17β-Estradiol replacement in young, adult and middle-aged female ovariectomized rats promotes improvement of spatial reference memory and an antidepressant effect and alters monoamines and BDNF levels in memory- and depression-related brain areas

Dimensional Affective Sensitivity to Hormones across the Menstrual Cycle (DASH-MC): A transdiagnostic framework for ovarian steroid influences on psychopathology

Fluctuations in progesterone (P4) and estradiol (E2) across the menstrual cycle can exert direct effects on biological systems implicated in neuropsychiatric disorders and represent a key biological source of variability in affective, cognitive, and behavioral disorders. Although these cyclical symptoms may be most readily identified when they occur exclusively in relation to the menstrual cycle, as in DSM-5 premenstrual dysphoric disorder, symptom changes of similar magnitude occur in a larger proportion of people with ongoing psychiatric disorders. Studies investigating cyclical regulation of brain and behavior often produce inconsistent results, which may be attributed to a lack of focus on specific hormonal events and individual differences in related sensitivities. We propose a transdiagnostic Dimensional Affective Sensitivity to Hormones across the Menstrual Cycle (DASH-MC) framework, postulating that atypical neural responses to several key hormonal events provoke specific temporal patterns of affective and behavioral change across the menstrual cycle. We review prospective and experimental evidence providing initial support for these dimensions, which include (1) luteal-onset negative affect caused by a sensitivity to E2 or P4 surges (mediated by neuroactive metabolites such as allopregnanolone), typified by irritability and hyperarousal; (2) perimenstrual-onset negative affect caused by a sensitivity to low or falling E2, typified by low mood and cognitive dysfunction; and (3) preovulatory-onset positive affect dysregulation caused by a sensitivity to E2 surges, typified by harmful substance use and other risky reward-seeking. This multidimensional, transdiagnostic framework for hormone sensitivity can inform more precise research on ovarian steroid regulation of psychopathology, including further mechanistic research, diagnostic refinement, and precision psychiatry treatment development. Additionally, given the high rates of hormone sensitivity across affective disorders, the DASH-MC may guide broader insights into the complex neurobiological vulnerabilities driving female-biased affective risk, as well as potential triggers and mechanisms of affective state change in psychiatric disorders.

Corticosterone disrupts spatial working memory during retention testing when highly taxed, which positively correlates with depressive-like behavior in middle-aged, ovariectomized female rats

Major Depressive Disorder affects 8.4 % of the U.S. population, particularly women during perimenopause. This study implemented a chronic corticosterone manipulation (CORT, a major rodent stress hormone) using middle-aged, ovariectomized female rats to investigate depressive-like behavior, anxiety-like symptoms, and cognitive ability. CORT (400 μg/ml, in drinking water) was administered for four weeks before behavioral testing began and continued throughout all behavioral assessments. Compared to vehicle-treated rats, CORT significantly intensified depressive-like behaviors: CORT decreased sucrose preference, enhanced immobility on the forced swim test, and decreased sociability on a choice task between a novel conspecific female rat and an inanimate object. Moreover, CORT enhanced anxiety-like behavior on a marble bury task by reducing time investigating tabasco-topped marbles. No effects were observed on novelty suppressed feeding or the elevated plus maze. For spatial working memory using an 8-arm radial arm maze, CORT did not alter acquisition but disrupted performance during retention. CORT enhanced the errors committed during the highest working memory load following a delay and during the last trial requiring the most items to remember; this cognitive metric positively correlated with a composite depressive-like score to reveal that as depressive-like symptoms increased, cognitive performance worsened. This protocol allowed for the inclusion of multiple behavioral assessments without stopping the CORT treatment needed to produce a MDD phenotype and to assess a battery of behaviors. Moreover, that when middle-age was targeted, chronic CORT produced a depressive-like phenotype in ovariectomized females, who also comorbidly expressed aspects of anxiety and cognitive dysfunction.

The effects of estrogens on spatial learning and memory in female rodents - A systematic review and meta-analysis

Estrogens have inconsistent effects on learning and memory in both the clinical and preclinical literature. Preclinical literature has the advantage of investigating an array of potentially important factors contributing to the varied effects of estrogens on learning and memory, with stringently controlled studies. This study set out to identify specific factors in the animal literature that influence the effects of estrogens on cognition, for possible translation back to clinical practice. The literature was screened and studies meeting strict inclusion criteria were included in the analysis. Eligible studies included female ovariectomized rodents with an adequate vehicle for the estrogen treatment, with an outcome of spatial learning and memory in the Morris water maze. Training days of the Morris water maze were used to assess acquisition of spatial learning, and the probe trial was used to evaluate spatial memory recall. Continuous outcomes were pooled using a random effects inverse variance method and reported as standardized mean differences with 95 % confidence intervals. Subgroup analyses were developed a priori to assess important factors. The overall analysis favoured treatment for the later stages of training and for the probe trial. Factors including the type of estrogen, route, schedule of administration, age of animals, timing relative to ovariectomy, and duration of treatment were all found to be important. The subgroup analyses showed that chronic treatment with 17β-estradiol, either cyclically or continuously, to young animals improved spatial recall. These results, observed in animals, can inform and guide further clinical research on hormone replacement therapy for cognitive benefits.

The Role of Estrogen across Multiple Disease Mechanisms

Estrogen is a significant hormone that is involved in a multitude of physiological and pathological processes. In addition to its pivotal role in the reproductive system, estrogen is also implicated in the pathogenesis of a multitude of diseases. Nevertheless, previous research on the role of estrogen in a multitude of diseases, including Alzheimer's disease, depression, cardiovascular disease, diabetes, osteoporosis, gastrointestinal diseases, and estrogen-dependent cancers, has concentrated on a single disease area, resulting in a lack of comprehensive understanding of cross-disease mechanisms. This has brought some challenges to the current treatment methods for these diseases, because estrogen as a potential therapeutic tool has not yet fully developed its potential. Therefore, this review aims to comprehensively explore the mechanism of estrogen in these seven types of diseases. The objective of this study is to describe the relationship between each disease and estrogen, including the ways in which estrogen participates in regulating disease mechanisms, and to outline the efficacy of estrogen in treating these diseases in clinical practice. By studying the role of estrogen in a variety of disease mechanisms, it is hoped that a more accurate theoretical basis and clinical guidance for future treatment strategies will be provided, thus promoting the effective management and treatment of these diseases.

The intersection between menopause and depression: overview of research using animal models

Menopausal women may experience symptoms of depression, sometimes even progressing clinical depression requiring treatment to improve quality of life. While varying levels of estrogen in perimenopause may contribute to an increased biological vulnerability to mood disturbances, the effectiveness of estrogen replacement therapy (ERT) in the relief of depressive symptoms remains controversial. Menopausal depression has a complex, multifactorial etiology, that has limited the identification of optimal treatment strategies for the management of this psychiatric complaint. Nevertheless, clinical evidence increasingly supports the notion that estrogen exerts neuroprotective effects on brain structures related to mood regulation. Indeed, research using preclinical animal models continues to improve our understanding of menopause and the effectiveness of ERT and other substances at treating depression-like behaviors. However, questions regarding the efficacy of ERT in perimenopause have been raised. These questions may be answered by further investigation using specific animal models of reduced ovarian function. This review compares and discusses the advantages and pitfalls of different models emulating the menopausal stages and their relationship with the onset of depressive-like signs, as well as the efficacy and mechanisms of conventional and novel ERTs in treating depressive-like behavior. Ovariectomized young rats, middle-to-old aged intact rats, and females treated with reprotoxics have all been used as models of menopause, with stages ranging from surgical menopause to perimenopause. Additionally, this manuscript discusses the impact of organistic and therapeutic variables that may improve or reduce the antidepressant response of females to ERT. Findings from these models have revealed the complexity of the dynamic changes occurring in brain function during menopausal transition, reinforcing the idea that the best approach is timely intervention considering the opportunity window, in addition to the careful selection of treatment according to the presence or absence of reproductive tissue. Additionally, data from animal models has yielded evidence to support new promising estrogens that could be considered as ERTs with antidepressant properties and actions in endocrine situations in which traditional ERTs are not effective.

Hormone replacement therapy did not alleviate temporomandibular joint inflammatory pain in ovariectomized rats

This study had the aim of examining the relationships between variations in estrogen levels resulting from ovariectomy, and estrogen hormone replacement therapy (HRT) in rats subjected to an orofacial inflammatory pain model. Eighty adult female Wistar rats were initially divided into 2 groups: Sham or ovariectomy (OVX-D1). Seven days later (D7), the rats were subjected to an unilateral infiltration of Freund's Complete Adjuvant (CFA) or saline solution into the right temporomandibular joint (TMJ). Then, rats received 17β-estradiol (28 µg/kg/day) or placebo for 21 days (D10-D31). Nociception was evaluated by the von Frey (VF) and the Hot Plate (HP) tests, and depressive-like behavior by the Forced Swimming (FS) test. On D32 all rats were euthanized and serum, hippocampus and brainstem were collected. The CFA groups presented a mechanical hyperalgesia until day 21 (p ≤ 0.05). No differences were observed among groups in the HP (p = 0.735), and in the immobility and swimming time of the FS (p = 0.800; p = 0.998, respectively). In the brainstem, there was a significant difference in the TNF-ɑ levels (p = 0.043), and a marginal significant difference in BDNF levels (p = 0.054), without differences among groups in the hippocampal BDNF and TNF-ɑ levels (p = 0.232; p = 0.081, respectively). In conclusion, the hormone replacement therapy did not alleviate orofacial pain in ovariectomized rats. However, there is a decrease in brainstem TNF-ɑ levels in the animals submitted to both models, which was partially reverted by HRT.

