Regulation of Adult Neurogenesis in Mammalian Brain

TREM2 promotes hippocampal neurogenesis through regulating microglial M2 polarization in APP/PS1 mice

Triggering receptor expressed on myeloid cells-2 (TREM2) mainly expressed on microglia in the brain, and its mutations can increase the risk of Alzheimer's disease (AD). Upregulation or activation of TREM2 has been found to ameliorate several pathological features of AD, such as the reduction of amyloid beta (Aβ) plaques and tau hyperphosphorylation. However, the effects of TREM2 on neurogenesis are little understood. Here, we aimed to investigate the effects of TREM2 on hippocampal neurogenesis associated with microglial M2 polarization in APP/PS1 mice. Lentivirus vectors were used to interfere with the expression of TREM2 on microglia in the hippocampus of APP/PS1 mice and BV2 cells. The supernatant was collected from BV2 cells as a conditioned medium (CM) to culture neural stem cells (NSCs) in vitro. Upregulation of TREM2 partially salvaged the proliferation of NSCs and the decrease of the number of immature/mature neurons in the hippocampus of APP/PS1 mice, which was accompanied by an improvement in cognitive ability. Furthermore, upregulation of TREM2 increased the M2 microglia marker CD206, brain-derived neurotrophic factor (BDNF), and anti-inflammatory factors, while decreased the M1 microglia markers CD16/32 and CD86 and pro-inflammatory factors in vivo and in vitro. Importantly, the upregulation of TREM2 also led to a significant increase in the phosphorylation of PI3K and Akt. In vitro, treatment with LY294002, a PI3K inhibitor, abolished the beneficial effects of TREM2 on shifting microglia from M1 to M2 and the proliferation and differentiation of NSCs. Taken together, these findings indicated that upregulation of TREM2 activated the PI3K/Akt signaling pathway to promote microglial M2 polarization and led to the secretion of more BDNF, accompanied by an improved hippocampal neurogenesis and spatial cognitive function in APP/PS1 mice. Thus, TREM2 might be a promising target for the treatment of neurodegenerative disease.

The subventricular zone structure, function and implications for neurological disease

The subventricular zone (SVZ) is a region surrounding the lateral ventricles that contains neural stem cells and neural progenitor cells, which can proliferate and differentiate into various neural and glial cells. SVZ cells play important roles in neurological diseases like neurodegeneration, neural injury, and glioblastoma multiforme. Investigating the anatomy, structure, composition, physiology, disease associations, and related mechanisms of SVZ is significant for neural stem cell therapy and treatment/prevention of neurological disorders. However, challenges remain regarding the mechanisms regulating SVZ cell proliferation, differentiation, and migration, delivering cells to damaged areas, and immune responses. In-depth studies of SVZ functions and related therapeutic developments may provide new insights and approaches for treating brain injuries and degenerative diseases, as well as a scientific basis for neural stem cell therapy. This review summarizes research findings on SVZ and neurological diseases to provide references for relevant therapies.

Environmental enrichment: a neurostimulatory approach to aging and ischemic stroke recovery and rehabilitation

Environmental enrichment (EE) represents a robust experimental framework exploring the intricate interplay between genes and the environment in shaping brain development and function. EE is recognized as a non-invasive intervention, easily translatable to elderly human cohorts, and extrapolated from research on animal aging models. Age is the most important risk factor for ischemic stroke. Research indicates that EE, characterized by increased sensory, cognitive, and social stimulation, leads to structural changes in the brain, such as enhanced dendritic complexity and synaptic density, particularly in the hippocampus and cortex. Tailored EE interventions for elderly stroke survivors include cognitively stimulating activities and participation in social groups. These interventions enhance cognitive function and support recovery by promoting neural repair. Additionally, EE helps to mitigate sensory deficits commonly observed in older adults, ultimately improving mental performance and quality of life. EE has shown promise in preventing relapse, enhancing attention, reducing anxiety, forestalling age-related DNA methylation alterations, and amplifying neurogenesis through heightened neural progenitor cell (NPC) populations. Aligning preclinical studies with clinical trials can enhance neurorehabilitation conditions for stroke patients, thereby optimizing the environments in which they recover. This can be achieved through the concerted efforts of multidisciplinary teams working collaboratively. This review explores how EE specifically impacts the aging brain and ischemic stroke, a major age-related neurological disorder with global health implications. The potential of enviro-mimetics and relevant clinical studies on EE's effects on ischemic stroke survivors are discussed. This review enhances our understanding of the effects of EE on aging and ischemic stroke, motivating further research aimed at refining strategies for stroke management and recovery.

The possible role of cerebrolysin in the management of vascular dementia: Leveraging concepts

Cerebrolysin (CBL) is a combination of neurotrophic peptides and amino acids derived from pig brains. CBL can cross the blood-brain barrier (BBB) and its biological effect is similar to the effect of endogenous neurotrophic effects. The mechanism of action of CBL is related to the induction of neurogenesis, neuroplasticity, neuroprotection, and neurotrophicity. Therefore, CBL may be effective against the development and progression of neurodegenerative diseases such as Alzheimer disease (AD) and cerebrovascular disorders such as vascular dementia (VD). Moreover, many studies highlighted that CBL is effective in the improvement of cognitive impairment in patients with neurodegenerative diseases. However, the underlying neuroprotective effects of CBL against the VD neuropathology were not fully elucidated. Thus, this review aims to discuss the possible therapeutic efficacy of CBL in the management of VD. In conclusion, CBL could be effective therapeutic strategy in preventing and treating VD by targeting neuroinflammation, BBB injury, and chronic cerebral hypoperfusion.

Cellular Stem Cell Therapy for Treating Traumatic Brain Injury: Strategies for Enhancement of Therapeutic Efficacy

Traumatic brain injury (TBI) influences a considerable population globally. TBI notably impacts both fatalities and disabilities worldwide. The mortality related to TBI is a significant concern in public health, affecting persons across various age groups and demographic profiles. More research and preventative interventions are required to alleviate TBIs' effects and optimize patient outcomes. Stem cell (SC) treatment exhibits promise as a viable strategy for addressing TBI due to its capacity to possibly restore or regenerate the compromised cells within the central nervous system. Additionally, it can influence the inflammatory response and increase neurogenesis and neuroplasticity. Increasing evidence has shown that SC transplantation has the potential to enhance functional recovery and decrease the extent of lesions in animal models of TBI. Nevertheless, several hurdles and ambiguities persist in determining the most effective source, dosage, administration method, timing, and mechanism of action for SC treatment for TBI. Further investigation is required to prove the safety and effectiveness of SC treatment for TBI in human subjects. This review brings insight into the strategies for utilizing SCs as cellular therapy for TBI, mainly based on preclinical investigations and TBI-induced animal models. In addition, this study also addresses many elements related to cell transfusion in the context of TBI, including considerations of cell amount, method, and timing. Integrating biomaterials and genetically altering SCs as potential strategies to enhance therapeutic efficacy are also presented. We also describe the potential of SCs in treating TBI and evaluate the effectiveness of cellular therapy and its corresponding outcomes.

Adaptogens in Long-Lasting Brain Fatigue: An Insight from Systems Biology and Network Pharmacology

Long-lasting brain fatigue is a consequence of stroke or traumatic brain injury associated with emotional, psychological, and physical overload, distress in hypertension, atherosclerosis, viral infection, and aging-related chronic low-grade inflammatory disorders. The pathogenesis of brain fatigue is linked to disrupted neurotransmission, the glutamate-glutamine cycle imbalance, glucose metabolism, and ATP energy supply, which are associated with multiple molecular targets and signaling pathways in neuroendocrine-immune and blood circulation systems. Regeneration of damaged brain tissue is a long-lasting multistage process, including spontaneously regulating hypothalamus-pituitary (HPA) axis-controlled anabolic-catabolic homeostasis to recover harmonized sympathoadrenal system (SAS)-mediated function, brain energy supply, and deregulated gene expression in rehabilitation. The driving mechanism of spontaneous recovery and regeneration of brain tissue is a cross-talk of mediators of neuronal, microglia, immunocompetent, and endothelial cells collectively involved in neurogenesis and angiogenesis, which plant adaptogens can target. Adaptogens are small molecules of plant origin that increase the adaptability of cells and organisms to stress by interaction with the HPA axis and SAS of the stress system (neuroendocrine-immune and cardiovascular complex), targeting multiple mediators of adaptive GPCR signaling pathways. Two major groups of adaptogens comprise (i) phenolic phenethyl and phenylpropanoid derivatives and (ii) tetracyclic and pentacyclic glycosides, whose chemical structure can be distinguished as related correspondingly to (i) monoamine neurotransmitters of SAS (epinephrine, norepinephrine, and dopamine) and (ii) steroid hormones (cortisol, testosterone, and estradiol). In this narrative review, we discuss (i) the multitarget mechanism of integrated pharmacological activity of botanical adaptogens in stress overload, ischemic stroke, and long-lasting brain fatigue; (ii) the time-dependent dual response of physiological regulatory systems to adaptogens to support homeostasis in chronic stress and overload; and (iii) the dual dose-dependent reversal (hormetic) effect of botanical adaptogens. This narrative review shows that the adaptogenic concept cannot be reduced and rectified to the various effects of adaptogens on selected molecular targets or specific modes of action without estimating their interactions within the networks of mediators of the neuroendocrine-immune complex that, in turn, regulates other pharmacological systems (cardiovascular, gastrointestinal, reproductive systems) due to numerous intra- and extracellular communications and feedback regulations. These interactions result in polyvalent action and the pleiotropic pharmacological activity of adaptogens, which is essential for characterizing adaptogens as distinct types of botanicals. They trigger the defense adaptive stress response that leads to the extension of the limits of resilience to overload, inducing brain fatigue and mental disorders. For the first time, this review justifies the neurogenesis potential of adaptogens, particularly the botanical hybrid preparation (BHP) of Arctic Root and Ashwagandha, providing a rationale for potential use in individuals experiencing long-lasting brain fatigue. The review provided insight into future research on the network pharmacology of adaptogens in preventing and rehabilitating long-lasting brain fatigue following stroke, trauma, and viral infections.

