic MR activation, reduces the mEPSC -but does not affect mIPSC- frequency; we observed no effect on mEPSC or mIPSC amplitude. As a result, overall spontaneous activity in the IL-PFC is suppressed. A potential role of GPER cannot be excluded, since G-15, an antagonist of GPER, also prevented the rapid effects of corticosterone.

Sex and hormonal status influence the anxiolytic-like effect of oxytocin in mice

Anxiety and depression are highly prevalent psychiatric disorders, affecting approximately 18% of the United States population. Evidence indicates that central oxytocin mediates social cognition, social bonding, and social anxiety. Although it is well-established that oxytocin ameliorates social deficits, less is known about the therapeutic effects of oxytocin in non-social contexts. We hypothesized that positive effects of oxytocin in social contexts are attributable to intrinsic effects of oxytocin on neural systems that are related to emotion regulation. The present study investigated the effect of intracerebroventricular (ICV) oxytocin administration (i.e., central action) on anxiety- and depression-like behavior in C57Bl/6J mice using non-social tests. Male and female mice received an ICV infusion of vehicle or oxytocin (100, 200, or 500 ng), then were tested in the elevated zero maze (for anxiety-like behavior) and the tail suspension test (for depression-like behavior). Oxytocin dose-dependently increased open zone occupancy and entries in the elevated zero maze and reduced immobility duration in the tail suspension test in both sexes. Oxytocin decreased anxiety and depression-like behavior in male and female mice. The observed effect of oxytocin on anxiolytic-like behavior appeared to be driven by the males. Given the smaller anxiolytic-like effect of oxytocin in the female mice and the established interaction between oxytocin and reproductive hormones (estrogen and progesterone), we also explored whether oxytocin sensitivity in females varies across estrous cycle phases and in ovariectomized females that were or were not supplemented with estrogen or progesterone. Oxytocin reduced anxiety-like behavior in female mice in proestrus/estrus, ovariectomized females (supplemented or not with estrogen or progesterone), but not females in metestrus/diestrus. Additionally, oxytocin reduced depression-like behavior in all groups tested with slight differences across the various hormonal statuses. These results suggest that the effect of oxytocin in depression- and anxiety-like behavior in mice can be influenced by sex and hormonal status.

G protein-coupled estrogen receptor: a promising therapeutic target for aldosterone-induced hypertension

Aldosterone is one of the most essential hormones synthesized by the adrenal gland because it regulates water and electrolyte balance. G protein-coupled estrogen receptor (GPER) is a newly discovered aldosterone receptor, which is proposed to mediate the non-genomic pathways of aldosterone while the hormone simultaneously interacts with mineralocorticoid receptor. In contrast to its cardio-protective role in postmenopausal women via its interaction with estrogen, GPER seems to trigger vasoconstriction effects and can further induce water and sodium retention in the presence of aldosterone, indicating two entirely different binding sites and effects for estrogen and aldosterone. Accumulating evidence also points to a role of aldosterone in mediating hypertension and its risk factors via the interaction with GPER. Therefore, with this review, we aimed to summarize the research on these interactions to help (1) elucidate the role of GPER activated by aldosterone in the blood vessels, heart, and kidney; (2) compare the non-genomic actions between aldosterone and estrogen mediated by GPER; and (3) address the potential of GPER as a new promising therapeutic target for aldosterone-induced hypertension.

Zebrafish as an emerging model to study estrogen receptors in neural development

Estrogens induce several regulatory signals in the nervous system that are mainly mediated through estrogen receptors (ERs). ERs are largely expressed in the nervous system, yet the importance of ERs to neural development has only been elucidated over the last decades. Accumulating evidence shows a fundamental role for estrogens in the development of the central and peripheral nervous systems, hence, the contribution of ERs to neural function is now a growing area of research. The conservation of the structure of the ERs and their response to estrogens make the zebrafish an interesting model to dissect the role of estrogens in the nervous system. In this review, we highlight major findings of ER signaling in embryonic zebrafish neural development and compare the similarities and differences to research in rodents. We also discuss how the recent generation of zebrafish ER mutants, coupled with the availability of several transgenic reporter lines, its amenability to pharmacological studies and in vivo live imaging, could help us explore ER function in embryonic neural development.