Prolame produces anxiolytic- and antidepressant-like effects in middle-aged female rats with less uterotrophic effects than 17β-estradiol

Estrogen hormone replacement therapy (EHRT), improving women's life quality at menopause, reduces anxiety and depression symptoms associated with ovarian hormonal decline. However, its potential adverse effects, like thromboembolism and cancer risk, limit its use. Prolame is a synthetic 17β-amino estrogen with antithrombotic actions that exerts anxiolytic- and antidepressant-like effects on young adult ovariectomized female rats. It is unknown if prolame's effects may be observed in age and endocrine conditions emulating menopause. This study aimed to identify the antidepressant- and anxiolytic-like effects of prolame and E2 (used as a reference estrogen treatment) in middle-aged female rats coursing with irregular cycles, in two different conditions: ovariectomized or gonadally intact. Results were compared with those from young adult ovariectomized rats. Prolame (60 or 120 μg/kg), 17β-estradiol (E2, 40 or 80 μg/kg), or vehicle were chronically administered, and their effects were evaluated in the elevated plus-maze, defensive burying behavior test, open field test, and forced swimming test. Uterotrophic actions were estimated by uterine weight related to body weight. Prolame and E2 produced robust anxiolytic- and antidepressant-like effects in young adult ovariectomized rats, but these effects were absent in gonadally intact middle-aged rats. Interestingly, only prolame induced anxiolytic- and antidepressant-like effects in middle-aged ovariectomized rats. Uterotrophic effects of prolame were weaker than E2 effects, notably in middle-aged females. Altogether, present data support the notion that prolame has the potential to be considered an EHRT with relevant psychoactive actions and with apparently lower adverse-side effects, especially in middle-aged populations.

Synaptotagmin-4 induces anhedonic responses to chronic stress via BDNF signaling in the medial prefrontal cortex

Stressful circumstances are significant contributors to mental illnesses such as major depressive disorder. Anhedonia, defined as loss of the ability to enjoy pleasure in pleasurable situations, including rewarding activities or social contexts, is considered a key symptom of depression. Although stress-induced depression is associated with anhedonia in humans and animals, the underlying molecular mechanisms of anhedonic responses remain poorly understood. In this study, we demonstrated that synaptotagmin-4 (SYT4), which is involved in the release of neurotransmitters and neurotrophic factors, is implicated in chronic stress-induced anhedonia. Employing chronic unpredictable stress (CUS), we evaluated two subpopulations of mice, susceptible (SUS, anhedonic) and resilient (RES, nonanhedonic), based on sucrose preference, which was strongly correlated with social reward. The FosTRAP (targeted recombination in active populations) system and optogenetic approach revealed that neural activity in the medial prefrontal cortex (mPFC) was significantly associated with CUS-induced anhedonic behavioral phenotypes. By conducting weighted gene coexpression network analysis of RNA sequencing data from the mPFC of SUS and RES mice, we identified Syt4 as a hub gene in a gene network that was unique to anhedonia. We also confirmed that Syt4 overexpression in the mPFC was pro-susceptible, while Syt4 knockdown was pro-resilient; the pro-susceptible effects of SYT4 were mediated through a reduction in brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (TrkB) signaling in the mPFC. These findings suggest that SYT4-BDNF interactions in the mPFC represent a crucial regulatory mechanism of anhedonic susceptibility to chronic stress.

The Impact of Sex Hormones on Transcranial Magnetic Stimulation Measures of Cortical Excitability: A Systematic Review and Considerations for Clinical Practice

ABSTRACT

Repetitive transcranial magnetic stimulation (rTMS) has emerged as a promising alternative for the treatment of major depressive disorder (MDD), although its clinical effectiveness varies substantially. The effects of sex hormone fluctuations on cortical excitability have been identified as potential factors that can explain this variability. However, data on how sex hormone changes affect clinical response to rTMS is limited. To address this gap, we reviewed the literature examining the effects of sex hormones and hormonal treatments on transcranial magnetic stimulation (TMS) measures of cortical excitability. Results show that variations of endogenous estrogen, testosterone, and progesterone have modulatory effects on TMS-derived measures of cortical excitability. Specifically, higher levels of estrogen and testosterone were associated with greater cortical excitability, while higher progesterone was associated with lower cortical excitability. This highlights the importance of additional investigation into the effects of hormonal changes on rTMS outcomes and circuit-specific physiological variables. These results call for TMS clinicians to consider performing more frequent motor threshold (MT) assessments in patients receiving high doses of estrogen, testosterone, and progesterone in cases such as in vitro fertilization, hormone replacement therapy, and gender-affirming hormonal treatments. It may also be important to consider physiological hormonal fluctuations and their impact on depressive symptoms and the MT when treating female patients with rTMS.

Memory impairments in rodent depression models: A link with depression theories

More than 80% of depressed patients struggle with learning new tasks, remembering positive events, or concentrating on a single topic. These neurocognitive deficits accompanying depression may be linked to functional and structural changes in the prefrontal cortex and hippocampus. However, their mechanisms are not yet completely understood. We conducted a narrative review of articles regarding animal studies to assess the state of knowledge. First, we argue the contribution of changes in neurotransmitters and hormone levels in the pathomechanism of cognitive dysfunction in animal depression models. Then, we used numerous neuroinflammation studies to explore its possible implication in cognitive decline. Encouragingly, we also observed a positive correlation between increased oxidative stress and a depressive-like state with concomitant memory deficits. Finally, we discuss the undeniable role of neurotrophin deficits in developing cognitive decline in animal models of depression. This review reveals the complexity of depression-related memory impairments and highlights the potential clinical importance of gathered findings for developing more reliable animal models and designing novel antidepressants with procognitive properties.

Adolescent raloxifene treatment in females prevents cognitive deficits in a neurodevelopmental rodent model of schizophrenia

The existence of sex differences in schizophrenia is a well documented phenomenon which led to the hypothesis that female sex hormones are neuroprotective and hence responsible for the more favorable disease characteristics seen in women. The current study sought to investigate the effects of estrogen-like agents administered during early adolescence on behavioral outcomes in adulthood using the neurodevelopmental maternal immune activation (MIA) rodent model of schizophrenia. Female MIA offspring were administered during the asymptomatic period of adolescence with either 17β-estradiol, raloxifene or saline and were tested in late adolescence and adulthood for schizophrenia-related behavioral performance. We report here that whereas adult female MIA offspring exhibited cognitive deficits in the form of retarded spatial learning, the administration of raloxifene during adolescence was sufficient in preventing these deficits and resulted in intact performance in the MIA group.

Potential Regulation of miRNA-29 and miRNA-9 by Estrogens in Neurodegenerative Disorders: An Insightful Perspective

Finding a link between a hormone and microRNAs (miRNAs) is of great importance since it enables the adjustment of genetic composition or cellular functions without needing gene-level interventions. The dicer-mediated cleavage of precursor miRNAs is an interface link between miRNA and its regulators; any disruption in this process can affect neurogenesis. Besides, the hormonal regulation of miRNAs can occur at the molecular and cellular levels, both directly, through binding to the promoter elements of miRNAs, and indirectly, via regulation of the signaling effects of the post-transcriptional processing proteins. Estrogenic hormones have many roles in regulating miRNAs in the brain. This review discusses miRNAs, their detailed biogenesis, activities, and both the general and estrogen-dependent regulations. Additionally, we highlight the relationship between miR-29, miR-9, and estrogens in the nervous system. Such a relationship could be a possible etiological route for developing various neurodegenerative disorders.

