Role of wnt signaling in the control of adult hippocampal functioning in health and disease: therapeutic implications

Differential changes in Wnt7 and Dkk1 levels in astrocytes exposed to glutamate or TNFα

Wnt signaling plays an important role in adult brain function, and its dysregulation has been implicated in the loss of neuronal homeostasis. Despite the existence of many studies on the participation of the Wnt pathway in adult neurons, its regulation in astrocytes has been scarcely explored. Several reports point to the presence of Wnt ligands in astrocytes and their possible impact on neuronal plasticity or neuronal death. We aimed to analyze the effect of the neurotransmitter glutamate and the inflammatory cytokine TNFα on the mRNA and protein levels of the canonical Wnt agonist Wnt7a and the antagonist Dkk1 in cultured astrocytes. Primary astrocyte cultures from rat cerebral cortices were exposed to glutamate or TNFα. Wnt7a and Dkk1 expression was analyzed by RT-qPCR and its protein abundance and distribution was assessed by immunofluorescence. We found high basal expression and protein levels of Wnt7a and Dkk1 in unstimulated astrocytes and overproduction of Dkk1 mRNA induced by the two stimuli. These results reveal the astrocytic source of the canonical Wnt ligands Wnt7a and Dkk1, whose levels are differentially regulated by glutamate and TNFα. Astrocytes are a significant source of Wnt ligands, the production of which can be differentially regulated under excitatory or proinflammatory conditions, thereby impacting neuronal function.

Restoring Impaired Neurogenesis and Alleviating Oxidative Stress by Cyanidin against Bisphenol A-induced Neurotoxicity: In Vivo and In Vitro Evidence

BACKGROUND

Bisphenol A (BPA) is a known neurotoxic compound with potentially harmful effects on the nervous system. Cyanidin (CYN) has shown promise as a neuroprotective agent.

OBJECTIVE

The current study aims to determine the efficacy of CYN against BPA-induced neuropathology.

METHODS

In vitro experiments utilized PC12 cells were pre-treated with gradient doses of CYN and further stimulated with 10ng/ml of BPA. DPPH radical scavenging activity, catalase activity, total ROS activity, and nitric oxide radical scavenging activity were done. In vivo assessments employed doublecortin immunohistochemistry of the brain in BPA-exposed Sprague-Dawley rats. Further, In silico molecular docking of CYN with all proteins involved in canonical Wnt signaling was performed using the Autodock v4.2 tool and BIOVIA Discovery Studio Visualizer.

RESULTS

IC50 values of CYN and ascorbic acid were determined using dose-response curves, and it was found to be 24.68 ± 0.563 μg/ml and 20.69 ± 1.591μg/ml, respectively. BPA-stimulated cells pre-treated with CYN showed comparable catalase activity with cells pre-treated with ascorbic acid (p = 0.0287). The reactive species production by CYN-treated cells was significantly decreased compared to BPA-stimulated cells (p <0.0001). Moreover, CYN significantly inhibited nitric oxide production compared to BPA stimulated and the control cells (p < 0.0001). In vivo CYN positively affected immature neuron quantity, correlating with dosage. During molecular docking analysis, CYN exhibited a binding affinity > -7 Kcal/mol with all the key proteins associated with the Wnt/β- catenin signaling cascade.

CONCLUSION

Conclusively, our finding suggests that CYN exhibited promise in counteracting BPAinduced oxidative stress, improving compromised neurogenesis in hippocampal and cortical regions, and displaying notable interactions with Wnt signaling proteins. Thereby, CYN could render its neuroprotective potential against BPA-induced neuropathology.

