Role of Dickkopf-1, an antagonist of the Wnt/beta-catenin signaling pathway, in estrogen-induced neuroprotection and attenuation of tau phosphorylation. J Neurosci. 2008;28:8430-8441. [PMID: 18716201 DOI: 10.1523/jneurosci.2752-08.2008]

Association between triglyceride glucose index and cognitive decline: A meta-analysis

BACKGROUND

The triglyceride glucose (TyG) index, a novel surrogate indicator for insulin resistance (IR), is believed to be associated with various diseases. However, its connection with cognitive decline remains controversy.

METHODS

The PubMed, EMBASE, Cochrane Library, Web of Science, and Medline databases were systematically searched up to October 2023 to assess the association between the TyG index and the risk of cognitive decline. Effect estimates and 95 % confidence intervals (CIs) were calculated using a random-effects model.

RESULTS

Our review included 3 cohort studies and 9 case-control/cross-sectional studies with a total of 5,603,350 participants. In comparison to a low TyG index, a higher TyG index was connected to an elevated risk of cognitive decline (RR/HR = 1.14, 95 % CI [1.11, 1.17], P < 0.05; OR = 1.75, 95 % CI [1.34, 2.29], P < 0.05). Furthermore, the dose-response analysis from the case-control/cross-sectional studies revealed a 1.42 times higher risk of cognitive decline per 1 mg/dl increment of the TyG index (OR = 1.42, 95 % CI [1.19, 1.69], P < 0.05).

LIMITATIONS

The inclusion of observational studies in the meta-analysis demonstrated a lower hierarchy of evidence compared to randomized controlled trials. Moreover, we incorporated a restricted number of studies and identified significant heterogeneity among them, potentially attributed to the presence of numerous confounding variables.

CONCLUSION

TyG index is related to cognitive decline. In view of some of the limitations of this study, further research will be necessary to confirm this relationship.

Health risks of Bisphenol-A exposure: From Wnt signaling perspective

Human beings are routinely exposed to chronic and low dose of Bisphenols (BPs) due to their widely pervasiveness in the environment. BPs hold similar chemical structures to 17β-estradiol (E2) and thyroid hormone, thus posing threats to human health by rendering the endocrine system dysfunctional. Among BPs, Bisphenol-A (BPA) is the best-known and extensively studied endocrine disrupting compound (EDC). BPA possesses multisystem toxicity, including reproductive toxicity, neurotoxicity, hepatoxicity and nephrotoxicity. Particularly, the central nervous system (CNS), especially the developing one, is vulnerable to BPA exposure. This review describes our current knowledge of BPA toxicity and the related molecular mechanisms, with an emphasis on the role of Wnt signaling in the related processes. We also discuss the role of oxidative stress, endocrine signaling and epigenetics in the regulation of Wnt signaling by BPA exposure. In summary, dysfunction of Wnt signaling plays a key role in BPA toxicity and thus can be a potential target to alleviate EDCs induced damage to organisms.

Gut-Brain Axis: Focus on Sex Differences in Neuroinflammation

In recent years, there has been a growing interest in the concept of the "gut-brain axis". In addition to well-studied diseases associated with an imbalance in gut microbiota, such as cancer, chronic inflammation, and cardiovascular diseases, research is now exploring the potential role of gut microbial dysbiosis in the onset and development of brain-related diseases. When the function of the intestinal barrier is altered by dysbiosis, the aberrant immune system response interacts with the nervous system, leading to a state of "neuroinflammation". The gut microbiota-brain axis is mediated by inflammatory and immunological mechanisms, neurotransmitters, and neuroendocrine pathways. This narrative review aims to illustrate the molecular basis of neuroinflammation and elaborate on the concept of the gut-brain axis by virtue of analyzing the various metabolites produced by the gut microbiome and how they might impact the nervous system. Additionally, the current review will highlight how sex influences these molecular mechanisms. In fact, sex hormones impact the brain-gut microbiota axis at different levels, such as the central nervous system, the enteric nervous one, and enteroendocrine cells. A deeper understanding of the gut-brain axis in human health and disease is crucial to guide diagnoses, treatments, and preventive interventions.

Ischemia-reperfusion injury: molecular mechanisms and therapeutic targets

Ischemia-reperfusion (I/R) injury paradoxically occurs during reperfusion following ischemia, exacerbating the initial tissue damage. The limited understanding of the intricate mechanisms underlying I/R injury hinders the development of effective therapeutic interventions. The Wnt signaling pathway exhibits extensive crosstalk with various other pathways, forming a network system of signaling pathways involved in I/R injury. This review article elucidates the underlying mechanisms involved in Wnt signaling, as well as the complex interplay between Wnt and other pathways, including Notch, phosphatidylinositol 3-kinase/protein kinase B, transforming growth factor-β, nuclear factor kappa, bone morphogenetic protein, N-methyl-D-aspartic acid receptor-Ca2+-Activin A, Hippo-Yes-associated protein, toll-like receptor 4/toll-interleukine-1 receptor domain-containing adapter-inducing interferon-β, and hepatocyte growth factor/mesenchymal-epithelial transition factor. In particular, we delve into their respective contributions to key pathological processes, including apoptosis, the inflammatory response, oxidative stress, extracellular matrix remodeling, angiogenesis, cell hypertrophy, fibrosis, ferroptosis, neurogenesis, and blood-brain barrier damage during I/R injury. Our comprehensive analysis of the mechanisms involved in Wnt signaling during I/R reveals that activation of the canonical Wnt pathway promotes organ recovery, while activation of the non-canonical Wnt pathways exacerbates injury. Moreover, we explore novel therapeutic approaches based on these mechanistic findings, incorporating evidence from animal experiments, current standards, and clinical trials. The objective of this review is to provide deeper insights into the roles of Wnt and its crosstalk signaling pathways in I/R-mediated processes and organ dysfunction, to facilitate the development of innovative therapeutic agents for I/R injury.

Sex and Sleep Disruption as Contributing Factors in Alzheimer's Disease

Alzheimer's disease (AD) affects more women than men, with women throughout the menopausal transition potentially being the most under researched and at-risk group. Sleep disruptions, which are an established risk factor for AD, increase in prevalence with normal aging and are exacerbated in women during menopause. Sex differences showing more disrupted sleep patterns and increased AD pathology in women and female animal models have been established in literature, with much emphasis placed on loss of circulating gonadal hormones with age. Interestingly, increases in gonadotropins such as follicle stimulating hormone are emerging to be a major contributor to AD pathogenesis and may also play a role in sleep disruption, perhaps in combination with other lesser studied hormones. Several sleep influencing regions of the brain appear to be affected early in AD progression and some may exhibit sexual dimorphisms that may contribute to increased sleep disruptions in women with age. Additionally, some of the most common sleep disorders, as well as multiple health conditions that impair sleep quality, are more prevalent and more severe in women. These conditions are often comorbid with AD and have bi-directional relationships that contribute synergistically to cognitive decline and neuropathology. The association during aging of increased sleep disruption and sleep disorders, dramatic hormonal changes during and after menopause, and increased AD pathology may be interacting and contributing factors that lead to the increased number of women living with AD.

Immune characteristics analysis and construction of a four-gene prognostic signature for lung adenocarcinoma based on estrogen reactivity

Lung adenocarcinoma (LUAD) is a common type of malignant tumor with poor prognosis and high mortality. In our previous studies, we found that estrogen is an important risk factor for LUAD, and different estrogen statuses can predict different prognoses. Therefore, in this study, we constructed a prognostic signature related to estrogen reactivity to determine the relationship between different estrogen reactivities and prognosis. We downloaded the LUAD dataset from The Cancer Genome Atlas (TCGA) database, calculated the estrogen reactivity of each sample, and divided them into a high-estrogen reactivity group and a low-estrogen reactivity group. The difference in overall survival between the groups was significant. We also analyzed the status of immune cell infiltration and immune checkpoint expression between the groups. We analyzed the differential gene expression between the groups and screened four key prognostic factors by the least absolute shrinkage and selection operator (LASSO) regression and univariable and multivariable Cox regression. Based on the four genes, a risk signature was established. To a certain extent, the receiver operating characteristic (ROC) curve showed the predictive ability of the risk signature, which was further verified using the GSE31210 dataset. We also determined the role of estrogen in LUAD using an orthotopic mouse model. Additionally, we developed a predictive nomogram combining the risk signature with other clinical characteristics. In conclusion, our four-gene prognostic signature based on estrogen reactivity had prognostic value and can provide new insights into the development of treatment strategies for LUAD.

Overlapping Neuroimmune Mechanisms and Therapeutic Targets in Neurodegenerative Disorders

Many potential immune therapeutic targets are similarly affected in adult-onset neurodegenerative diseases, such as Alzheimer's (AD) disease, Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and frontotemporal dementia (FTD), as well as in a seemingly distinct Niemann-Pick type C disease with primarily juvenile onset. This strongly argues for an overlap in pathogenic mechanisms. The commonly researched immune targets include various immune cell subsets, such as microglia, peripheral macrophages, and regulatory T cells (Tregs); the complement system; and other soluble factors. In this review, we compare these neurodegenerative diseases from a clinical point of view and highlight common pathways and mechanisms of protein aggregation, neurodegeneration, and/or neuroinflammation that could potentially lead to shared treatment strategies for overlapping immune dysfunctions in these diseases. These approaches include but are not limited to immunisation, complement cascade blockade, microbiome regulation, inhibition of signal transduction, Treg boosting, and stem cell transplantation.

