Adult neurogenesis in Alzheimer's disease

Identification of a novel pyrrolo[2,3-b]pyridine compound as a potent glycogen synthase kinase 3β inhibitor for treating Alzheimer's disease

Herein, a novel pyrrolo[2,3-b]pyridine-based glycogen synthase kinase 3β (GSK-3β) inhibitor, S01, was rationally designed and synthesised to target Alzheimer's disease (AD). S01 inhibited GSK-3β, with an IC50 of 0.35 ± 0.06 nM, and had an acceptable kinase selectivity for 24 structurally similar kinases. Western blotting assays indicated that S01 efficiently increased the expression of p-GSK-3β-Ser9 and decreased p-tau-Ser396 levels in a dose-dependent manner. In vitro cell experiments, S01 showed low cytotoxicity to SH-SY5Y cells, significantly upregulated the expression of β-catenin and neurogenesis-related biomarkers, and effectively promoted the outgrowth of differentiated neuronal neurites. Moreover, S01 substantially ameliorated dyskinesia in AlCl3-induced zebrafish AD models at a concentration of 0.12 μM, which was more potent than Donepezil (8 μM) under identical conditions. Acute toxicity experiments further confirmed the safety of S01 in vivo. Our findings suggested that S01 is a prospective GSK-3β inhibitor and can be tested as a candidate for treating AD.

Multimodal beneficial effects of BNN27, a nerve growth factor synthetic mimetic, in the 5xFAD mouse model of Alzheimer's disease

Alzheimer's Disease (AD) is an incurable and debilitating progressive, neurodegenerative disorder which is the leading cause of dementia worldwide. Neuropathologically, AD is characterized by the accumulation of Aβ amyloid plaques in the microenvironment of brain cells and neurovascular walls, chronic neuroinflammation, resulting in neuronal and synaptic loss, myelin and axonal failure, as well as significant reduction in adult hippocampal neurogenesis. The hippocampal formation is particularly vulnerable to this degenerative process, due to early dysfunction of the cholinergic circuit. Neurotrophic factors consist major regulatory molecules and their decline in AD is considered as an important cause of disease onset and progression. Novel pharmacological approaches are targeting the downstream pathways controlled by neurotrophins, such as nerve growth factor (NGF) receptors, TrkA and p75NTR, which enhance hippocampal neurogenic capacity and neuroprotective mechanisms, and potentially counteract the neurotoxic effects of amyloid deposition. BNN27 is a non-toxic, newly developed 17-spiro-steroid analog, penetrating the blood-brain-barrier (BBB) and mimicking the neuroprotective effects of NGF, acting as selective activator of its receptors, both TrkA and p75NTR, thus promoting survival of various neuronal cell types. Our present research aims at determining whether and which aspects of the AD-related pathology, BNN27 is able to alleviate, exploring the cellular and molecular AD components and link these changes with improvements in the cognitive performance of an animal AD model, the 5xFAD mice. Our results clearly indicate that BNN27 administration significantly reduced amyloid-β load in whole brain of the animals, enhanced adult hippocampal neurogenesis, restored cholinergic function and synaptogenesis, reducing inflammatory activation and leading to significant restoration of cognitive functions. BNN27 may represent a new lead multimodal molecule with neuroprotective, neurogenic and anti-neuroinflammatory actions for developing druggable anti-Alzheimeric agents. Proteomics data are available via ProteomeXchange with the identifier PXD044699.

Cerebral small vessel disease: The impact of glymphopathy and sleep disorders

The glymphatic system, a vital brain perivascular network for waste clearance, hinges on the functionality of the aquaporin 4 (AQP4) water channel. Alarmingly, AQP4 single nucleotide polymorphisms (SNPs) are linked to impaired glymphatic clearance, or glymphopathy, which contributes to sleep disturbances and various age-related neurodegenerative diseases. Despite the critical role of glymphopathy and sleep disturbances in cerebral small vessel disease (CSVD) - a silent precursor to age-related neurodegenerative disorders - their interplay remains underexplored. CSVD is a major cause of stroke and dementia, yet its pathogenesis is not fully understood. Emerging evidence implicates glymphopathy and sleep disorders as pivotal factors in age-related CSVD, exacerbating the condition by hindering waste removal and compromising blood-brain barrier (BBB) integrity. Advanced imaging techniques promise to enhance diagnosis and monitoring, while lifestyle modifications and personalised medicine present promising treatment avenues. This narrative review underscores the need for a multidisciplinary approach to understanding glymphopathy and sleep disorders in CSVD. By exploring their roles, emphasising the necessity for longitudinal studies, and discussing potential therapeutic interventions, this paper aims to pave the way for new research and therapeutic directions in CSVD management.