Neurogenesis, A Potential Target for Intermittent Hypoxia Leading to Cognitive Decline

As a sleep breathing disorder, characterized by intermittent hypoxia (IH) and Obstructive sleep apnea (OSA), is believed to decrease the cognitive function of patients. Many factors are thought to be responsible for cognitive decline in OSA patients. Neurogenesis, a process by which neural stem cells (NSCs) differentiate into new neurons in the brain, is a major determinant affecting cognitive function. However, there is no clear relationship between IH or OSA and neurogenesis. In recent years, increasing numbers of studies on IH and neurogenesis are documented. Therefore, this review summarizes the effects of IH on neurogenesis; then discusses the influencing factors that may cause these effects and the potential signaling pathways that may exist. Finally, based on this impact, we discuss potential methods and future directions for improving cognition.

Region-Specific Characteristics of Astrocytes and Microglia: A Possible Involvement in Aging and Diseases

Although different regions of the brain are dedicated to specific functions, the intra- and inter-regional heterogeneity of astrocytes and microglia in these regions has not yet been fully understood. Recently, an advancement in various technologies, such as single-cell RNA sequencing, has allowed for the discovery of astrocytes and microglia with distinct molecular fingerprints and varying functions in the brain. In addition, the regional heterogeneity of astrocytes and microglia exhibits different functions in several situations, such as aging and neurodegenerative diseases. Therefore, investigating the region-specific astrocytes and microglia is important in understanding the overall function of the brain. In this review, we summarize up-to-date research on various intra- and inter-regional heterogeneities of astrocytes and microglia, and provide information on how they can be applied to aging and neurodegenerative diseases.

Molecular mechanisms of developmental pathways in neurological disorders: a pharmacological and therapeutic review

Developmental signalling pathways such as Wnt/β-catenin, Notch and Sonic hedgehog play a central role in nearly all the stages of neuronal development. The term 'embryonic' might appear to be a misnomer to several people because these pathways are functional during the early stages of embryonic development and adulthood, albeit to a certain degree. Therefore, any aberration in these pathways or their associated components may contribute towards a detrimental outcome in the form of neurological disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and stroke. In the last decade, researchers have extensively studied these pathways to decipher disease-related interactions, which can be used as therapeutic targets to improve outcomes in patients with neurological abnormalities. However, a lot remains to be understood in this domain. Nevertheless, there is strong evidence supporting the fact that embryonic signalling is indeed a crucial mechanism as is manifested by its role in driving memory loss, motor impairments and many other processes after brain trauma. In this review, we explore the key roles of three embryonic pathways in modulating a range of homeostatic processes such as maintaining blood-brain barrier integrity, mitochondrial dynamics and neuroinflammation. In addition, we extensively investigated the effect of these pathways in driving the pathophysiology of a range of disorders such as Alzheimer's, Parkinson's and diabetic neuropathy. The concluding section of the review is dedicated to neurotherapeutics, wherein we identify and list a range of biological molecules and compounds that have shown enormous potential in improving prognosis in patients with these disorders.

Molecular Insights to the Wnt Signaling During Alzheimer's Disorder: a Potential Target for Therapeutic Interventions

In the adult brain, Wnt signaling is crucial for neurogenesis, and it also regulates neuronal development, neuronal maturation, neuronal differential, and proliferation. Impaired Wnt signaling pathways are associated with enhanced levels of amyloid-β, reduced β-catenin levels, and increased expression of GSK-3β enzyme, suggesting its direct association with the pathogenesis of Alzheimer's disorder (AD). These findings are consolidated by reports where activation of Wnt signaling by genetic factors and pharmacological intervention has improved the cognitive functions in animals and restored neurogenesis in the adult brain. Various natural and synthetic molecules have been identified that modulate Wnt signaling in the adult brain and promote neurogenesis and alleviate behavioral dysfunction. These molecules include lithium, valproic acid, ethosuximide, selenomethionine, curcumin, andrographolide, xanthoceraside, huperzine A, pyridostigmine, ginkgolide-B, ricinine, cannabidiol, and resveratrol. These molecules are associated with the DKK1 and GSK-3β inhibition and β-catenin stabilization along with their effects on neurogenesis, neuronal proliferation, and differentiation in the hippocampus through modulation of Wnt signaling and thereby could prove beneficial in the management of AD pathogenesis. Although modulation of the Wnt signaling seems to suggest to be promising in the management of AD, unfortunately, most of the literature available for the association of Wnt signaling and AD pathogenesis is either from preclinical studies or post-mortem brain. Therefore, it will be interesting to understand the role of Wnt signaling in AD patients, and a rigorous investigation could provide us with a better understanding of AD pathogenesis and the identification of novel targets for therapeutic interventions.