PFT-α protects the blood-brain barrier through the Wnt/β-catenin pathway after acute ischemic stroke

The dysfunction of blood-brain barrier (BBB) plays a pivotal role in brain injury and subsequent neurological deficits of ischemic stroke. The current study aimed to examine the potential correlation between p53 inhibition and the neuroprotective effect of on the BBB. Rat middle cerebral artery occlusion and reperfusion model (MCAO/R) and oxygen-glucose deprivation/re-oxygenation model (OGD/R) were employed to simulate cerebral ischemia-reperfusion (CI/R) injury occurrence in vivo and in vitro. mNSS and TTC staining were applied to evaluate neurological deficits and brain infarct volumes. Evans blue (EB) staining was carried out to examine the permeability of BBB. RT-qPCR and Western blot to examine the mRNA and protein levels. Cell viabilities were detected by CCK-8. Flow cytometry and ELISA assay were employed to examine apoptosis and neuroinflammation levels. TEER value and sodium fluorescein were carried out to explore the permeability of HBMEC cells. PFT-α inhibited P53 and promoted the expression of β-catenin and cyclin D1, which were reversed by DKK1. PFT-α inhibited neurological deficits, brain infarct volume, neuroinflammation, apoptosis, and BBB integrity than the MCAO/R rats; however, this inhibition was reversed by DKK1. PFT-α promoted OGD/R-induced cell viability in NSCs, and suppressed inflammation and apoptosis, but DKK1 weakened the effect of PFT-α. PFT-α increased OGD/R-induced TEER values in cerebrovascular endothelial cells, inhibited sodium fluorescein permeability, and increased the mRNA levels of tight junction protein, but they were all attenuated by DKK1. PFT-α protects the BBB after acute ischemic stroke via the Wnt/β-catenin pathway, which in turn improves neurological function.

Elucidation of Pharmacological Mechanism Underlying the Anti-Alzheimer's Disease Effects of Evodia rutaecarpa and Discovery of Novel Lead Molecules: An In Silico Study

Alzheimer's disease (AD) is a brain disease with a peculiarity of multiformity and an insidious onset. Multiple-target drugs, especially Chinese traditional medicine, have achieved a measure of success in AD treatment. Evodia rutaecarpa (Juss.) Benth. (Wuzhuyu, WZY, i.e., E. rutaecarpa), a traditional Chinese herb, has been identified as an effective drug to cure migraines. To our surprise, our in silico study showed that rather than migraines, Alzheimer's disease was the primary disease to which the E. rutaecarpa active compounds were targeted. Correspondingly, a behavioral experiment showed that E. rutaecarpa extract could improve impairments in learning and memory in AD model mice. However, the mechanism underlying the way that E. rutaecarpa compounds target AD is still not clear. For this purpose, we employed methods of pharmacology networking and molecular docking to explore this mechanism. We found that E. rutaecarpa showed significant AD-targeting characteristics, and alkaloids of E. rutaecarpa played the main role in binding to the key nodes of AD. Our research detected that E. rutaecarpa affects the pathologic development of AD through the serotonergic synapse signaling pathway (SLC6A4), hormones (PTGS2, ESR1, AR), anti-neuroinflammation (SRC, TNF, NOS3), transcription regulation (NR3C1), and molecular chaperones (HSP90AA1), especially in the key nodes of PTGS2, AR, SLCA64, and SRC. Graveoline, 5-methoxy-N, N-dimethyltryptamine, dehydroevodiamine, and goshuyuamide II in E. rutaecarpa show stronger binding affinities to these key proteins than currently known preclinical and clinical drugs, showing a great potential to be developed as lead molecules for treating AD.

WNT-β Catenin Signaling as a Potential Therapeutic Target for Neurodegenerative Diseases: Current Status and Future Perspective

Wnt/β-catenin (WβC) signaling pathway is an important signaling pathway for the maintenance of cellular homeostasis from the embryonic developmental stages to adulthood. The canonical pathway of WβC signaling is essential for neurogenesis, cell proliferation, and neurogenesis, whereas the noncanonical pathway (WNT/Ca²⁺ and WNT/PCP) is responsible for cell polarity, calcium maintenance, and cell migration. Abnormal regulation of WβC signaling is involved in the pathogenesis of several neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), and spinal muscular atrophy (SMA). Hence, the alteration of WβC signaling is considered a potential therapeutic target for the treatment of neurodegenerative disease. In the present review, we have used the bibliographical information from PubMed, Google Scholar, and Scopus to address the current prospects of WβC signaling role in the abovementioned neurodegenerative diseases.

Soluble and insoluble protein aggregates, endoplasmic reticulum stress, and vascular dysfunction in Alzheimer's disease and cardiovascular diseases

Dementia refers to a particular group of symptoms characterized by difficulties with memory, language, problem-solving, and other thinking skills that affect a person's ability to perform everyday activities. Alzheimer's disease (AD) is the most common form of dementia, affecting about 6.2 million Americans aged 65 years and older. Likewise, cardiovascular diseases (CVDs) are a major cause of disability and premature death, impacting 126.9 million adults in the USA, a number that increases with age. Consequently, CVDs and cardiovascular risk factors are associated with an increased risk of AD and cognitive impairment. They share important age-related cardiometabolic and lifestyle risk factors, that make them among the leading causes of death. Additionally, there are several premises and hypotheses about the mechanisms underlying the association between AD and CVD. Although AD and CVD may be considered deleterious to health, the study of their combination constitutes a clinical challenge, and investigations to understand the mechanistic pathways for the cause-effect and/or shared pathology between these two disease constellations remains an active area of research. AD pathology is propagated by the amyloid β (Aβ) peptides. These peptides give rise to small, toxic, and soluble Aβ oligomers (SPOs) that are nonfibrillar, and it is their levels that show a robust correlation with the extent of cognitive impairment. This review will elucidate the interplay between the effects of accumulating SPOs in AD and CVDs, the resulting ER stress response, and their role in vascular dysfunction. We will also address the potential underlying mechanisms, including the possibility that SPOs are among the causes of vascular injury in CVD associated with cognitive decline. By revealing common mechanistic underpinnings of AD and CVD, we hope that novel experimental therapeutics can be designed to reduce the burden of these devastating diseases. Graphical abstract Alzheimer's disease (AD) pathology leads to the release of Aβ peptides, and their accumulation in the peripheral organs has varying effects on various components of the cardiovascular system including endoplasmic reticulum (ER) stress and vascular damage. Image created with BioRender.com.

Stabilization of nuclear β-catenin by inhibiting KDM2A mediates cerebral ischemic tolerance

Hypoxic postconditioning (HPC) with 8% oxygen increases nuclear accumulation of β-catenin through activating the classical Wnt pathway, thereby alleviating transient global cerebral ischemia (tGCI)-induced neuronal damage in the hippocampal CA1 subregion of adult rats. However, little is understood about the regulatory mechanism of nuclear β-catenin in HPC-mediated cerebral ischemic tolerance. Although lysine(K)-specific demethylase 2A (KDM2A) has been known as a crucial regulator of nuclear β-catenin destabilization, whether it plays an important role through modulating nuclear β-catenin in cerebral ischemic tolerance induced by HPC remains unknown. In this study, we explored the molecular mechanism of stabilizing nuclear β-catenin by inhibiting KDM2A-mediated demethylation in the HPC-offered neuroprotection against tGCI. In addition, we confirmed that nuclear methylated-β-catenin in CA1 decreased and nuclear β-catenin turnover increased after tGCI, which were reversed by HPC. The administration with methyltransferase inhibitor AdOx abrogated HPC-induced methylation and stabilization of nuclear β-catenin in CA1, as well as the neuroprotection against tGCI. Notably, HPC downregulated the expression of KDM2A in CA1 and reduced the interaction between KDM2A and β-catenin in the nucleus after tGCI. The knockdown of KDM2A with small-interfering RNA could upregulate nuclear methylated-β-catenin and stabilize β-catenin, thereby increasing survivin in CA1 and improving the cognitive function of rats after tGCI. Opposite results were observed by the administration of KDM2A-carried adenovirus vector. Furthermore, we demonstrated that KDM2A mediates the demethylation of nuclear β-catenin through jumonji C (JmjC) domain of KDM2A in HEK-293T and SH-SY5Y cells. Our data support that the inhibition of KDM2A-mediated demethylation of nuclear β-catenin contributes to HPC-induced neuroprotection against tGCI.