Ameliorating Effect of the Edible Mushroom Hericium erinaceus on Depressive-Like Behavior in Ovariectomized Rats

Estrogen deficiency during menopause causes a variety of neurological symptoms, including depression. The edible Lion's Mane mushroom, Hericium erinaceus (Bull.: Fr.) Pers. (HE), is a medicinal mushroom that has the potential for a neuroprotective effect and ameliorating neurological diseases, such as depression, anxiety, and neurodegenerative diseases. HE contains phytoestrogens, including daidzein and genistein. However, the ameliorating effect of HE on menopausal symptoms is not well understood. Here we investigated the impact of methanol extract of the HE fruiting body on depressive-like behavior in postmenopausal model rats. The activation of estrogen receptor alpha (ERα) causes body weight loss and uterine weight gain. Body weight gain and uterine weight loss by estrogen deficiency in ovariectomized (OVX) rats were reversed with 17β-estradiol (E₂) but not with HE. Thus, the phytoestrogens in HE may hardly activate ERα. Estrogen receptor beta (ERβ) is expressed in the brain, and activation of ERβ ameliorates menopausal depressive symptoms. Notably, depressive-like behavior in OVX rats evaluated in forced swim test was reduced by administration of not only E₂ but also HE for 92 d. Long-term activation of ERα increases the risk of breast and uterine cancers. HE, therefore, may be effective in treating menopausal depression without the risk of carcinogenesis caused by ERα activation.

Transcriptomic Profile Identifies Hippocampal Sgk1 as the Key Mediator of Ovarian Estrogenic Regulation on Spatial Learning and Memory and Aβ Accumulation

Previous studies have shown that ovarian estrogens are involved in the occurrence and pathology of Alzheimer's disease (AD) through regulation on hippocampal synaptic plasticity and spatial memory; however, the underlying mechanisms have not yet been elucidated at the genomic scale. In this study, we established the postmenopausal estrogen-deficient model by ovariectomy (OVX). Then, we used high-throughput Affymetrix Clariom transcriptomics and found 143 differentially expressed genes in the hippocampus of OVX mice with the absolute fold change ≥ 1.5 and P < 0.05. GO analysis showed that the highest enrichment was seen in long-term memory. Combined with the response to steroid hormone enrichment and GeneMANIA network prediction, the serum and glucocorticoid-regulated kinase 1 gene (Sgk1) was found to be the most potent candidate for ovarian estrogenic regulation. Sgk1 overexpression viral vectors (oSgk1) were then constructed and injected into the hippocampus of OVX mice. Morris water maze test revealed that the impaired spatial learning and memory induced by OVX was rescued by Sgk1 overexpression. Additionally, the altered expression of synaptic proteins and actin remodeling proteins and changes in CA1 spine density and synapse density induced by OVX were also significantly reversed by oSgk1. Moreover, the OVX-induced increase in Aβ-producing BACE1 and Aβ and the decrease in insulin degrading enzyme were significantly reversed by oSgk1. The above results show that multiple pathways and genes are involved in ovarian estrogenic regulation of the function of the hippocampus, among which Sgk1 may be a novel potent target against estrogen-sensitive hippocampal dysfunctions, such as Aβ-initiated AD.

Dietary Supplementation With Tinospora cordifolia Improves Anxiety-Type Behavior and Cognitive Impairments in Middle-Aged Acyclic Female Rats

The midlife transition period in women marks the progressive flattening of neurological health along with increased adiposity, dyslipidemia, frailty, and inflammatory responses mainly attributed to the gradual decline in estrogen levels. Conflicting reports of hormone replacement therapy (HRT) necessitate the exploration of novel therapeutic interventions using bioactive natural products having the least toxicity and a holistic mode of action for the preservation of metabolic homeodynamics with aging in women. The present study was planned to investigate the effects of aging and/or a high-fat diet (HFD) on cognitive impairments and anxiety and further their management by dietary supplement with the Tinospora cordifolia stem powder (TCP). Acyclic female rats were included in this study as the model system of the perimenopause phase of women along with young 3-4 months old rats as controls. Rats were fed on with and without TCP supplemented normal chow or HFD for 12 weeks. Animals fed on a TCP supplemented normal chow showed consistent management of body weight over a 12-week regimen although their calorie intake was much higher in comparison to their age-matched controls. Post-regimen, neurobehavioral tests, such as novel object recognition and elevated plus maze, performed on these animals showed improvement in their learning and memory abilities as well as the anxiety-like behavior. Furthermore, due to the presence of multiple components, TCP was observed to modulate the expression of key marker proteins to ameliorate neuroinflammation and apoptosis and promote cell survival and synaptic plasticity in the hippocampus and the prefrontal cortex (PFC) regions of the brain. These findings suggest that TCP supplementation in diet during the midlife transition period in women may be a potential interventional strategy for the management of menopause-associated anxiety and cognitive impairments and healthy aging.

Ahi1 regulates serotonin production by the GR/ERβ/TPH2 pathway involving sexual differences in depressive behaviors

BACKGROUND

Depression is one of the most common psychiatric diseases. The monoamine transmitter theory suggests that neurotransmitters are involved in the mechanism of depression; however, the regulation on serotonin production is still unclear. We previously showed that Ahi1 knockout (KO) mice exhibited depression-like behavior accompanied by a significant decrease in brain serotonin.

METHODS

In the present study, western blot, gene knockdown, immunofluorescence, dual-luciferase reporter assay, and rescue assay were used to detect changes in the Ahi1/GR/ERβ/TPH2 pathway in the brains of male stressed mice and male Ahi1 KO mice to explain the pathogenesis of depression-like behaviors. In addition, E2 levels in the blood and brain of male and female mice were measured to investigate the effect on the ERβ/TPH2 pathway and to reveal the mechanisms for the phenomenon of gender differences in depression-like behaviors.

RESULTS

We found that the serotonin-producing pathway-the ERβ/TPH2 pathway was inhibited in male stressed mice and male Ahi1 KO mice. We further demonstrated that glucocorticoid receptor (GR) as a transcription factor bound to the promoter of ERβ that contains glucocorticoid response elements and inhibited the transcription of ERβ. Our recent study had indicated that Ahi1 regulates the nuclear translocation of GR upon stress, thus proposing the Ahi1/GR/ERβ/TPH2 pathway for serotonin production. Interestingly, female Ahi1 KO mice did not exhibit depressive behaviors, indicating sexual differences in depressive behaviors compared with male mice. Furthermore, we found that serum 17β-estradiol (E2) level was not changed in male and female mice; however, brain E2 level significantly decreased in male but not female Ahi1 KO mice. Further, ERβ agonist LY-500307 increased TPH2 expression and 5-HT production. Therefore, both Ahi1 and E2 regulate the ERβ/TPH2 pathway and involve sexual differences in brain serotonin production and depressive behaviors.

CONCLUSIONS

In conclusion, although it is unclear how Ahi1 controls E2 secretion in the brain, our findings demonstrate that Ahi1 regulates serotonin production by the GR/ERβ/TPH2 pathway in the brain and possibly involves the regulation on sex differences in depressive behaviors. Video Abstract.

Sex Differences in Affective Dysfunction and Alterations in Parvalbumin in Rodent Models of Early Life Adversity

The early life environment markedly influences brain and behavioral development, with adverse experiences associated with increased risk of anxiety and depressive phenotypes, particularly in females. Indeed, early life adversity (ELA) in humans (i.e., caregiver deprivation, maltreatment) and rodents (i.e., maternal separation, resource scarcity) is associated with sex-specific emergence of anxious and depressive behaviors. Although these disorders show clear sex differences in humans, little attention has been paid toward evaluating sex as a biological variable in models of affective dysfunction; however, recent rodent work suggests sex-specific effects. Two widely used rodent models of ELA approximate caregiver deprivation (i.e., maternal separation) and resource scarcity (i.e., limited bedding). While these approaches model aspects of ELA experienced in humans, they span different portions of the pre-weaning developmental period and may therefore differentially contribute to underlying mechanistic risk. This is borne out in the literature, where evidence suggests differences in trajectories of behavior depending on the type of ELA and/or sex; however, the neural underpinning of these differences is not well understood. Because anxiety and depression are thought to involve dysregulation in the balance of excitatory and inhibitory signaling in ELA-vulnerable brain regions (e.g., prefrontal cortex, amygdala, hippocampus), outcomes are likely driven by alterations in local and/or circuit-specific inhibitory activity. The most abundant GABAergic subtypes in the brain, accounting for approximately 40% of inhibitory neurons, contain the calcium-binding protein Parvalbumin (PV). As PV-expressing neurons have perisomatic and proximal dendritic targets on pyramidal neurons, they are well-positioned to regulate excitatory/inhibitory balance. Recent evidence suggests that PV outcomes following ELA are sex, age, and region-specific and may be influenced by the type and timing of ELA. Here, we suggest the possibility of a combined role of PV and sex hormones driving differences in behavioral outcomes associated with affective dysfunction following ELA. This review evaluates the literature across models of ELA to characterize neural (PV) and behavioral (anxiety- and depressive-like) outcomes as a function of sex and age. Additionally, we detail a putative mechanistic role of PV on ELA-related outcomes and discuss evidence suggesting hormone influences on PV expression/function which may help to explain sex differences in ELA outcomes.