Expression and function of estrogen receptors and estrogen-related receptors in the brain and their association with Alzheimer's disease

While estrogens are well known for their pivotal role in the female reproductive system, they also play a crucial function in regulating physiological processes associated with learning and memory in the brain. Moreover, they have neuroprotective effects in the pathogenesis of Alzheimer's disease (AD). Importantly, AD has a higher incidence in older and postmenopausal women than in men, and estrogen treatment might reduce the risk of AD in these women. In general, estrogens bind to and activate estrogen receptors (ERs)-mediated transcriptional machineries, and also stimulate signal transduction through membrane ERs (mERs). Estrogen-related receptors (ERRs), which share homologous sequences with ERs but lack estrogen-binding capabilities, are widely and highly expressed in the human brain and have also been implicated in AD pathogenesis. In this review, we primarily provide a summary of ER and ERR expression patterns in the human brain. In addition, we summarize recent studies on their role in learning and memory. We then review and discuss research that has elucidated the functions and importance of ERs and ERRs in AD pathogenesis, including their role in Aβ clearance and the reduction of phosphorylated tau levels. Elucidation of the mechanisms underlying ER- and ERR-mediated transcriptional machineries and their functions in healthy and diseased brains would provide new perspectives for the diagnosis and treatment of AD. Furthermore, exploring the potential role of estrogens and their receptors, ERs, in AD will facilitate a better understanding of the sex differences observed in AD, and lead to novel sex-specific therapeutic approaches.

Connecting G protein-coupled estrogen receptor biomolecular mechanisms with the pathophysiology of preeclampsia: a review

BACKGROUND

Throughout the course of pregnancy, small maternal spiral arteries that are in contact with fetal tissue undergo structural remodeling, lose smooth muscle cells, and become less responsive to vasoconstrictors. Additionally, placental extravillous trophoblasts invade the maternal decidua to establish an interaction between the fetal placental villi with the maternal blood supply. When successful, this process enables the transport of oxygen, nutrients, and signaling molecules but an insufficiency leads to placental ischemia. In response, the placenta releases vasoactive factors that enter the maternal circulation and promote maternal cardiorenal dysfunction, a hallmark of preeclampsia (PE), the leading cause of maternal and fetal death. An underexplored mechanism in the development of PE is the impact of membrane-initiated estrogen signaling via the G protein-coupled estrogen receptor (GPER). Recent evidence indicates that GPER activation is associated with normal trophoblast invasion, placental angiogenesis/hypoxia, and regulation of uteroplacental vasodilation, and these mechanisms could explain part of the estrogen-induced control of uterine remodeling and placental development in pregnancy.

CONCLUSION

Although the relevance of GPER in PE remains speculative, this review provides a summary of our current understanding on how GPER stimulation regulates some of the features of normal pregnancy and a potential link between its signaling network and uteroplacental dysfunction in PE. Synthesis of this information will facilitate the development of innovative treatment options.

Involvement of the G-Protein-Coupled Estrogen Receptor-1 (GPER) Signaling Pathway in Neurodegenerative Disorders: A Review

The G-protein-coupled estrogen receptor-1 (GPER) is an extranuclear estrogen receptor that regulates the expression of several downstream signaling pathways with a variety of biological actions including cell migration, proliferation, and apoptosis in different parts of the brain area. It is endogenously activated by estrogen, a steroidal hormone that binds to GPER receptors which help in maintaining cellular homeostasis and neuronal integrity as well as influences neurogenesis. In contrast, neurodegenerative disorders are a big problem for society, and still many people suffer from motor and cognitive impairments. Research to date reported that GPER has the potential to whittle down motor abnormalities and cognitive dysfunction by limiting the progression of neurodegenerative disorders. Although several findings suggest that GPER activation accelerated transcription of the PI3K/Akt/Gsk-3β and ERK1/2 signaling pathway that halt disease progression by decreasing oxidative stress, neuroinflammation, and apoptosis. Accordingly, the goal of this review is to highlight the basic mechanism of GPER signaling pathway-mediated neuroprotection in various neurodegenerative disorders including Parkinson's disease (PD), Huntington's disease (HD), Tardive dyskinesia (TD), and Epilepsy. This review also discusses the role of the GPER activators which might be a promising therapeutic target option to treat neurodegenerative disorders. All the data were obtained from published articles in PubMed (353), Web of Science (788), and Scopus (770) databases using the search terms: GPER, PD, HD, TD, epilepsy, and neurodegenerative disorders.