Identification of a Novel Wnt Antagonist Based Therapeutic and Diagnostic Target for Alzheimer's Disease Using a Stem Cell-Derived Model

Currently, all the existing treatments for Alzheimer's disease (AD) fail to stall progression due to longer duration of time between onset of the symptoms and diagnosis of the disease, raising the necessity of effective diagnostics and novel treatment. Specific molecular regulation of the onset and progression of disease is not yet elucidated. This warranted investigation of the role of Wnt signaling regulators which are thought to be involved in neurogenesis. The AD model was established using amyloid beta (Aβ) in human mesenchymal stem cells derived from amniotic membranes which were differentiated into neuronal cell types. In vivo studies were carried out with Aβ or a Wnt antagonist, AD201, belonging to the sFRP family. We further created an AD201-knockdown in vitro model to determine the role of Wnt antagonism. BACE1 upregulation, ChAT and α7nAChR downregulation with synapse and functionality loss with increases in ROS confirmed the neurodegeneration. Reduced β-catenin and increased AD201 expression indicated Wnt/canonical pathway inhibition. Similar results were exhibited in the in vivo study along with AD-associated behavioural and molecular changes. AD201-knockdown rescued neurons from Aβ-induced toxicity. We demonstrated for the first time a role of AD201 in Alzheimer's disease manifestation, which indicates a promising disease target and biomarker.

Blockage of KHSRP-NLRP3 by MCC950 Can Reverse the Effect of Manganese-Induced Neuroinflammation in N2a Cells and Rat Brain

Manganese neurotoxicity has been reported to cause a neurodegenerative disease known as parkinsonism. Previous reports have shown that the expression of the KH-type splicing regulatory protein (KHSRP), a nucleic acid-binding protein, and NLRP3 is increased upon Mn exposure. However, the relation between these two during Mn toxicity has not been fully deduced. The mouse neuroblastoma (N2a) and SD rats are treated with LPS and MnCl2 to evaluate the expression of KHSRP and NLRP3. Further, the effect of the NLRP3 inhibitor MCC950 is checked on the expression of NLRP3, KHSRP and pro-inflammatory markers (TNFα, IL-18 and IL-1β) as well as the caspase-1 enzyme. Our results demonstrated an increment in NLRP3 and KHSRP expression post-MnCl2 exposure in N2a cells and rat brain, while on the other hand with LPS exposure only NLRP3 expression levels were elevated and KHSRP was found to be unaffected. An increased expression of KHSRP, NLRP3, pro-inflammatory markers and the caspase-1 enzyme was observed to be inhibited with MCC950 treatment in MnCl2-exposed cells and rats. Manganese exposure induces NLRP3 and KHSRP expression to induce neuroinflammation, suggesting a correlation between both which functions in toxicity-related pathways. Furthermore, MCC950 treatment reversed the role of KHSRP from anti-inflammatory to pro-inflammatory.

Over-expression of survivin could prevent the oxidative stress and toxicity of rotenone in SH-SY5Y cells

OBJECTIVES

It is important to find novel therapeutic molecular targets for curing Parkinson's disease (PD). Accordingly, this study aimed to evaluate the effect of over-expression of the survivin gene, a gene frequently reported as neuroprotective, on the in vitro model of PD.

MATERIALS AND METHODS

Survivin was over-expressed in SH-SY5Y cells. Next, the cells were treated with rotenone (500 nM) for 24 hr. Then, viability and the total antioxidant capacity were assessed. The expression levels of 15 important genes of key cellular processes (oxidative stress, apoptosis, cell cycle, and autophagy) were assessed. The studied genes included survivin, superoxide dismutase, catalase, BAX, bcl2, caspase 3, caspase 8, caspase 9, p53, SMAC, β-catenin, mTOR, AMPK, ATG7, RPS18. The apoptosis level and the frequency of cell cycle stages were assessed by flow cytometry. For analyzing the data, the ANOVA test followed by Tukey's test was used to evaluate the significant differences between the experimental groups. P<0.05 was considered significant.

RESULTS

Survivin could significantly decrease the rotenone-induced apoptosis in SH-SY5Y cells. The rotenone treatment led to down-regulation of catalase and up-regulation of bax, bcl2, caspase 3, caspase 8, P53, β-catenin, and ATG7. Survivin could significantly neutralize the effect of rotenone in most the genes. It could also increase the total antioxidant capacity of SH-SY5Y cells.

CONCLUSION

Survivin could prevent the toxic effect of rotenone on SH-SY5Y cells during the development of in vitro PD model via regulating the genes of key cellular processes, including anti-oxidation, apoptosis, cell cycle, and autophagy.

Androgens Regulate Tau Phosphorylation Through Phosphatidylinositol 3-Kinase-Protein Kinase B-Glycogen Synthase Kinase 3β Signaling

Age-related testosterone depletion in men is a risk factor for Alzheimer's disease (AD). How testosterone modulates AD risk remains to be fully elucidated, although regulation of tau phosphorylation has been suggested as a contributing protective action. To investigate the relationship between testosterone and tau phosphorylation, we first evaluated the effect of androgen status on tau phosphorylation in 3xTg-AD mice. Depletion of endogenous androgens via gonadectomy resulted in increased tau phosphorylation that was prevented by acute testosterone treatment. Parallel alterations in the phosphorylation of both glycogen synthase kinase 3β (GSK3β) and protein kinase B (Akt) suggest possible components of the underlying signaling pathway. To further explore mechanism, primary cultured neurons were treated with a physiological concentration of testosterone or its active metabolite dihydrotestosterone (DHT). Results showed that testosterone and DHT induced significant decreases in phosphorylated tau and significant increases in phosphorylation of Akt and GSK3β. Pharmacological inhibition of phosphatidylinositol 3-kinase (PI3K) effectively inhibited androgen-induced increases in Akt and GSK3β phosphorylation, and decreases in tau phosphorylation. In addition, androgen receptor (AR) knock-down by small interfering RNA prevented androgen-induced changes in the phosphorylation of Akt, GSK3β and tau, suggesting an AR-dependent mechanism. Additional experiments demonstrated androgen-induced changes in Akt, GSK3β and tau phosphorylation in AR-expressing PC12 cells but not in AR-negative PC12 cells. Together, these results suggest an AR-dependent pathway involving PI3K-Akt-GSK3β signaling through which androgens can reduce tau phosphorylation. These findings identify an additional protective mechanism of androgens that can improve neural health and inhibit development of AD.

Gender differences in progressive supranuclear palsy

The gender differences in progressive supranuclear palsy (PSP) are not extensively studied. The objective of this study was to determine the gender differences in the phenotypic expression and progression in PSP. We did a retrospective review of medical records of patients diagnosed with PSP over a 21-year period. The interval between disease onset and attainment of the five clinical disability milestones namely wheel chair dependency, unintelligible speech, severe dysphagia, severe cognitive impairment and urinary catheterization was used to determine the progression. Data was analysed from the case records of 334 patients with PSP. 209 patients (62.2%) were male and 125 (37.4%) among the patients were women (male:female ratio = 1.6:1). Males had older age at onset with longer duration of illness at time of presentation. Tremors were more common, PSP-P phenotype was more frequent and time to attain wheelchair dependency was earlier in males. Falls within 1 year of disease onset, apathy and executive dysfunction were more frequent and time to attain unintelligible speech, severe dysphagia and cognitive impairment were earlier in females. This study in a large cohort of clinically diagnosed cases of PSP has showed that gender differences exist in PSP in terms of clinical characteristics, progression of the disease.

Mitigating Effect of Estrogen in Alzheimer’s Disease-Mimicking Cerebral Organoid

Alzheimer’s disease (AD) is the most common condition in patients with dementia and affects a large population worldwide. The incidence of AD is expected to increase in future owing to the rapid expansion of the aged population globally. Researchers have shown that women are twice more likely to be affected by AD than men. This phenomenon has been attributed to the postmenopausal state, during which the level of estrogen declines significantly. Estrogen is known to alleviate neurotoxicity in the brain and protect neurons. While the effects of estrogen have been investigated in AD models, to our knowledge, they have not been investigated in a stem cell-based three-dimensional in vitro system. Here, we designed a new model for AD using induced pluripotent stem cells (iPSCs) in a three-dimensional, in vitro culture system. We used 5xFAD mice to confirm the potential of estrogen in alleviating the effects of AD pathogenesis. Next, we confirmed a similar trend in an AD model developed using iPSC-derived cerebral organoids, in which the key characteristics of AD were recapitulated. The findings emphasized the potential of estrogen as a treatment agent for AD and also showed the suitability of AD-recapitulating cerebral organoids as a reliable platform for disease modeling and drug screening.

