More than a decade of estrogen neuroprotection

Baohuoside I suppresses the NLRP3 inflammasome activation via targeting GPER to fight against Parkinson's disease

BACKGROUND

Accumulating evidence indicates the crucial role of microglia-mediated inflammation and the NLR family pyrin domain containing 3 (NLRP3) inflammasome-mediated pyroptosis in the pathogenesis of Parkinson's disease (PD). Baohuoside I, a natural flavonoid extracted from Herba Epimedii, has been shown to possess anti-inflammatory effects, but its potential neuroprotective effects and mechanism against PD have not been documented.

STUDY DESIGN AND METHODS

The anti-inflammatory effects of Baohuoside I were evaluated by LPS-induced BV2 cells or primary microglia isolated from wide type or G protein-coupled estrogen receptor (GPER) gene knockout mice. The underlying mechanism related to GPER-mediated NLRP3 inflammasome inhibition was further explored using LPS-induced GPER+/+ or GPER-/- mouse models of PD. The neuroprotective effects of Baohuoside I were detected through western blot analysis, real-time PCR, molecular docking, mouse behavioral tests, immunofluorescence, and immunohistochemistry.

RESULTS

Baohuoside I significantly alleviated LPS-induced neuroinflammation by inhibiting the activation of NF-κB signal and the increase of pyroptosis levels as evidenced by the downregulated expression of pyroptosis-related proteins (NLRP3, ASC, pro-Caspase-1, IL-1β) in microglia cells. Intragastric administration of Baohuoside I protected against LPS-induced motor dysfunction and loss of dopaminergic neurons, reduced pro-inflammatory cytokines expressions, and inhibited microglial (Iba-1) and astrocyte (GFAP) activation in the nigrostriatal pathway in LPS-induced mouse model of PD. Pretreatment with GPER antagonist G15 in microglia cells or GPER gene deletion in mice significantly blocked the inhibitory effects of Baohuoside I on LPS-induced neuroinflammation and activation of the NLRP3/ASC/Caspase-1 pathway. Molecular docking further indicated that Baohuoside I might bind to GPER directly with a binding energy of -10.4 kcal/mol.

CONCLUSION

Baohuoside I provides neuroprotective effects against PD by inhibiting the activation of the NF-κB signal and NLRP3/ASC/Caspase-1 pathway. The molecular target for its anti-inflammatory effects is proved to be GPER in the PD mouse model. Baohuoside I may be a valuable anti-neuroinflammatory agent and a drug with well-defined target for the treatment of PD.

Long-term hypogonadism diminishes the neuroprotective effects of dietary genistein in young adult ovariectomized rats after transient focal ischemia

Increasing age disproportionately increases the risk of stroke among women compared to men of similar age, especially after menopause. One of the reasons for this observation is a sharp drop in circulating estrogens. However, the timing of initiation of estrogen replacement after menopause is associated with mixed beneficial and detrimental effects, hence contributing to widespread mistrust of estrogen use. Agents including soy isoflavones are being assessed as viable alternatives to estrogen therapy. In this study, we hypothesized that the neuroprotective effects of genistein, a soy isoflavone are less sensitive to the length of hypogonadism in young adult ovariectomized rats following cerebral ischemia. We expected that long-term hypogonadism will worsen motor and cognitive function, increase post-stroke inflammation with no effect on the neuroprotection of genistein. We compared the effect of treatment with dietary genistein (GEN) on short-term (2 weeks) and long-term hypogonadism (12 weeks) in young adult ovariectomized Sprague-Dawley rats on sensorimotor function, cognition and inflammation after focal ischemia. Dorsal Silastic implant of 17β-estradiol (E2) was used as a control for hormone therapy. Long-term hypogonadism stroked rats performed worse than the short-term hypogonadism stroked rats on the motor and cognitive function tests. GEN did not improve neurological assessment and motor learning after either short-term or long-term hypogonadism. GEN improved cognitive flexibility after short-term hypogonadism but not after the long-term. Both GEN and E2 reduced tissue loss after short-term hypogonadism and reduced GFAP expression at the contralateral side of ischemia after long-term hypogonadism. The length of hypogonadism may differentially influence the neuroprotective effects of both GEN and E2 on the motor and cognitive functions in young adult rats.

Neurotherapeutic applications of nanomedicine for treating Alzheimer's disease

Alzheimer's disease (AD) is a progressive, irreversible, fatal brain disease which disturbs cognitive functions. It affects 35 million people worldwide and the number of people suffering may increase to 100 million by 2050 if no effective treatments are available. The present treatment improves cognitive functions and provide temporary symptomatic relief, but do not stop or delay the disease progression. Moreover, they are mainly available as conventional oral dosage forms and these conventional oral medications lack brain specificity and also produce side effects which leads to poor patient compliance. Brain drug targeting by nanomedicines is a promising approach to improve brain targeting specificity, brain bioavailability and patient compliance. The present review discuses about the currently available pharmacotherapy for AD and the neurotherapeutic applications as well as the advancements of nanomedicine for treating AD. It also highlights the recent advancements of various nanomedicines containing phytopharmaceuticals for treating AD. It is believed that nanomedicines containing approved drugs can be transformed into the clinics hence improve the life style of AD patients.

Aging-Related Calcium Dysregulation in Rat Entorhinal Neurons Homologous with the Human Entorhinal Neurons in which Alzheimer's Disease Neurofibrillary Tangles First Appear

Aging is the leading risk factor for idiopathic Alzheimer’s disease (AD), indicating that normal aging processes promote AD and likely are present in the neurons in which AD pathogenesis originates. In AD, neurofibrillary tangles (NFTs) appear first in entorhinal cortex, implying that aging processes in entorhinal neurons promote NFT pathogenesis. Using electrophysiology and immunohistochemistry, we find pronounced aging-related Ca^{2 +} dysregulation in rat entorhinal neurons homologous with the human neurons in which NFTs originate. Considering that humans recapitulate many aspects of animal brain aging, these results support the hypothesis that aging-related Ca^{2 +} dysregulation occurs in human entorhinal neurons and promotes NFT pathogenesis.

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.