G protein-coupled estrogen receptor (GPER) selective agonist G1 attenuates the neurobehavioral, molecular and biochemical alterations induced in a valproic acid rat model of autism

AIMS

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder with a rising prevalence in boys rather than girls. G protein-coupled estrogen receptor (GPER) activation by its agonist G1 showed a neuroprotective effect, similar to estradiol. The present study aimed to examine the potential of the selective GPER agonist G1 therapy on the behavioral, histopathological, biochemical, and molecular alterations induced in a valproic acid (VPA)-rat model of autism.

MAIN METHODS

VPA (500 mg/kg) was intraperitoneally administered to female Wistar rats (on gestational day 12.5) to induce the VPA-rat model of autism. The male offspring were intraperitoneally administered with G1 (10 and 20 μg/kg) for 21 days. After the treatment process, rats performed behavioral assessments. Then, sera and hippocampi were collected for biochemical and histopathological examinations and gene expression analysis.

KEY FINDINGS

GPER agonist G1 attenuated behavioral deficits, including hyperactivity, declined spatial memory and social preferences, anxiety, and repetitive behavior in VPA rats. G1 improved neurotransmission and reduced oxidative stress and histological alteration in the hippocampus. G1 reduced serum free T levels and interleukin-1β and up-regulated GPER, RORα, and aromatase gene expression levels in the hippocampus.

SIGNIFICANCE

The present study suggests that activation of GPER by its selective agonist G1 altered the derangements induced in a VPA-rat model of autism. G1 normalized free T levels via up-regulation of hippocampal RORα and aromatase gene expression. G1 provoked estradiol neuroprotective functions via up-regulation of hippocampal GPER expression. The G1 treatment and GPER activation provide a promising therapeutic approach to counteract the autistic-like symptoms.

Disruption of α-Synuclein proteostasis in the striatum and midbrain of long-term ovariectomized female mice

Epidemiological studies have demonstrated that women are less susceptible to Parkinson's disease (PD) than men. Estrogen exposure is hypothesized to confer protection against dopaminergic neuronal loss in patients with PD. Although the accumulation and propagation of α-synuclein (α-Syn) are closely linked to the clinical progression of PD, no relevant research has examined whether α-Syn proteostasis in the brain is altered in women after menopause. In this study, we established long-term ovariectomized (OVX) mice to simulate late post-menopause and investigated the expression and aggregation of α-Syn following the ovariectomy procedure. We observed that the OVX mice exhibited a significant increase in the expression and aggregation of α-Syn in the striatum and midbrain accompanied by impaired motor performance at 3 months after ovariectomy. The accumulation of α-Syn did not result in a significant loss of nigral dopaminergic neurons but did enhance autophagy and neuroglial activation. These findings imply that menopause may disrupt α-Syn proteostasis and exacerbate the accumulation of α-Syn in the basal ganglia circuit.

The role of oestrogen in determining sexual dimorphism in energy balance

Energy balance is determined by caloric intake and the rate at which energy is expended, with the latter comprising resting energy expenditure, physical activity and adaptive thermogenesis. The regulation of both energy intake and expenditure exhibits clear sexual dimorphism, with young women being relatively protected against weight gain and the development of cardiometabolic diseases. Preclinical studies have indicated that females are more sensitive to the satiety effects of leptin and insulin compared to males. Furthermore, females have greater thermogenic activity than males, whereas resting energy expenditure is generally higher in males than females. In addition to this, in post-menopausal women, the decline in sex steroid concentration, particularly in oestrogen, is associated with a shift in the distribution of adipose tissue and overall increased propensity to gain weight. Oestrogens are known to regulate energy balance and weight homeostasis via effects on both food intake and energy expenditure. Indeed, 17β-oestradiol treatment increases melanocortin signalling in the hypothalamus to cause satiety. Furthermore, oestrogenic action at the ventromedial hypothalamus has been linked with increased energy expenditure in female mice. We propose that oestrogen action on energy balance is multi-faceted and is fundamental to determining sexual dimorphism in weight control. Furthermore, evidence suggests that the decline in oestrogen levels leads to increased risk of weight gain and development of cardiometabolic disease in women across the menopausal transition.