Multifocal Cerebral Microinfarcts Modulate Early Alzheimer’s Disease Pathology in a Sex-Dependent Manner

Alzheimer’s disease (AD) constitutes a major cause of dementia, affecting more women than men. It is characterized by amyloid-β (Aβ) deposition and neurofibrillary tangles (NFTs) formation, associated with a progressive cognitive decline. Evidence indicates that AD onset increases the prevalence of cerebral microinfarcts caused by vascular pathologies, which occur in approximately in half of AD patients. In this project, we postulated that multifocal cerebral microinfarcts decisively influence early AD-like pathology progression in a sex dependent manner in young APP/PS1 mice. For this purpose, we used a novel approach to model multifocal microinfarcts in APP/PS1 mice via the sporadic occlusions of the microvasculature. Our findings indicate that microinfarcts reduced Aβ deposits without affecting soluble Aβ levels in the brain of male and female APP/PS1 mice, while causing rapid and prolonged cognitive deficits in males, and a mild and transient cognitive decline in females. In male APP/PS1 mice, microinfarcts triggered an acute hypoperfusion followed by a chronic hyperperfusion. Whereas in female APP/PS1 mice, microinfarcts caused an acute hypoperfusion, which was recovered in the chronic phase. Microinfarcts triggered a robust microglial activation and recruitment of peripheral monocytes to the lesion sites and Aβ plaques more potently in female APP/PS1 mice, possibly accounting for the reduced Aβ deposition. Finally, expression of Dickkopf-1 (DKK1), which plays a key role in mediating synaptic and neuronal dysfunction in AD, was strongly induced at the lesion sites of male APP/PS1 mice, while its expression was reduced in females. Our findings suggest that multifocal microinfarcts accelerate AD pathology more potently in young males compared to young females independently upon Aβ pathology via modulation of neurovascular coupling, inflammatory response, and DKK1 expression. Our results suggest that the effects of microinfarcts should be taken into consideration in AD diagnosis, prognosis, and therapies.

Targeting the non-classical estrogen pathway in neurodegenerative diseases and brain injury disorders

Estrogens can alter the biology of various tissues and organs, including the brain, and thus play an essential role in modulating homeostasis. Despite its traditional role in reproduction, it is now accepted that estrogen and its analogues can exert neuroprotective effects. Several studies have shown the beneficial effects of estrogen in ameliorating and delaying the progression of neurodegenerative diseases, including Alzheimer's and Parkinson's disease and various forms of brain injury disorders. While the classical effects of estrogen through intracellular receptors are more established, the impact of the non-classical pathway through receptors located at the plasma membrane as well as the rapid stimulation of intracellular signaling cascades are still under active research. Moreover, it has been suggested that the non-classical estrogen pathway plays a crucial role in neuroprotection in various brain areas. In this mini-review, we will discuss the use of compounds targeting the non-classical estrogen pathway in their potential use as treatment in neurodegenerative diseases and brain injury disorders.

Testosterone attenuates sevoflurane-induced tau phosphorylation and cognitive impairment in neonatal male mice

BACKGROUND

Sevoflurane anaesthesia induces phosphorylation of the microtubule-associated protein tau and cognitive impairment in neonatal, but not adult, mice. The underlying mechanisms remain largely to be determined. Sex hormones can be neuroprotective, but little is known about the influence of testosterone on age-dependent anaesthesia effects.

METHODS

Six- and 60-day-old male mice received anaesthesia with sevoflurane 3% for 2 h daily for 3 days. Morris water maze, immunoassay, immunoblotting, co-immunoprecipitation, nanobeam technology, and electrophysiology were used to assess cognition; testosterone concentrations; tau phosphorylation; glycogen synthase kinase-3β (GSK3β) activation; binding or interaction between tau and GSK3β; and neuronal activation in mice, cells, and neurones.

RESULTS

Compared with 60-day-old male mice, 6-day-old male mice had lower testosterone concentrations (3.03 [0.29] vs 0.44 [0.12] ng ml^-1; P<0.01), higher sevoflurane-induced tau phosphorylation in brain (133 [20]% vs 100 [6]% in 6-day-old mice, P<0.01; 103 [8]% vs 100 [13]% in 60-day-old mice, P=0.77), and sevoflurane-induced cognitive impairment. Testosterone treatment increased brain testosterone concentrations (1.76 [0.10] vs 0.39 [0.05] ng ml^-1; P<0.01) and attenuated the sevoflurane-induced tau phosphorylation and cognitive impairment in neonatal male mice. Testosterone inhibited the interaction between tau and GSK3β, and attenuated sevoflurane-induced inhibition of excitatory postsynaptic currents in hippocampal neurones.

CONCLUSIONS

Lower brain testosterone concentrations in neonatal compared with adult male mice contributed to age-dependent tau phosphorylation and cognitive impairment after sevoflurane anaesthesia. Testosterone might attenuate the sevoflurane-induced tau phosphorylation and cognitive impairment by inhibiting the interaction between tau and GSK3β.

On the Common Journey of Neural Cells through Ischemic Brain Injury and Alzheimer's Disease

Ischemic brain injury and Alzheimer's disease (AD) both lead to cell death in the central nervous system (CNS) and thus negatively affect particularly the elderly population. Due to the lack of a definitive cure for brain ischemia and AD, it is advisable to carefully study, compare, and contrast the mechanisms that trigger, and are involved in, both neuropathologies. A deeper understanding of these mechanisms may help ameliorate, or even prevent, the destructive effects of neurodegenerative disorders. In this review, we deal with ischemic damage and AD, with the main emphasis on the common properties of these CNS disorders. Importantly, we discuss the Wnt signaling pathway as a significant factor in the cell fate determination and cell survival in the diseased adult CNS. Finally, we summarize the interesting findings that may improve or complement the current sparse and insufficient treatments for brain ischemia and AD, and we delineate prospective directions in regenerative medicine.

17β-oestradiol alleviates endoplasmic reticulum stress injury induced by chronic cerebral hypoperfusion through the Haemoglobin/HIF 1α signalling pathway in ovariectomized rats

Endoplasmic reticulum stress (ERS) is known to be an essential target in protecting against ischaemic brain injury. In this study, using a vascular dementia (VaD) animal model induced by bilateral common carotid artery occlusion (BCCAO), we evaluated the effect and mechanism of 17β-oestradiol (E2) against VaD by inhibiting ERS at the early stage (14 d, 21 d, 28 d) and late stage (3 m) after BCCAO in the hippocampal CA1 region of ovariectomized rats. The results showed that the activation of the PERK-eIF2α-ATF4-CHOP axis, a typical ERS pathway, was significantly increased at the early and late stages after BCCAO. JNK (c-Jun N-terminal kinase)-cJun, a pro-death pathway, also displayed the same pattern as the ERS axis. E2 treatment profoundly suppressed the impairments caused by BCCAO. Further mechanistic studies revealed that cerebral blood flow (CBF) was sharply decreased at 14 d and returned to the normal level at 21 d after BCCAO. E2 could not change CBF, while it unexpectedly enhanced the ability to carry oxygen. This is evidenced by the fact that the protein expression of haemoglobin α/β (Hα/β), an oxygen carrier, robustly increased at BCCAO 21 d and 3 m after E2 treatment. The oxygen carrier increased strongly after 21 d and 3 m of BCCAO treated with E2. Moreover, E2 correspondingly enhanced the protein expression of hypoxia-inducible factor 1α (HIF 1α) in both the early and late stage after BCCAO in the hippocampal CA1 region. Finally, E2 administration markedly decreased the activities of caspase-8, caspase-3, and caspase-12 and increased the number of NeuN-positive cells. These findings suggest that E2 serves as a neuroprotectant to alleviate VaD by suppressing ERS injury involving the haemoglobin/HIF 1α signalling pathway.

Sex hormones, vascular factors and cognition

After more than a century of research, we have failed to develop a pharmacological prevention or cure for dementia. There are strong indicators that sex hormones influence cognition. In this paper we discuss the role of these hormones at the intersection between vascular disease and dementia, in light of the mounting literature covering the shared risk factors, pathological features alongside the timeline of hormonal change with the evolution of vascular and neurodegenerative disease. Interactive risk factors and the role of inflammation over the duration of disease evolution are highlighted. Our summary tables assessing the impact of estrogen-based hormone therapy on cognition over the past 45 years illustrate the effort expended to determine the ideal age for intervention and the type, dose, administration, and duration of therapy that might improve or protect cognition as well as alleviate menopausal symptoms. As the prevalence of dementia is rising and is higher in women, it is crucial we advance our knowledge from the "inconclusive" position statement on menopausal hormone therapy of the US Preventive Services Task Force.

PTEN Reduces BMP9-Induced Osteogenic Differentiation Through Inhibiting Wnt10b in Mesenchymal Stem Cells

Bone morphogenetic protein 9 (BMP9) is one of the most efficacious osteogenic cytokines. PTEN and Wnt10b are both implicated in regulating the osteogenic potential of BMP9, but the potential relationship between them is unknown. In this study, we determined whether PTEN could reduce the expression of Wnt10b during the osteogenic process initialized by BMP9 in mesenchymal stem cells (MSCs) and the possible molecular mechanism. We find that PTEN is inhibited by BMP9 in MSCs, but Wnt10b is increased simultaneously. The BMP9-induced osteogenic markers are reduced by PTEN but increased by silencing PTEN. The effects of knockdown PTEN on elevating BMP9-induced osteogenic markers are almost abolished by knockdown of Wnt10b. On the contrary, the BMP9-increased ALP activities and mineralization are both inhibited by PTEN but almost reversed by the combination of Wnt10b. Bone masses induced by BMP9 are enhanced by knockdown of PTEN, which is reduced by knockdown of Wnt10b. The BMP9-increased Wnt10b is decreased by PTEN but enhanced by knockdown of PTEN. Meanwhile, the BMP9-induced Wnt10b is also reduced by a PI3K-specific inhibitor (Ly294002) or rapamycin, respectively. The BMP9-induced phosphorylation of CREB or Smad1/5/9 is also reduced by PTEN, but enhanced by PTEN knockdown. In addition, p-CREB interacts with p-Smad1/5/9 in MSCs, and p-CREB or p-Smad1/5/9 are both enriched at the promoter region of Wnt10b. Our findings indicate that inhibitory effects of PTEN on BMP9's osteogenic potential may be partially mediated through decreasing the expression of Wnt10b via the disturbance of interaction between CREB and BMP/Smad signaling.