The cognitive impairment and risk factors of the older people living in high fluorosis areas: DKK1 need attention

Objective

To evaluate cognitive impairment and risk factors of elders in high fluoride drinking water areas and investigate whether DKK1 is involved in this disorder.

Methods

MoCA-B and AD-8 were used to measure the cognitive functions of 272 and 172 subjects over the age of 60 came from the high and normal fluoride drinking water areas respectively, general information and peripheral blood were collected, the level of SOD, GSH and MDA were measured, mRNA level of DKK1, the concentration of blood fluoride and the polymorphism of APOE were tested.

Results

The blood fluoride concentration, mRNA level of DKK1 and ratio of abnormal cognitive function of subjects in high fluorine drinking water areas were higher than those in normal areas. The level of SOD of subjects in high fluorine drinking water was low compared with those in normal areas. The level of MDA and GSH had no difference between the two crowds in different fluorine drinking water areas. There were differences in cigarette smoking, education, dental status, hypertension, hyperlipidaemia and APOE results between the two crowds in different fluorine drinking water areas. The mRNA level of DKK1 and the level of cognitive function showed a positive correlation and DKK1 was one of five risk factors involved in cognitive impairment of older people living in high fluorosis areas.

Conclusions

The cognitive functions could be impaired in the older people living in high fluoride drinking water areas, and DKK1 may as a potential intervention point of this brain damage process need attention.

Parkinson's disease, aging and adult neurogenesis: Wnt/β-catenin signalling as the key to unlock the mystery of endogenous brain repair

A common hallmark of age-dependent neurodegenerative diseases is an impairment of adult neurogenesis. Wingless-type mouse mammary tumor virus integration site (Wnt)/β-catenin (WβC) signalling is a vital pathway for dopaminergic (DAergic) neurogenesis and an essential signalling system during embryonic development and aging, the most critical risk factor for Parkinson's disease (PD). To date, there is no known cause or cure for PD. Here we focus on the potential to reawaken the impaired neurogenic niches to rejuvenate and repair the aged PD brain. Specifically, we highlight WβC-signalling in the plasticity of the subventricular zone (SVZ), the largest germinal region in the mature brain innervated by nigrostriatal DAergic terminals, and the mesencephalic aqueduct-periventricular region (Aq-PVR) Wnt-sensitive niche, which is in proximity to the SNpc and harbors neural stem progenitor cells (NSCs) with DAergic potential. The hallmark of the WβC pathway is the cytosolic accumulation of β-catenin, which enters the nucleus and associates with T cell factor/lymphoid enhancer binding factor (TCF/LEF) transcription factors, leading to the transcription of Wnt target genes. Here, we underscore the dynamic interplay between DAergic innervation and astroglial-derived factors regulating WβC-dependent transcription of key genes orchestrating NSC proliferation, survival, migration and differentiation. Aging, inflammation and oxidative stress synergize with neurotoxin exposure in "turning off" the WβC neurogenic switch via down-regulation of the nuclear factor erythroid-2-related factor 2/Wnt-regulated signalosome, a key player in the maintenance of antioxidant self-defense mechanisms and NSC homeostasis. Harnessing WβC-signalling in the aged PD brain can thus restore neurogenesis, rejuvenate the microenvironment, and promote neurorescue and regeneration.