Estrous Cycle Mediates Midbrain Neuron Excitability Altering Social Behavior upon Stress

The estrous cycle is a potent modulator of neuron physiology. In rodents, in vivo ventral tegmental area (VTA) dopamine (DA) activity has been shown to fluctuate across the estrous cycle. Although the behavioral effect of fluctuating sex steroids on the reward circuit is well studied in response to drugs of abuse, few studies have focused on the molecular adaptations in the context of stress and motivated social behaviors. We hypothesized that estradiol fluctuations across the estrous cycle acts on the dopaminergic activity of the VTA to alter excitability and stress response. We used whole-cell slice electrophysiology of VTA DA neurons in naturally cycling, adult female C57BL/6J mice to characterize the effects of the estrous cycle and the role of 17β-estradiol on neuronal activity. We show that the estrous phase alters the effect of 17β-estradiol on excitability in the VTA. Behaviorally, the estrous phase during a series of acute variable social stressors modulates subsequent reward-related behaviors. Pharmacological inhibition of estrogen receptors in the VTA before stress during diestrus mimics the stress susceptibility found during estrus, whereas increased potassium channel activity in the VTA before stress reverses stress susceptibility found during estrus as assessed by social interaction behavior. This study identifies one possible potassium channel mechanism underlying the increased DA activity during estrus and reveals estrogen-dependent changes in neuronal function. Our findings demonstrate that the estrous cycle and estrogen signaling changes the physiology of DA neurons resulting in behavioral differences when the reward circuit is challenged with stress.SIGNIFICANCE STATEMENT The activity of the ventral tegmental area encodes signals of stress and reward. Dopaminergic activity has been found to be regulated by both local synaptic inputs as well as inputs from other brain regions. Here, we provide evidence that cycling sex steroids also play a role in modulating stress sensitivity of dopaminergic reward behavior. Specifically, we reveal a correlation of ionic activity with estrous phase, which influences the behavioral response to stress. These findings shed new light on how estrous cycle may influence dopaminergic activity primarily during times of stress perturbation.

Molecular Characterization of the Dual Effect of the GPER Agonist G-1 in Glioblastoma

Glioblastoma (GBM) is the most common primary brain tumor in adults. Despite conventional treatment, consisting of a chirurgical resection followed by concomitant radio-chemotherapy, the 5-year survival rate is less than 5%. Few risk factors are clearly identified, but women are 1.4-fold less affected than men, suggesting that hormone and particularly estrogen signaling could have protective properties. Indeed, a high GPER1 (G-protein-coupled estrogen receptor) expression is associated with better survival, especially in women who produce a greater amount of estrogen. Therefore, we addressed the anti-tumor effect of the GPER agonist G-1 in vivo and characterized its molecular mechanism of action in vitro. First, the antiproliferative effect of G-1 was confirmed in a model of xenografted nude mice. A transcriptome analysis of GBM cells exposed to G-1 was performed, followed by functional analysis of the differentially expressed genes. Lipid and steroid synthesis pathways as well as cell division processes were both affected by G-1, depending on the dose and duration of the treatment. ANGPTL4, the first marker of G-1 exposure in GBM, was identified and validated in primary GBM cells and patient samples. These data strongly support the potential of G-1 as a promising chemotherapeutic compound for the treatment of GBM.