Muscle Cathepsin B treatment improves behavioral and neurogenic deficits in a mouse model of Alzheimer's Disease

Muscle secretes factors during exercise that enhance cognition. Myokine Cathepsin B (Ctsb) is linked to memory function, but its role in neurodegenerative disease is unclear. Here we show that AAV-vector-mediated Ctsb overexpression in skeletal muscle in an Alzheimer's Disease (AD) mouse model (APP/PS1), improves motor coordination, memory function and adult hippocampal neurogenesis, while plaque pathology and neuroinflammation remain unchanged. Additionally, in AD mice, Ctsb treatment modifies hippocampal, muscle and plasma proteomic profiles to resemble that of wildtype controls. Conversely, in wildtype mice, Ctsb expression causes memory deficits and results in protein profiles across tissues that are comparable to AD control mice. In AD mice, Ctsb treatment increases the abundance of hippocampal proteins involved in mRNA metabolism and protein synthesis, including those relevant to adult hippocampal neurogenesis and memory function. Furthermore, Ctsb treatment enhances plasma metabolic and mitochondrial processes, and reduces inflammatory responses. In muscle, Ctsb expression elevates protein translation in AD mice, whereas in wildtype mice mitochondrial proteins decrease. Overall, the biological changes in the treatment groups are consistent with effects on memory function. Thus, skeletal muscle Ctsb application has potential as an AD therapeutic intervention.

Adult Neurogenesis in the Subventricular Zone of Patients with Huntington's and Parkinson's Diseases and following Long-Term Treatment with Deep Brain Stimulation

OBJECTIVE

Parkinson's and Huntington's diseases are characterized by progressive neuronal loss. Previous studies using human postmortem tissues have shown the impact of neurodegenerative disorders on adult neurogenesis. The extent to which adult neural stem cells are activated in the subventricular zone and whether therapeutic treatments such as deep brain stimulation promote adult neurogenesis remains unclear. The goal of the present study is to assess adult neural stem cells activation and neurogenesis in the subventricular zone of patients with Huntington's and Parkinson's diseases who were treated or not by deep brain stimulation.

METHODS

Postmortem brain samples from Huntington's and Parkinson's disease patients who had received or not long-term deep brain stimulation of the subthalamic nucleus were used.

RESULTS

Our results indicate a significant increase in the thickness of the subventricular zone and in the density of proliferating cells and activated stem cells in the brain of Huntington's disease subjects and Parkinson's disease patients treated with deep brain stimulation. We also observed an increase in the density of immature neurons in the brain of these patients.

INTERPRETATION

Overall, our data indicate that long-term deep brain stimulation of the subthalamic nucleus promotes cell proliferation and neurogenesis in the subventricular zone that are reduced in Parkinson's disease. Taken together, our results also provide a detailed characterization of the cellular composition of the adult human subventricular zone and caudate nucleus in normal condition and in Parkinson's and Huntington's diseases and demonstrate the plasticity of these regions in response to neurodegeneration. ANN NEUROL 2025.

Emerging Pro-neurogenic Therapeutic Strategies for Neurodegenerative Diseases: A Review of Pre-clinical and Clinical Research

The neuroscience community has largely accepted the notion that functional neurons can be generated from neural stem cells in the adult brain, especially in two brain regions: the subventricular zone of the lateral ventricles and the subgranular zone in the dentate gyrus of the hippocampus. However, impaired neurogenesis has been observed in some neurodegenerative diseases, particularly in Alzheimer's, Parkinson's, and Huntington's diseases, and also in Lewy Body dementia. Therefore, restoration of neurogenic function in neurodegenerative diseases emerges as a potential therapeutic strategy to counteract, or at least delay, disease progression. Considering this, the present study summarizes the different neuronal niches, provides a collection of the therapeutic potential of different pro-neurogenic strategies in pre-clinical and clinical research, providing details about their possible modes of action, to guide future research and clinical practice.

Catalpol promotes hippocampal neurogenesis and synaptogenesis in rats after multiple cerebral infarctions by mitochondrial regulation: involvement of the Shh signaling pathway

Introduction

Ischemic stroke greatly threatens human life and health. Neuro-restoration is considered to be the critical points in reestablishing neurological function and improving the quality of life of patients. Catalpol is the main active ingredient of the Chinese herbal medicine Dihuang, which has the beneficial efficacy in traditional remedy, is closely related to the mitochondrial morphology and function. In the present study, we investigated whether catalpol has a neurorestorative effect after multiple cerebral infarctions and its underlying mechanisms.

Methods

In this study, male 8-week-old Sprague-Dawley (SD) rats were grouped according to neurological deficit scores to minimize differences between groups the second day: sham group, model group, Ginkgo biloba P.E (EGb) (Ginaton:18 mg/kg) group, model + CAT 30 mg/kg group (CAT 30), model + CAT 60 mg/kg group (CAT 60), and model + CAT 120 mg/kg group (CAT 120). From the first day to the fourteenth day after MCI, rats were given the corresponding doses of drugs by gastric administration every day(1 mL/100g), and from day 7 to day 14, all rats were injected with Brdu solution (50 mg/kg) i.p. Neuro-Function was assessed by the neurologic deficit scores. Then we observed measurement of brain atrophy and fluorescent Nissl staining. The expression of BrdU+/DCX+ cells and the BDNF concentrations were tested to observe the neuro-restoration effect. Transmission electron microscope (TEM) and Western blot (WB) were used to observed synaptogenesis. we observed the restoration of mitochondrial function by detecting the intracortical calcium and T-AOC content. Finally, we examined the protein and mRNA expression of shh signaling pathway through q-PCR and WB.

Results

Catalpol alleviated neurological deficits, reduced the degree of brain atrophy, as well as minimize pathological damage in the hippocampus and cortex. In addition, catalpol also promoted hippocampal neurogenesis and synaptogenesis by improving the mitochondrial structure and promoting mitochondrial function, as evidenced by the up-regulation of positive expression of both Recombinant Doublecortin (DCX) and 5-Bromodeoxyuridinc (BrdU), the enhancement of the Total antioxidant capacity (T-AOC), and the increase in the expression of synapse-associated proteins, Synaptophysin (SYP) and post-synaptic density-95 (PSD-95). Finally, we observed that catalpol up-regulated the expression of Sonic hedgehog (Shh) and Glioma-associated homologue-1 (GLI-1), factors related to the Shh signaling pathway.

Discussion

In conclusion, catalpol may regulate mitochondria through activation of the Shh signaling pathway and exert its role in promoting hippocampal neurogenesis and synaptogenesis.

Neuroplasticity-related effects of vitamin D relevant to its neuroprotective effects: A narrative review

The pathophysiology of a wide range of central nervous system (CNS) disorders, such as neurodegenerative and psychiatric diseases, has been associated with impairment of neurogenic and synaptogenic processes. Therefore, pharmacological and/or nutritional strategies based on the stimulation and/or restoration of these processes may have beneficial effects against diseases in which these processes are impaired. In this context, vitamin D has emerged as a promising neuroprotective compound. Due to its pleiotropic properties, it can interact with multiple molecular targets and thereby affect different cell types, including neurons and glial cells. This neurosteroid contributes to CNS homeostasis by non-genomic and genomic mechanisms through its interaction with vitamin D receptors (VDRs). Among several properties of this vitamin, its role in neuronal proliferation and differentiation as well as in synaptic plasticity has received attention. Considering this background, this narrative review aims to highlight the neuroplasticity-related mechanisms of vitamin D that may be associated with its neuroprotective effects.