Nanomedicine in Alzheimer's disease: Amyloid beta targeting strategy

The treatment of Alzheimer's disease (AD) is up to today one of the most unsuccessful examples of biomedical science. Despite the high number of literature evidences detailing the multifactorial and complex etiopathology of AD, no cure is yet present on the market and the available treatments are only symptomatic. The reasons could be ascribed on two main factors: (i) lack of ability of the majority of drugs to cross the blood-brain barrier (BBB), thus excluding the brain for any successful therapy; (ii) lack of selectivity and specificity of drugs, decreasing the efficacy of even potent anti-AD drugs. The exploitation of specifically engineered nanomedicines planned to cross the BBB and to target the most "hot" site of action (i.e., β-amyloid) is one of the most interesting innovations in drug delivery and could reasonably represent an promising choice for possible treatments and even early-diagnosis of AD. In this chapter, we therefore outline the most talented approaches in AD treatment with a specific focus on the main advantages/drawbacks and future possible translation to clinic application.

Inflammatory Responses are Sex Specific in Chronic Hypoxic-Ischemic Encephalopathy

Neonatal hypoxic-ischemic encephalopathy (HIE) is increasingly recognized as a sexually dimorphic disease. Male infants are not only more vulnerable to ischemic insult; they also suffer more long-term cognitive deficits compared with females with comparable brain damage. The innate immune response plays a fundamental role in mediating acute neonatal HIE injury. However, the mechanism underlying the sex difference in chronic HIE is still elusive. The present study investigated the sex difference in HIE outcomes and inflammatory response in the chronic stage (30 days after HIE). Postnatal day 10 (P10) male and female C57BL/6 pups were subjected to 60-min Rice-Vanucci model (RVM) to induce HIE. Brain atrophy and behavioral deficits were analyzed to measure stroke outcomes at 30 days of HIE. Flow cytometry (FC) was performed to examine central (microglial activation) and peripheral immune responses. Serum levels of cytokines and sex hormones were determined by enzyme-linked immunosorbent assay (ELISA). Neurogenesis was quantified by 5-Bromo-2'-deoxyuridine (BrdU) incorporation with neurons. Results showed males had worse HIE outcomes than females at the endpoint. Female microglia exhibited a more robust anti-inflammatory response that was corresponding to an enhanced expression of CX3C chemokine receptor 1 (CX3CR1) than males. More infiltration of peripheral lymphocytes was seen in male vs. female HIE brains. Cytokine levels of tumor necrosis factor (TNF)-α and interleukin (IL)-10 were more upregulated in males and females respectively than their counterparts. Neurogenesis was more highly induced in females vs. males. No significant difference in circulating hormonal level was found between males and females after HIE. We conclude that a sex dichotomy in pro- and anti-inflammatory response underlies the sex-specific chronic HIE outcomes, and an enhanced neurogenesis in females also contribute to the sex difference.

Estrogens as neuroprotectants: Estrogenic actions in the context of cognitive aging and brain injury

There is ample empirical evidence to support the notion that the biological impacts of estrogen extend beyond the gonads to other bodily systems, including the brain and behavior. Converging preclinical findings have indicated a neuroprotective role for estrogen in a variety of experimental models of cognitive function and brain insult. However, the surprising null or even detrimental findings of several large clinical trials evaluating the ability of estrogen-containing hormone treatments to protect against age-related brain changes and insults, including cognitive aging and brain injury, led to hesitation by both clinicians and patients in the use of exogenous estrogenic treatments for nervous system outcomes. That estrogen-containing therapies are used by tens of millions of women for a variety of health-related applications across the lifespan has made identifying conditions under which benefits with estrogen treatment will be realized an important public health issue. Here we provide a summary of the biological actions of estrogen and estrogen-containing formulations in the context of aging, cognition, stroke, and traumatic brain injury. We have devoted special attention to highlighting the notion that estrogen appears to be a conditional neuroprotectant whose efficacy is modulated by several interacting factors. By developing criteria standards for desired beneficial peripheral and neuroprotective outcomes among unique patient populations, we can optimize estrogen treatments for attenuating the consequences of, and perhaps even preventing, cognitive aging and brain injury.

Sex-dependent mitochondrial respiratory impairment and oxidative stress in a rat model of neonatal hypoxic-ischemic encephalopathy

Increased male susceptibility to long-term cognitive deficits is well described in clinical and experimental studies of neonatal hypoxic-ischemic encephalopathy. While cell death signaling pathways are known to be sexually dimorphic, a sex-dependent pathophysiological mechanism preceding the majority of secondary cell death has yet to be described. Mitochondrial dysfunction contributes to cell death following cerebral hypoxic-ischemia (HI). Several lines of evidence suggest that there are sex differences in the mitochondrial metabolism of adult mammals. Therefore, this study tested the hypothesis that brain mitochondrial respiratory impairment and associated oxidative stress is more severe in males than females following HI. Maximal brain mitochondrial respiration during oxidative phosphorylation was two-fold more impaired in males following HI. The endogenous antioxidant glutathione was 30% higher in the brain of sham females compared to males. Females also exhibited increased glutathione peroxidase (GPx) activity following HI injury. Conversely, males displayed a reduction in mitochondrial GPx4 protein levels and mitochondrial GPx activity. Moreover, a 3-4-fold increase in oxidative protein carbonylation was observed in the cortex, perirhinal cortex, and hippocampus of injured males, but not females. These data provide the first evidence for sex-dependent mitochondrial respiratory dysfunction and oxidative damage, which may contribute to the relative male susceptibility to adverse long-term outcomes following HI. Lower basal GSH levels, lower post-hypoxic mitochondrial glutathione peroxidase (mtGPx) activity, and mitochondrial glutathione peroxidase 4 (mtGPx4) protein levels may contribute to the susceptibility of the male brain to oxidative damage and mitochondrial dysfunction following neonatal hypoxic-ischemia (HI). Treatment of male pups with acetyl-L-carnitine (ALCAR) protects against the loss of mtGPx activity, mtGPx4 protein, and increases in protein carbonylation after HI. These findings provide novel insight into the pathophysiology of sexually dimorphic outcomes following HI.

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

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

Nanotherapeutic strategies for the treatment of Alzheimer's disease

Alzheimer's disease (AD), the most common form of dementia, is now representing one of the largest unmet medical needs. However, no effective treatment is now available to impede the progression of AD or delay its onset. There are two major challenges for the development of effective therapy for AD. First, the exact cause for AD onset is still unknown. Second, brain drug delivery is significantly hindered by the blood-brain barrier (BBB). In this review, we will summarize the pathological understanding about AD and the related treatments, compare BBB and its effect on brain drug delivery under normal and AD conditions and review the nanotherapeutic strategies that have been developed for AD therapy in recent years.