Neural stem and progenitor cells support and protect adult hippocampal function via vascular endothelial growth factor secretion

Adult neural stem and progenitor cells (NSPCs) reside in the dentate gyrus (DG) of the hippocampus throughout the lifespan of most mammalian species. In addition to generating new neurons, NSPCs may alter their niche via secretion of growth factors and cytokines. We recently showed that adult DG NSPCs secrete vascular endothelial growth factor (VEGF), which is critical for maintaining adult neurogenesis. Here, we asked whether NSPC-derived VEGF alters hippocampal function independent of adult neurogenesis. We found that loss of NSPC-derived VEGF acutely impaired hippocampal memory, caused neuronal hyperexcitability and exacerbated excitotoxic injury. Conversely, we observed that overexpression of VEGF reduced microglial response to excitotoxic injury. We also found that NSPCs generate substantial proportions of total DG VEGF and VEGF disperses widely throughout the DG, both of which help explain how this anatomically-restricted cell population could modulate function broadly. These findings suggest that NSPCs actively support and protect DG function via secreted VEGF, thereby providing a non-neurogenic functional dimension to endogenous NSPCs.

Improving executive functioning and reducing the risk of Alzheimer's disease with music therapy: A narrative review of potential neural mechanisms

The incidence of Alzheimer's disease (AD) and the concurrent cost of healthcare will increase as the population continues to age. Pharmaceutical interventions effectively manage symptoms of AD but carry side effects and ineffectively address underlying causes and disease prevention. Non-pharmaceutical interventions for AD, such as music training and therapy do not carry these side effects and can improve symptoms, and should therefore be explored as stand-alone or co-therapy for AD. In addition, music encapsulates modifiable lifestyle factors, such as cognitive stimulation, that have been shown to delay progression of and prevent AD. However, the neural mechanisms underpinning how music improves AD symptoms are not fully understood and whether music can target compensatory processes, activate neural networks, or even slow or prevent AD needs further research. Research suggests neural mechanism may involve stimulating brain areas to promote neurogenesis, dopaminergic rewards systems, and the default mode network (DMN). Alternatively, this review proposes that music improve symptoms of AD via the fronto-parietal control network (FPCN), the salience network (SN) and DMN, and neural compensation. This review will then present evidence for how music could activate the FPCN, SN, and DMN to improve their efficiency, organization, and cognitive functions they govern, protecting the brain from damage, slowing progression, and possibly preventing AD. Establishing how music improves symptoms of AD can lead to tailored music therapy protocols that target functional neural networks responsible for impaired executive functions common in AD.

An Optimal Beneficiary Profile to Ensure Focused Interventions for Older Adults

Background: Aging is a lifelong process, and many chronic diseases and geriatric syndromes are influenced by lifestyle factors. For active aging and maintaining functional capacity facilitate health, there are essential aspects in geriatric care. Our objective was to create a specific profile focusing on the characteristics of a possible optimal beneficiary of a newly developed program that is meant to increase the social inclusion and participation in social life of older adults. Methods: The profile was built based on a mixed design, a quantitative and qualitative analysis that identified the typology of an optimal beneficiary of a newly developed yoga program. The quantitative analysis (50 subjects from NIGG "Ana Aslan" Bucharest) identified the main predictors impacting subjects' willingness to participate in a yoga program based on their pathologies at a mental and/or physical level. The main materials used for this were the Clinical Assessment Scales for the Elderly (CASE-SF) and the Quality-of-Life Assessment Questionnaire (WHOQOL-BREF). The qualitative analysis consisted of four focus groups (10 subjects from NIGG "Ana Aslan" and 7 subjects from GNSPY), aiming to provide the in-depth reasons for participating in a yoga program. Results: The results showed that a diagnosed physical impairment was correlated with an increased willingness to participate in yoga classes, while a mental pathology was associated with a decreased willingness to participate in such a program. Five main themes emerged from the qualitative analysis. Conclusions: The profile provides answers related to the specifics of the beneficiary based on their motivation, limits, and personality traits.