Estrus cycle-dependent working memory effects of prefrontal cortex corticotropin-releasing factor neurotransmission

The prefrontal cortex (PFC) supports a diversity of cognitive processes. Impairment in PFC-dependent cognition is associated with multiple psychiatric disorders, including those known to display sex differences. Our ability to treat this impairment is limited, in part due to an incomplete understanding of the neural mechanisms that support PFC-dependent cognition. In previous studies in male rats, we demonstrated that corticotropin-releasing factor (CRF) receptors and neurons in caudal dorsomedial PFC (dmPFC) regulate PFC-dependent working memory. Subcortically, CRF can exert sex-specific actions, a subset of which are ovarian steroid dependent. To date, the cognitive actions of dmPFC CRF neurotransmission in females are unknown. To address this gap, the current studies examined the effects of chemogenetic and pharmacological manipulations of CRF receptors and neurons within the dmPFC of female rats tested in a spatial working memory task. Outside of proestrus, activation of both CRF receptors and neurons in the caudal, but not rostral, dmPFC impaired working memory. Meanwhile, blockade of CRF receptors in the caudal dmPFC or globally in the brain, improved working memory performance, similar to that seen in males. In contrast, these effects were not observed during proestrus. These observations demonstrate that while CRF neurotransmission in the PFC regulates working memory similarly in males and females, these actions are not observed in females when ovarian steroids are at peak levels.

Magel2 knockdown in hypothalamic POMC neurons innervating the medial amygdala reduces susceptibility to diet-induced obesity

Hyperphagia and obesity profoundly affect the health of children with Prader-Willi syndrome (PWS). The Magel2 gene among the genes in the Prader-Willi syndrome deletion region is expressed in proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARC). Knockout of the Magel2 gene disrupts POMC neuronal circuits and functions. Here, we report that loss of the Magel2 gene exclusively in ARC^POMC neurons innervating the medial amygdala (MeA) causes a reduction in body weight in both male and female mice fed with a high-fat diet. This anti-obesity effect is associated with an increased locomotor activity. There are no significant differences in glucose and insulin tolerance in mice without the Magel2 gene in ARC^POMC neurons innervating the MeA. Plasma estrogen levels are higher in female mutant mice than in controls. Blockade of the G protein-coupled estrogen receptor (GPER), but not estrogen receptor-α (ER-α), reduces locomotor activity in female mutant mice. Hence, our study provides evidence that knockdown of the Magel2 gene in ARC^POMC neurons innervating the MeA reduces susceptibility to diet-induced obesity with increased locomotor activity through activation of central GPER.

Estrogen Up-Regulates Iron Transporters and Iron Storage Protein Through Hypoxia Inducible Factor 1 Alpha Activation Mediated by Estrogen Receptor β and G Protein Estrogen Receptor in BV2 Microglia Cells

Estrogen is a steroid hormone produced mainly by the ovaries. It has been found that estrogen could regulate iron metabolism in neurons and astrocytes in different ways. The role of estrogen on iron metabolism in microglia is currently unknown. In this study, we investigated the effect and mechanism of 17β-estrogen (E2) on iron transport proteins. We found that following E2 treatment for 24h in BV2 microglial cell lines, the iron importer divalent metal transporter 1 (DMT1) and iron exporter ferroportin 1 (FPN1) were up-regulated , iron storage protein ferritin (FT) was increased. The protein levels of iron regulatory proteins (IRPs) and hepcidin remained unchanged, but hypoxia inducible factor 1 alpha (HIF-1α) was up-regulated. Two kinds of estrogen receptor β (ERβ) antagonist G15 and G protein estrogen receptor (GPER) antagonist PHTPPcould block the effects of E2 in BV2 microglial cell lines. These results suggest that estrogen could increase the protein expressions of DMT1, FPN1, FT-L and FT-H in BV2 microglia cells, which were not related to the regulation of IRP1 and hepcidin, but to the upregulation of HIF-1α. In addition, estrogen might regulate the expressions of iron-related proteins through both ER β and GPER in BV2 microglia cells.

Organizational Effects of Estrogens and Androgens on Estrogen and Androgen Receptor Expression in Pituitary and Adrenal Glands in Adult Male and Female Rats