Decoding the development of the human hippocampus

The hippocampus is an important part of the limbic system in the human brain that has essential roles in spatial navigation and the consolidation of information from short-term memory to long-term memory^1,2. Here we use single-cell RNA sequencing and assay for transposase-accessible chromatin using sequencing (ATAC-seq) analysis to illustrate the cell types, cell linage, molecular features and transcriptional regulation of the developing human hippocampus. Using the transcriptomes of 30,416 cells from the human hippocampus at gestational weeks 16-27, we identify 47 cell subtypes and their developmental trajectories. We also identify the migrating paths and cell lineages of PAX6⁺ and HOPX⁺ hippocampal progenitors, and regional markers of CA1, CA3 and dentate gyrus neurons. Multiomic data have uncovered transcriptional regulatory networks of the dentate gyrus marker PROX1. We also illustrate spatially specific gene expression in the developing human prefrontal cortex and hippocampus. The molecular features of the human hippocampus at gestational weeks 16-20 are similar to those of the mouse at postnatal days 0-5 and reveal gene expression differences between the two species. Transient expression of the primate-specific gene NBPF1 leads to a marked increase in PROX1⁺ cells in the mouse hippocampus. These data provides a blueprint for understanding human hippocampal development and a tool for investigating related diseases.

Elevations in Serum Dickkopf-1 and Disease Progression in Community-Dwelling Older Adults With Mild Cognitive Impairment and Mild-to-Moderate Alzheimer's Disease

Background: Disruption of Wnt signaling has been implicated in dysfunctional synaptic plasticity, the degree of which correlates with Alzheimer's disease severity. We sought to examine whether serum levels of Dickkopf-1 (Dkk-1), a Wnt antagonist, are associated with global disease progression in older adults with mild cognitive impairment (MCI) and mild-to-moderate AD. Methods: We prospectively followed 88 older adults with MCI and mild-to-moderate AD attending a Memory Clinic. Cognitive performance, functional performance and neuropsychological symptoms were assessed at baseline and after 1 year. We reviewed neuroimaging for white matter changes and medial temporal atrophy, and performed ApoE genotyping at baseline. Serum Dkk-1 was assayed at baseline and 1 year, along with blood biomarkers of inflammation and endocrine dysfunction. We defined global disease progression ("progressors") as an increase in Clinical Dementia Rating Sum-of-Boxes (CDR-SB) score by >2 points at 1 year. Results: Fifteen (17.0%) participants had global disease progression. At baseline, there was no difference in cognitive performance and neuropsychiatric symptoms between groups, although progressors were more impaired in instrumental activities of daily living (p = 0.008). Progressors had significantly greater deterioration in cognitive performance (p = 0.002), with significantly worse functional performance and more severe neuropsychiatric symptoms (p = 0.042) at follow-up. Serum inflammatory and endocrine biomarkers at baseline and 1 year were similar between progressors and non-progressors. Serum Dkk-1 had increased significantly from baseline amongst progressors, while non-progressors exhibited decremental Dkk-1 over time (Dkk-1_change: 354.304 ± 670.467 vs. -173.582 ± 535.676 ng/ml, p = 0.001). Adjusting for age, gender and baseline cognitive performance, incremental Dkk-1 independently predicted global cognitive decline (p = 0.012). Conclusion: Our results suggest progressively dysfunctional Wnt signaling through Dkk-1 antagonism contributes to disease progression amongst older adults with MCI and mild-moderate AD.