Dexmedetomidine Attenuates Neuroinflammation-Mediated Hippocampal Neurogenesis Impairment in Sepsis-Associated Encephalopathy Mice through Central α2A-Adrenoceptor

Sepsis-associated encephalopathy (SAE), one of the common complications of sepsis, is associated with higher ICU mortality, prolonged hospitalization, and long-term cognitive decline. Sepsis can induce neuroinflammation, which negatively affects hippocampal neurogenesis. Dexmedetomidine has been shown to protect against SAE. However, the potential mechanism remains unclear. In this study, we added lipopolysaccharide (LPS)-stimulated astrocytes-conditioned media (LPS-CM) to neural stem cells (NSCs) culture, which were pretreated with dexmedetomidine in the presence or absence of the α2-adrenoceptor antagonist yohimbine or the α2A-adrenoceptor antagonist BRL-44408. LPS-CM impaired the neurogenesis of NSCs, characterized by decreased proliferation, enhanced gliogenesis, and declined viability. Dexmedetomidine alleviated LPS-CM-induced impairment of neurogenesis in a dose-dependent manner. Yohimbine, as well as BRL-44408, reversed the effects of dexmedetomidine. We established a mouse model of SAE via cecal ligation and perforation (CLP). CLP-induced astrocyte-related neuroinflammation and hippocampal neurogenesis deficits, accompanied by learning and memory decline, which were reversed by dexmedetomidine. The effect of dexmedetomidine was blocked by BRL-44408. Collectively, our findings support the conclusion that dexmedetomidine can protect against SAE, likely mediated by the combination of inhibiting neuroinflammation via the astrocytic α2A-adrenoceptor with attenuating neuroinflammation-induced hippocampal neurogenesis deficits via NSCs α2A-adrenoceptor.

Adeno-associated Virus-mediated Ezh2 Knockdown Reduced the Increment of Newborn Neurons Induced by Forebrain Ischemia in Gerbil Dentate Gyrus

It is established that neurogenesis of dentate gyrus is increased after ischemic insult, although the regulatory mechanisms have not yet been elucidated. In this study, we focused on Ezh2 which suppresses gene expression through catalyzing trimethylation of lysine 27 of histone 3. Male gerbils were injected with adeno-associated virus (AAV) carrying shRNA targeting to Ezh2 into right dentate gyrus 2 weeks prior to forebrain ischemia. One week after ischemia, animals were injected with thymidine analogue to label proliferating cells. Three weeks after ischemia, animals were killed for histological analysis. AAV-mediated knockdown of Ezh2 significantly decreased the ischemia-induced increment of proliferating cells, and the proliferated cells after ischemia showed significantly longer migration from subgranular zone (SGZ), compared to the control group. Furthermore, the number of neural stem cells in SGZ significantly decreased after ischemia with Ezh2 knockdown group. Of note, Ezh2 knockdown did not affect the number of proliferating cells or the migration from SGZ in the non-ischemic condition. Our data showed that, specifically after ischemia, Ezh2 knockdown shifted the balance between self-renewal and differentiation toward differentiation in adult dentate gyrus.

Hippocampal neurogenesis modulated by Quinic acid: A therapeutic strategy for the neurodegenerative disorders

Neural progenitor cells (NPCs) reside in the brain and participate in the mechanism of neurogenesis that permits the brain to generate the building blocks for enhancement of cognitive abilities and acquisition of new skills. The existence of NPCs in brain has opened a novel dimension of research to explore their potential for treatment of various neurodegenerative disorders. The present study provides novel insights into the intracellular mechanisms in neuronal cells proliferation, maturation and differentiation regulated by Quinic acid (QA). Furthermore, this study might help in discovery and development of lead molecule that can overcome the challenges in the treatment of neurodegenerative diseases. The growth supporting effect of QA was studied using MTT assay. For that purpose, hippocampal cell cultures of neonatal rats were treated with different concentrations of QA and incubated for 24, 48 and 72 h. Gene and protein expressions of the selected molecular markers nestin, neuron-specific class III beta-tubulin (Tuj-1), neuronal nuclear protein (NeuN), neuronal differentiation 1 (NeuroD1), glial fibrillary acidic protein (GFAP), neuroligin (NLGN) and vimentin were analyzed. QA-induced cell proliferation and differentiation of hippocampal progenitor cells was also accompanied by significantly increased expression of progenitor and immature neuronal marker, mature neuronal marker and differentiating factor, that is, nestin, Tuj-1, NeuN and NeuroD1, respectively. On the other hand, vimentin downregulation and constant GFAP expression were observed following QA treatment. Additionally, the effects of QA on the recovery of stressed cells was studied using in vitro model of oxygen glucose deprivation (OGD). It was observed that hippocampal cells were able to recover from OGD following the treatment with QA. These findings suggest that QA treatment promotes hippocampal neurogenesis by proliferating and differentiating of NPCs and recovers neurons from stress caused by OGD. Thus, the neurogenic potential of QA can be explored for the treatment of neurodegenerative disorders.

Developmental exposure to nonylphenol leads to depletion of the neural precursor cell pool in the hippocampal dentate gyrus

Developmental exposure to nonylphenol (NP) results in irreversible impairments of the central nervous system (CNS). The neural precursor cell (NPC) pool located in the subgranular zone (SGZ), a substructure of the hippocampal dentate gyrus, is critical for the development of hippocampal circuits and some hippocampal functions such as learning and memory. However, the effects of developmental exposure to NP on this pool remain unclear. Thus, our aim was to clarify the impacts of developmental exposure to NP on this pool and to explore the potential mechanisms. Animal models of developmental exposure to NP were created by treating Wistar rats with NP during pregnancy and lactation. Our data showed that developmental exposure to NP decreased Sox2-and Ki67-positive cells in the SGZ of offspring. Inhibited activation of Shh signaling and decreased levels of its downstream mediators, E2F1 and cyclins, were also observed in pups developmentally exposed to NP. Moreover, we established the in vitro model in the NE-4C cells, a neural precursor cell line, to further investigate the effect of NP exposure on NPCs and the underlying mechanisms. Purmorphamine, a small purine-derived hedgehog agonist, was used to specifically modulate the Shh signaling. Consistent with the in vivo results, exposure to NP reduced cell proliferation by inhibiting the Shh signaling in NE-4C cells, and purmorphamine alleviated this reduction in cell proliferation by restoring this signaling. Altogether, our findings support the idea that developmental exposure to NP leads to inhibition of the NPC proliferation and the NPC pool depletion in the SGZ located in the dentate gyrus. Furthermore, we also provided the evidence that suppressed activation of Shh signaling may contribute to the effects of developmental exposure to NP on the NPC pool.

The impact of flavonoids and BDNF on neurogenic process in various physiological/pathological conditions including ischemic insults: a narrative review

OBJECTIVE

Ischemic stroke is the leading cause of mortality and disability worldwide with more than half of survivors living with serious neurological sequelae thus, it has recently attracted considerable attention in the field of medical research. Neurogenesis is the process of formation of new neurons in the brain, including the human brain, from neural stem/progenitor cells [NS/PCs] which reside in neurogenic niches that contain the necessary substances for NS/PC proliferation, differentiation, migration, and maturation into functioning neurons which can integrate into a pre-existing neural network.Neurogenesis can be modulated by many exogenous and endogenous factors, pathological conditions. Both brain-derived neurotrophic factor, and flavonoids can modulate the neurogenic process in physiological conditions and after various pathological conditions including ischemic insults.

AIM

This review aims to discuss neurogenesis after ischemic insults and to determine the role of flavonoids and BDNF on neurogenesis under physiological and pathological conditions with a concentration on ischemic insults to the brain in particular.

METHOD

Relevant articles assessing the impact of flavonoids and BDNF on neurogenic processes in various physiological/pathological conditions including ischemic insults within the timeline of 1965 until 2023 were searched using the PubMed database.

CONCLUSIONS

The selected studies have shown that ischemic insults to the brain induce NS/PC proliferation, differentiation, migration, and maturation into functioning neurons integrating into a pre-existing neural network. Flavonoids and BDNF can modulate neurogenesis in the brain in various physiological/pathological conditions including ischemic insults. In conclusion, flavonoids and BDNF may be involved in post-ischemic brain repair processes through enhancing endogenous neurogenesis.