Alzheimer's Disease-Derived Outer Membrane Vesicles Exacerbate Cognitive Dysfunction, Modulate the Gut Microbiome, and Increase Neuroinflammation and Amyloid-β Production

Although our understanding of the molecular biology of Alzheimer's disease (AD) continues to improve, the etiology of the disease, particularly the involvement of gut microbiota disturbances, remains a challenge. Outer membrane vesicles (OMVs) play a key role in central nervous system diseases, but the impact of OMVs on AD progression remains unclear. In this study, we hypothesized that AD-derived OMVs (OMVsAD) were a risk factor in AD pathology. To test our hypothesis, young APP/PS1 mice (AD mice) were given OMVsAD by gavage. Young AD mice were euthanized 120 days after gavage to assess the intestinal barrier, gut microbiota diversity, mediators of neuroinflammation, glial markers, amyloid burden, and short-chain fatty acid (SCFA) levels. Our results showed that OMVsAD accelerated cognitive dysfunction after 120 days of intragastric administration. Morris water maze experiment and new object recognition test showed that OMVsAD caused significantly poorer spatial ability learning and memory of the AD mice. We observed the OMVsAD-treated APP/PS1 mice display OMVs disrupting the intestinal barrier compared with controls of normal human-derived OMVs. Compared with the OMVsHC group, claudin-5 and ZO-1 related to the intestinal barrier were significantly downregulated in the OMVsAD group. The OMVsAD activate microglia in the cerebral cortex and hippocampus of AD mice, and the levels of IL-1β, IL-6, TNF-α, and NF-Κb were upregulated. We also found that OMVsAD increased Aβ production. 16S rRNA sequencing showed that OMVsAD negatively regulated the α- and β-diversity index of intestinal flora and reduced the levels of SCFA. OMVsAD may change the intestinal flora of young AD, damage the intestinal mucosa and blood-brain barrier, and accelerate AD neuropathological damage.

Plasma tryptophan levels are linked to hippocampal integrity and cognitive function in individuals with mild cognitive impairment

Tryptophan has been shown to improve cognitive functions, but whether these benefits emanate from changes in hippocampal structure or other mechanisms like enhanced serotonin pathways remains unclear. This study aimed to examine the relationship between tryptophan levels and hippocampal volumes in individuals with mild cognitive impairment (MCI) and to determine if changes in hippocampal volume correlate with cognitive function. A total of 499 individuals with MCI were recruited based on ADNI's clinical criteria. Cognitive function was assessed using the ADAS-Cog scale, and hippocampal volumes were measured through MRI using semi-automated Medtronic Surgical Navigation Technologies (SNT). Tryptophan levels in plasma were analyzed using a nuclear magnetic resonance (NMR)-based assay. This study used two models: One unadjusted and another adjusted for covariates such as age, gender, handedness, and ApoE ɛ3 and ɛ4. In both models, higher tryptophan levels were significantly associated with increased bilateral hippocampal volumes, with a stronger effect in the left hippocampus. Furthermore, larger hippocampal volumes were linked to improved cognitive performance. Mediation analysis showed that hippocampal volumes mediated the relationship between plasma tryptophan levels and cognitive function. These findings suggested that elevated plasma tryptophan levels support cognitive health by maintaining hippocampal structural integrity, underscoring its potential role in preserving cognitive function in individuals with MCI.

Sulfonic acid functionalized β-amyloid peptide aggregation inhibitors and antioxidant agents for the treatment of Alzheimer's disease: Combining machine learning, computational, in vitro and in vivo approaches