Salvador-Warts-Hippo pathway regulates sensory organ development via caspase-dependent nonapoptotic signaling

The fundamental roles for the Salvador–Warts–Hippo (SWH) pathway are widely characterized in growth regulation and organ size control. However, the function of SWH pathway is less known in cell fate determination. Here we uncover a novel role of the SWH signaling pathway in determination of cell fate during neural precursor (sensory organ precursor, SOP) development. Inactivation of the SWH pathway in SOP of the wing imaginal discs affects caspase-dependent bristle patterning in an apoptosis-independent process. Such nonapoptotic functions of caspases have been implicated in inflammation, proliferation, cellular remodeling, and cell fate determination. Our data indicate an effect on the Wingless (Wg)/Wnt pathway. Previously, caspases were proposed to cleave and activate a negative regulator of Wg/Wnt signaling, Shaggy (Sgg)/GSK3β. Surprisingly, we found that a noncleavable form of Sgg encoded from the endogenous locus after CRISPR-Cas9 modification supported almost normal bristle patterning, indicating that Sgg might not be the main target of the caspase-dependent nonapoptotic process. Collectively, our results outline a new function of SWH signaling that crosstalks to caspase-dependent nonapoptotic signaling and Wg/Wnt signaling in neural precursor development, which might be implicated in neuronal pathogenesis.

Panoramic Visualization of Circulating MicroRNAs Across Neurodegenerative Diseases in Humans

Neurodegenerative diseases (NDs) such as Alzheimer’s disease (AD), Parkinson’s disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), and dementia pose one of the greatest health challenges this century. Although these NDs have been looked at as single entities, the underlying molecular mechanisms have never been collectively visualized to date. With the advent of high-throughput genomic and proteomic technologies, we now have the opportunity to visualize these diseases in a whole new perspective, which will provide a clear understanding of the primary and secondary events vital in achieving the final resolution of these diseases guiding us to new treatment strategies to possibly treat these diseases together. We created a knowledge base of all microRNAs known to be differentially expressed in various body fluids of ND patients. We then used several bioinformatic methods to understand the functional intersections and differences between AD, PD, ALS, and MS. These results provide a unique panoramic view of possible functional intersections between AD, PD, MS, and ALS at the level of microRNA and their cognate genes and pathways, along with the entities that unify and separate them. While the microRNA signatures were apparent for each ND, the unique observation in our study was that hsa-miR-30b-5p overlapped between all four NDS, and has significant functional roles described across NDs. Furthermore, our results also show the evidence of functional convergence of miRNAs which was associated with the regulation of their cognate genes represented in pathways that included fatty acid synthesis and metabolism, ECM receptor interactions, prion diseases, and several signaling pathways critical to neuron differentiation and survival, underpinning their relevance in NDs. Envisioning this group of NDs together has allowed us to propose new ways of utilizing circulating miRNAs as biomarkers  and in visualizing diverse NDs more holistically . The critical molecular insights gained through the discovery of ND-associated miRNAs, overlapping miRNAs, and the functional convergence of microRNAs on vital pathways strongly implicated in neurodegenerative processes can prove immensely valuable in the identifying new generation of biomarkers, along with the development of miRNAs into therapeutics.

Dkk1 involvement and its potential as a biomarker in pancreatic ductal adenocarcinoma

Dickkopf-1 (Dkk1)'s dysregulation has been implicated in the pathogenesis of a variety of cancers. It is part of the Dkk family of proteins that includes Dkk2, Dkk3 and Dkk4. This family of secreted proteins shares similar conserved cysteine domains and inhibits the Wnt/b-catenin pathway by causing proteasomal B-catenin degradation, inducing apoptosis, and preventing cell proliferation. Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer mortality in the United States due to the late stage of diagnosis and the limited effectiveness of current therapy. Dkk1 is found increased in PADC patients' specimens and serum. Dkk1 can be a promising biomarker specific to PDAC, which has the potential to increase PDAC survival rates through improving early stage detection and monitoring progression compared to current biomarker gold standards. In addition, recent studies suggest that Dkk1 could be an excellent target for cancer immunotherapy. Interestingly, Dkk1-CKAP4-PI3K/AKT signal pathway also plays role in pancreatic cancer cell proliferation. In this review, we present the multiple mechanisms of Dkk1 in PDAC studied thus far and explore its function, regulation, and clinical applications in gynecological cancers including pancreatic ductal adenocarcinoma (PDAC), breast, ovarian, cervical, and endometrial cancer. Further research into Dkk1's mechanism and use as a diagnostic tool, alone or in combination with other biomarkers, could prove clinically useful for better understanding the pathology of PDAC and improving its early detection and treatment.