Sex steroid hormones, such as androgens and estrogens, are known to exert organizational action at perinatal periods and activational effects during adulthood on the brain and peripheral tissues. These organizational effects are essential for the establishment of biological axes responsible for regulating behaviors, such as reproduction, stress, and emotional responses. Estradiol (E2), testosterone, and their metabolites exert their biological action through genomic and non-genomic mechanisms, bounding to canonical receptors, such as estrogen receptor (ER)α, ERβ, and androgen receptor (AR) or membrane receptors, such as the G protein-coupled estrogen receptor (GPER), respectively. Expression of ERs and AR was found to be different between males and females both in the brain and peripheral tissues, suggesting a sex-dependent regulation of their expression and function. Therefore, studying the ERs and AR distribution and expression levels is key to understand the central and peripheral role of sex steroids in the establishment of sex-specific behaviors in males and females. We investigated the organizational effects of estrogens and androgens in the pituitary and adrenal glands of adult male and female rats. For this, selective blockade of AR with flutamide or 5α-reductase with finasteride or aromatase with letrozole during the first 5 days of life has been performed in male and female pups and then quantification of ERs and AR expression in both glands has been carried out in adulthood. Data show that inhibition of dihydrotestosterone (DHT) and E2 production during the first five postnatal days mainly decreases the ER expression in male to female values and AR expression in female to male levels in the pituitary gland and increases AR expression in female to male levels in the adrenal gland. In contrast, blocking the action of androgens differentially modulates the ERs in males and females and decreases AR in both males and females in both glands. Altogether, the results suggest that neonatal modifications of the androgen and estrogen pathways can potentially lead to permanent modifications of the neuroendocrine functions of the pituitary and adrenal glands in the adulthood of both sexes.

Modulatory Effects of Estradiol and Its Mixtures with Ligands of GPER and PPAR on MAPK and PI3K/Akt Signaling Pathways and Tumorigenic Factors in Mouse Testis Explants and Mouse Tumor Leydig Cells

The present study was designed to evaluate how estradiol alone or in combination with G protein-coupled estrogen receptor (GPER) agonists and GPER and peroxisome proliferator-activated receptor (PPAR) antagonists alter the expression of tumor growth factor β (TGF-β), cyclooxygenase-2 (COX-2), hypoxia inducible factor 1-alpha (HIF-1α), and vascular endothelial growth factor (VEGF) in mouse testis explants and MA-10 mouse tumor Leydig cells. In order to define the hormone-associated signaling pathway, the expression of MAPK and PI3K/Akt was also examined. Tissue explants and cells were treated with estradiol as well as GPER agonist (ICI 182,780), GPER antagonist (G-15), PPARα antagonist (GW6471), and PPARγ antagonist (T00709072) in various combinations. First, we showed that in testis explants GPER and PPARα expressions were activated by the GPER agonist and estradiol (either alone or in mixtures), whereas PPARγ expression was activated only by GPER agonist. Second, increased TGF-β expression and decreased COX-2 expression were found in all experimental groups of testicular explants and MA-10 cells, except for up-regulated COX-2 expression in estradiol-treated cells, compared to respective controls. Third, estradiol treatment led to elevated expression of HIF-1α and VEGF, while their lower levels versus control were noted in the remaining groups of explants. Finally, we demonstrated the up-regulation of MAPK and PI3Kp85/Akt expressions in estradiol-treated groups of both ex vivo and in vitro models, whereas estradiol in mixtures with compounds of agonistic or antagonistic properties either up-regulated or down-regulated signaling kinase expression levels. Our results suggest that a balanced estrogen level and its action together with proper GPER and PPAR signaling play a key role in the maintenance of testis homeostasis. Moreover, changes in TGF-β and COX-2 expressions (that disrupted estrogen pathway) as well as disturbed GPER-PPAR signaling observed after estradiol treatment may be involved in testicular tumorigenesis.

Neuronal GPER Participates in Genistein-Mediated Neuroprotection in Ischemic Stroke by Inhibiting NLRP3 Inflammasome Activation in Ovariectomized Female Mice

Estrogen replacement therapy (ERT) is potentially beneficial for the prevention and treatment of postmenopausal cerebral ischemia but inevitably increases the risk of cerebral hemorrhage and breast cancer when used for a long period of time. Genistein, a natural phytoestrogen, has been reported to contribute to the recovery of postmenopausal ischemic stroke with reduced risks. However, the underlying mechanism of genistein-mediated neuroprotection remains unclear. We reported that genistein exerted significant neuroprotective effects by enhancing the expression of neuronal G protein-coupled estrogen receptor (GPER) in the ischemic penumbra after cerebral reperfusion in ovariectomized (OVX) mice, and this effect was achieved through GPER-mediated inhibition of nod-like receptor protein 3 (NLRP3) inflammasome activation. In addition, we found that peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) was the pivotal molecule that participated in GPER-mediated inhibition of NLRP3 inflammasome activation in OVX mice after ischemia/reperfusion (I/R) injury. Our data suggest that the neuronal GPER/PGC-1α pathway plays an important role in genistein-mediated neuroprotection against I/R injury in OVX mice.