Daidzein Alleviates Hypothalamic-Pituitary-Adrenal Axis Hyperactivity, Ameliorates Depression-Like Behavior, and Partly Rectifies Circulating Cytokine Imbalance in Two Rodent Models of Depression

Depression is one very common mental health disorder which can cause morbidity and mortality if not addressed. Recent studies have provided strong evidence that depression may be accompanied by immune activation, secondary inflammatory reaction, and hyperactivity of the Hypothalamic Pituitary Adrenal (HPA) axis. It is well-known that it takes at least 2 weeks for conventional antidepressants, especially SSRIs (Selective serotonin reuptake inhibitors) to produce effects. To better understand the mechanism of antidepressant effects on depression and subsequently further elucidate the pathogenesis of depression, we selected phytestrogen daidzein (DD) to observe its effects on the depression-like and anxiety-like behavior in two different rodent models of depression which were induced by learned helplessness and chronic mild stress (CMS) and then simultaneous evaluation of the depression-like behavior, the activity of HPA axis, and circulatory cytokines. Our results showed that daidzein attenuated depression-like behaviors through alleviating HPA axis hyperactivity, decreasing the levels of stress-related hormones, and partly rectifying some inflammatory cytokines imbalance in both the rodent models of depression.

Effects of Radix Polygalae on Cognitive Decline and Depression in Estradiol Depletion Mouse Model of Menopause

Postmenopausal syndrome refers to symptoms caused by the gradual decrease in female hormones after mid-40 years. As a target organ of estrogen, decrease in estrogen causes various changes in brain function such as a decrease in choline acetyltransferase and brain-derived neurotrophic factor; thus, postmenopausal women experience cognitive decline and more depressive symptoms than age-matched men. Radix Polygalae has been used for memory boosting and as a mood stabilizer and its components have shown neuroprotective, antidepressant, and stress relief properties. In a mouse model of estrogen depletion induced by 4-vinylcyclohexene diepoxide, Radix Polygalae was orally administered for 3 weeks. In these animals, cognitive and depression-related behaviors and molecular changes related to these behaviors were measured in the prefrontal cortex and hippocampus. Radix Polygalae improved working memory and contextual memory and despair-related behaviors in 4-vinylcyclohexene diepoxide-treated mice without increasing serum estradiol levels in this model. In relation to these behaviors, choline acetyltransferase and brain-derived neurotrophic factor in the prefrontal cortex and hippocampus and bcl-2-associated athanogene expression increased in the hippocampus. These results implicate the possible benefit of Radix Polygalae in use as a supplement of estrogen to prevent conditions such as postmenopausal depression and cognitive decline.

Therapeutic Targets and Mechanism of Xingpi Jieyu Decoction in Depression: A Network Pharmacology Study

Background

Depression is a common mental disease that lacks effective therapeutic drugs with good curative effects and few adverse reactions. Traditional Chinese medicine (TCM) has the advantages of multiple components, multiple channels, and fewer adverse reactions in the treatment of depression. Although Xingpi Jieyu Decoction (XPJYD) demonstrates a good therapeutic effect on depression, the pharmacological mechanism underlying its antidepressant effect is still unclear.

Methods

We used a network pharmacology strategy, including the construction and analysis of a complex drug-disease network, to explore the complex mechanism of XPJYD treatment of depression. In addition, molecular docking technology was used to preliminarily study the binding ability of the potential active components and core therapeutic targets of XPJYD.

Results

The network pharmacology results showed 42 targets of XPJYD that are involved in depression. PPI network analysis demonstrated that the top 10 core targets were AKT1, VEGFA, MAPK8, FOS, ESR1, NR3C1, IL6, HIF1A, NOS3, and AR. The molecular docking results showed that the binding energies of beta sitosterol with AR, FOS, AKT1, VEGFA, NR3C1, and NOS3 were less than −7.0 kcal·mol⁻¹, indicating a good docking effect. The GO enrichment analysis results showed that the XPJYD antidepression mechanism mainly involves the following biological processes such as apoptotic signaling pathway, cellular response to lipid, inflammatory response, and others. The KEGG analysis results indicated that XPJYD may regulate 13 pathways such as PI3K-Akt signaling pathway and estrogen signaling pathway in the treatment of depression.

Conclusions

This study reflects the characteristics of the mechanism of action by which XPJYD treats depression, which includes multiple components, multiple targets, and multiple pathways, and provides a biological basis for further verification and a novel perspective for drug discovery in depression.

Protective effect of metformin against ovariectomy induced depressive- and anxiety-like behaviours in rats: role of oxidative stress

Several studies have shown that low estrogen levels can lead to an increase in the incidence of depression and anxiety during menopause. The hippocampus and prefrontal cortex are parts of the brain involved in depressive- and anxiety-like behaviors. Recent studies have revealed that metformin has neuroprotective effects mainly due to its antioxidant properties. The aim of the present study was to examine the therapeutic potential of metformin in depressive- and anxiety-like behavior as well as oxidative stress in the prefrontal cortex and hippocampus of ovariectomized rats. Young female Wistar Albino rats were distributed into four groups (n:8): control, metformin-administered control, ovariectomized and metformin administered ovariectomized groups. Metformin (25 mg/kg) was administered daily by oral gavage for 2 weeks. Forced swimming test and open field test were performed to evaluate depression- and anxiety-like behaviors, respectively. Following the treatment with metformin, the tissues of the hippocampus and prefrontal cortex were isolated for the measurement of malondialdehyde, reduced glutathione and ascorbic acid contents. Ovariectomy resulted in depressive- and anxiety-like behaviors, and besides, increased content of malondialdehyde in both prefrontal cortex and hippocampus. The levels of ascorbic acid and glutathione were found to be reduced in ovariectomized rats. Metformin treatment significantly decreased depressive behaviour and malondialdehyde content in the prefrontal cortex. Reducing oxidative stress of the prefrontal cortex was suggested as a possible mechanism implicated in the beneficial effects of metformin on ovariectomy-induced depressive-like behaviour. We believe that the therapeutic efficiency of metformin needs to be tested for potential clinical use in surgical menopause or gonadal hormone deficiency women with depression.

Hippocampal Aromatase Knockdown Aggravates Ovariectomy-Induced Spatial Memory Impairment, Aβ Accumulation and Neural Plasticity Deficiency in Adult Female Mice

Ovarian estrogens (mainly 17β estradiol, E2) have been involved in the regulation of the structure of hippocampus, the center of spatial memory. In recent years, high levels of aromatase (AROM), the estrogen synthase, has been localized in hippocampus; and this hippocampus-derived E2 seems to be functional in synaptic plasticity and spatial memory as ovarian E2 does. However, the contribution of ovarian E2 and hippocampal E2 to spatial memory and neural plasticity remains unclear. In this study, AROM-specific RNA interference AAVs (shAROM) were constructed and injected into the hippocampus of control or ovariectomized (OVX) mice. Four weeks later the spatial learning and memory behavior was examined with Morris water maze, the expression of hippocampal Aβ related proteins, selected synaptic proteins and CA1 synapse density, actin polymerization related proteins and CA1 spine density were also examined. The results showed that while OVX and hippocampal shAROM contributed similarly to most of the parameters examined, shAROM induced more increase in BACE1 (amyloidogenic β-secretase), more decrease in neprilysin (Aβ remover) and Profilin-1 (actin polymerization inducer). More importantly, combined OVX and shAROM treatment displayed most significant impairment of spatial learning and memory as well as decrease in synaptic plasticity compared to OVX or shAROM alone. In conclusion, the above results clearly demonstrated the crucial role of hippocampal E2 in the regulation of the structure and function of hippocampus besides ovarian E2, indicating that hippocampal E2 content should also be taken into consideration during estrogenic replacement.

Increased risk of depression before and after unilateral or bilateral oophorectomy: A self-controlled case series study using a nationwide cohort in South Korea

BACKGROUND

There is insufficient evidence of the association between oophorectomy and depression.

METHODS

A nationwide medical records database of South Korea was used to investigate incidence rate ratios (IRRs) of major depressive disorder before and after oophorectomy (n = 36,284) using a self-controlled case series design. Outcomes before and after hysterectomy (n = 25,415) were identified to compare with those around oophorectomy.

RESULTS

In all oophorectomy and hysterectomy groups, the risk of depression was increased before and after surgery, peaking immediately before or after the operation, with no significant difference in the pattern of the results according to type of surgery. In the bilateral oophorectomy group, the IRR was increased between 2-3 months before the surgery, peaking immediately before surgery at 1.39 (95% CI: 1.30-1.49, p < .0001), and remained heightened for one-year postexposure. Subgroup analyses performed according to ovarian cancer, age group, and hormone replacement therapy produced results similar to those of the main outcome.

LIMITATIONS

Because we used claims data, the detailed clinical information related to oophorectomy is lacking. There is possibility that time-varying confounder besides age and season might have affected the results CONCLUSIONS: The risk of depression increased before and after oophorectomy. The increase in risk of depression started before oophorectomy and peaked immediately before or after the operation, but no significant differences between unilateral and bilateral surgery and cancer and noncancer or among age groups were noted.

Selective ER-β agonists alleviate neuronal deficits in insulin-resistant estrogen-deficient rats

OBJECTIVE

The present study aimed to determine the effect of estrogen receptor (ER) agonists on depression and memory impairment in insulin-resistant ovariectomized (OVX) rats.