Liraglutide Protects Neurite Outgrowth of Cortical Neurons Under Oxidative Stress though Activating the Wnt Pathway

BACKGROUND

Neurogenesis including neurite outgrowth is important for brain plasticity under physiological conditions and in brain repair after injury. Liraglutide has been found to have neuroprotective action in the risk of central nervous system disease. However, the effect and the potential mechanism of liraglutide-induced neurite outgrowth in primary cortical neurons under oxidative stress remain poorly documented.

METHODS

In the text, H₂O₂ was used to mimic ischemia injury in primary cortical neurons. The viability and apoptosis of cell was assessed by Cell Counting Kit-8 and Hoechst 33342. Immunofluorescence method was used to examine the effect of liraglutide on neurite outgrowth in cortical neuron under H₂O₂ condition. Then, the potential mechanisms involving the Wnt pathway were investigated. The expression of β-catenin, c-myc, and cyclin D1 was determined using quantitative real-time polymerase chain reaction and Western blot.

RESULTS

Liraglutide significantly increased the viability and alleviated the apoptosis rate of cortical neurons induced by H₂O₂. Next, liraglutide promoted neurite outgrowth, which could be partially inhibited by the Wnt pathway inhibitor Xav939. Besides, liraglutide induced an increase of β-catenin, c-myc, and cyclin D1 levels, which could also be blocked in the presence of Xav939.

CONCLUSIONS

These results illustrate that liraglutide exerts neurotrophin-like activity in cortical neurons under oxidative stress condition, partly through activating the Wnt pathway.

miRNA-431 Prevents Amyloid-β-Induced Synapse Loss in Neuronal Cell Culture Model of Alzheimer's Disease by Silencing Kremen1

Synapse loss is well regarded as the underlying cause for the progressive decline of memory function over the course of Alzheimer's disease (AD) development. Recent observations suggest that the accumulation of the Wnt antagonist Dickkopf-1 (Dkk1) in the AD brain plays a critical role in triggering synaptic degeneration. Mechanistically, Dkk1 cooperates with Kremen1 (Krm1), its transmembrane receptor, to block the Wnt/β-catenin signaling pathway. Here, we show that silencing Krm1 with miR-431 prevents amyloid-β-mediated synapse loss in cortico-hippocampal cultures isolated from triple transgenic 3xTg-AD mice. Exposure to AβDDL (an amyloid-β derived diffusive ligand) or Dkk1 reduced the number of pre- and post-synaptic puncta in primary neuronal cultures, while treatment with miR-431 prevented synapse loss. In addition, treatment with miR-431 also prevented neurite degeneration. Our findings demonstrate that miR-431 protects synapses and neurites from Aβ-toxicity in an AD cell culture model and may be a promising therapeutic target.

Aberrant DNA methylation associated with Alzheimer's disease in the superior temporal gyrus

Abnormal DNA methylation patterns have been demonstrated to be associated with the pathogenesis of Alzheimer's disease (AD). The present study aimed to identify differential methylation in the superior temporal gyrus (STG) of patients with late-onset AD based on epigenome-wide DNA methylation data by bioinformatics analysis. The genome-wide DNA methylation data in the STG region of 34 patients with late-onset AD and 34 controls without dementia were recruited from the Gene Expression Omnibus database. Through systemic quality control, differentially methylated CpG sites were determined by the Student's t-test and mean methylation value differences between the two conditions. Hierarchical clustering analysis was applied to assess the classification performance of differentially methylated CpGs. Functional analysis was performed to investigate the biological functions of the genes associated with differentially methylated CpGs. A total of 17,895 differentially methylated CpG sites were initially identified, including 11,822 hypermethylated CpGs and 6,073 hypomethylated CpGs. Further analysis examined 2,211 differentially methylated CpGs (covering 1,991 genes). AD subjects demonstrated distinctive DNA methylation patterns when compared with the controls, with a classification accuracy value of 1. Hypermethylation was mainly detected for genes regulating the cell cycle progression, whereas hypomethylation was observed in genes involved in transcription factor binding. The present study demonstrated widespread and distinctive DNA methylation alterations in late-onset AD. Identification of AD-associated epigenetic biomarkers may allow for the development of novel diagnostic and therapeutic targets.