Astrocyte-Derived Estrogen Regulates Reactive Astrogliosis and is Neuroprotective following Ischemic Brain Injury

Expression of the 17β-estradiol (E2) synthesis enzyme aromatase is highly upregulated in astrocytes following brain injury. However, the precise role of astrocyte-derived E2 in the injured brain remains unclear. In the current study, we generated a glial fibrillary acidic protein (GFAP) promoter-driven aromatase knock-out (GFAP-ARO-KO) mouse model to deplete astrocyte-derived E2 in the brain and determine its roles after global cerebral ischemia (GCI) in male and female mice. GFAP-ARO-KO mice were viable and fertile, with normal gross brain structure, normal morphology, intensity and distribution of astrocytes, normal aromatase expression in neurons, and normal cognitive function basally. In contrast, after GCI, GFAP-ARO-KO mice: (1) lacked the normal elevation of astrocyte aromatase and hippocampal E2 levels; (2) had significantly attenuated reactive astrogliosis; and (3) displayed enhanced neuronal damage, microglia activation, and cognitive deficits. RNA-sequencing (RNA-seq) analysis revealed that the ischemic GFAP-ARO-KO mouse hippocampus failed to upregulate the "A2" panel of reactive astrocyte genes. In addition, the JAK-STAT3 pathway, which is critical for the induction of reactive astrogliosis, was significantly downregulated in the GFAP-ARO-KO hippocampus following GCI. Finally, exogenous E2 administration fully rescued the compromised JAK-STAT3 pathway and reactive astrogliosis, and reversed the enhanced neuronal damage and microglial activation in the GFAP-ARO-KO mice after GCI, suggesting that the defects in the KO mice are because of a loss of E2 rather than an increase in precursor androgens. In conclusion, the current study provides novel genetic evidence for a beneficial role of astrocyte-derived E2 in reactive astrogliosis, microglial activation, and neuroprotection following an ischemic injury to the brain.SIGNIFICANCE STATEMENT Following cerebral ischemia, reactive astrocytes express the enzyme aromatase and produce 17β-estradiol (E2), although the precise role of astrocyte-derived E2 is poorly understood. In this study, we generated a glial fibrillary acidic protein (GFAP) promoter-driven aromatase knock-out (GFAP-ARO-KO) mouse to deplete astrocyte-derived E2 and elucidate its roles after global cerebral ischemia (GCI). The GFAP-ARO-KO mice exhibited significantly attenuated reactive astrogliosis, as well as enhanced microglial activation, neuronal damage, and cognitive dysfunction after GCI. Transcriptome analysis further revealed that astrocyte-derived E2 was critical for the induction of the JAK-STAT3 signaling pathway, as well as the A2 reactive astrocyte phenotype after ischemia. Collectively, these findings indicate that astrocyte-derived E2 has a key role in the regulation of reactive astrogliosis, microglial activation, and neuroprotection after cerebral ischemia.

Theta-burst transcranial magnetic stimulation promotes stroke recovery by vascular protection and neovascularization

Rationale: The integrity and function of the blood-brain barrier (BBB) is compromised after stroke. The current study was performed to examine potential beneficial effects and underlying mechanisms of repetitive transcranial magnetic stimulation (rTMS) on angiogenesis and vascular protection, function, and repair following stroke, which are largely unknown.

Methods: Using a rat photothrombotic (PT) stroke model, continuous theta-burst rTMS was administered once daily to the infarcted hemisphere for 5 min, beginning 3 h after PT stroke. This treatment was applied for 6 days. BBB integrity, blood flow, vascular associated proteins, angiogenesis, integrity of neuronal morphology and structure, and behavioral outcome were measured and analyzed at 6 and/or 22 days after PT stroke.

Results: We report that rTMS significantly mitigated BBB permeabilization and preserved important BBB components ZO-1, claudin-5, occludin, and caveolin-1 from PT-induced degradation. Damage to vascular structure, morphology, and perfusion was ameliorated by rTMS, resulting in improved local tissue oxygenation. This was accompanied with robust protection of critical vascular components and upregulation of regulatory factors. A complex cytokine response was induced by PT, particularly at the late phase. Application of rTMS modulated this response, ameliorating levels of cytokines related to peripheral immune cell infiltration. Further investigation revealed that rTMS promoted and sustained post-ischemic angiogenesis long-term and reduced apoptosis of newborn and existing vascular endothelial cells. Application of rTMS also inhibited PT-induced excessive astrocyte-vasculature interactions and stimulated an A1 to A2 shift in vessel-associated astrocytes. Mechanistic studies revealed that rTMS dramatically increased levels of PDGFRβ associated with A2 astrocytes and their adjacent vasculature. As well, A2 astrocytes displayed marked amplification of the angiogenesis-related factors VEGF and TGFβ. PT induced a rise in vessel-associated expression of HIF-1α that was starkly intensified by rTMS treatment. Finally, rTMS preserved neuronal morphology, synaptic structure integrity and behavioral outcome.

Conclusions: These results indicate that rTMS can exert powerful protective and restorative effects on the peri-infarct microvasculature after PT stroke by, in part, promoting HIF-1α signaling and shifting vessel-associated astrocytic polarization to the A2 phenotype. This study provides further support for the potent protective effects of rTMS in the context of ischemic stroke, and these findings implicate vascular repair and protection as an important underlying phenomenon.

Wnt Pathway: An Emerging Player in Vascular and Traumatic Mediated Brain Injuries

The Wnt pathway, which comprises the canonical and non-canonical pathways, is an evolutionarily conserved mechanism that regulates crucial biological aspects throughout the development and adulthood. Emergence and patterning of the nervous and vascular systems are intimately coordinated, a process in which Wnt pathway plays particularly important roles. In the brain, Wnt ligands activate a cell-specific surface receptor complex to induce intracellular signaling cascades regulating neurogenesis, synaptogenesis, neuronal plasticity, synaptic plasticity, angiogenesis, vascular stabilization, and inflammation. The Wnt pathway is tightly regulated in the adult brain to maintain neurovascular functions. Historically, research in neuroscience has emphasized essentially on investigating the pathway in neurodegenerative disorders. Nonetheless, emerging findings have demonstrated that the pathway is deregulated in vascular- and traumatic-mediated brain injuries. These findings are suggesting that the pathway constitutes a promising target for the development of novel therapeutic protective and restorative interventions. Yet, targeting a complex multifunctional signal transduction pathway remains a major challenge. The review aims to summarize the current knowledge regarding the implication of Wnt pathway in the pathobiology of ischemic and hemorrhagic stroke, as well as traumatic brain injury (TBI). Furthermore, the review will present the strategies used so far to manipulate the pathway for therapeutic purposes as to highlight potential future directions.

Neuron-Derived Estrogen Is Critical for Astrocyte Activation and Neuroprotection of the Ischemic Brain

17β-Estradiol (E2) is produced from androgens via the action of the enzyme aromatase. E2 is known to be made in neurons in the brain, but the functions of neuron-derived E2 in the ischemic brain are unclear. Here, we used a forebrain neuron-specific aromatase KO (FBN-ARO-KO) mouse model to deplete neuron-derived E2 in the forebrain and determine its roles after global cerebral ischemia. We demonstrated that ovariectomized female FBN-ARO-KO mice exhibited significantly attenuated astrocyte activation, astrocytic aromatization, and decreased hippocampal E2 levels compared with FLOX mice. Furthermore, FBN-ARO-KO mice had exacerbated neuronal damage and worse cognitive dysfunction after global cerebral ischemia. Similar results were observed in intact male mice. RNA-seq analysis revealed alterations in pathways and genes associated with astrocyte activation, neuroinflammation, and oxidative stress in FBN-ARO-KO mice. The compromised astrocyte activation in FBN-ARO-KO mice was associated with robust downregulation of the astrocyte-derived neurotrophic factors, BDNF and IGF-1, as well as the astrocytic glutamate transporter, GLT-1. Νeuronal FGF2, which acts in a paracrine manner to suppress astrocyte activation, was increased in FBN-ARO-KO neurons. Interestingly, blocking FGF2 signaling by central injection of FGFR3-neutralizing antibody was able to reverse the diminishment in neuroprotective astrocyte reactivity, and attenuate neuronal damage in FBN-ARO-KO mice. Moreover, in vivo E2 replacement suppressed FGF2 signaling and rescued the compromised reactive astrogliosis and cognitive deficits. Collectively, our data provide novel genetic evidence for a beneficial role of neuron-derived E2 in astrocyte activation, neuroprotection, and cognitive preservation following ischemic injury to the brain.