FGF1

Fibroblast Growth Factor 1 (Fgf1), also known as acidic FGF (aFGF), is involved in the regulation of various biological processes, ranging from development to disease pathogenesis. It is a single chain polypeptide and is highly expressed in adult brain and kidney tissues. Its expression has been shown to be directed by multiple tissue-specific promoters, which generate transcripts of varying lengths. During development the Fgf1 gene is widely expressed, including in the neural tube, heart and lung. Mouse mutants for this gene are normal under standard laboratory conditions. However, when Fgf1 mutants are exposed to a high fat diet, an aggressive diabetic phenotype has been reported, along with aberrant adipose tissue expansion. Ongoing research on FGF1 and its signalling pathways holds promise for greater understanding of developmental processes as well as the development of novel therapeutic interventions for diseases including diabetes.

Exploring the triad: VPS35, neurogenesis, and neurodegenerative diseases

Vacuolar protein sorting 35 (VPS35), a critical component of the retromer complex, plays a pivotal role in the pathogenesis of neurodegenerative diseases (NDs). It is involved in protein transmembrane sorting, facilitating the transport from endosomes to the trans-Golgi network (TGN) and plasma membrane. Recent investigations have compellingly associated mutations in the VPS35 gene with neurodegenerative disorders such as Parkinson's and Alzheimer's disease. These genetic alterations are implicated in protein misfolding, disrupted autophagic processes, mitochondrial dysregulation, and synaptic impairment. Furthermore, VPS35 exerts a notable impact on neurogenesis by influencing neuronal functionality, protein conveyance, and synaptic performance. Dysregulation or mutation of VPS35 may escalate the progression of neurodegenerative conditions, underscoring its pivotal role in safeguarding neuronal integrity. This review comprehensively discusses the role of VPS35 and its functional impairments in NDs. Furthermore, we provide an overview of the impact of VPS35 on neurogenesis and further explore the intricate relationship between neurogenesis and NDs. These research advancements offer novel perspectives and valuable insights for identifying potential therapeutic targets in the treatment of NDs.

Role of histone modifications in neurogenesis and neurodegenerative disease development

Progressive neuronal dysfunction and death are key features of neurodegenerative diseases; therefore, promoting neurogenesis in neurodegenerative diseases is crucial. With advancements in proteomics and high-throughput sequencing technology, it has been demonstrated that histone post-transcriptional modifications (PTMs) are often altered during neurogenesis when the brain is affected by disease or external stimuli and that the degree of histone modification is closely associated with the development of neurodegenerative diseases. This review aimed to show the regulatory role of histone modifications in neurogenesis and neurodegenerative diseases by discussing the changing patterns and functional significance of histone modifications, including histone methylation, acetylation, ubiquitination, phosphorylation, and lactylation. Finally, we explored the control of neurogenesis and the development of neurodegenerative diseases by artificially modulating histone modifications.

Altered Morpho-Functional Features of Neurogenesis in Zebrafish Embryos Exposed to Non-Combustion-Derived Magnetite

Neurogenesis is the process by which new brain cells are formed. This crucial event emerges during embryonic life and proceeds in adulthood, and it could be influenced by environmental pollution. Non-combustion-derived magnetite represents a portion of the coarse particulate matter (PM) contributing to air and water pollution in urban settings. Studies on humans have reported that magnetite and other iron oxides have significant damaging effects at a central level, where these particles accumulate and promote oxidative stress. Similarly, magnetite nanoparticles can cross the placenta and damage the embryo brain during development, but the impact on neurogenesis is still unknown. Furthermore, an abnormal Fe cation concentration in cells and tissues might promote reactive oxygen species (ROS) generation and has been associated with multiple neurodegenerative conditions. In the present study, we used zebrafish as an in vivo system to analyze the specific effects of magnetite on embryonic neurogenesis. First, we characterized magnetite using mineralogical and spectroscopic analyses. Embryos treated with magnetite at sub-lethal concentrations showed a dose-response increase in ROS in the brain, which was accompanied by a massive decrease in antioxidant genes (sod2, cat, gsr, and nrf2). In addition, a higher number of apoptotic cells was observed in embryos treated with magnetite. Next, interestingly, embryos exposed to magnetite displayed a decrease in neural staminal progenitors (nestin, sox2, and pcna markers) and a neuronal marker (elavl3). Finally, we observed significative increases in apoeb (specific microglia marker) and interleukin-1b (il1b), confirming a status of inflammation in the brain embryos treated with magnetite. Our study represents the very first in vivo evidence concerning the effects of magnetite on brain development.

RNA-Seq time-course analysis of neural precursor cell transcriptome in response to herpes simplex Virus-1 infection

The neurogenic niches within the central nervous system serve as essential reservoirs for neural precursor cells (NPCs), playing a crucial role in neurogenesis. However, these NPCs are particularly vulnerable to infection by the herpes simplex virus 1 (HSV-1). In the present study, we investigated the changes in the transcriptome of NPCs in response to HSV-1 infection using bulk RNA-Seq, compared to those of uninfected samples, at different time points post infection and in the presence or absence of antivirals. The results showed that NPCs upon HSV-1 infection undergo a significant dysregulation of genes playing a crucial role in aspects of neurogenesis, including genes affecting NPC proliferation, migration, and differentiation. Our analysis revealed that the CREB signaling, which plays a crucial role in the regulation of neurogenesis and memory consolidation, was the most consistantly downregulated pathway, even in the presence of antivirals. Additionally, cholesterol biosynthesis was significantly downregulated in HSV-1-infected NPCs. The findings from this study, for the first time, offer insights into the intricate molecular mechanisms that underlie the neurogenesis impairment associated with HSV-1 infection.

Astrocytic endothelin-1 overexpression impairs learning and memory ability in ischemic stroke via altered hippocampal neurogenesis and lipid metabolism

Vascular etiology is the second most prevalent cause of cognitive impairment globally. Endothelin-1, which is produced and secreted by endothelial cells and astrocytes, is implicated in the pathogenesis of stroke. However, the way in which changes in astrocytic endothelin-1 lead to poststroke cognitive deficits following transient middle cerebral artery occlusion is not well understood. Here, using mice in which astrocytic endothelin-1 was overexpressed, we found that the selective overexpression of endothelin-1 by astrocytic cells led to ischemic stroke-related dementia (1 hour of ischemia; 7 days, 28 days, or 3 months of reperfusion). We also revealed that astrocytic endothelin-1 overexpression contributed to the role of neural stem cell proliferation but impaired neurogenesis in the dentate gyrus of the hippocampus after middle cerebral artery occlusion. Comprehensive proteome profiles and western blot analysis confirmed that levels of glial fibrillary acidic protein and peroxiredoxin 6, which were differentially expressed in the brain, were significantly increased in mice with astrocytic endothelin-1 overexpression in comparison with wild-type mice 28 days after ischemic stroke. Moreover, the levels of the enriched differentially expressed proteins were closely related to lipid metabolism, as indicated by Kyoto Encyclopedia of Genes and Genomes pathway analysis. Liquid chromatography-mass spectrometry nontargeted metabolite profiling of brain tissues showed that astrocytic endothelin-1 overexpression altered lipid metabolism products such as glycerol phosphatidylcholine, sphingomyelin, and phosphatidic acid. Overall, this study demonstrates that astrocytic endothelin-1 overexpression can impair hippocampal neurogenesis and that it is correlated with lipid metabolism in poststroke cognitive dysfunction.

Differential effects of antiseizure medications on neurogenesis: Evidence from cells to animals

Neurogenesis, the process of generating functionally integrated neurons from neural stem and progenitor cells, is involved in brain development during embryonic stages but continues throughout life. Adult neurogenesis plays essential roles in many brain functions such as cognition, brain plasticity, and repair. Abnormalities in neurogenesis have been described in many neuropsychiatric and neurological disorders, including epilepsy. While sharing a common property of suppressing seizures, accumulating evidence has shown that some antiseizure medications (ASM) exhibit neuroprotective potential in the non-epileptic models including Parkinson's disease, Alzheimer's disease, cerebral ischemia, or traumatic brain injury. ASM are a heterogeneous group of medications with different mechanisms of actions. Therefore, it remains to be revealed whether neurogenesis is a class effect or related to them all. In this comprehensive literature study, we reviewed the literature data on the influence of ASM on the neurogenesis process during brain development and also in the adult brain under physiological or pathological conditions. Meanwhile, we discussed the underlying mechanisms associated with the neurogenic effects of ASM by linking the reported in vivo and in vitro studies. PubMed, Web of Science, and Google Scholar databases were searched until the end of February 2023. A total of 83 studies were used finally. ASM can modulate neurogenesis through the increase or decrease of proliferation, survival, and differentiation of the quiescent NSC pool. The present article indicated that the neurogenic potential of ASM depends on the administered dose, treatment period, temporal administration of the drug, and normal or disease context.