Methods of reactivation and reprogramming of neural stem cells for neural repair

Research on the biology of adult neural stem cells (NSCs) and induced NSCs (iNSCs), as well as NSC-based therapies for diseases in central nervous system (CNS) has started to generate the expectation that these cells may be used for treatments in CNS injuries or disorders. Recent technological progresses in both NSCs themselves and their derivatives have brought us closer to therapeutic applications. Adult neurogenesis presents in particular regions in mammal brain, known as neurogenic niches such as the dental gyrus (DG) in hippocampus and the subventricular zone (SVZ), within which adult NSCs usually stay for long periods out of the cell cycle, in G0. The reactivation of quiescent adult NSCs needs orchestrated interactions between the extrinsic stimulis from niches and the intrinsic factors involving transcription factors (TFs), signaling pathway, epigenetics, and metabolism to start an intracellular regulatory program, which promotes the quiescent NSCs exit G0 and reenter cell cycle. Extrinsic and intrinsic mechanisms that regulate adult NSCs are interconnected and feedback on one another. Since endogenous neurogenesis only happens in restricted regions and steadily fails with disease advances, interest has evolved to apply the iNSCs converted from somatic cells to treat CNS disorders, as is also promising and preferable. To overcome the limitation of viral-based reprogramming of iNSCs, bioactive small molecules (SM) have been explored to enhance the efficiency of iNSC reprogramming or even replace TFs, making the iNSCs more amenable to clinical application. Despite intense research efforts to translate the studies of adult and induced NSCs from the bench to bedside, vital troubles remain at several steps in these processes. In this review, we examine the present status, advancement, pitfalls, and potential of the two types of NSC technologies, focusing on each aspects of reactivation of quiescent adult NSC and reprogramming of iNSC from somatic cells, as well as on progresses in cell-based regenerative strategies for neural repair and criteria for successful therapeutic applications.

Ethosuximide Induces Hippocampal Neurogenesis and Reverses Cognitive Deficits in an Amyloid-β Toxin-induced Alzheimer Rat Model via the Phosphatidylinositol 3-Kinase (PI3K)/Akt/Wnt/β-Catenin Pathway

Neurogenesis involves generation of new neurons through finely tuned multistep processes, such as neural stem cell (NSC) proliferation, migration, differentiation, and integration into existing neuronal circuitry in the dentate gyrus of the hippocampus and subventricular zone. Adult hippocampal neurogenesis is involved in cognitive functions and altered in various neurodegenerative disorders, including Alzheimer disease (AD). Ethosuximide (ETH), an anticonvulsant drug is used for the treatment of epileptic seizures. However, the effects of ETH on adult hippocampal neurogenesis and the underlying cellular and molecular mechanism(s) are yet unexplored. Herein, we studied the effects of ETH on rat multipotent NSC proliferation and neuronal differentiation and adult hippocampal neurogenesis in an amyloid β (Aβ) toxin-induced rat model of AD-like phenotypes. ETH potently induced NSC proliferation and neuronal differentiation in the hippocampus-derived NSC in vitro. ETH enhanced NSC proliferation and neuronal differentiation and reduced Aβ toxin-mediated toxicity and neurodegeneration, leading to behavioral recovery in the rat AD model. ETH inhibited Aβ-mediated suppression of neurogenic and Akt/Wnt/β-catenin pathway gene expression in the hippocampus. ETH activated the PI3K·Akt and Wnt·β-catenin transduction pathways that are known to be involved in the regulation of neurogenesis. Inhibition of the PI3K·Akt and Wnt·β-catenin pathways effectively blocked the mitogenic and neurogenic effects of ETH. In silico molecular target prediction docking studies suggest that ETH interacts with Akt, Dkk-1, and GSK-3β. Our findings suggest that ETH stimulates NSC proliferation and differentiation in vitro and adult hippocampal neurogenesis via the PI3K·Akt and Wnt·β-catenin signaling.