SIGNIFICANCE STATEMENT Following cerebral ischemia, astrocytes become highly reactive and can exert neuroprotection through the release of neurotrophic factors and clearance of neurotoxic glutamate. The current study advances our understanding of this process by demonstrating that neuron-derived 17β-estradiol (E2) is neuroprotective and critical for induction of reactive astrocytes and their ability to produce astrocyte-derived neurotrophic factors, BDNF and IGF-1, and the glutamate transporter, GLT-1 after ischemic brain damage. These beneficial effects of neuron-derived E2 appear to be due, at least in part, to suppression of neuronal FGF2 signaling, which is a known suppressor of astrocyte activation. These findings suggest that neuron-derived E2 is neuroprotective after ischemic brain injury via a mechanism that involves suppression of neuronal FGF2 signaling, thereby facilitating astrocyte activation.

Effect of Wnt signaling pathway on neurogenesis after cerebral ischemia and its therapeutic potential

Neurogenesis process in the chronic phase of ischemic stroke has become the focus of research on stroke treatment recently, mainly through the activation of related pathways to increase the differentiation of neural stem cells (NSCs) in the brain sub-ventricular zone (SVZ) and subgranular zone (SGZ) of hippocampal dentate gyrus (DG) areas into neurons, promoting neurogenesis. While there is still debate about the longevity of active adult neurogenesis in humans, the SVZ and SGZ have the capacity to upregulate neurogenesis in response to cerebral ischemia, which opens discussion about potential treatment strategies to harness this neuronal regenerative response. Wnt signaling pathway is one of the most important approaches potentially targeting on neurogenesis after cerebral ischemia, appropriate activation of which in NSCs may help to improve the sequelae of cerebral ischemia. Various therapeutic approaches are explored on preclinical stage to target endogenous neurogenesis induced by Wnt signaling after stroke onset. This article describes the composition of Wnt signaling pathway and the process of neurogenesis after cerebral ischemia, and emphatically introduces the recent studies on the mechanisms of this pathway for post-stroke neurogenesis and the therapeutic possibility of activating the pathway to improve neurogenesis after stroke.

Sex hormones and proteins involved in brain plasticity

It is well known that peripheral sex steroid hormones cross the blood-brain barrier and control a broad spectrum of reproductive behaviors. However, their role in other essential brain functions was investigated since the 1980s, when the accumulation of pregnenolone and dehydroepiandrosterone in the brain of mammalian species was determined. Since then, numerous studies have demonstrated the participation of sex hormones in brain plasticity processes. Sex hormones through both genomic and non-genomic mechanisms of action are capable of inducing gene transcription or activating signaling cascades that result in the promotion of different physiological and pathological events of brain plasticity, such as remodeling or formation of dendritic spines, neurogenesis, synaptogenesis or myelination. In this chapter, we will present the effects of sex hormones and proteins involved in brain plasticity.

Chronic exposure to environmentally relevant concentrations of bisphenol S differentially affects cognitive behaviors in adult female zebrafish

Evidence is emerging that environmental exposure to bisphenol S (BPS), a substitute for bisphenol A (BPA), to humans and wildlife is on the rise. However, research on the neurobehavioral effects of this endocrine disruptive chemical is still in its infancy. In this study, we aimed to investigate the effects of long-term exposure to environmentally relevant concentrations of BPS on recognition memory and its mechanism(s) of action, especially focusing on the glutamatergic/ERK/CREB pathway in the brain. Adult female zebrafish were exposed to the vehicle, 17β-estradiol (E2, 1 μg/L), or BPS (1, 10 and 30 μg/L) for 120 days. Fish were then tested in the object recognition (OR), object placement (OP), and social recognition tasks (SR). Chronic exposure to E2 and 1 μg/L of BPS improved fish performance in OP task. This was associated with an up-regulation in the mRNA expression of several subtypes of metabotropic and ionotropic glutamate receptors, an increase in the phosphorylation levels of ERK1/2 and CREB, and an elevated transcript abundance of several immediate early genes involved in synaptic plasticity and memory formation. In contrast, the exposure to 10 and 30 μg/L of BPS attenuated fish performance in all recognition memory tasks. The impairment of these memory functions was associated with a marked down-regulation in the expression and activity of genes and proteins involved in glutamatergic/ERK/CREB signaling cascade. Collectively, our study demonstrated that the long-term exposure to BPS elicits hermetic effects on the recognition memory in zebrafish. Furthermore, the effect of BPS on the recognition memory seems to be mediated by the glutamatergic/ERK/CREB signaling pathway.

Effects of letrozole and clomiphene citrate on Wnt signaling pathway in endometrium of polycystic ovarian syndrome and healthy women†

Polycystic ovary syndrome (PCOS) is an endocrine disorder in women of reproductive age. In addition to anovulation, endometrial dysfunction can reduce fertility in PCOS. The cyclical changes of endometrium are controlled by estrogen and progesterone via modulating the Wnt/B-catenin pathway. Clomiphene citrate (CC) and letrozole are used to induce ovulation; unlike letrozole, there is a discrepancy between ovulation and pregnancy rates in CC-treated cycles. Because of the anti-estrogenic effects of CC on endometrium, we compared the expression of the key molecules of the Wnt/B-catenin pathway in the endometrium of women taking CC and letrozole. This study included PCOS and healthy women divided into the groups stimulated with letrozole (5 mg) or CC (100 mg) as well as NO-treatment groups. The endometrial thickness and hormonal profile were measured on day 12 of the menses. Using real-time polymerase chain reaction and western blot, we evaluated mRNA and protein expression of B-catenin, glycogen synthase kinase 3 beta (GSK3B), dickkopf Wnt signaling pathway inhibitor 1 (DKK1), and estrogen receptor 1 (ESR1) in the endometrial samples. Significantly, the mean serum estrogen and progesterone were lower and higher, respectively, in letrozole than CC groups. The endometrial thickness was significantly reduced in CC. The proteins expression of active B-catenin, inactive GSK3B, and ESR1 were significantly decreased in CC-treated groups. The mRNA and protein assessment of DKK1 showed significantly higher expression in CC. Our results indicate that letrozole can provide an acceptable activation of the Wnt/B-catenin pathway, resulting in adequate proliferation of endometrium in the women receiving letrozole compared to CC.

Estrogen Signaling in Alzheimer's Disease: Molecular Insights and Therapeutic Targets for Alzheimer's Dementia

Estrogens play a crucial physiological function in the brain; however, debates exist concerning the role of estrogens in Alzheimer's disease (AD). Women during pre-, peri-, or menopause periods are more susceptible for developing AD, suggesting the connection of sex factors and a decreased estrogen signaling in AD pathogenesis. Yet, the underlying mechanism of estrogen-mediated neuroprotection is unclarified and is complicated by the existence of estrogen-related factors. Consequently, a deeper analysis of estrogen receptor (ER) expression and estrogen-metabolizing enzymes could interpret the importance of estrogen in age-linked cognitive alterations. Previous studies propose that hormone replacement therapy may attenuate AD onset in postmenopausal women, demonstrating that estrogen signaling is important for the development and progression of AD. For example, ERα exerts neuroprotection against AD by maintaining intracellular signaling cascades and study reported reduced expression of ERα in hippocampal neurons of AD patients. Similarly, reduced expression of ERβ in female AD patients has been associated with abnormal function in mitochondria and improved markers of oxidative stress. In this review, we discuss the critical interaction between estrogen signaling and AD. Moreover, we highlight the potential of targeting estrogen-related signaling for therapeutic intervention in AD.

TBHQ improved neurological recovery after traumatic brain injury by inhibiting the overactivation of astrocytes

Traumatic brain injury (TBI) is a major leading cause of death and long-term disability. Although astrocytes play a key role in neuroprotection after TBI in the early stage, the overactivation of astrocytes can lead to long-term functional deficits, and the underlying pathophysiological mechanisms remain unclear. In addition, it is unknown whether the nuclear factor erythroid 2-related factor2/haem oxygenase-1 (Nrf-2/HO-1) pathway could elicit a neuroprotective effect by decreasing astrocyte overactivation after TBI. We aimed to study the effects of tert-butylhydroquinone (TBHQ) in reducing astrocyte overactivation after TBI and explored the underlying mechanisms. We first established a controlled cortical impact (CCI) model in rats and performed Haematoxylin and eosin (H&E) staining to observe brain tissue damage. The cognitive function of rats was assessed by modified neurological severity scoring (mNSS) and Morris water maze (MWM) test. Astrocyte and microglia activation was detected by immunofluorescence staining. Oxidative stress conditions were investigated using Western blotting. An enzyme-linked immunosorbent assay (ELISA) was designed to assess the level of the proinflammatory factor tumour necrosis factor-alpha (TNF-α). Dihydroethidium (DHE) staining was used to detect reactive oxygen species (ROS). Apoptosis was assessed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. The results showed that the administration of TBHQ ameliorated motor function and cognitive deficits and decreased the lesion volume. In addition, TBHQ significantly decreased astrocyte overactivation, diminished the pro-inflammatory phenotype M1 and inflammatory cytokines production after TBI, increased Nrf-2 nuclear accumulation, and enhanced the levels of the Nrf-2 downstream antioxidative genes HO-1 and NADPH-quinone oxidoreductase-1 (NQO-1). Furthermore, TBHQ treatment alleviated apoptosis and neuronal death in the cerebral cortex. Overall, our data indicated that the upregulation of Nrf-2 expression could enhance neuroprotection and decrease astrocyte overactivation and might represent a new theoretical basis for treating TBI.