METHODS

Rats underwent bilateral ovariectomy, and low-dose streptozotocin (STZ) and a high-fat diet (58% fat, 25% protein, and 17% carbohydrates as a percentage of kilocalories) were administered to induce an estrogen-deficient insulin-resistant state. After 1 week of STZ administration, rats were treated with 17β-estradiol (17βE2) and selective ER-α (propylpyrazoletriol) and ER-β (diarylpropionitrile) agonists (10 μg/kg subcutaneously). Memory was evaluated using the Morris water maze and depression using the forced swim test.

RESULTS

Treatment with selective ER-β agonist and 17βE2 but not with selective ER-α agonist significantly modulated the neurobehavioral deficits in insulin-resistant OVX rats. These neurobehavioral parameters were further correlated with brain-derived neurotrophic factor (BDNF) levels and acetylcholinesterase (AChE) activity. Selective ER-β agonist and 17βE2 significantly modulated BDNF levels and AChE activity in insulin-resistant OVX rats. Significant increases in estradiol and uterine weight were observed in 17βE2-treated rats, but selective ER agonists did not show any effect.

CONCLUSION

ER-β agonist can be an effective strategy for the mitigation of memory loss and depression in an estrogen-deficient insulin-resistant state without all of the deleterious feminizing effects that occur with the use of 17βE2.

Ginkgo biloba extract (GbE) attenuates obesity and anxious/depressive-like behaviours induced by ovariectomy

While several pieces of evidence link obesity and mood disorders in menopause, the mechanisms involved are not yet fully understood. We have previously demonstrated that Ginkgo biloba extract (GbE) both attenuated diet-induced obesity of male rats and restored serotonin-induced hypophagia in ovariectomized female rats. The present study aimed at exploring whether GbE treatment ameliorates ovariectomy-related obesity and anxious/depressive-like behaviours. Wistar female rats were either ovariectomized (OVX) or sham-operated (Sham). After 2 months, either 500 mg/kg of GbE or vehicle were administered daily by gavage for 14 days. Anxious/depressive-like behaviours were assessed by the Elevated Plus Maze and the Forced Swim Tests, respectively. Ovariectomy caused high visceral adiposity, hyperleptinemia, and hypercholesterolemia, and increased the anxiety index (p = 0.048 vs. Sham + GbE) while it decreased the latency to immobility (p = 0.004 vs. Sham). GbE treatment in OVX rats improved body composition, adiponectin levels and blood lipid profile. It also reduced the anxiety index (p = 0.004) and increased the latency to immobility (p = 0.003) of OVX rats. Linear regression analysis demonstrated that leptin (p = 0.047) and total cholesterol levels (p = 0.022) were associated with anxious-like behaviours while body adiposity (p = 0.00005) was strongly associated with depressive-like behaviours. The results showed that GbE therapy was effective in attenuating the deleterious effects of ovariectomy on body composition, lipid profile, and anxious/depressive-like behaviours. Further studies are warranted to better understand the therapeutic potential of GbE in menopause.

Intranasal 17β-Estradiol Modulates Spatial Learning and Memory in a Rat Model of Surgical Menopause

Exogenously administered 17β-estradiol (E2) can improve spatial learning and memory, although E2 also exerts undesired effects on peripheral organs. Clinically, E2 has been solubilized in cyclodextrin for intranasal administration, which enhances brain-specific delivery. Prior work shows that the cyclodextrin structure impacts region-specific brain distribution of intranasally administered small molecules. Here, we investigated (1) cyclodextrin type-specific modulation of intranasal E2 brain distribution, and (2) cognitive and peripheral tissue effects of intranasal E2 in middle-aged ovariectomized rats. First, brain and peripheral organ distribution of intranasally administered, tritiated E2 was measured for E2 solubilized freely or in one of four cyclodextrin formulations. The E2-cyclodextrin formulation with greatest E2 uptake in cognitive brain regions versus uterine horns was then compared to free E2 on learning, memory, and uterine measures. Free E2 improved spatial reference memory, whereas E2-cyclodextrin impaired spatial working memory compared to their respective controls. Both E2 formulations increased uterine horn weights relative to controls, with E2-cyclodextrin resulting in the greatest uterine horn weight, suggesting increased uterine stimulation. Thus, intranasal administration of freely solubilized E2 is a strategic delivery tool that can yield a cognitively beneficial impact of the hormone alongside decreased peripheral effects compared to intranasal administration of cyclodextrin solubilized E2.

Association between depression risk and polycystic ovarian syndrome in young women: a retrospective nationwide population-based cohort study (1998-2013)

STUDY QUESTION

Is polycystic ovarian syndrome (PCOS) in women associated with the increasing incidence of depression in an East Asian population?

SUMMARY ANSWER

Younger PCOS patients (aged 15-29 years), but not middle-aged patients, have an increased risk of depression in Taiwan.

WHAT IS KNOWN ALREADY

During reproductive age, 6-10% of women have PCOS. Among them, ~40% experience depression, mostly at young ages.

STUDY DESIGN, SIZE, DURATION

This is a retrospective population-based cohort study analysing depression risk in Taiwanese women using data from a nationwide database containing 1998-2013 data of nearly 1 million people.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We included 15- to 50-year-old women newly diagnosed with PCOS during 1998-2013 from the Taiwan National Health Insurance Research Database as the PCOS cohort (n = 7684) and then randomly matched them 4 : 1 by sex, age and index year with women without PCOS as the comparison cohort (n = 30 736). We used multivariable Cox proportional hazard regression analysis to determine the association between PCOS and depression risk [hazard ratio (HR) with 95% confidence interval (CI)].

MAIN RESULTS AND THE ROLE OF CHANCE

The incidence of depression was higher in the PCOS group than in the comparison group (6.67 vs. 4.82 per 1000 person-years; adjusted HR = 1.28, 95% CI = 1.12-1.46). PCOS patients aged 15-29 years had a significantly higher depression risk (adjusted HR = 1.39, 95% CI = 1.18-1.65); no such significant association was noted among patients aged 30-39 years and 40-50 years.

LIMITATIONS, REASONS FOR CAUTION

A history of malignancy, which may increase depression, could not be obtained for our study patients. Moreover, we could not obtain a family history of depression, a relevant risk factor for depression. Finally, the database has no records of body mass index, which may influence depression outcome.

WIDER IMPLICATIONS OF THE FINDINGS

In Taiwan, younger PCOS patients (15-29 years), but not the middle-aged patients, have an increased risk of depression. Our findings provide vital information to patients, clinicians, the Taiwan Government and other developing Asian countries to improve the PCOS treatment strategies in the future. Routine screening for depression in PCOS patients may be implemented into the health practice.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported in part by the Taiwan Ministry of Health and Welfare Clinical Trial Center (MOHW108-TDU-B-212-133 004), China Medical University Hospital, Academia Sinica Stroke Biosignature Project (BM10701010021), MOST Clinical Trial Consortium for Stroke (MOST 107-2321-B-039 -004-), Tseng-Lien Lin Foundation, Taichung, Taiwan and Katsuzo and Kiyo Aoshima Memorial Funds, Japan. No competing interest existed.

TRIAL REGISTRATION NUMBER

N/A.

17β-Estradiol augments the neuroprotective effect of agomelatine in depressive- and anxiety-like behaviors in ovariectomized rats

RATIONALE AND OBJECTIVE

Estradiol decline has been associated with depression and anxiety in post-menopausal women. Agomelatine (Ago) is an agonist of the melatonergic MT1/MT2 receptors and an antagonist of the serotonergic 5-HT2c receptors. The present study aimed to evaluate the effects of combining Ago with 17β-estradiol (E2) on ovariectomy (OVX)-induced depressive- and anxiety-like behaviors in young adult female rats.

METHODS

OVX rats were treated with Ago (40 mg/kg/day, p.o.) for 10 days starting 1 week after surgery alone or combined with two doses of E2 (40 μg/kg/day, s.c.) given before behavioral testing.

RESULTS

Co-administration of E2 enhanced the anti-depressant and anxiolytics effects of Ago as evidenced by decreased immobility time in the forced swimming test, as well as increased time spent in the open arms and number of entries to open arms in the elevated plus-maze. In parallel, Ago increased hippocampal norepinephrine, dopamine, melatonin, and brain-derived neurotrophic factor (BDNF). Meanwhile, Ago-treated rats exhibited reduced hippocampal nuclear factor kappa beta (NF-kB) P65 expression and pro-inflammatory cytokine level. Ago upregulated estrogen receptor (ER α and β) mRNA expression in the hippocampus of OVX rats and elevated serum estradiol levels. Co-administration of E2 with Ago synergistically decreased NF-kB P65 expression and pro-inflammatory cytokines, and increased BDNF levels.