Sex Hormones Regulate Cytoskeletal Proteins Involved in Brain Plasticity

In the brain of female mammals, including humans, a number of physiological and behavioral changes occur as a result of sex hormone exposure. Estradiol and progesterone regulate several brain functions, including learning and memory. Sex hormones contribute to shape the central nervous system by modulating the formation and turnover of the interconnections between neurons as well as controlling the function of glial cells. The dynamics of neuron and glial cells morphology depends on the cytoskeleton and its associated proteins. Cytoskeletal proteins are necessary to form neuronal dendrites and dendritic spines, as well as to regulate the diverse functions in astrocytes. The expression pattern of proteins, such as actin, microtubule-associated protein 2, Tau, and glial fibrillary acidic protein, changes in a tissue-specific manner in the brain, particularly when variations in sex hormone levels occur during the estrous or menstrual cycles or pregnancy. Here, we review the changes in structure and organization of neurons and glial cells that require the participation of cytoskeletal proteins whose expression and activity are regulated by estradiol and progesterone.

Regulation of object recognition and object placement by ovarian sex steroid hormones

The ovarian hormones 17β-estradiol (E2) and progesterone (P4) are potent modulators of hippocampal memory formation. Both hormones have been demonstrated to enhance hippocampal memory by regulating the cellular and molecular mechanisms thought to underlie memory formation. Behavioral neuroendocrinologists have increasingly used the object recognition and object placement (object location) tasks to investigate the role of E2 and P4 in regulating hippocampal memory formation in rodents. These one-trial learning tasks are ideal for studying acute effects of hormone treatments on different phases of memory because they can be administered during acquisition (pre-training), consolidation (post-training), or retrieval (pre-testing). This review synthesizes the rodent literature testing the effects of E2 and P4 on object recognition (OR) and object placement (OP), and the molecular mechanisms in the hippocampus supporting memory formation in these tasks. Some general trends emerge from the data. Among gonadally intact females, object memory tends to be best when E2 and P4 levels are elevated during the estrous cycle, pregnancy, and in middle age. In ovariectomized females, E2 given before or immediately after testing generally enhances OR and OP in young and middle-aged rats and mice, although effects are mixed in aged rodents. Effects of E2 treatment on OR and OP memory consolidation can be mediated by both classical estrogen receptors (ERα and ERβ), and depend on glutamate receptors (NMDA, mGluR1) and activation of numerous cell signaling cascades (e.g., ERK, PI3K/Akt, mTOR) and epigenetic processes (e.g., histone acetylation, DNA methylation). Acute P4 treatment given immediately after training also enhances OR and OP in young and middle-aged ovariectomized females by activating similar cell signaling pathways as E2 (e.g., ERK, mTOR). The few studies that have administered both hormones in combination suggest that treatment can enhance OR and OP, but that effects are highly dependent on factors such as dose and timing of administration. In addition to providing more detail on these general conclusions, this review will discuss directions for future avenues of research into the hormonal regulation of object memory.

Gender-related protection from or vulnerability to severe CNS diseases: gonado-structural and/or gonado-activational? A meta-analysis of relevant epidemiological studies

BACKGROUND

A vast scientific literature has dealt with gender-specific risk for brain disorder. That field is evolving toward a consensus to the effect that the estrogen hormone family is outstandingly and uniquely neuroprotective. However, the epidemiology relevant to this general outlook remains piecemeal.

METHOD

The present investigation strategically formats the relevant epidemiological findings around the world in order to quantitatively meta-analyze gender ratio of risk for a variety of relevant severe central nervous system (CNS) diseases at all three gonadal stages of the life cycle, pre pubertal, post adolescent/pre menopausal, and post menopausal.

RESULTS

The data quantitatively establish that (1) no single epidemiological study should be cited as evidence of gender-specific neuroprotection against the most common severe CNS diseases because the gender-specific risk ratios are contradictory from one study to the other; (2) risk for severe CNS disease is indeed significantly gender-specific, but either gender can be protected: it depends on the disease, not at all on the age bracket.

CONCLUSION

Our assay of gender-specific risk for severe brain disease around the world has not been able to support the idea according to which any one gender-prevalent gonadal steroid hormone dominates as a neuroprotective agent at natural concentrations.

FK506-binding protein 1b/12.6: a key to aging-related hippocampal Ca2+ dysregulation?

It has been recognized for some time that the Ca(2+)-dependent slow afterhyperpolarization (sAHP) is larger in hippocampal neurons of aged compared with young animals. In addition, extensive studies since have shown that other Ca(2+)-mediated electrophysiological responses are increased in hippocampus with aging, including Ca(2+) transients, L-type voltage-gated Ca(2+) channel activity, Ca(2+) spike duration and action potential accommodation. Elevated Ca(2+)-induced Ca(2+) release from ryanodine receptors (RyRs) appears to drive amplification of the Ca(2+) responses. Components of this Ca(2+) dysregulation phenotype correlate with deficits in cognitive function and plasticity, indicating they may play critical roles in aging-related impairment of brain function. However, the molecular mechanisms underlying aging-related Ca(2+) dysregulation are not well understood. FK506-binding proteins 1a and 1b (FKBP1a/1b, also known as FKBP12/12.6) are immunophilin proteins that bind the immunosuppressant drugs FK506 and rapamycin. In muscle cells, FKBP1a/1b also bind RyRs and inhibits Ca(2+)-induced Ca(2+) release, but it is not clear whether FKBPs act similarly in brain cells. Recently, we found that selectively disrupting hippocampal FKBP1b function in young rats, either by microinjecting adeno-associated viral vectors expressing siRNA, or by treatment with rapamycin, increases the sAHP and recapitulates much of the hippocampal Ca(2+) dysregulation phenotype. Moreover, in microarray studies, we found FKBP1b gene expression was downregulated in hippocampus of aging rats and early-stage Alzheimer's disease subjects. These results suggest the novel hypothesis that declining FKBP function is a key factor in aging-related Ca(2+) dysregulation in the brain and point to potential new therapeutic targets for counteracting unhealthy brain aging.