Restoring Wnt/β-catenin signaling is a promising therapeutic strategy for Alzheimer's disease

Alzheimer’s disease (AD) is an aging-related neurological disorder characterized by synaptic loss and dementia. Wnt/β-catenin signaling is an essential signal transduction pathway that regulates numerous cellular processes including cell survival. In brain, Wnt/β-catenin signaling is not only crucial for neuronal survival and neurogenesis, but it plays important roles in regulating synaptic plasticity and blood-brain barrier integrity and function. Moreover, activation of Wnt/β-catenin signaling inhibits amyloid-β production and tau protein hyperphosphorylation in the brain. Critically, Wnt/β-catenin signaling is greatly suppressed in AD brain via multiple pathogenic mechanisms. As such, restoring Wnt/β-catenin signaling represents a unique opportunity for the rational design of novel AD therapies.

Molecular mechanisms and cellular events involved in the neuroprotective actions of estradiol. Analysis of sex differences

Estradiol, either from peripheral or central origin, activates multiple molecular neuroprotective and neuroreparative responses that, being mediated by estrogen receptors or by estrogen receptor independent mechanisms, are initiated at the membrane, the cytoplasm or the cell nucleus of neural cells. Estrogen-dependent signaling regulates a variety of cellular events, such as intracellular Ca²⁺ levels, mitochondrial respiratory capacity, ATP production, mitochondrial membrane potential, autophagy and apoptosis. In turn, these molecular and cellular actions of estradiol are integrated by neurons and non-neuronal cells to generate different tissue protective responses, decreasing blood-brain barrier permeability, oxidative stress, neuroinflammation and excitotoxicity and promoting synaptic plasticity, axonal growth, neurogenesis, remyelination and neuroregeneration. Recent findings indicate that the neuroprotective and neuroreparative actions of estradiol are different in males and females and further research is necessary to fully elucidate the causes for this sex difference.

Dickkopf-1 blocks 17β-estradiol-enhanced object memory consolidation in ovariectomized female mice

The memory-enhancing effects of 17β-estradiol (E₂) depend upon rapid activation of several cell-signaling cascades within the dorsal hippocampus (DH). Among the many cell-signaling pathways that mediate memory processes, Wnt/β-catenin signaling has emerged as a potential key player because of its importance to hippocampal development and synaptic plasticity. However, whether E₂ interacts with Wnt/β-catenin signaling to promote memory consolidation is unknown. Therefore, the present study examined whether Wnt/β-catenin signaling within the DH is necessary for E₂-induced memory consolidation in ovariectomized mice tested in the object recognition and object placement tasks. Ovariectomized C57BL/6 mice received immediate post-training infusions of E₂ or vehicle into the dorsal third ventricle plus the endogenous Wnt/β-catenin antagonist Dickkopf-1 (Dkk-1) or vehicle into the DH to assess whether the memory-enhancing effects of E₂ depend on activation of Wnt/β-catenin signaling. Our results suggest that Dkk-1 blocks E₂-induced memory enhancement as hypothesized, but may do so by only moderately blunting Wnt/β-catenin signaling while concurrently activating Wnt/JNK signaling. The current study provides novel insights into the mechanisms through which E₂ enhances memory consolidation in the DH, as well as critical information about the mechanistic actions of Dkk-1.

Hypoxic postconditioning activates the Wnt/β-catenin pathway and protects against transient global cerebral ischemia through Dkk1 Inhibition and GSK-3β inactivation

The Wingless/Int (Wnt)/β-catenin pathway plays an essential role in cell survival. Although postconditioning with 8% oxygen can alleviate transient global cerebral ischemia (tGCI)-induced neuronal damage in hippocampal CA1 subregion in adult rats as demonstrated by our previous studies, little is understood about the role of Wnt/β-catenin pathway in hypoxic postconditioning (HPC)-induced neuroprotection. This study tried to investigate the involvement of Wnt/β-catenin pathway in HPC-induced neuroprotection against tGCI and explore the underlying molecular mechanism thereof. We observed that HPC elevated nuclear β-catenin level as well as increased Wnt3a and decreased Dickkopf-1 (Dkk1) expression in CA1 after tGCI. Accordingly, HPC enhanced the expression of survivin and reduced the ratio of B-cell lymphoma/lewkmia-2 (Bcl-2)-associated X protein (Bax) to Bcl-2 following reperfusion. Moreover, our study has shown that these effects of HPC were abolished by lentivirus-mediated overexpression of Dkk1, and that the overexpression of Dkk1 completely reversed HPC-induced neuroprotection. Furthermore, HPC suppressed the activity of glycogen synthase kinase-3β (GSK-3β) in CA1 after tGCI, and the inhibition of GSK-3β activity with SB216763 increased the nuclear accumulation of β-catenin, up-regulated the expression of survivin, and reduced the ratio of Bax to Bcl-2, thus preventing the delayed neuronal death after tGCI. Finally, the administration of LY294002, an inhibitor of PI3K, increased GSK-3β activity and blocked nuclear β-catenin accumulation, thereby decreasing survivin expression and elevating the Bax-to-Bcl-2 ratio after HPC. These results suggest that activation of the Wnt/β-catenin pathway through Dkk1 inhibition and PI3K/protein kinase B pathway-mediated GSK-3β inactivation contributes to the neuroprotection of HPC against tGCI.-Zhan, L., Liu, D., Wen, H., Hu, J., Pang, T., Sun, W., Xu, E. Hypoxic postconditioning activates the Wnt/β-catenin pathway and protects against transient global cerebral ischemia through Dkk1 inhibition and GSK-3β inactivation.

Gastrodin attenuates proliferation and inflammatory responses in activated microglia through Wnt/β-catenin signaling pathway

Microglia contribute to the regulation of neuroinflammation and play an important role in the pathogenesis of brain disorders. Thus, regulation of neuroinflammation triggered by activation of microglia has become a promising therapeutic strategy. Here, we investigated the beneficial effects of Gastrodin in activated microglia and analyzed the underlying molecular mechanisms. Microglia activation was regulated by Gastrodin not only in terms of microglia population size but also production of inflammatory mediators. Gastrodin inhibited the expression of inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α), cyclin-D1 and Ki67 in lipopolysaccharide (LPS)-stimulated BV-2 or primary microglia. Gastrodin also suppressed the expression of iNOS and Ki67 in activated microglia in three-day-old LPS-injected postnatal rats. In addition, the present results have shown that Gastrodin inhibited LPS-induced phosphorylation of glycogen synthase kinase-3β (GSK-3β) at Ser 9 and β-catenin activity. We further extended our investigation to determine whether Wnt/β-catenin signaling pathway was involved in the anti-inflammatory and anti-proliferation function of Gastrodin. β-Catenin antagonist (XAV939) was used to block LPS-mediated upregulation of iNOS, TNF-α, cyclin-D1, nitric oxide (NO) and the number of cells in the G2/M+S phase of cell cycle. Moreover, treatment with LiCl, a special Wnt/β-catenin pathway agonist significantly blocked Gastrodin-mediated down-regulation of iNOS, TNF-α, cyclin-D1, NO and the number of cells in the G2/M+S phase of cell cycle in LPS-stimulated BV-2 microglia. Taken together, the present results suggested that Gastrodin mediated anti-inflammatory and anti-proliferation effects in activated microglia by modulating the Wnt/β-catenin signaling pathway.

Okadaic Acid and Hypoxia Induced Dementia Model of Alzheimer's Type in Rats

Alzheimer's disease (AD) is the most common cause of progressive decline of memory function in aged humans. To study about a disease mechanism and progression, animal models for the specific disease are needed. For AD, although highly valid animal models exist, none of the existing models recapitulates all aspects of human AD. The pathogenic mechanisms involved in AD are diverse and thus it is difficult to recapitulate human AD in model organisms. Intracerebroventricular (ICV) injection of okadaic acid (OKA), a protein phosphatase 2A (PP2A) inhibitor, in rats causes neurotoxicity associated with neurofibrillary degeneration. However, this model lacks amyloid pathology as observed in AD. We aimed at combining two different treatments and hence producing a better animal model of AD which may mimic most of the neuropathological, neurobehavioral, and neurochemical changes observed in AD. For this, OKA (200 ng) was microinjected bilaterally into the hippocampus of male Wistar rats followed by exposure of same rats to hypoxic conditions (10%) for 3 days. The result of which, the combination model exhibited tau hyperphosphorylation along with Aβ upregulation as evident by western blotting and immunohistochemistry. The observed changes were accompanied with dysfunction of neurotransmitter system, i.e., decreased acetylcholine activity and expression. This combinatorial model also exhibited cognitive deficiency which was assessed by Morris water maze and avoidance tests along with enhanced oxidative stress which is thought to be a major player in AD pathogenesis. Taken together, we established an easily reproducible and reliable rat model for sporadic dementia of Alzheimer's type in rats which allows effective testing of new therapeutic strategies.