Dietary Astaxanthin: A Promising Antioxidant and Anti-Inflammatory Agent for Brain Aging and Adult Neurogenesis

Decreased adult neurogenesis, or the gradual depletion of neural stem cells in adult neurogenic niches, is considered a hallmark of brain aging. This review provides a comprehensive overview of the intricate relationship between aging, adult neurogenesis, and the potential neuroregenerative properties of astaxanthin, a carotenoid principally extracted from the microalga Haematococcus pluvialis. The unique chemical structure of astaxanthin enables it to cross the blood-brain barrier and easily reach the brain, where it may positively influence adult neurogenesis. Astaxanthin can affect molecular pathways involved in the homeostasis, through the activation of FOXO3-related genetic pathways, growth, and regeneration of adult brain neurons, enhancing cell proliferation and the potency of stem cells in neural progenitor cells. Furthermore, astaxanthin appears to modulate neuroinflammation by suppressing the NF-κB pathway, reducing the production of pro-inflammatory cytokines, and limiting neuroinflammation associated with aging and chronic microglial activation. By modulating these pathways, along with its potent antioxidant properties, astaxanthin may contribute to the restoration of a healthy neurogenic microenvironment, thereby preserving the activity of neurogenic niches during both normal and pathological aging.

JUN upregulation drives aberrant transposable element mobilization, associated innate immune response, and impaired neurogenesis in Alzheimer's disease

Adult neurogenic decline, inflammation, and neurodegeneration are phenotypic hallmarks of Alzheimer's disease (AD). Mobilization of transposable elements (TEs) in heterochromatic regions was recently reported in AD, but the underlying mechanisms are still underappreciated. Combining functional genomics with the differentiation of familial and sporadic AD patient derived-iPSCs into hippocampal progenitors, CA3 neurons, and cerebral organoids, we found that the upregulation of the AP-1 subunit, c-Jun, triggers decondensation of genomic regions containing TEs. This leads to the cytoplasmic accumulation of HERVK-derived RNA-DNA hybrids, the activation of the cGAS-STING cascade, and increased levels of cleaved caspase-3, suggesting the initiation of programmed cell death in AD progenitors and neurons. Notably, inhibiting c-Jun effectively blocks all these downstream molecular processes and rescues neuronal death and the impaired neurogenesis phenotype in AD progenitors. Our findings open new avenues for identifying therapeutic strategies and biomarkers to counteract disease progression and diagnose AD in the early, pre-symptomatic stages.

Bioactive Compounds and Their Influence on Postnatal Neurogenesis

Since postnatal neurogenesis was revealed to have significant implications for cognition and neurological health, researchers have been increasingly exploring the impact of natural compounds on this process, aiming to uncover strategies for enhancing brain plasticity. This review provides an overview of postnatal neurogenesis, neurogenic zones, and disorders characterized by suppressed neurogenesis and neurogenesis-stimulating bioactive compounds. Examining recent studies, this review underscores the multifaceted effects of natural compounds on postnatal neurogenesis. In essence, understanding the interplay between postnatal neurogenesis and natural compounds could bring novel insights into brain health interventions. Exploiting the therapeutic abilities of these compounds may unlock innovative approaches to enhance cognitive function, mitigate neurodegenerative diseases, and promote overall brain well-being.

The anti-viral immune response of the adult host robustly modulates neural stem cell activity in spatial, temporal, and sex-specific manners

Viruses induce a wide range of neurological sequelae through the dysfunction and death of infected cells and persistent inflammation in the brain. Neural stem cells (NSCs) are often disturbed during viral infections. Although some viruses directly infect and kill NSCs, the antiviral immune response may also indirectly affect NSCs. To better understand how NSCs are influenced by a productive immune response, where the virus is successfully resolved and the host survives, we used the CD46+ mouse model of neuron-restricted measles virus (MeV) infection. As NSCs are spared from direct infection in this model, they serve as bystanders to the antiviral immune response initiated by selective infection of mature neurons. MeV-infected mice showed distinct regional and temporal changes in NSCs in the primary neurogenic niches of the brain, the hippocampus and subventricular zone (SVZ). Hippocampal NSCs increased throughout the infection (7 and 60 days post-infection; dpi), while mature neurons transiently declined at 7 dpi and then rebounded to basal levels by 60 dpi. In the SVZ, NSC numbers were unchanged, but mature neurons declined even after the infection was controlled at 60 dpi. Further analyses demonstrated sex, temporal, and region-specific changes in NSC proliferation and neurogenesis throughout the infection. A relatively long-term increase in NSC proliferation and neurogenesis was observed in the hippocampus; however, neurogenesis was reduced in the SVZ. This decline in SVZ neurogenesis was associated with increased immature neurons in the olfactory bulb in female, but not male mice, suggesting potential migration of newly-made neurons out of the female SVZ. These sex differences in SVZ neurogenesis were accompanied by higher infiltration of B cells and greater expression of interferon-gamma and interleukin-6 in female mice. Learning, memory, and olfaction tests revealed no overt behavioral changes after the acute infection subsided. These results indicate that antiviral immunity modulates NSC activity in adult mice without inducing gross behavioral deficits among those tested, suggestive of mechanisms to restore neurons and maintain adaptive behavior, but also revealing the potential for robust NSC disruption in subclinical infections.

Genome-wide association study of hippocampal blood-oxygen-level-dependent-cerebral blood flow correlation in Chinese Han population

Correlation between blood-oxygen-level-dependent (BOLD) and cerebral blood flow (CBF) has been used as an index of neurovascular coupling. Hippocampal BOLD-CBF correlation is associated with neurocognition, and the reduced correlation is associated with neuropsychiatric disorders. We conducted the first genome-wide association study of the hippocampal BOLD-CBF correlation in 4,832 Chinese Han subjects. The hippocampal BOLD-CBF correlation had an estimated heritability of 16.2-23.9% and showed reliable genome-wide significant association with a locus at 3q28, in which many variants have been linked to neuroimaging and cerebrospinal fluid markers of Alzheimer's disease. Gene-based association analyses showed four significant genes (GMNC, CRTC2, DENND4B, and GATAD2B) and revealed enrichment for mast cell calcium mobilization, microglial cell proliferation, and ubiquitin-related proteolysis pathways that regulate different cellular components of the neurovascular unit. This is the first unbiased identification of the association of hippocampal BOLD-CBF correlation, providing fresh insights into the genetic architecture of hippocampal neurovascular coupling.

Integrated metabolomic and transcriptomic analysis reveals perturbed glycerophospholipid metabolism in mouse neural stem cells exposed to cadmium

Cadmium (Cd) is a ubiquitous heavy metal with neurotoxicity. Our previous study reported that Cd could inhibit the proliferation of mouse neural stem cells (mNSCs). However, the underlying mechanisms are obscure. In recent years, the rapid growth of multi-omics techniques enables us to explore the cellular responses that occurred after toxicant exposure at the molecular level. In this study, we used a combination of metabolomics and transcriptomics approaches to investigate the effects of exposure to Cd on mNSCs. After treatment with Cd, the metabolites and transcripts in mNSCs changed significantly with 110 differentially expressed metabolites and 2135 differentially expressed genes identified, respectively. The altered metabolites were mainly involved in glycerophospholipid metabolism, arginine and proline metabolism, arginine biosynthesis, glyoxylate and dicarboxylate metabolism. Meanwhile, the transcriptomic data demonstrated perturbed membrane function and signal transduction. Furthermore, integrated analysis of metabolomic and transcriptomic data suggested that glycerophospholipid metabolism might be the major metabolic pathway affected by Cd in mNSCs. More interestingly, the supplementation of lysophosphatidylethanolamine (LPE) attenuated Cd-induced mitochondrial impairment and the inhibition of cell proliferation and differentiation in mNSCs, further supporting our analysis. Overall, the study provides new insights into the mechanisms of Cd-induced neurotoxicity.

The Designer Drug αPHP Affected Cell Proliferation and Triggered Deathly Mechanisms in Murine Neural Stem/Progenitor Cells

Increasing reports of neurological and psychiatric outcomes due to psychostimulant synthetic cathinones (SCs) have recently raised public concern. However, the understanding of neurotoxic mechanisms is still lacking, particularly for the under-investigated αPHP, one of the major MDPV derivatives. In particular, its effects on neural stem/progenitor cell cultures (NSPCs) are still unexplored. Therefore, in the current in vitro study, the effects of increasing αPHP concentrations (25-2000 μM), on cell viability/proliferation, morphology/ultrastructure, genotoxicity and cell death pathways, have been evaluated after exposure in murine NSPCs, using a battery of complementary techniques, i.e., MTT and clonogenic assay, flow cytometry, immunocytochemistry, TEM, and patch clamp. We revealed that αPHP was able to induce a dose-dependent significant decrease of the viability, proliferation and clonal capability of the NSPCs, paralleled by the resting membrane potential depolarization and apoptotic/autophagic/necroptotic pathway activation. Moreover, ultrastructural alterations were clearly observed. Overall, our current findings demonstrate that αPHP, damaging NSPCs and the morpho-functional fundamental units of adult neurogenic niches may affect neurogenesis, possibly triggering long-lasting, irreversible CNS damage. The present investigation could pave the way for a broadened understanding of SCs toxicology, needed to establish an appropriate treatment for NPS and the potential consequences for public health.