Estrogen regulation of spine density and excitatory synapses in rat prefrontal and somatosensory cerebral cortex

The steroid hormone, 17β-estradiol (E2) has been reported to enhance executive functions that are known to be mediated by the prefrontal cortex (PFC), although the underlying mechanisms remain unclear. To shed light on the potential mechanisms, we examined the effect of E2 in vivo upon spine density in the rat PFC and the somatosensory cortex (SSC), which has been implicated to be a transient storage site for information that can also contribute to working memory. The results revealed that E2 significantly enhanced the number of dendritic spines in both the SSC and PFC, as well as the expression of spinophilin. In vitro studies revealed further mechanistic insights by demonstrating that E2 enhanced AMPA GluR1 receptor expression and excitatory glutamatergic synapse formation in rat cortical neurons, without an effect upon inhibitory GABAergic synapse formation. Furthermore, E2 rapidly enhanced ERK and Akt activation in cortical neurons, and inhibitors of ERK and Akt activation significantly attenuated E2 induction of excitatory glutamatergic synapses. Administration of E2-BSA likewise significantly enhanced excitatory glutamatergic synapses in cortical neurons, and administration of an ER antagonist, ICI182,780 and a non-NMDA receptor antagonist (NBQX) significantly attenuated the effect of E2 upon enhancement of excitatory glutamatergic synapses, suggesting mediation by extranuclear estrogen receptors and involvement of non-NMDA receptor activation and signaling. As a whole, the studies demonstrate that E2 enhances spine density in both the PFC and SSC, and that E2 enhances excitatory glutamatergic synapse formation in cortical neurons via a rapid extranuclear ER-mediated signaling mechanism that involves up-regulation of GluR1 and mediation by Akt and ERK signaling pathways.

Long-term pioglitazone treatment improves learning and attenuates pathological markers in a mouse model of Alzheimer's disease

Thiazolidinediones (TZDs) are agonists at peroxisome proliferator-activated gamma-type (PPAR-γ) receptors and are used clinically for the treatment of type 2 diabetes where they have been shown to reestablish insulin sensitivity, improve lipid profiles, and reduce inflammation. Recent work also suggests that TZDs may be beneficial in Alzheimer's disease (AD), ameliorating cognitive decline early in the disease process. However, there have been only a few studies identifying mechanisms through which cognitive benefits may be exerted. Starting at 10 months of age, the triple transgenic mouse model of AD (3xTg-AD) with accelerated amyloid-β (Aβ) deposition and tau pathology was treated with the TZD pioglitazone (PIO-Actos) at 18 mg/Kg body weight/day. After four months, PIO-treated animals showed multiple beneficial effects, including improved learning on the active avoidance task, reduced serum cholesterol, decreased hippocampal amyloid-β and tau deposits, and enhanced short- and long-term plasticity. Electrophysiological membrane properties and post-treatment blood glucose levels were unchanged by PIO. Gene microarray analyses of hippocampal tissue identified predicted transcriptional responses following TZD treatment as well as potentially novel targets of TZDs, including facilitation of estrogenic processes and decreases in glutamatergic and lipid metabolic/cholesterol dependent processes. Taken together, these results confirm prior animal studies showing that TZDs can ameliorate cognitive deficits associated with AD-related pathology, but also extend these findings by pointing to novel molecular targets in the brain.

An exploratory dimensional approach to premenstrual manifestation of obsessive-compulsive disorder symptoms: a multicentre study

OBJECTIVE

In women with obsessive-compulsive disorder (OCD), symptom severity appears to fluctuate over the course of the menstrual cycle. The objective of this paper was to compare female OCD patients with and without premenstrual worsening of obsessive-compulsive symptoms (OCS), in terms of the clinical characteristics of OCD.

METHODS

This was a cross-sectional study involving 455 women with OCD, of whom 226 (49.7%) had experienced premenstrual OCS worsening and 229 (50.3%) had not (PMOCS-worse and PMOCS-same groups, respectively). Data were collected with the original and dimensional versions of the Yale-Brown obsessive-compulsive scale, as well as with the Beck Depression Inventory (BDI) and Beck anxiety inventory (BAI).

RESULTS

We found significant differences between the PMOCS-same and PMOCS-worse groups, the latter showing a higher frequency of suicidal ideation (P<.001), suicide attempts (P=.027), current use of selective serotonin reuptake inhibitors (P=.022), lifetime use of mood stabilisers (P=.015), and sexual/religious obsessions (P<.001; OR=1.90), as well as higher scores on the BDI (P<.001) and BAI (P<.001).

CONCLUSION

Underscoring the fact that OCD is a heterogeneous disorder, there appears to be a subgroup of female OCD patients in whom the premenstrual period is associated with a higher frequency of sexual/religious obsessions, depression, anxiety, and suicidality. This might be attributable to hormonal fluctuations. Further studies are warranted in order to investigate this hypothesis by evaluating such patients at different phases of the menstrual cycle, as well as measuring hormonal levels.

Developmental regulation of neuronal genes by DNA methylation: environmental influences

Steroid hormones have wide-ranging organizational, activational and protective actions in the brain. In particular, the organizational effects of early exposure to 17β-estradiol (E2) and glucocorticoids are essential for long-lasting behavioral and cognitive functions. Both steroid hormones mediate many of their actions through intracellular receptors that act as transcription factors. In the rodent cerebral cortex, estrogen receptor mRNA and protein expression are high early in postnatal life and declines dramatically as the animal approaches puberty. An understanding of the molecular mechanisms driving this developmental regulation of gene expression is critical for understanding the complex events that determine lasting brain physiology and prime the plasticity of neurons. Gene expression can be suppressed by the epigenetic modification of the promoter regions by DNA methylation that results in gene silencing. Indeed, the decrease in ERα mRNA expression in the cortex during development is accompanied by an increase in promoter methylation. Numerous environmental stimuli can alter the DNA methylation that occurs for ERα, glucocorticoid receptors, as well as many other critical genes involved in neuronal development. For example, maternal behavior toward pups can alter epigenetic regulation of ERα mRNA expression. Additionally perinatal stress and exposure to environmental estrogens can also have lasting effects on gene expression by modifying DNA methylation of these important genes. Taken together, there appears to be a critical window during development where, outside factors that alter epigenetic programming can have lasting effects on neuronal gene expression.

Neuroprotective effects of nonfeminizing estrogens in retinal photoreceptor neurons

PURPOSE

Retinal diseases such as macular degeneration and glaucoma are disorders that target specific retinal neurons that can ultimately lead to vision loss. Under these conditions and pathologies, retinal neurons can die via apoptosis that may be due to increased oxidative stress. The neuroprotective effects of 17β-estradiol (E2) and three synthetic nonfeminizing estrogen analogs (ZYC-26, ZYC-23, and ZYC-3) were investigated to examine their abilities to protect retinal neurons against glutamate toxicity.

METHODS

Using an in vitro model of glutamate-induced cell death in 661W cells, a mouse cone photoreceptor cell line, shown to express both estrogen receptors (ERs) via immunoblotting, was pretreated with E2 and its analogs and cell viability were assessed.