17β-Estradiol attenuates the influence of chronic activated microglia on SH-SY5Y cell proliferation via canonical WNT signaling pathway

The decline in circulating estrogen following menopause or aging is likely to initiate chronic inflammatory disorders, leading to neurodegenerative disease. Though, WNT1 paracrine molecules are crucial in embryonic neuroblastoma cell proliferation, very less is known about its role in adult brain that is associated with estrogen as preventive therapeutic strategy. The present study evidenced for the first time that 17β-estradiol (E2), a potent form of estrogen, could compensate the chronic neuroinflammation-associated loss of neurons by upregulating canonical WNT signaling pathway. Lipopolysaccharide was used to induce inflammatory responses in microglial cell line. The increased secretion of IL-6 cytokine was confirmed as a marker of chronic microglial activation. LPS-conditioned microglial media significantly reduced the viable cells and proliferative markers, BrdU and CyclinD1 in SH-SY5Y. It also decreased the expression of canonical WNT signaling components; WNT1 and β-catenin, which were significantly rescued with pre- and co-treatment of 10 nM E2. Furthermore, estrogen antagonist ICI 182,780 abolished the E2-mediated recovery in WNT1 expression. Whereas, canonical WNT receptor antagonist, Dkk1 was able to inhibit E2-mediated recovery in the expression of downstream component, β-catenin. It suggests a promising role of canonical WNT signaling pathway in estrogen mediated prevention of neuronal cell loss under chronic neuroinflammatory condition.

Dickkopf-3 Causes Neuroprotection by Inducing Vascular Endothelial Growth Factor

Dickkopf-3 (Dkk3) is an atypical member of the Dkk family of Wnt inhibitors, which has been implicated in the pathophysiology of neurodegenerative disorders. However, the role of Dkk3 in mechanisms of cell degeneration and protection is unknown. We used Dkk3 knockout mice to examine how endogenous Dkk3 influences ischemic brain damage. In addition, we used primary cultures of astrocytes or mixed cultures of astrocytes and neurons to investigate the action of Dkk3 on cell damage and dissect the underlying molecular mechanisms. In a model of focal brain ischemia induced by permanent middle cerebral artery (MCA) occlusion (MCAO) Dkk3^−/− mice showed a significantly greater infarct size with respect to their wild-type counterparts at all time points investigated (1, 3 and 7 days after MCAO). Immunohistochemical analysis showed that Dkk3 expression was enhanced at the borders of the ischemic focus, and was predominantly detected in astrocytes. This raised the possibility that Dkk3 produced by astrocytes acted as a protective molecule. We tested this hypothesis using either primary cultures of cortical astrocytes or mixed cortical cultures containing both neurons and astrocytes. Genetic deletion of Dkk3 was permissive to astrocyte damage induced by either oxidative stress or glucose deprivation. In addition, application of human recombinant Dkk3 (hrDkk3) was highly protective against oxidative stress in cultured astrocytes. We tested the hypothesis that the protective activity of Dkk3 was mediated byvascular endothelial growth factor (VEGF). Interestingly, glucose deprivation up-regulated both Dkk3 and VEGF in cultured astrocytes prepared from wild-type mice. VEGF induction was not observed in astrocytes lacking Dkk3 (i.e., in cultures prepared from Dkk3^−/− mice). In mixed cultures of cortical cells, excitotoxic neuronal death induced by a brief pulse with N-methyl-D-aspartate (NMDA) was significantly enhanced when Dkk3 was lacking in astrocytes, whereas post-NMDA addition of hrDkk3 was neuroprotective. Neuroprotection by hrDkk3 was significantly reduced by pharmacological blockade of type-2 VEGF receptors and was mimicked by hrVEGF. These data offer the first evidence that Dkk3 protects both neurons and astrocytes against a variety of toxic insults, and at least in culture, protection involves VEGF induction.

WWOX Phosphorylation, Signaling, and Role in Neurodegeneration

Homozygous null mutation of tumor suppressor WWOX/Wwox gene leads to severe neural diseases, metabolic disorders and early death in the newborns of humans, mice and rats. WWOX is frequently downregulated in the hippocampi of patients with Alzheimer’s disease (AD). In vitro analysis revealed that knockdown of WWOX protein in neuroblastoma cells results in aggregation of TRAPPC6AΔ, TIAF1, amyloid β, and Tau in a sequential manner. Indeed, TRAPPC6AΔ and TIAF1, but not tau and amyloid β, aggregates are present in the brains of healthy mid-aged individuals. It is reasonable to assume that very slow activation of a protein aggregation cascade starts sequentially with TRAPPC6AΔ and TIAF1 aggregation at mid-ages, then caspase activation and APP de-phosphorylation and degradation, and final accumulation of amyloid β and Tau aggregates in the brains at greater than 70 years old. WWOX binds Tau-hyperphosphorylating enzymes (e.g., GSK-3β) and blocks their functions, thereby supporting neuronal survival and differentiation. As a neuronal protective hormone, 17β-estradiol (E2) binds WWOX at an NSYK motif in the C-terminal SDR (short-chain alcohol dehydrogenase/reductase) domain. In this review, we discuss how WWOX and E2 block protein aggregation during neurodegeneration, and how a 31-amino-acid zinc finger-like Zfra peptide restores memory loss in mice.

Wnt/β-catenin signaling as a potential target for novel epilepsy therapies

Epilepsy is one of the most common neurological disorders, and yet many afflicted individuals are resistant to all available therapeutic treatments. Existing pharmaceutical treatments function primarily to reduce hyperexcitability and prevent seizures, but fail to influence the underlying pathophysiology of the disorder. Recently, research efforts have focused on identifying alternative mechanistic targets for anti-epileptogenic therapies that can prevent the development of chronic epilepsy. The Wnt/β-catenin pathway, one possible target, has been demonstrated to be disrupted in both acute and chronic phases of epilepsy. Wnt/β-catenin signaling can regulate many seizure-induced changes in the brain, including neurogenesis and neuronal death, as well as can influence seizure susceptibility and potentially the development of chronic epilepsy. Several genome-wide studies and in vivo knockout animal models have provided evidence for an association between disrupted Wnt/β-catenin signaling and epilepsy. Furthermore, approved pharmaceutical drugs and other small molecule compounds that target components of the β-catenin destruction complex or antagonize endogenous inhibitors of the pathway have shown to be protective following seizures. However, additional studies are needed to determine the optimal time period in which modulation of the pathway may be most beneficial. Overall, disrupted molecular networks such as Wnt/β-catenin signaling, could be a promising anti-epileptogenic target for future epilepsy therapies.

Fanconi anemia complementation group C protection against oxidative stress‑induced β‑cell apoptosis

Diabetes mellitus (DM) and other glucose metabolism abnormalities are commonly observed in individuals with Fanconi anemia (FA). FA causes an impaired response to DNA damage due to genetic defects in a cluster of genes encoded proteins involved in DNA repair. However, the mechanism by which FA is associated with DM has not been clearly elucidated. Fanconi anemia complementation group C (FANCC) is a component of FA nuclear clusters. Evidence suggests that cytoplasmic FANCC has a role in protection against oxidative stress‑induced apoptosis. As oxidative stress‑mediated β‑cell dysfunction is one of the contributors to DM pathogenesis, the present study aimed to investigate the role of FANCC in pancreatic β‑cell response to oxidative stress. Small interfering RNA‑mediated FANCC suppression caused a loss of protection against oxidative stress‑induced apoptosis, and that overexpression of FANCC reduced this effect in the human 1.1B4 β‑cell line. These findings were confirmed by Annexin V‑FITC/PI staining, caspase 3/7 activity assay, and expression levels of anti‑apoptotic and pro‑apoptotic genes. Insulin and glucokinase mRNA expression were also decreased in FANCC‑depleted 1.1B4 cells. The present study demonstrated the role of FANCC in protection against oxidative stress‑induced β‑cell apoptosis and established another mechanism that associates FANCC deficiency with β‑cell dysfunction. The finding that FANCC overexpression reduced β‑cell apoptosis advances the potential for an alternative approach to the treatment of DM caused by FANCC defects.

Male and Female Mice Exhibit Divergent Responses of the Cortical Vasculature to Traumatic Brain Injury

We previously reported that traumatic brain injuries (TBI) alter the cerebrovasculature near the injury site in rats, followed by revascularization over a 2-week period. Here, we tested our hypothesis that male and female adult mice have differential cerebrovascular responses following a moderate controlled cortical impact (CCI). Using in vivo magnetic resonance imaging (MRI), a new technique called vessel painting, and immunohistochemistry, we found no differences between males and females in lesion volume, neurodegeneration, blood-brain barrier (BBB) alteration, and microglia activation. However, females exhibited more astrocytic hypertrophy and heme-oxygenase-1 (HO-1) induction at 1 day post-injury (dpi), whereas males presented with increased endothelial activation and expression of β-catenin, shown to be involved in angiogenesis. At 7 dpi, we observed an increase in the number of vessels and an enhancement in vessel complexity in the injured cortex of males compared with females. Cerebrovasculature recovers differently after CCI, suggesting biological sex should be considered when designing new therapeutic agents.