Diagnostic value of SFRP1 as a favorable predictive and prognostic biomarker in patients with prostate cancer

Growing genetic and molecular biological evidence suggests that the disruption of balance between Secreted Frizzled-Related Protein-1 (SFRP1) and β-catenin plays an important role in the initiation and development of multiple cancers. The aim of this study was to examine whether the expression of SFRP1 and β-catenin is associated with the clinical-pathologic features of patients with prostate cancer (PCa), and to evaluate their potential roles as predictive and prognostic biomarkers. In this study, a total of 61 patients with PCa and 10 patients with benign prostatic hyperplasia were included, and we showed that the expression of SFRP1 and β-catenin was correlated with the Gleason score, survival rate and response for endocrine therapy of PCa. The survival rates of PCa patients with low SFRP1 expression (P = 0.016) or high β-catenin expression (P = 0.004) were significantly poorer. A negative correlation (r = -0.275, P = 0.032) between SFRP1 and β-catenin was observed by Chi-square test. Multivariate analysis suggested that SFRP1 (hazard ratio, 0.429; 95% confidence intervals, 0.227–0.812; P = 0.009) may serve as an independent predictive and prognostic factor for PCa. We also showed that the protein and mRNA levels of SFRP1 in androgen-dependent PCa cell line LNCaP were significantly higher than those in androgen-independent PCa cell lines DU145 and PC3. However, the protein level of β-catenin in LNCaP cells was significantly lower than that in DU145 and PC3 cells, and no significant difference of β-catenin mRNA level was observed in LNCaP, DU145 and PC3 cells. Bisulfite sequencing PCR assay revealed significantly lower methylation level of SFRP1 promoter in LNCaP cells than that in DU145 and PC3 cells. Taken together, these findings suggest that SFRP1, which expression inversely correlates with that of β-catenin, is a favorable predictive and prognostic biomarker.

Neurogenesis in the embryonic and adult brain: same regulators, different roles

Neurogenesis persists in adult mammals in specific brain areas, known as neurogenic niches. Adult neurogenesis is highly dynamic and is modulated by multiple physiological stimuli and pathological states. There is a strong interest in understanding how this process is regulated, particularly since active neuronal production has been demonstrated in both the hippocampus and the subventricular zone (SVZ) of adult humans. The molecular mechanisms that control neurogenesis have been extensively studied during embryonic development. Therefore, we have a broad knowledge of the intrinsic factors and extracellular signaling pathways driving proliferation and differentiation of embryonic neural precursors. Many of these factors also play important roles during adult neurogenesis, but essential differences exist in the biological responses of neural precursors in the embryonic and adult contexts. Because adult neural stem cells (NSCs) are normally found in a quiescent state, regulatory pathways can affect adult neurogenesis in ways that have no clear counterpart during embryogenesis. BMP signaling, for instance, regulates NSC behavior both during embryonic and adult neurogenesis. However, this pathway maintains stem cell proliferation in the embryo, while it promotes quiescence to prevent stem cell exhaustion in the adult brain. In this review, we will compare and contrast the functions of transcription factors (TFs) and other regulatory molecules in the embryonic brain and in adult neurogenic regions of the adult brain in the mouse, with a special focus on the hippocampal niche and on the regulation of the balance between quiescence and activation of adult NSCs in this region.