Genetically engineered neural stem cells (NSCs) therapy for neurological diseases; state-of-the-art

Neural stem cells (NSCs) are multipotent stem cells with remarkable self-renewal potential and also unique competencies to differentiate into neurons, astrocytes, and oligodendrocytes (ODCs) and improve the cellular microenvironment. In addition, NSCs secret diversity of mediators, including neurotrophic factors (e.g., BDNF, NGF, GDNF, CNTF, and NT-3), pro-angiogenic mediators (e.g., FGF-2 and VEGF), and anti-inflammatory biomolecules. Thereby, NSCs transplantation has become a reasonable and effective treatment for various neurodegenerative disorders by their capacity to induce neurogenesis and vasculogenesis and dampen neuroinflammation and oxidative stress. Nonetheless, various drawbacks such as lower migration and survival and less differential capacity to a particular cell lineage concerning the disease pathogenesis hinder their application. Thus, genetic engineering of NSCs before transplantation is recently regarded as an innovative strategy to bypass these hurdles. Indeed, genetically modified NSCs could bring about more favored therapeutic influences post-transplantation in vivo, making them an excellent option for neurological disease therapy. This review for the first time offers a comprehensive review of the therapeutic capability of genetically modified NSCs rather than naïve NSCs in neurological disease beyond brain tumors and sheds light on the recent progress and prospect in this context.

Minocycline improves autism-related behaviors by modulating microglia polarization in a mouse model of autism

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder with few pharmacological treatments. Minocycline, a tetracycline derivative that inhibits microglial activation, has been well-identified with anti-inflammatory properties and neuroprotective effects. A growing body of research suggests that ASD is associated with neuroinflammation, abnormal neurotransmitter levels, and neurogenesis. Thus, we hypothesized that minocycline could improve autism-related behaviors by inhibiting microglia activation and altering neuroinflammation. To verify our hypothesis, we used a mouse model of autism, BTBR T + Itpr3tf/J (BTBR). As expected, minocycline administration rescued the sociability and repetitive, stereotyped behaviors of BTBR mice while having no effect in C57BL/6J mice. We also found that minocycline improved neurogenesis and inhibited microglia activation in the hippocampus of BTBR mice. In addition, minocycline treatment inhibited Erk1/2 phosphorylation in the hippocampus of BTBR mice. Our findings show that minocycline administration alleviates ASD-like behaviors in BTBR mice and improves neurogenesis, suggesting that minocycline supplementation might be a potential strategy for improving ASD symptoms.

Unveiling the Neural Environment in Cancer: Exploring the Role of Neural Circuit Players and Potential Therapeutic Strategies

The regulation of the immune environment within the tumor microenvironment has provided new opportunities for cancer treatment. However, an important microenvironment surrounding cancer that is often overlooked despite its significance in cancer progression is the neural environment surrounding the tumor. The release of neurotrophic factors from cancer cells is implicated in cancer growth and metastasis by facilitating the infiltration of nerve cells into the tumor microenvironment. This nerve-tumor interplay can elicit cancer cell proliferation, migration, and invasion in response to neurotransmitters. Moreover, it is possible that cancer cells could establish a network resembling that of neurons, allowing them to communicate with one another through neurotransmitters. The expression levels of players in the neural circuits of cancers could serve as potential biomarkers for cancer aggressiveness. Notably, the upregulation of certain players in the neural circuit has been linked to poor prognosis in specific cancer types such as breast cancer, pancreatic cancer, basal cell carcinoma, and stomach cancer. Targeting these players with inhibitors holds great potential for reducing the morbidity and mortality of these carcinomas. However, the efficacy of anti-neurogenic agents in cancer therapy remains underexplored, and further research is necessary to evaluate their effectiveness as a novel approach for cancer treatment. This review summarizes the current knowledge on the role of players in the neural circuits of cancers and the potential of anti-neurogenic agents for cancer therapy.

Human hippocampal astrocytes: Computational dissection of their transcriptome, sexual differences and exosomes across ageing and mild-cognitive impairment

The role of astrocytes in Alzheimer's disease is often disregarded. Hence, characterization of astrocytes along their early evolution toward Alzheimer would be greatly beneficial. However, due to their exquisite responsiveness, in vivo studies are difficult. So public microarray data of hippocampal homogenates from (healthy) young, (healthy) elder and elder with mild cognitive impairment (MCI) were subjected to re-analysis by a multi-step computational pipeline. Ontologies and pathway analyses were compared after determining the differential genes that, belonging to astrocytes, have splice forms. Likewise, the subset of molecules exportable to exosomes was also determined. The results showed that astrocyte's phenotypes changed significantly. While already 'activated' astrocytes were found in the younger group, major changes occurred during ageing (increased vascular remodelling and response to mechanical stimulus, diminished long-term potentiation and increased long-term depression). MCI's astrocytes showed some 'rejuvenated' features, but their sensitivity to shear stress was markedly lost. Importantly, most of the changes showed to be sex biassed. Men's astrocytes are enriched in a type 'endfeet-astrocytome', whereas women's astrocytes appear close to the 'scar-forming' type (prone to endothelial dysfunction, hypercholesterolemia, loss of glutamatergic synapses, Ca+2 dysregulation, hypoxia, oxidative stress and 'pro-coagulant' phenotype). In conclusion, the computational dissection of the networks based on the hippocampal gene isoforms provides a relevant proxy to in vivo astrocytes, also revealing the occurrence of sexual differences. Analyses of the astrocytic exosomes did not provide an acceptable approximation to the overall functioning of astrocytes in the hippocampus, probably due to the selective cellular mechanisms which charge the cargo molecules.

Serotonergic mediation of the brain-wide neurogenesis: Region-dependent and receptor-type specific roles on neurogenic cellular transformation

Brain serotonin (5-hydroxytryptamine, 5-HT) is a key molecule for the mediation of depression-related brain states, but the neural mechanisms underlying 5-HT mediation need further investigation. A possible mechanism of the therapeutic antidepressant effects is neurogenic cell production, as stimulated by 5-HT signaling. Neurogenesis, the proliferation of neural stem cells (NSCs), and cell differentiation and maturation occur across brain regions, particularly the hippocampal dentate gyrus and the subventricular zone, throughout one's lifespan. 5-HT plays a major role in the mediation of neurogenic processes, which in turn leads to the therapeutic effect on depression-related states. In this review article, we aim to identify how the neuronal 5-HT system mediates the process of neurogenesis, including cell proliferation, cell-type differentiation and maturation. First, we will provide an overview of the neurogenic cell transformation that occurs in brain regions containing or lacking NSCs. Second, we will review brain region-specific mechanisms of 5-HT-mediated neurogenesis by comparing regions localized to NSCs, i.e., the hippocampus and subventricular zone, with those not containing NSCs. Highlighting these 5-HT mechanisms that mediate neurogenic cell production processes in a brain-region-specific manner would provide unique insights into the role of 5-HT in neurogenesis and its associated effects on depression.

A Mild Dose of Aspirin Promotes Hippocampal Neurogenesis and Working Memory in Experimental Ageing Mice

Aspirin has been reported to prevent memory decline in the elderly population. Adult neurogenesis in the hippocampus has been recognized as an underlying basis of learning and memory. This study investigated the effect of aspirin on spatial memory in correlation with the regulation of hippocampal neurogenesis and microglia in the brains of ageing experimental mice. Results from the novel object recognition (NOR) test, Morris water maze (MWM), and cued radial arm maze (cued RAM) revealed that aspirin treatment enhances working memory in experimental mice. Further, the co-immunohistochemical assessments on the brain sections indicated an increased number of doublecortin (DCX)-positive immature neurons and bromodeoxyuridine (BrdU)/neuronal nuclei (NeuN) double-positive newly generated neurons in the hippocampi of mice in the aspirin-treated group compared to the control group. Moreover, a reduced number of ionized calcium-binding adaptor molecule (Iba)-1-positive microglial cells was evident in the hippocampus of aspirin-treated animals. Recently, enhanced activity of acetylcholinesterase (AChE) in circulation has been identified as an indicative biomarker of dementia. The biochemical assessment in the blood of aspirin-treated mice showed decreased activity of AChE in comparison with that of the control group. Results from this study revealed that aspirin facilitates hippocampal neurogenesis which might be linked to enhanced working memory.