RESULTS

It was observed that E2 and estrogen analogs, ZYC-26 and ZYC-3, were protective against a 5 mM glutamate insult in 661W cells. The neuroprotective abilities of ZYC-26 and ZYC-3 were autonomous of estrogen receptor-α (ERα) and ERβ demonstrated by their ability to protect in the presence of ICI 182780, a pan-ER antagonist with a high affinity for the estrogen receptor. Treatment with PPT and DPN, ERα- and ERβ-specific agonists, respectively, did not protect the 661W cells from the glutamate insult. Studying the membrane ER (mER) or GPR30 did show that activation of the receptor by G1 protected the retinal neuron from insult, whereas G15, an antagonist of the mER was not able to antagonize the protection previously seen.

CONCLUSIONS

These data demonstrate that nonfeminizing estrogens may emerge as useful compounds for neuroprotection of retinal cells.

Female reproductive issues in multiple sclerosis

Multiple sclerosis (MS) is more common in females than males and frequently affects women during their reproductive years. Thus, issues surrounding pregnancy and reproduction are of concern to women with MS. This review documents studies that shed light on reproductive issues in women with MS. The available literature was searched for papers relating to pregnancy and MS. Pregnancy is protective in MS in the short term, perhaps due to modulation of the immune system in pregnancy. It also possible that changes in the brain in pregnancy could protect against the effects of inflammation. The long-term effects of pregnancy also seem to be beneficial to MS, perhaps due to long-term epigenetic changes or possibly due to the effects of fetal microchimerism. Obstetric outcomes in women with MS are similar to those in the general population. In addition, there have been no reports of severe fetal abnormalities in babies exposed to first-line MS therapies. There is no good evidence that breast-feeding is protective in MS. There is no evidence that oral contraceptive pill use predisposes to MS, nor influences the clinical course of MS. After menopause, there is possible deterioration of MS, but it’s difficult to disentangle this from the effects of aging and the natural progressive history of MS. The strong biological effect of pregnancy on MS deserves further study, so that these mechanisms can possibly be replicated as therapies for MS.

Serum brain-derived neurotrophic factor: determinants and relationship with depressive symptoms in a community population of middle-aged and elderly people

OBJECTIVES

Brain-derived neurotrophic factor (BDNF) is involved in major depressive disorder and neurodegenerative diseases. Clinical studies, showing decreased serum BDNF levels, are difficult to interpret due to limited knowledge of potential confounders and mixed results for age and sex effects. We explored potential determinants of serum BDNF levels in a community sample of 1230 subjects.

METHODS

Multiple linear regression analyses with serum BDNF level as the dependent variable were conducted to explore the effect of four categories of potential BDNF determinants (sampling characteristics, sociodemographic variables, lifestyle factors and somatic diseases) and of self-reported depressive symptoms (Beck's Depression Inventory (BDI).

RESULTS

Our results show that BDNF levels decline with age in women, whereas in men levels remain stable. Moreover, after controlling for age and gender, the assays still showed lower serum BDNF levels with higher BDI sum scores. Effects remained significant after correction for two main confounders (time of sampling and smoking), suggesting that they serve as molecular trait factors independent of lifestyle factors.

CONCLUSIONS

Given the age-sex interaction on serum BDNF levels and the known association between BDNF and gonadal hormones, research is warranted to delineate the effects of the latter interaction on the risk of psychiatric and neurodegenerative diseases.

Oestrogen signalling and neuroprotection in cerebral ischaemia

17β-Oestradiol (E(2)) is an important hormone signal that regulates multiple tissues and functions in the body. This review focuses on the neuroprotective actions of E(2) in the brain against cerebral ischaemia and the potential underlying mechanisms. A particular focus of the review will be on the role of E(2) to attenuate NADPH oxidase activation, superoxide and reactive oxygen species generation and reduce oxidative stress in the ischaemic brain as a potentially key neuroprotective mechanism. Evidence of a potential novel role of extranuclear oestrogen receptors in mediating E(2) signalling and neuroprotective actions is also discussed. An additional subject is the growing evidence indicating that periods of long-term oestrogen deprivation, such as those occurring after menopause or surgical menopause, may lead to loss or attenuation of E(2) signalling and neuroprotective actions in the brain, as well as enhanced sensitivity of the hippocampus to ischaemic stress damage. These findings have important implications with respect to the 'critical period hypothesis', which proposes that oestrogen replacement must be initiated at peri-menopause in humans to exert its beneficial cardiovascular and neural effects. The insights gained from these various studies will prove valuable for guiding future directions in the field.

Impact of atomoxetine on subjective attention and memory difficulties in perimenopausal and postmenopausal women

OBJECTIVE

Perimenopausal and postmenopausal women frequently report midlife onset of impairments of attention, organization, and short-term memory. We sought to determine whether these cognitive symptoms in healthy women in the menopause transition without a history of attention-deficit/hyperactivity disorder (ADHD) would respond to treatment with atomoxetine (ATX), a medication demonstrated to be effective in reducing similar cognitive impairments in adults with ADHD.

METHODS

Sixteen healthy women with complaints of midlife-onset subjective difficulties in memory and concentration/attention and without a history of ADHD or other psychiatric disorders were enrolled in a double-blind, placebo-controlled crossover study of ATX 80 mg/day. Treatment arms were 6 weeks long, separated by a 4-week washout. The Brown Attention Deficit Disorder Scale (BADDS) was used to systematically elicit self-report of perceived cognitive difficulties in executive function. Participants also underwent neuropsychological testing, behavioral assessments, and vital signs monitoring.

RESULTS

Mean baseline BADDS scores were 37.9 for all 16 participants and 42.3 for the 12 who completed both arms of the study. Total BADDS scores decreased significantly from baseline during ATX treatment but not placebo treatment. ATX treatment was superior to placebo in reducing the BADDS working memory cluster score, whereas there was a trend for ATX superiority for the BADDS attention/concentration cluster score. ATX did not differ from placebo with respect to effects on neuropsychological tests, behavioral assessments, or cardiac vital signs.

CONCLUSIONS

Perimenopausal and postmenopausal women presenting with midlife-onset subjective cognitive difficulties may experience significant subjective improvement in memory and attention/concentration with ATX treatment.