CONCLUSION

E2 augmented the neuroprotective effect of Ago in OVX rats via its anti-inflammatory and neurotrophic effects. The combined treatment of E2 and Ago should be further investigated as a treatment of choice for depression, anxiety, and sleep disturbances associated with menopause.

Role of Ovarian Hormones in the Modulation of Sleep in Females Across the Adult Lifespan

Ovarian hormones, including 17β-estradiol, are implicated in numerous physiological processes, including sleep. Beginning at puberty, girls report more sleep complaints than boys, which is maintained throughout the reproductive life stage. Sleep problems are exacerbated during the menopausal transition, evidenced by greater risk for sleep disorders. There is emerging evidence that menopause-associated hormone loss contributes to this elevated risk, but age is also an important factor. The extent to which menopause-associated sleep disturbance persists into postmenopause above and beyond the effects of age remains unknown. Untreated sleep disturbances have important implications for cognitive health, as they are emerging as risk factors for dementia. Given that sleep loss impairs memory, an important knowledge gap concerns the role played by menopause-associated hormone loss in exacerbating sleep disturbance and, ultimately, cognitive function in aging women. In this review, we take a translational approach to illustrate the contribution of ovarian hormones in maintaining the sleep-wake cycle in younger and middle-aged females, with evidence implicating 17β-estradiol in supporting the memory-promoting effects of sleep. Sleep physiology is briefly reviewed before turning to behavioral and neural evidence from young females linking 17β-estradiol to sleep-wake cycle maintenance. Implications of menopause-associated 17β-estradiol loss is also reviewed before discussing how ovarian hormones may support the memory-promoting effects of sleep, and why menopause may exacerbate pathological aging via effects on sleep. While still in its infancy, this research area offers a new sex-based perspective on aging research, with a focus on a modifiable risk factor for pathological aging.

Interplay between hormones and exercise on hippocampal plasticity across the lifespan

The hippocampus is a brain structure known to play a central role in cognitive function (namely learning and memory) as well as mood regulation and affective behaviors due in part to its ability to undergo structural and functional changes in response to intrinsic and extrinsic stimuli. While structural changes are achieved through modulation of hippocampal neurogenesis as well as alterations in dendritic morphology and spine remodeling, functional (i.e., synaptic) changes can be noted through the strengthening (i.e., long-term potentiation) or weakening (i.e., long-term depression) of the synapses. While age, hormone homeostasis, and levels of physical activity are some of the factors known to module these forms of hippocampal plasticity, the exact mechanisms through which these factors interact with each other at a given moment in time are not completely understood. It is well known that hormonal levels vary throughout the lifespan of an individual and it is also known that physical exercise can impact hormonal homeostasis. Thus, it is reasonable to speculate that hormone modulation might be one of the various mechanisms through which physical exercise differently impacts hippocampal plasticity throughout distinct periods of an individual's life. The present review summarizes the potential relationship between physical exercise and different types of hormones (namely sex, metabolic, and stress hormones) and how this relationship may mediate the effects of physical activity during three distinct life periods, adolescence, adulthood, and senescence. Overall, the vast majority of studies support a beneficial role of exercise in maintaining hippocampal hormonal levels and consequently, hippocampal plasticity, cognition, and mood regulation.

The role of CREB and BDNF in neurobiology and treatment of Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia worldwide. β-amyloid peptide (Aβ) is currently assumed to be the main cause of synaptic dysfunction and cognitive impairments in AD, but the molecular signaling pathways underlying its neurotoxic consequences have not yet been completely explored. Additional investigations regarding these pathways will contribute to development of new therapeutic targets. In context, developing evidence suggest that Aβ decreases brain-derived neurotrophic factor (BDNF) mostly by lowering phosphorylated cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) protein. In fact, it has been observed that brain or serum levels of BDNF appear to be beneficial markers for cognitive condition. In addition, the participation of transcription mediated by CREB has been widely analyzed in the memory process and AD development. Designing pharmacologic or genetic therapeutic approaches based on the targeting of CREB-BDNF signaling could be a promising treatment potential for AD. In this review, we summarize data demonstrating the role of CREB-BDNF signaling pathway in cognitive status and mediation of Aβ toxicity in AD. Finally, we also focus on the developing intervention methods for improvement of cognitive decline in AD based on targeting of CREB-BDNF pathway.

Antidepressant effect of BE360, a new selective estrogen receptor modulator, activated via CREB/BDNF, Bcl-2 signaling pathways in ovariectomized mice

We have previously reported that the carborane compound BE360, a novel selective estrogen receptor modulator, has a therapeutic potential against dementia. This study aimed to explore the effects and underlying mechanisms of BE360 on depression-like behaviors in ovariectomized (OVX) mice subjected to subchronic stress, which are postmenopausal depression models. BE360 was subcutaneously administrated using a mini-osmotic pump, for 2 weeks. Depression-like behaviors were evaluated using the forced swimming test. Neurogenesis in the hippocampal dentate gyrus (DG) was measured by analyzing cells expressing doublecortin (DCX) following 5-bromo-2'-deoxyuridine (BrdU) uptake. The levels of phosphorylated cyclic-AMP response element-binding protein (p-CREB), brain-derived neurotrophic factor (BDNF), and Bcl-2 were measured using immunohistochemistry or immunoblotting. Depression-like behaviors in OVX + Stress-exposed mice improved after chronic treatment with BE360. BE360 treatment in OVX + Stress-exposed mice increased p-CREB, BDNF, and Bcl-2 expressions in the hippocampus. Immunohistochemistry showed that the number of BrdU/DCX double-positive cells in the DG of the hippocampus, which decreased significantly in OVX + Stress-exposed mice, increased after subchronic treatment with BE360. The present study demonstrates that BE360 exerts antidepressant effects via hippocampal neurogenesis, potentially activated through CREB/BDNF, Bcl-2 signaling pathways. These results indicate that BE360 may have therapeutic potential against postmenopausal depression.

The Impact of Estradiol on Neurogenesis and Cognitive Functions in Alzheimer's Disease

Alzheimer's disease (AD) is described as cognitive and memory impairments with a sex-related epidemiological profile, affecting two times more women than men. There is emerging evidence that alternations in the hippocampal neurogenesis occur at the early stage of AD. Therapies that may effectively slow, stop, or regenerate the dying neurons in AD are being extensively investigated in the last few decades, but none has yet been found to be effective. The regulation of endogenous neurogenesis is one of the main therapeutic targets for AD. Mounting evidence indicates that the neurosteroid estradiol (17β-estradiol) plays a supporting role in neurogenesis, neuronal activity, and synaptic plasticity of AD. This effect may provide preventive and/or therapeutic approaches for AD. In this article, we discuss the molecular mechanism of potential estradiol modulatory action on endogenous neurogenesis, synaptic plasticity, and cognitive function in AD.

Effects of estrogen deprivation on memory and expression of related proteins in ovariectomized mice

Background

The ovariectomized (OVX) rodent model is most widely used for studying the influence of estrogen deprivation on memory. However, the results of these studies are inconsistent, in that the memory of OVX rodents shows either impairment or no change. These inconsistent outcomes increase the difficulty of researching neurochemical mechanisms and evaluating drug efficacy. One possible explanation for these discrepancies might be that the time point for memory examination after OVX varies considerably among studies. The aim of our study was to investigate the effects of estrogen deprivation on memory and the expression of memory-related proteins at different times after OVX.

Methods

Novel object recognition (NOR), step-through passive avoidance (STPA) and the Morris water maze (MWM) were performed to evaluate the memory performance of mice at different times after OVX. The expressions of BDNF, TrkB, ULK1 and LC3II/LC3I in the hippocampus were also assessed to explore the relevant mechanisms.

Results

After OVX, a significant memory impairment was found in the STPA test at 4 weeks. In the NOR and MWM tests, however, memory deficits were not observed until 8 weeks post-OVX. Interestingly, at 8 weeks, a memory rebound was found in the STPA test. In the hippocampus, the levels of BDNF and TrkB in OVX mice were markedly decreased at 4 and 8 weeks. Subsequently, a significant decrease in the ULK1 and LC3II/LC3I level in OVX mice was observed at 8 weeks.

Conclusions

Memory impairment in mice was observed as early as 4 weeks after OVX, although there was a possibility of memory rebound with the prolongation of estrogen deprivation. Eight weeks of estrogen deprivation would be more likely to induce hippocampus-dependent memory impairment. This progressive impairment of memory might be due to the downregulation of the BDNF/TrkB signaling pathway at the early post-OVX stage, while the decrease of autophagy level in the later stage might also contribute to these progressive alterations. The underlying relationship between the BDNF/TrkB signaling pathway and autophagy in this progressive impairment of memory requires further study.