Transposons contribute to the acquisition of cell type-specific cis-elements in the brain

Mammalian brains have evolved in stages over a long history to acquire higher functions. Recently, several transposable element (TE) families have been shown to evolve into cis-regulatory elements of brain-specific genes. However, it is not fully understood how TEs are important for gene regulatory networks. Here, we performed a single-cell level analysis using public data of scATAC-seq to discover TE-derived cis-elements that are important for specific cell types. Our results suggest that DNA elements derived from TEs, MER130 and MamRep434, can function as transcription factor-binding sites based on their internal motifs for Neurod2 and Lhx2, respectively, especially in glutamatergic neuronal progenitors. Furthermore, MER130- and MamRep434-derived cis-elements were amplified in the ancestors of Amniota and Eutheria, respectively. These results suggest that the acquisition of cis-elements with TEs occurred in different stages during evolution and may contribute to the acquisition of different functions or morphologies in the brain.

Purpurin ameliorates D-galactose-induced aging phenotypes in mouse hippocampus by reducing inflammatory responses

Purpurin, an anthraquinone, has potent anti-oxidant and anti-inflammatory effects in various types of brain damage. In a previous study, we showed that purpurin exerts neuroprotective effects against oxidative and ischemic damage by reducing pro-inflammatory cytokines. In the present study, we investigated the effects of purpurin against D-galactose-induced aging phenotypes in mice. Exposure to 100 mM D-galactose significantly decreased cell viability in HT22 cells, and purpurin treatment significantly ameliorated the reduction of cell viability, formation of reactive oxygen species, and lipid peroxidation in a concentration-dependent manner. Treatment with 6 mg/kg purpurin significantly improved D-galactose-induced memory impairment in the Morris water maze test in C57BL/6 mice and alleviated the reduction of proliferating cells and neuroblasts in the subgranular zone of the dentate gyrus. In addition, purpurin treatment significantly mitigated D-galactose-induced changes of microglial morphology in the mouse hippocampus and the release of pro-inflammatory cytokines such as interleukin-1β, interleukin-6, and tumor necrosis factor-α. In addition, purpurin treatment significantly ameliorated D-galactose-induced phosphorylation of c-Jun N-terminal kinase and cleavage of caspase-3 in HT22 cells. These results suggest that purpurin can delay aging by reducing the inflammatory cascade and phosphorylation of the c-Jun N-terminal in the hippocampus.

Glucocorticoids Orchestrate Adult Hippocampal Plasticity: Growth Points and Translational Aspects

The review analyzes modern concepts about the control of various mechanisms of the hippocampal neuroplasticity in adult mammals and humans by glucocorticoids. Glucocorticoid hormones ensure the coordinated functioning of key components and mechanisms of hippocampal plasticity: neurogenesis, glutamatergic neurotransmission, microglia and astrocytes, systems of neurotrophic factors, neuroinflammation, proteases, metabolic hormones, neurosteroids. Regulatory mechanisms are diverse; along with the direct action of glucocorticoids through their receptors, there are conciliated glucocorticoid-dependent effects, as well as numerous interactions between various systems and components. Despite the fact that many connections in this complex regulatory scheme have not yet been established, the study of the factors and mechanisms considered in the work forms growth points in the field of glucocorticoid-regulated processes in the brain and primarily in the hippocampus. These studies are fundamentally important for the translation into the clinic and the potential treatment/prevention of common diseases of the emotional and cognitive spheres and respective comorbid conditions.

Long-lasting restoration of memory function and hippocampal synaptic plasticity by focused ultrasound in Alzheimer's disease

BACKGROUND

Focused ultrasound (FUS) is a medical technology that non-invasively stimulates the brain and has been applied in thermal ablation, blood-brain barrier (BBB) opening, and neuromodulation. In recent years, numerous experiences and indications for the use of FUS in clinical and preclinical studies have rapidly expanded. Focused ultrasound-mediated BBB opening induces cognitive enhancement and neurogenesis; however, the underlying mechanisms have not been elucidated.

METHODS

Here, we investigate the effects of FUS-mediated BBB opening on hippocampal long-term potentiation (LTP) and cognitive function in a 5xFAD mouse model of Alzheimer's disease (AD). We applied FUS with microbubble to the hippocampus and LTP was measured 6 weeks after BBB opening using FUS. Field recordings were made with a concentric bipolar electrode positioned in the CA1 region using an extracellular glass pipette filled with artificial cerebrospinal fluid. Morris water maze and Y-maze was performed to test cognitive function.

RESULTS

Our results demonstrated that FUS-mediated BBB opening has a significant impact on increasing LTP at Schaffer collateral - CA1 synapses and rescues cognitive dysfunction and working memory. These effects persisted for up to 7 weeks post-treatment. Also, FUS-mediated BBB opening in the hippocampus increased PKA phosphorylation.

CONCLUSION

Therefore, it could be a promising treatment for neurodegenerative diseases as it remarkably increases LTP, thereby improving working memory.

Functions and distribution of calpain-calpastatin system components in brain during mammal ontogeny

Calpain and calpastatin are the key components of the calcium-dependent proteolytic system. Calpains are regulatory, calcium-dependent, cytoplasmic proteinases, and calpastatin is the endogenous inhibitor of calpains. Due to the correlation between changes in the activity of the calpain-calpastatin system in the brain and central nervous system (CNS) pathology states, this proteolytic system is a prime focus of research on CNS pathological processes, generally characterized by calpain activity upregulation. The present review aims to generalize existing data on cerebral calpain distribution and function through mammalian ontogenesis. Special attention is given to the most recent studies on the topic as more information on calpain-calpastatin system involvement in normal CNS development and functioning has become available. We also discuss data on calpain and calpastatin activity and production in different brain regions during ontogenesis as comparative analysis of these results in association with ontogeny processes can reveal brain regions and developmental stages with pronounced function of the calpain system.

Intergenerational Perioperative Neurocognitive Disorder

Accelerated neurocognitive decline after general anesthesia/surgery, also known as perioperative neurocognitive disorder (PND), is a widely recognized public health problem that may affect millions of patients each year. Advanced age, with its increasing prevalence of heightened stress, inflammation, and neurodegenerative alterations, is a consistent contributing factor to the development of PND. Although a strong homeostatic reserve in young adults makes them more resilient to PND, animal data suggest that young adults with pathophysiological conditions characterized by excessive stress and inflammation may be vulnerable to PND, and this altered phenotype may be passed to future offspring (intergenerational PND). The purpose of this narrative review of data in the literature and the authors' own experimental findings in rodents is to draw attention to the possibility of intergenerational PND, a new phenomenon which, if confirmed in humans, may unravel a big new population that may be affected by parental PND. In particular, we discuss the roles of stress, inflammation, and epigenetic alterations in the development of PND. We also discuss experimental findings that demonstrate the effects of surgery, traumatic brain injury, and the general anesthetic sevoflurane that interact to induce persistent dysregulation of the stress response system, inflammation markers, and behavior in young adult male rats and in their future offspring who have neither trauma nor anesthetic exposure (i.e., an animal model of intergenerational PND).

Light Alcohol Consumption Promotes Early Neurogenesis Following Ischemic Stroke in Adult C57BL/6J Mice

Ischemic stroke is one of the leading causes of death and disability worldwide. Neurogenesis plays a crucial role in postischemic functional recovery. Alcohol dose-dependently affects the prognosis of ischemic stroke. We investigated the impact of light alcohol consumption (LAC) on neurogenesis under physiological conditions and following ischemic stroke. C57BL/6J mice (three months old) were fed with 0.7 g/kg/day ethanol (designed as LAC) or volume-matched water (designed as control) daily for eight weeks. To evaluate neurogenesis, the numbers of 5-bromo-2-deoxyuridine (BrdU)+/doublecortin (DCX)+ and BrdU+/NeuN+ neurons were assessed in the subventricular zone (SVZ), dentate gyrus (DG), ischemic cortex, and ischemic striatum. The locomotor activity was determined by the accelerating rotarod and open field tests. LAC significantly increased BrdU+/DCX+ and BrdU+/NeuN+ cells in the SVZ under physiological conditions. Ischemic stroke dramatically increased BrdU+/DCX+ and BrdU+/NeuN+ cells in the DG, SVZ, ischemic cortex, and ischemic striatum. The increase in BrdU+/DCX+ cells was significantly greater in LAC mice compared to the control mice. In addition, LAC significantly increased BrdU+/NeuN+ cells by about three folds in the DG, SVZ, and ischemic cortex. Furthermore, LAC reduced ischemic brain damage and improved locomotor activity. Therefore, LAC may protect the brain against ischemic stroke by promoting neurogenesis.