Regulation of choline acetyltransferase expression by 17 β-oestradiol in NSC-34 cells and in the spinal cord

Motoneurones located in the ventral horn of the spinal cord conciliate cholinergic innervation of skeletal muscles. These neurones appear to be exceedingly affected in neurodegenerative diseases such as amyotrophic lateral sclerosis. The dysfunction of motoneurones is typically accompanied by alterations of cholinergic metabolism and signalling, as demonstrated by a decrease in choline acetyltransferase (ChAT) expression. 17 β-Oestradiol (E(2)) is generally accepted as neuroprotective factor in the brain under acute toxic and neurodegenerative conditions and also appears to exert a protective role for motoneurones. In the present study, we attempted to analyse the role of E(2) signalling on ChAT expression in the motoneurone-like cell line NSC-34 and in vivo. In a first step, we demonstrated the presence of oestrogen receptor α and β in NSC-34 cells, as well as in the cervical and lumbar parts, of the male mouse spinal cord. Subsequently, we investigated the effect of E(2) treatment on ChAT expression. The application of E(2) significantly increased the transcription of ChAT in NSC-34 cells and in the cervical but not lumbar part of the spinal cord. Our results indicate that E(2) can influence the cholinergic system by increasing ChAT expression in the mouse spinal cord. This mechanism might support motoneurones, in addition to survival-promoting mechanisms, in the temporal balance toxic or neurodegenerative challenges.

Neuroprotective actions of estradiol and novel estrogen analogs in ischemia: translational implications

This review highlights our investigations into the neuroprotective efficacy of estradiol and other estrogenic agents in a clinically relevant animal model of transient global ischemia, which causes selective, delayed death of hippocampal CA1 neurons and associated cognitive deficits. We find that estradiol rescues a significant number of CA1 pyramidal neurons that would otherwise die in response to global ischemia, and this is true when hormone is provided as a long-term pretreatment at physiological doses or as an acute treatment at the time of reperfusion. In addition to enhancing neuronal survival, both forms of estradiol treatment induce measurable cognitive benefit in young animals. Moreover, estradiol and estrogen analogs that do not bind classical nuclear estrogen receptors retain their neuroprotective efficacy in middle-aged females deprived of ovarian hormones for a prolonged duration (8weeks). Thus, non-feminizing estrogens may represent a new therapeutic approach for treating the neuronal damage associated with global ischemia.

C terminus of Hsc70-interacting protein (CHIP)-mediated degradation of hippocampal estrogen receptor-alpha and the critical period hypothesis of estrogen neuroprotection

Recent work suggests that timing of 17β-estradiol (E2) therapy may be critical for observing a beneficial neural effect. Along these lines, E2 neuroprotection, but not its uterotropic effect, was shown to be lost following long-term E2 deprivation (LTED), and this effect was associated with a significant decrease of estrogen receptor-α (ERα) in the hippocampus but not the uterus. The purpose of the current study was to determine the mechanism underlying the ERα decrease and to determine whether aging leads to a similar loss of hippocampal ERα and E2 sensitivity. The results of the study show that ERα in the rat hippocampal CA1 region but not the uterus undergoes enhanced interaction with the E3 ubiquitin ligase C terminus of heat shock cognate protein 70 (Hsc70)-interacting protein (CHIP) that leads to its ubiquitination/proteasomal degradation following LTED (10-wk ovariectomy). E2 treatment initiated before but not after LTED prevented the enhanced ERα-CHIP interaction and ERα ubiquitination/degradation and was fully neuroprotective against global cerebral ischemia. Administration of a proteasomal inhibitor or CHIP antisense oligonucleotides to knock down CHIP reversed the LTED-induced down-regulation of ERα. Further work showed that these observations extended to natural aging, because aged rats showed enhanced CHIP interaction; ubiquitination and degradation of both hippocampal ERα and ERβ; and, importantly, a correlated loss of E2 neuroprotection against global cerebral ischemia. In contrast, E2 administration to middle-aged rats was still capable of exerting neuroprotection. As a whole, the study provides support for a "critical period" for E2 neuroprotection of the hippocampus and provides important insight into the mechanism underlying the critical period.

Detection of novel mutations and review of published data suggests that hereditary spastic paraplegia caused by spastin (SPAST) mutations is found more often in males

BACKGROUND

Hereditary spastic paraplegia (HSP) is characterised in its pure form by slowly progressive spastic paraparesis. Around 40% of autosomal dominant (AD) cases are caused by mutations in SPAST, encoding spastin.

PATIENTS AND METHODS

The clinical and investigation details of all patients with a SPAST mutation identified through our centre were reviewed. All published reports of SPAST mutations where the sex of patients was given were subsequently analysed in order to determine whether there is evidence of one sex being preferentially affected.

RESULTS

In total 22 probable pathogenic changes were detected, including 11 novel ones. One patient carried two adjacent missense mutations. The pathogenicity of a further novel missense mutation is uncertain. Most patients had a pure phenotype, although mild peripheral neuropathy was sometimes present. The total number of patients with SPAST mutations was 27, as three of the previously known mutations were present in more than one person. The excess of males over females in our population (17:10) prompted us to review all published studies where the sex of the patients was given (n=31). A significant excess of males was identified (ratio 1.29, p=0.0007).

CONCLUSIONS

Our results are consistent with data suggesting that SPAST mutations mostly cause a pure HSP phenotype. The excess of males in our sample and in published reports suggests that penetrance or severity may be sex-dependent, and merits further investigation as it may have important implications for counselling.

Effects of gender in amyotrophic lateral sclerosis

BACKGROUND

There is evidence that amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND), is more common in men than in women and that gender influences the clinical features of the disease. The causes of this are unknown.

OBJECTIVE

This review examines the gender differences that are found in ALS and postulates reasons for these differences.

METHODS

A literature review of PubMed (with no date limits) was performed to find information about gender differences in the incidence, prevalence, and clinical features of ALS, using the search terms ALS or MND and gender or sex, ALS prevalence, and SOD1 mice and gender. Articles were reviewed for information about gender differences, together with other articles that were already known to the authors.

RESULTS

The incidence and prevalence of ALS are greater in men than in women. This gender difference is seen in large studies that included all ALS patients (sporadic and familial), but is not seen when familial ALS is studied independently. Men predominate in the younger age groups of patients with ALS. Sporadic ALS has different clinical features in men and women, with men having a greater likelihood of onset in the spinal regions, and women tending to have onset in the bulbar region. Gender appears to have no clear effect on survival. In animals with superoxide dismutase 1 (sod1) mutations, sex does affect the clinical course of disease, with earlier onset in males. Possible reasons for the differences in ALS between men and women include different exposures to environmental toxins, different biological responses to exogenous toxins, and possibly underlying differences between the male and female nervous systems and different abilities to repair damage.

CONCLUSIONS

There is a complex interaction between gender and clinical phenotypes in ALS. Understanding the causes of the gender differences could give clues to processes that modify the disease.