Sex Differences in Social Cognition

In this review we explore the sex differences underlying various types of social cognition. Particular focus will be placed on the behaviors of social recognition, social learning, and aggression. Known similarities and differences between sexes in the expressions of these behaviors and the known brain regions where these behaviors are mediated are discussed. The role that the sex hormones (estrogens and androgens) have as well as possible interactions with other neurochemicals, such as oxytocin, vasopressin, and serotonin is reviewed as well. Finally, implications about these findings on the mediation of social cognition are mediated and the sex differences related to humans are considered.

Assessment of G Protein-Coupled Oestrogen Receptor Expression in Normal and Neoplastic Human Tissues Using a Novel Rabbit Monoclonal Antibody

In addition to the classical oestrogen receptors, ERα and ERβ, a G protein-coupled oestrogen receptor (GPER) has been identified that primarily mediates the rapid, non-genomic signalling of oestrogens. Data on GPER expression at the protein level are contradictory; therefore, the present study was conducted to re-evaluate GPER expression by immunohistochemistry to obtain broad GPER expression profiles in human non-neoplastic and neoplastic tissues, especially those not investigated in this respect so far. We developed and thoroughly characterised a novel rabbit monoclonal anti-human GPER antibody, 20H15L21, using Western blot analyses and immunocytochemistry. The antibody was then applied to a large series of formalin-fixed, paraffin-embedded human tissue samples. In normal tissue, GPER was identified in distinct cell populations of the cortex and the anterior pituitary; islets and pancreatic ducts; fundic glands of the stomach; the epithelium of the duodenum and gallbladder; hepatocytes; proximal tubules of the kidney; the adrenal medulla; and syncytiotrophoblasts and decidua cells of the placenta. GPER was also expressed in hepatocellular, pancreatic, renal, and endometrial cancers, pancreatic neuroendocrine tumours, and pheochromocytomas. The novel antibody 20H15L21 will serve as a valuable tool for basic research and the identification of GPER-expressing tumours during histopathological examinations.

Estrogen receptors observed at extranuclear neuronal sites and in glia in the nucleus accumbens core and shell of the female rat: Evidence for localization to catecholaminergic and GABAergic neurons

Estrogens affect dopamine-dependent diseases/behavior and have rapid effects on dopamine release and receptor availability in the nucleus accumbens (NAc). Low levels of nuclear estrogen receptor (ER) α and ERβ are seen in the NAc, which cannot account for the rapid effects of estrogens in this region. G-protein coupled ER 1 (GPER1) is observed at low levels in the NAc shell, which also likely does not account for the array of estrogens' effects in this region. Prior studies demonstrated membrane-associated ERs in the dorsal striatum; these experiments extend those findings to the NAc core and shell. Single- and dual-immunolabeling electron microscopy determined whether ERα, ERβ, and GPER1 are at extranuclear sites in the NAc core and shell and whether ERα and GPER1 were localized to catecholaminergic or γ-aminobutyric acid-ergic (GABAergic) neurons. All three ERs are observed, almost exclusively, at extranuclear sites in the NAc, and similarly distributed in the core and shell. ERα, ERβ, and GPER1 are primarily in axons and axon terminals suggesting that estrogens affect transmission in the NAc via presynaptic mechanisms. About 10% of these receptors are found on glia. A small proportion of ERα and GPER1 are localized to catecholaminergic terminals, suggesting that binding at these ERs alters release of catecholamines, including dopamine. A larger proportion of ERα and GPER1 are localized to GABAergic dendrites and terminals, suggesting that estrogens alter GABAergic transmission to indirectly affect dopamine transmission in the NAc. Thus, the localization of ERs could account for the rapid effects of estrogen in the NAc.