Bisphenol-A (BPA) Impairs Hippocampal Neurogenesis via Inhibiting Regulation of the Ubiquitin Proteasomal System

The ubiquitin-proteasome system (UPS) controls protein homeostasis to maintain cell functionality and survival. Neurogenesis relies on proteasome function, and a defective proteasome system during brain development leads to neurological disorders. An endocrine-disrupting xenoestrogen bisphenol-A (BPA) used in plastic products adversely affects human health and causes neurotoxicity. Previously, we reported that BPA reduces neural stem cells (NSCs) proliferation and differentiation, impairs myelination and mitochondrial protein import, and causes excessive mitochondrial fragmentation leading to cognitive impairments in rats. Herein, we examined the effect(s) of prenatal BPA exposure on UPS functions during NSCs proliferation and differentiation in the hippocampus. Rats were orally treated with 40 µg/kg body weight BPA during day 6 gestation to day 21 postnatal. BPA significantly reduced proteasome activity in a cellular extract of NSCs. Immunocytochemistry exhibited a significant reduction of 20S proteasome/Nestin⁺ and PSMB5/Nestin⁺ cells in NSCs culture. BPA decreased 20S/Tuj1⁺ and PSMB5/Tuj1⁺ cells, indicating disrupted UPS during neuronal differentiation. BPA reduced the expression of UPS genes, 20S, and PSMB5 protein levels and proteasome activity in the hippocampus. It significantly reduced overall protein synthesis by the loss of Nissl substances in the hippocampus. Pharmacological activation of UPS by a bioactive triterpenoid 18α-glycyrrhetinic acid (18α GA) caused increased proteasome activities, significantly increased neurosphere size and number, and enhanced NSCs proliferation in BPA exposed culture, while proteasome inhibition by MG132 further aggravates BPA-mediated effects. In silico studies demonstrated that BPA strongly binds to catalytic sites of UPS genes (PSMB5, TRIM11, Parkin, and PSMD4) which may result in UPS inactivation. These results suggest that BPA significantly reduces NSCs proliferation by impairing UPS, and UPS activation by 18α GA could suppress BPA-mediated neurotoxicity and exerts neuroprotection.

Dietary Flavonoids and Adult Neurogenesis: Potential Implications for Brain Aging

Adult neurogenesis deficiency has been proposed to be a common hallmark in different age-related neurodegenerative diseases. The administration of flavonoids is currently reported as a potentially beneficial strategy for preventing brain aging alterations, including adult neurogenesis decline. Flavonoids are a class of plant-derived dietary polyphenols that have drawn attention for their neuroprotective and pro-cognitive effects. Although they undergo extensive metabolism and localize in the brain at low concentrations, flavonoids are now believed to improve cerebral vasculature and interact with signal transduction cascades involved in the regulation of adult neurogenesis. Furthermore, many dietary flavonoids have been shown to reduce oxidative stress and neuroinflammation, improving the neuronal microenvironment where adult neurogenesis occurs. The overall goal of this review is to summarize the evidence supporting the role of flavonoids in modulating adult neurogenesis as well as to highlight how these dietary agents may be promising candidates in restoring healthy brain function during physiological and pathological aging.

Implication of Hippocampal Neurogenesis in Autism Spectrum Disorder: Pathogenesis and Therapeutic Implications

Autism spectrum disorder (ASD) is a cluster of heterogeneous neurodevelopmental conditions with atypical social communication and repetitive sensory-motor behaviors. The formation of new neurons from neural precursors in the hippocampus has been unequivocally demonstrated in the dentate gyrus of rodents and non-human primates. Accumulating evidence sheds light on how the deficits in the hippocampal neurogenesis may underlie some of the abnormal behavioral phenotypes in ASD. In this review, we describe the current evidence concerning pre-clinical and clinical studies supporting the significant role of hippocampal neurogenesis in ASD pathogenesis, discuss the possibility of improving hippocampal neurogenesis as a new strategy for treating ASD, and highlight the prospect of emerging pro-neurogenic therapies for ASD.

From cradle to grave: neurogenesis, neuroregeneration and neurodegeneration in Alzheimer's and Parkinson's diseases

Two of the most common neurodegenerative disorders - Alzheimer's and Parkinson's diseases - are characterized by synaptic dysfunction and degeneration that culminate in neuronal loss due to abnormal protein accumulation. The intracellular aggregation of hyper-phosphorylated tau and the extracellular aggregation of amyloid beta plaques form the basis of Alzheimer's disease pathology. The major hallmark of Parkinson's disease is the loss of dopaminergic neurons in the substantia nigra pars compacta, following the formation of Lewy bodies, which consists primarily of alpha-synuclein aggregates. However, the discrete mechanisms that contribute to neurodegeneration in these disorders are still poorly understood. Both neuronal loss and impaired adult neurogenesis have been reported in animal models of these disorders. Yet these findings remain subject to frequent debate due to a lack of conclusive evidence in post mortem brain tissue from human patients. While some publications provide significant findings related to axonal regeneration in Alzheimer's and Parkinson's diseases, they also highlight the limitations and obstacles to the development of neuroregenerative therapies. In this review, we summarize in vitro and in vivo findings related to neurogenesis, neuroregeneration and neurodegeneration in the context of Alzheimer's and Parkinson's diseases.

p73 isoforms meet evolution of metastasis

Cancer largely adheres to Darwinian selection. Evolutionary forces are prominent during metastasis, the final and incurable disease stage, where cells acquire combinations of advantageous phenotypic features and interact with a dynamically changing microenvironment, in order to overcome the metastatic bottlenecks, while therapy exerts additional selective pressures. As a strategy to increase their fitness, tumors often co-opt developmental and tissue-homeostasis programs. Herein, 25 years after its discovery, we review TP73, a sibling of the cardinal tumor-suppressor TP53, through the lens of cancer evolution. The TP73 gene regulates a wide range of processes in embryonic development, tissue homeostasis and cancer via an overwhelming number of functionally divergent isoforms. We suggest that TP73 neither merely mimics TP53 via its p53-like tumor-suppressive functions, nor has black-or-white-type effects, as inferred by the antagonism between several of its isoforms in processes like apoptosis and DNA damage response. Rather, under dynamic conditions of selective pressure, the various p73 isoforms which are often co-expressed within the same cancer cells may work towards a common goal by simultaneously activating isoform-specific transcriptional and non-transcriptional programs. Combinatorial co-option of these programs offers selective advantages that overall increase the likelihood for successfully surpassing the barriers of the metastatic cascade. The p73 functional pleiotropy-based capabilities might be present in subclonal populations and expressed dynamically under changing microenvironmental conditions, thereby supporting clonal expansion and propelling evolution of metastasis. Deciphering the critical p73 isoform patterns along the spatiotemporal axes of tumor evolution could identify strategies to target TP73 for prevention and therapy of cancer metastasis.

Metabolic regulation of the neural stem cell fate: Unraveling new connections, establishing new concepts

The neural stem cell niche is a key regulator participating in the maintenance, regeneration, and repair of the brain. Within the niche neural stem cells (NSC) generate new neurons throughout life, which is important for tissue homeostasis and brain function. NSCs are regulated by intrinsic and extrinsic factors with cellular metabolism being lately recognized as one of the most important ones, with evidence suggesting that it may serve as a common signal integrator to ensure mammalian brain homeostasis. The aim of this review is to summarize recent insights into how metabolism affects NSC fate decisions in adult neural stem cell niches, with occasional referencing of embryonic neural stem cells when it is deemed necessary. Specifically, we will highlight the implication of mitochondria as crucial regulators of NSC fate decisions and the relationship between metabolism and ependymal cells. The link between primary cilia dysfunction in the region of hypothalamus and metabolic diseases will be examined as well. Lastly, the involvement of metabolic pathways in ependymal cell ciliogenesis and physiology regulation will be discussed.

Mesenchymal stem cells and exosomes improve cognitive function in the aging brain by promoting neurogenesis

Biologically speaking, normal aging is a spontaneous and inevitable process of organisms over time. It is a complex natural phenomenon that manifests itself in the form of degenerative changes in structures and the decline of functions, with diminished adaptability and resistance. Brain aging is one of the most critical biological processes that affect the physiological balance between health and disease. Age-related brain dysfunction is a severe health problem that contributes to the current aging society, and so far, there is no good way to slow down aging. Mesenchymal stem cells (MSCs) have inflammation-inhibiting and proliferation-promoting functions. At the same time, their secreted exosomes inherit the regulatory and therapeutic procedures of MSCs with small diameters, allowing high-dose injections and improved therapeutic efficiency. This manuscript describes how MSCs and their derived exosomes promote brain neurogenesis and thereby delay aging by improving brain inflammation.