A Modified Formulation of Sutaehwan Ameliorates Menopausal Anxiety, Depression and Heart Hypertrophy in the VCD-Induced Menopausal Mouse Model

Sutaehwan (STH) has been used in Korean medicine for the treatment of abortus habitualis such as fetal restlessness in the uterus. Previously, we reported that a modified formulation of STH, Sutaehwan-Gami, has phytoestrogen-like properties in an ovariectomized menopausal rat model. However, the therapeutic effects of STH and the precise mechanisms by which STH affects various menopausal symptoms remain poorly understood. The current study was designed to explore the effects of a modified form of STH on menopausal anxiety, depression and heart hypertrophy and its mechanisms in 4-vinylcyclohexene diepoxide (VCD)-induced menopausal mouse models. VCD-induced menopausal model mice were fed a modified form of STH, which contained water extract of 3 herbs (called STH_KP17001) at a dose of 100 or 300 mg/kg/d or as a positive control, estradiol at a dose of 0.2 mg/kg/d with standard mouse pellets for 13 weeks. The results show that STH_KP17001 significantly restored the VCD-induced weight reduction of uterine and ovary through the phosphorylation of extracellular signal-regulated kinase (ERK) and protein kinase B (AKT) in the uterus and ovary. Moreover, STH_KP17001 showed slight proliferative effects and estrogen receptor α phosphorylation in MCF-7 cells. Treatment with STH_KP17001 reversed VCD-induced anxiety and depression through AMP-activated protein kinase (AMPK) activation and brain-derived neurotrophic factor (BDNF) expression in the cerebral cortex, while improving heart hypertrophy through inactivation of inhibitor of kappaB α (IκBα) in the heart. The results indicate that STH_KP17001 improves menopause-induced anxiety, depression and heart hypertrophy, implying its protective role for the management of menopausal symptoms.

Effects of Puerarin on the Ovariectomy-Induced Depressive-Like Behavior in ICR Mice and Its Possible Mechanism of Action

Daily treatment of ovariectomized (OVX) ICR mice with puerarin, a glycosyl isoflavone isolated from the root bark of Pueraria candollei var. mirifica, and 17β-estradiol attenuated ovariectomy-induced depression-like behavior, as indicated by a decrease in immobility times in the tail suspension test (TST) and the forced swimming test (FST), an increase in the uterine weight and volume, a decrease in serum corticosterone levels, and dose-dependently normalized the downregulated transcription of the brain-derived neurotrophic factor (BDNF) and estrogen receptor (Erβ and Erα) mRNAs. Like 17β-estradiol, puerarin also inhibited ovariectomy-induced suppression of neurogenesis in the dentate gyrus of the hippocampus (increased the number of doublecortin (DCX)-immunosuppressive cells). These results suggest that puerarin exerts antidepressant-like effects in OVX animals, possibly by attenuating the OVX-induced hyperactivation of the HPA axis and/or normalizing the downregulated transcription of BDNF and ER mRNA in the brain.

Synaptic plasticity in hippocampal CA1 neurons and learning behavior in acute kidney injury, and estradiol replacement in ovariectomized rats

Background

Neurological complications may occur in patients with acute or chronic renal failure; however, in cases of acute renal failure, the signs and symptoms are usually more pronounced, and progressed rapidly. Oxidative stress and nitric oxide in the hippocampus, following kidney injury may be involved in cognitive impairment in patients with uremia. Although many women continue taking hormone therapy for menopausal symptom relief, but there are also some controversies about the efficacy of exogenous sex hormones, especially estrogen therapy alone, in postmenopausal women with kidney injury. Herein, to the best of our knowledge for the first time, spatial memory and synaptic plasticity at the CA1 synapse of a uremic ovariectomized rat model of menopause was characterized by estradiol replacement alone.

Results

While estradiol replacement in ovariectomized rats without uremia, promotes synaptic plasticity, it has an impairing effect on spatial memory through hippocampal oxidative stress under uremic conditions, with no change on synaptic plasticity. It seems that exogenous estradiol potentiated the deleterious effect of acute kidney injury (AKI) with increasing hippocampal oxidative stress.

Conclusions

Although, estrogen may have some positive effects on cognitive function in healthy subjects, but its efficacy in menopause subjects under uremic states such as renal transplantation, needs to be further investigated in terms of dosage and duration.

Humanin, a Mitochondrial-Derived Peptide Released by Astrocytes, Prevents Synapse Loss in Hippocampal Neurons

Astroglial cells are crucial for central nervous system (CNS) homeostasis. They undergo complex morpho-functional changes during aging and in response to hormonal milieu. Ovarian hormones positively affect different astroglia parameters, including regulation of cell morphology and release of neurotrophic and neuroprotective factors. Thus, ovarian hormone loss during menopause has profound impact in astroglial pathophysilogy and has been widely associated to the process of brain aging. Humanin (HN) is a secreted mitochondrial-encoded peptide with neuroprotective effects. It is localized in several tissues with high metabolic rate and its expression decreases with age. In the brain, humanin has been found in glial cells in physiological conditions. We previously reported that surgical menopause induces hippocampal mitochondrial dysfunction that mimics an aging phenotype. However, the effect of ovarian hormone deprivation on humanin expression in this area has not been studied. Also, whether astrocytes express and release humanin and the regulation of such processes by ovarian hormones remain elusive. Although humanin has also proven to be beneficial in ameliorating cognitive impairment induced by different insults, its putative actions on structural synaptic plasticity have not been fully addressed. In a model of surgical menopause in rats, we studied hippocampal humanin expression and localization by real-time quantitative polymerase chain reaction (RT-qPCR) and double immunohistochemistry, respectively. Humanin production and release and ovarian hormone regulation of such processes were studied in cultured astrocytes by flow cytometry and ELISA, respectively. Humanin effects on glutamate-induced structural synaptic alterations were determined in primary cultures of hippocampal neurons by immunocytochemistry. Humanin expression was lower in the hippocampus of ovariectomized rats and its immunoreactivity colocalized with astroglial markers. Chronic ovariectomy also promoted the presence of less complex astrocytes in this area. Ovarian hormones increased humanin intracellular content and release by cultured astrocytes. Humanin prevented glutamate-induced dendritic atrophy and reduction in puncta number and total puncta area for pre-synaptic marker synaptophysin in cultured hippocampal neurons. In conclusion, astroglial functional and morphological alterations induced by chronic ovariectomy resemble an aging phenotype and could affect astroglial support to neuronal function by altering synaptic connectivity and functionality. Reduced astroglial-derived humanin may represent an underlying mechanism for synaptic dysfunction and cognitive decline after menopause.

Venlafaxine Mitigates Depressive-Like Behavior in Ovariectomized Rats by Activating the EPO/EPOR/JAK2 Signaling Pathway and Increasing the Serum Estradiol Level

Reduced estradiol levels are associated with depression in women during the transition to and after menopause. A considerable number of studies focusing on the theme of treating depression through the activation of erythropoietin (EPO)-induced signaling pathways have been published. Venlafaxine is an approved antidepressant drug that inhibits both serotonin and norepinephrine transporters. The aim of the present study was to investigate the effects of venlafaxine on the depressive-like behaviors and serum estradiol levels in female rats following ovariectomy (OVX) and the possible roles of EPO-induced signaling pathways. Venlafaxine (10 mg/kg/day) was orally administered to OVX rats over a period of 4 weeks using two different treatment regimens: either starting 24 h or 2 weeks after OVX. Venlafaxine showed a superior efficacy in inducing antidepressant-like effects after an acute treatment (24 h post-OVX) than after the delayed treatment (2 weeks post-OVX) and was characterized by a decreased immobility time in the forced swimming test. In parallel, venlafaxine induced EPO and EPO receptor mRNA expression and increased levels of phospho-Janus kinase 2 (p-JAK2), phospho-signal transducer and activator of transcription 5, and phospho-extracellular signal-regulated kinase 1/2 in the hippocampus of OVX rats. Meanwhile, rats exhibited a marked reduction in the hippocampal Bax/Bcl2 ratio, caspase-3 activity, and tumor necrosis factor alpha levels after venlafaxine treatment. Venlafaxine also increased the hippocampal brain-derived neurotrophic factor and serum estradiol levels. Based on these findings, venlafaxine exerts a neuroprotective effect on OVX rats that is at least partially attributed to the activation of EPO/EPOR/JAK2 signaling pathways, anti-apoptotic activities, anti-inflammatory activities, and neurotrophic activities, as well as an increase in serum estradiol level. Graphical Abstract ᅟ.

Resveratrol ameliorates estrogen deficiency-induced depression- and anxiety-like behaviors and hippocampal inflammation in mice

RATIONALE

Resveratrol (RSV) has been indicated to exhibit beneficial effects on depression and anxiety treatment by suppression of inflammatory processes. Depression triggered by deficiency of estrogen and anxiety-like behaviors are associated with inflammation. The role of RSV in ovariectomized mice is unclear.

OBJECTIVES

We examine whether the RSV, a Sirt1 activator, alleviates ovariectomy-induced anxiety- and depression-like behaviors through the inhibition of inflammatory processes.

METHODS

Female C57BL/6J mice (6-8 weeks of age, 17-20 g) were ovariectomized and treated with RSV at a dose of 20 mg/kg for 2 weeks. Depression- and anxiety-like behaviors were compared with vehicle-injected control animals. Immunohistochemistry and qPCR were used to detect inflammation in the hippocampal region.