Role of gender in multiple sclerosis: clinical effects and potential molecular mechanisms

Multiple sclerosis (MS) is more prevalent in females than males, and this female predominance is increasing as time goes by. Additionally, gender appears to play critical roles in development, progression and treatment of MS, and is therefore an aspect that should always be considered in the design and interpretation of research and clinical trials for MS. In this review, factors that could potentially explain the gender-biased observations in MS are discussed. These include sex-specific differences between the male and female immune systems and nervous systems, genetic and epigenetic or environmental-related effects, the effects of gonadal hormones, and materno-fetal interactions.

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

17β-estradiol is a hormone with far-reaching organizational, activational and protective actions in both male and female brains. The organizational effects of early estrogen exposure are essential for long-lasting behavioral and cognitive functions. Estradiol mediates many of its effects through the intracellular receptors, estrogen receptor-alpha (ERα) and estrogen receptor-beta (ERβ). In the rodent cerebral cortex, estrogen receptor expression is high early in postnatal life and declines dramatically as the animal approaches puberty. This decline is accompanied by decreased expression of ERα mRNA. This change in expression is the same in both males and females in the developing isocortex and hippocampus. An understanding of the molecular mechanisms involved in the regulation of estrogen receptor alpha (ERα) gene expression is critical for understanding the developmental, as well as changes in postpubertal expression of the estrogen receptor. One mechanism of suppressing gene expression is by the epigenetic modification of the promoter regions by DNA methylation that results in gene silencing. The decrease in ERα mRNA expression during development is accompanied by an increase in promoter methylation. Another example of regulation of ERα gene expression in the adult cortex is the changes that occur following neuronal injury. Many animal studies have demonstrated that the endogenous estrogen, 17β-estradiol, is neuroprotective. Specifically, low levels of estradiol protect the cortex from neuronal death following middle cerebral artery occlusion (MCAO). In females, this protection is mediated through an ERα-dependent mechanism. ERα expression is rapidly increased following MCAO in females, but not in males. This increase is accompanied by a decrease in methylation of the promoter suggesting a return to the developmental program of gene expression within neurons. Taken together, during development and in adulthood, regulation of ERα gene expression in the cortex can occur by DNA methylation and in a sex-dependent fashion in the adult brain.

Mechanisms of estrogens' dose-dependent neuroprotective and neurodamaging effects in experimental models of cerebral ischemia

Ever since the hypothesis was put forward that estrogens could protect against cerebral ischemia, numerous studies have investigated the mechanisms of their effects. Despite initial studies showing ameliorating effects, later trials in both humans and animals have yielded contrasting results regarding the fundamental issue of whether estrogens are neuroprotective or neurodamaging. Therefore, investigations of the possible mechanisms of estrogen actions in brain ischemia have been difficult to assess. A recently published systematic review from our laboratory indicates that the dichotomy in experimental rat studies may be caused by the use of insufficiently validated estrogen administration methods resulting in serum hormone concentrations far from those intended, and that physiological estrogen concentrations are neuroprotective while supraphysiological concentrations augment the damage from cerebral ischemia. This evidence offers a new perspective on the mechanisms of estrogens’ actions in cerebral ischemia, and also has a direct bearing on the hormone replacement therapy debate. Estrogens affect their target organs by several different pathways and receptors, and the mechanisms proposed for their effects on stroke probably prevail in different concentration ranges. In the current article, previously suggested neuroprotective and neurodamaging mechanisms are reviewed in a hormone concentration perspective in an effort to provide a mechanistic framework for the dose-dependent paradoxical effects of estrogens in stroke. It is concluded that five protective mechanisms, namely decreased apoptosis, growth factor regulation, vascular modulation, indirect antioxidant properties and decreased inflammation, and the proposed damaging mechanism of increased inflammation, are currently supported by experiments performed in optimal biological settings.

Effects of estrogen on beta-amyloid-induced cholinergic cell death in the nucleus basalis magnocellularis

Alzheimer disease is characterized by accumulation of β-amyloid (Aβ) and cognitive dysfunctions linked to early loss of cholinergic neurons. As estrogen-based hormone replacement therapy has beneficial effects on cognition of demented patients, and it may prevent memory impairments, we investigated the effect of estrogen-pretreatment on Aβ-induced cholinergic neurodegeneration in the nucleus basalis magnocellularis (NBM). We tested which Aβ species induces the more pronounced cholinotoxic effect in vivo. We injected different Aβ assemblies in the NBM of mice, and measured cholinergic cell and cortical fiber loss. Spherical Aβ oligomers had the most toxic effect. Pretreatment of ovariectomized mice with estrogen before Aβ injection decreased cholinergic neuron loss and partly prevented fiber degeneration. By using proteomics, we searched for proteins involved in estrogen-mediated protection and in Aβ toxicity 24 h following injection. The change in expression of, e.g., DJ-1, NADH ubiquinone oxidoreductase, ATP synthase, phosphatidylethanolamine-binding protein 1, protein phosphatase 2A and dimethylarginine dimethylaminohydrolase 1 support our hypothesis that Aβ induces mitochondrial dysfunction, decreases MAPK signaling, and increases NOS activation in NBM. On the other hand, altered expression of, e.g., MAP kinase kinase 1 and 2, protein phosphatase 1 and 2A by Aβ might increase MAPK suppression and NOS signaling in the cortical target area. Estrogen pretreatment reversed most of the changes in the proteome in both areas. Our experiments suggest that regulation of the MAPK pathway, mitochondrial pH and NO production may all contribute to Aβ toxicity, and their regulation can be prevented partly by estrogen pretreatment.

Development and evaluation of polymer nanoparticles for oral delivery of estradiol to rat brain in a model of Alzheimer's pathology

The purpose of this study was to develop tween 80 (T-80) coated polylactide-co-glycolide (PLGA) nanoparticles that can deliver estradiol to the brain upon oral administration. Estradiol containing nanoparticles were made by a single emulsion technique and T-80 coating was achieved by incubating the re-constituted nanoparticles at different concentrations of T-80. The process of T-80 coating on the nanoparticles was optimized and the pharmacokinetics of estradiol nanoparticles was studied as a function of T-80 coating. The nanoparticles were then evaluated in an ovariectomized (OVX) rat model of Alzheimer's disease (AD) that mimics the postmenopausal conditions. The nanoparticles bound T-80 were found to proportionally increase from 9.72 ± 1.07 mg to 63.84 ± 3.59 mg with an increase in the initial concentration T-80 from 1% to 5% and were stable in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). Orally administered T-80 coated nanoparticles resulted in significantly higher brain estradiol levels after 24h (1.969 ± 0.197 ng/g tissue) as compared to uncoated ones (1.105 ± 0.136 ng/g tissue) at a dose of 0.2mg/rat, suggesting a significant role of surface coating. Moreover, these brain estradiol levels were almost similar to those obtained after administration of the same dose of drug suspension via 100% bioavailable intramuscular route (2.123 ± 0.370 ng/g tissue), indicating the increased fraction of bioavailable drug reaching the brain when administered orally. Also, the nanoparticle treated group was successful in preventing the expression of amyloid beta-42 (Aβ42) immunoreactivity in the hippocampus region of brain. Together, the results indicate the potential of nanoparticles for oral delivery of estradiol to brain.