Alzheimer's disease (AD) is characterized as a neurodegenerative disorder that is caused by plaque formation by accumulating β-amyloid (Aβ), leading to neurocognitive function and impaired mental development. Thus, targeting Aβ represents a promising target for the development of therapeutics in AD management. Several functionalized sulfonic acid molecules have been reported, including tramiprosate prodrug, which is currently in clinical trial III and exhibits a good response in mild to moderate AD patients. Therefore, expanding upon this approach, we hypothesized that the sulfonic acid functionalized aromatic class molecule might demonstrate a good inhibitory effect against β-amyloid aggregation, leading to a decrease in the progression burden of AD. We used computational and in vitro approaches to establish effective compounds. As a result, three potent hit molecules were selected based on binding score as well as availability. In the case of safety profile of compounds, in vitro using human neuroblastoma SH-SY5Y cells and in vivo using C. elegans was performed at doses up to 500 μM; no difference in viability was exhibited between control and treatment groups. However, H2O2-induced ROS stress was significantly reduced in neuroblastoma cells after treatment. The AFM and ThT-embedded β-amyloid1-42 kinetic studies confirmed B-PEA-MBSA and H-HPA-NSA potency. H-HPA-NSA arrested elongation phase of Aβ aggregation in kinetic study at a lower concentration (10 μM), while B-PEA-MBSA reduced the intensity of stationary phase at a dose of 100 μM. Thus, based on the outcomes, it can be suggested that B-PEA-MBSA and H-HPA-NSA can prevent β-amyloid aggregation with mild to moderate AD.

Synthesis and biological evaluation of novel pyrrolo[2,3-b]pyridine derivatives as potent GSK-3β inhibitors for treating Alzheimer's disease

The development of potent glycogen synthase kinase-3β (GSK-3β) inhibitor has been increasingly recognized as the candidate treatment against the multifactorial pathogenic mechanism of Alzheimer's disease (AD). This study prepared various new pyrrolo[2,3-b]pyridine derivatives, evaluated the anti-AD activities and detected the security based on the structure-guided rational design. Our results indicated that many pyrrolo[2,3-b]pyridine derivatives had strong GSK-3β inhibitory activities, particularly compounds 41, 46 and 54, with the half maximal inhibitory concentrations (IC50) of 0.22, 0.26 and 0.24 nM, respectively, and each of them generally possessed GSK-3β selectivity over 24 structurally similar kinases. In addition, further targeting studies at the cellular level revealed that compound 41 increased GSK-3β phosphorylation at Ser9 site dose-dependently for inhibiting GSK-3β activity, therefore inhibiting the hyperphosphorylation of tau protein by decreasing the p-tau-Ser396 abundance. Moreover, 41 up-regulated β-catenin and neurogenesis-related markers (GAP43 and MAP-2), thereby promoting neurite outgrowth of neurons in SH-SY5Y cells. According to the in vitro cells assay, 41 showed the lower cytotoxicity to SH-SY5Y cells with a survival rate of over 70 % at the concentration of 100 μM. In vivo efficacy and acute toxicity experiments showed that, 41 effectively ameliorated the dyskinesia in AlCl3-induced zebrafish AD models and exhibited its low-toxicity nature in C57BL/6 mice. Overall, the pyrrolo[2,3-b]pyridine derivative 41 could serve as a promising GSK-3β inhibitor for treating AD.

Exercise alleviates cognitive decline of natural aging rats by upregulating Notch-mediated autophagy signaling

Notch signaling, a classical signaling pathway of neurogenesis, is downregulated during the aging and age-related neurodegenerative diseases. Exercise has been proposed as an effective lifestyle intervention for delaying cognitive decline. However, it remains unclear whether exercise intervention could alleviate cognitive decline by modulating neurogenesis in naturally aging rats. In this study, 21-month-old natural aging rats were used to study brain aging. The natural aging rats underwent different forms of exercise training (aerobic exercise or strength training or comprehensive exercise with aerobic exercise and strength training) for 12 consecutive weeks. The cognitive function of natural aging rats was determined by Morris Water Maze. Notch signaling, autophagy-related proteins and hippocampal neurogenesis were examined by immunofluorescence, qRT-PCR and Western blot. Results showed that natural aging rats exhibited cognitive decline, accumulation of AD pathological proteins (APP and Aβ), and decreased neurogenesis (decreased DCX, Ki67 and GFAP), compared with the young control rats. Moreover, a significant decline in Notch signaling and autophagy was found in the hippocampus of natural aging rats. However, different forms of exercise upregulated Notch signaling and its downstream target genes, as well as autophagy-related proteins, including LC3, Beclin1, and p62. In summary, our data suggest that different forms of exercise can mitigate brain aging by upregulating Notch signaling and autophagy, thereby increasing hippocampal neurogenesis and improves spatial learning and memory abilities.