RESULTS

Ovariectomized mice were observed to suffer from anxiety- and depression-like behaviors. These effects were attenuated by treatment with RSV. Immunohistochemical staining results showed that RSV could reverse the increase of microglial activation in the hippocampal dentate gyrus. At a molecular level, RSV inhibited the activation of NLRP3 and NF-κB in the hippocampal region caused by deficiency of estrogen.

CONCLUSIONS

RSV suppressed the production of inflammatory cytokines by enhancing Sirt1 levels. Our findings indicated that RSV-induced Sirt1 activation counteracted estrogen deficiency-induced psychobehavioral changes via inhibition of inflammatory processes in the hippocampus. In anxiety and depression disorders, RSV is supposed to be an effective treatment for postmenopausal changes.

Establishment and evaluation of a novel mouse model of peri/postmenopausal depression

Women are believed to be more vulnerable to develop depressive symptoms during the perimenopause compared to postmenopause. The traditional bilateral ovariectomy and chronic mild stress (CMS) stimulation animal model produces a postmenopausal depressive-like state but the transition from perimenopausal period to postmenopausal period was ignored. Thus we establish a novel animal model in which the mice were stimulated by CMS for three months and removed the ovaries by two-step operation, and then evaluate whether this novel model could be much better for preclinical study used as a peri/postmenopause depressive model. The present study systemically evaluated the changes induced by two-step ovariectomy plus CMS in the mice. The depression-like behaviors, the levels of corticosterone, estrogen, pro-inflammatory factors, neurotransmitters, as well as brain-derived neurotrophic factor were determined; the changes of estrogen receptors, serotonin receptors, uterine weight and bone microarchitecture were also observed. The results show that the behaviors and biochemical indexes of mice changed gradually over time. Our study suggests that this two-step ovariectomy operation plus CMS successfully establishes a more reasonable peri/postmenopausal depression animal model which effectively simulates the clinical symptoms of peri/postmenopausal depressive women.

Sex Differences in Antidepressant Effect of Sertraline in Transgenic Mouse Models

The main purpose of this study is to explore sex differences in the antidepressant effect of sertraline in genetic knockout or overexpression estrogen-synthesizing enzyme aromatase (Ar) gene mouse models in the forced swim test (FST). Our results demonstrated a significant reduction of depression-like behavior in the mice with overexpression of brain aromatase (Thy1-Ar) compared to sex- and age-matched Ar^+/− mice or wild type control mice. Using HPLC analysis, we also found an association between the brain estrogen-related antidepressive behavior and the regulation of serotonin (5-HT) system. Interestingly, a single dose administration of sertraline (10 mg/kg, i.p.) induced reduction of immobility time was found in all genotypes, except male Ar^+/− mice. While the underlying mechanisms of sex-specific response on antidepressive effect of sertraline remain to be investigated, our data showed that female mice appear to be more sensitive to sertraline-induced changes of 5-HT system than male mice in the prefrontal cortex (PFC) and the hippocampus (HPC). Further investigation of sex-specific effect of brain estrogen on antidepressant is needed.

ERβ agonist alters RNA splicing factor expression and has a longer window of antidepressant effectiveness than estradiol after long-term ovariectomy

BACKGROUND

Estrogen therapy (ET), an effective treatment for perimenopausal depression, often fails to ameliorate symptoms when initiated late after the onset of menopause. Our previous work has suggested that alternative splicing of RNA might mediate these differential effects of ET.

METHODS

Female Sprague–Dawley rats were treated with estradiol (E2) or vehicle 6 days (early ET) or 180 days (late ET) after ovariectomy (OVX). We investigated the differential expression of RNA splicing factors and tryptophan hydroxylase 2 (TPH2) protein using a customized RT2 Profiler PCR Array, reverse-transcription polymerase chain reaction, immunoprecipitation and behaviour changes in clinically relevant early and late ET.

RESULTS

Early ET, but not late ET, prolonged swimming time in the forced swim test and reduced anxiety-like behaviours in the elevated plus maze. It reversed OVX-increased (SFRS7 and SFRS16) or OVX-decreased (ZRSR2 and CTNNB1) mRNA levels of splicing factors and ERβ splicing changes in the brains of OVX rats. Early ET, but not late ET, also increased the expression of TPH2 and decreased monoamine oxidase A levels in the dorsal raphe in the brains of OVX rats. In late ET, only diarylpropionitrile (an ERβ-specific agonist) achieved similar results — not E2 (an ERα and ERβ agonist) or propylpyrazoletriol (an ERα-specific agonist).

LIMITATIONS

Our experimental paradigm mimicked early and late ET in the clinical setting, but the contribution of age and OVX might be difficult to distinguish.

CONCLUSION

These findings suggest that ERβ alternative splicing and altered responses in the regulatory system for serotonin may mediate the antidepressant efficacy of ET associated with the timing of therapy initiation. It is likely that ERβ-specific ligands would be effective estrogen-based antidepressants late after the onset of menopause.

Impact of central and peripheral estrogen treatment on anxiety and depression phenotypes in a mouse model of postmenopausal obesity

Obesity and diabetes increase the risk of depression, and the incidence of these conditions increases rapidly after menopause, but few animal models of postmenopausal obesity have been available. We developed a mouse model of postmenopausal obesity that exhibited anxiety and depressive phenotypes in behavioral tests. To examine the effect of estradiol (E2) in the model, we prepared 4 experimental groups: 1) control, sham-operated female C57BL/6 mice fed a regular diet; 2) OVX-HF, ovariectomized (OVX) mice fed a high-fat diet (HF); 3) E2-SC, OVX-HF mice administered subcutaneous (SC) E2 (50 μg/kg/day); and 4) E2-ICV, OVX-HF mice administered intracerebroventricular (ICV) E2 (1 μg/kg/day). OVX-HF mice exhibited anxiety phenotypes in the open field test, but not in the light-dark box test, and E2 treatment via both routes effectively ameliorated it. OVX-HF mice demonstrated depressive phenotypes in the tail suspension test and forced swim test. Both E2 treatments achieved significant improvement in the tail suspension test, but not in the forced swim test. Serum corticosterone levels did not differ among the groups. Hippocampal expression of glucocorticoid receptor mRNA and serotonin 1A receptor mRNA was significantly increased in OVX-HF mice and was decreased in E2-treated mice. The hypothalamic level of pro-brain-derived neurotrophic factor (proBDNF) protein was tended to decrease in OVX-HF mice, but neither E2 treatment increased it. Since this mouse model exhibited anxiety and depressive phenotypes in relatively short experimental periods without genetic manipulations, it would be useful for further exploring psychiatric phenotypes or screening of therapeutic candidates in postmenopausal obesity.

High-Fat Feeding Improves Anxiety-Type Behavior Induced by Ovariectomy in Rats

Menopause-induced changes may include increased incidence of both depression/anxiety and obesity. We hypothesized that behavioral changes that may develop after ovarian failure could be related to neurochemical and metabolic aspects affected by this condition and that high-fat intake may influence these associations. The present study investigated in rats the effects of ovariectomy, either alone or combined with high-fat diets enriched with either lard or fish-oil, on metabolic, behavioral and monoaminergic statuses, and on gene expression of neuropeptides and receptors involved in energy balance and mood regulation. Female rats had their ovaries removed and received either standard chow (OvxC) or high-fat diets enriched with either lard (OvxL) or fish-oil (OvxF) for 8 weeks. The Sham group received only chow diet. Ovariectomy increased feed efficiency and body weight gain and impaired glucose homeostasis and serotonin-induced hypophagia, effects either maintained or even accentuated by the lard diet but counteracted by the fish diet. The OvxL group developed obesity and hyperleptinemia. Regarding components of hypothalamic serotonergic system, both ovariectomy alone or combined with the fish diet increased 5-HT2C expression while the lard diet reduced 5-HT1B mRNA. Ovariectomy increased the anxiety index, as derived from the elevated plus maze test, while both high-fat groups showed normalization of this index. In the forced swimming test, ovariectomy allied to high-lard diet, but not to fish-oil diet, reduced the latency to immobility, indicating vulnerability to a depressive-like state. Linear regression analysis showed hippocampal AgRP to be negatively associated with the anxiety index and hypothalamic AgRP to be positively associated with the latency to immobility. These AgRp gene expression associations are indicative of a beneficial involvement of this neuropeptide on both depression and anxiety measures. The present findings demonstrate metabolic, neurochemical and behavioral alterations after ovaries removal and highlight a positive effect of high-fat feeding on the anxiety-like behavior shown by ovariectomized animals. Since the polyunsaturated ômega-3 intake (fish diet), unlike the saturated fat intake (lard diet), failed to induce deleterious metabolic or neurochemical consequences, further studies are needed focusing on the potential of this dietary component as an adjuvant anxiolytic agent after menopause.