Functional interactions between steroid hormones and neurotrophin BDNF

Brain-derived neurotrophic factor (BDNF), a critical neurotrophin, regulates many neuronal aspects including cell differentiation, cell survival, neurotransmission, and synaptic plasticity in the central nervous system (CNS). Though BDNF has two types of receptors, high affinity tropomyosin-related kinase (Trk)B and low affinity p75 receptors, BDNF positively exerts its biological effects on neurons via activation of TrkB and of resultant intracellular signaling cascades including mitogen-activated protein kinase/extracellular signal-regulated protein kinase, phospholipase Cγ, and phosphoinositide 3-kinase pathways. Notably, it is possible that alteration in the expression and/or function of BDNF in the CNS is involved in the pathophysiology of various brain diseases such as stroke, Parkinson’s disease, Alzheimer’s disease, and mental disorders. On the other hand, glucocorticoids, stress-induced steroid hormones, also putatively contribute to the pathophysiology of depression. Interestingly, in addition to the reduction in BDNF levels due to increased glucocorticoid exposure, current reports demonstrate possible interactions between glucocorticoids and BDNF-mediated neuronal functions. Other steroid hormones, such as estrogen, are involved in not only sexual differentiation in the brain, but also numerous neuronal events including cell survival and synaptic plasticity. Furthermore, it is well known that estrogen plays a role in the pathophysiology of Parkinson’s disease, Alzheimer’s disease, and mental illness, while serving to regulate BDNF expression and/or function. Here, we present a broad overview of the current knowledge concerning the association between BDNF expression/function and steroid hormones (glucocorticoids and estrogen).

Neuroprotective actions of selective estrogen receptor modulators

Decreasing levels of sex hormones with aging may have a negative impact on brain function, since this decrease is associated with the progression of neurodegenerative disorders, increased depressive symptoms and other psychological disturbances. Extensive evidence from animal studies indicates that sex steroids, in particular estradiol, are neuroprotective. However, the potential benefits of estradiol therapy for the brain are counterbalanced by negative, life-threatening risks in the periphery. A potential therapeutic alternative to promote neuroprotection is the use of selective estrogen receptor modulators (SERMs), which may be designed to act with tissue selectivity as estrogen receptor agonists in the brain and not in other organs. Currently available SERMs act not only with tissue selectivity, but also with cellular selectivity within the brain and differentially modulate the activation of microglia, astroglia and neurons. Finally, SERMs may promote the interaction of estrogen receptors with the neuroprotective signaling of growth factors, such as the phosphatidylinositol 3-kinase/glycogen synthase kinase 3 pathway.

Effects of estrogen on AF64A-induced apoptosis in NG108-15 cells

In this study, we show that pretreatment with physiological concentrations (1-100 nM) of 17beta-estradiol decreased apoptosis induced by ethylcholine aziridinium (AF64A), a choline toxin, in the cholinergic neuronal cell line NG108-15. These protective effects were observed after short-term (30 min) pretreatment, and were blocked by treatment with an estrogen receptor antagonist and inhibitors of phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase kinase (MEK). The protective effects were, however, not reversed by a protein synthesis inhibitor. Furthermore, we examined the effects of 17beta-estradiol on choline uptake in NG108-15 cells. Although choline uptake was inhibited by a selective inhibitor of choline uptake, hemicholinium-3, it was not altered by treatment with 17beta-estradiol. These results indicated that the protective effect of 17beta-estradiol on AF64A-induced apoptosis could be nongenomic, and that this effect may be due to the activation of PI3K/Akt and/or MEK/extracellular signal-regulated kinase (ERK) pathways.

Estrogen and cognitive functions

Although the effects of estrogen on sexual behavior in mammals are well known, its role on other types of behavior, including cognition, have only recently been recognized. This review summarizes work conducted in our laboratory and others with the aim of identifying the effects of estrogen on cognitive functions. The first section will briefly describe the neurobiology of estrogen. The second section will discuss the effects of estrogen on cognitive behaviors in mammals, as well as the physiological relevance of these effects and their applicability to human health and disease. The third section will detail the role of estrogen on working memory in humans and nonhuman primates, and in rodents. Finally, the concluding section will briefly describe the relationship between estrogen and the aging brain.

Mitochondrial bioenergetic deficit precedes Alzheimer's pathology in female mouse model of Alzheimer's disease

Mitochondrial dysfunction has been proposed to play a pivotal role in neurodegenerative diseases, including Alzheimer's disease (AD). To address whether mitochondrial dysfunction precedes the development of AD pathology, we conducted mitochondrial functional analyses in female triple transgenic Alzheimer's mice (3xTg-AD) and age-matched nontransgenic (nonTg). Mitochondrial dysfunction in the 3xTg-AD brain was evidenced by decreased mitochondrial respiration and decreased pyruvate dehydrogenase (PDH) protein level and activity as early as 3 months of age. 3xTg-AD mice also exhibited increased oxidative stress as manifested by increased hydrogen peroxide production and lipid peroxidation. Mitochondrial amyloid beta (Abeta) level in the 3xTg-AD mice was significantly increased at 9 months and temporally correlated with increased level of Abeta binding to alcohol dehydrogenase (ABAD). Embryonic neurons derived from 3xTg-AD mouse hippocampus exhibited significantly decreased mitochondrial respiration and increased glycolysis. Results of these analyses indicate that compromised mitochondrial function is evident in embryonic hippocampal neurons, continues unabated in females throughout the reproductive period, and is exacerbated during reproductive senescence. In nontransgenic control mice, oxidative stress was coincident with reproductive senescence and accompanied by a significant decline in mitochondrial function. Reproductive senescence in the 3xTg-AD mouse brain markedly exacerbated mitochondrial dysfunction. Collectively, the data indicate significant mitochondrial dysfunction occurs early in AD pathogenesis in a female AD mouse model. Mitochondrial dysfunction provides a plausible mechanistic rationale for the hypometabolism in brain that precedes AD diagnosis and suggests therapeutic targets for prevention of AD.