Efficacy and molecular mechanisms of hesperidin in mitigating Alzheimer's disease: A systematic review

Hesperidin, a flavonoid glycoside, is a natural phenolic compound that has broad biological effects. Increasing evidence suggests that hesperidin inhibits the occurrence and development of neurodegenerative diseases, including Alzheimer's disease (AD). This article reviews the neuropharmacological mechanisms of hesperidin in the prevention and treatment of AD through in vitro and in vivo studies. A systematic review of preclinical studies was conducted using PubMed, Web of Science, Scopus, and Google Scholar (up to July 1, 2024). The neuroprotective potential of hesperidin was mediated through mechanisms such as inhibition of β-amyloid (Aβ) aggregation, enhancement of endogenous antioxidant defense functions, reduction of neuroinflammation and apoptosis, improvement of mitochondrial dysfunction, regulation of autophagy, and promotion of neurogenesis. Despite various preclinical studies on the role of hesperidin in AD, its exact effects on humans remain unclear. Few clinical trials have indicated that dietary supplements rich in hesperidin can improve cerebral blood flow, cognition, and memory performance. The neuroprotective effect of hesperidin may be exerted via regulating different molecular pathways, including the RAGE/NF-κB, Akt/Nrf2, and AMPK/BDNF/CREB pathways. However, further clinical trials are needed to confirm the neuroprotective effects of this natural flavonoid compound and to assess its safety.

Olfactory deficits in aging and Alzheimer's-spotlight on inhibitory interneurons

Cognitive function in healthy aging and neurodegenerative diseases like Alzheimer's disease (AD) correlates to olfactory performance. Aging and disease progression both show marked olfactory deficits in humans and rodents. As a clear understanding of what causes olfactory deficits is still missing, research on this topic is paramount to diagnostics and early intervention therapy. A recent development of this research is focusing on GABAergic interneurons. Both aging and AD show a change in excitation/inhibition balance, indicating reduced inhibitory network functions. In the olfactory system, inhibition has an especially prominent role in processing information, as the olfactory bulb (OB), the first relay station of olfactory information in the brain, contains an unusually high number of inhibitory interneurons. This review summarizes the current knowledge on inhibitory interneurons at the level of the OB and the primary olfactory cortices to gain an overview of how these neurons might influence olfactory behavior. We also compare changes in interneuron composition in different olfactory brain areas between healthy aging and AD as the most common neurodegenerative disease. We find that pathophysiological changes in olfactory areas mirror findings from hippocampal and cortical regions that describe a marked cell loss for GABAergic interneurons in AD but not aging. Rather than differences in brain areas, differences in vulnerability were shown for different interneuron populations through all olfactory regions, with somatostatin-positive cells most strongly affected.

Recent advancement in understanding of Alzheimer's disease: Risk factors, subtypes, and drug targets and potential therapeutics

Alzheimer's disease (AD) is a significant neocortical degenerative disorder characterized by the progressive loss of neurons and secondary alterations in white matter tracts. Understanding the risk factors and mechanisms underlying AD is crucial for developing effective treatments. The risk factors associated with AD encompass a wide range of variables, including gender differences, family history, and genetic predispositions. Additionally, environmental factors such as air pollution and lifestyle-related conditions like cardiovascular disease, gut pathogens, and liver pathology contribute substantially to the development and progression of AD and its subtypes. This review provides current update and deeper insights into the role of diverse risk factors, categorizing AD into its distinct subtypes and elucidating their specific pathophysiological mechanisms. Unlike previous studies that often focus on isolated aspects of AD, our review integrates these factors to offer a comprehensive understanding of the disease. Furthermore, the review explores a variety of drug targets linked to the neuropathology of different AD subtypes, highlighting the potential for targeted therapeutic interventions. We further discussed the novel therapeutic options and categorized them according to their targets. The roles of different drug targets were comprehensively studied, and the mechanism of action of their inhibitors was discussed in detail. By comprehensively covering the interplay of risk factors, subtype differentiation, and drug targets, this review provides a deeper understanding of AD and suggests directions for future research and therapeutic strategies.

Farnesylthiosalicylic Acid Through Inhibition of Galectin-3 Improves Neuroinflammation in Alzheimer Disease via Multiple Pathways

AIMS

Many factors affect the neuroinflammatory response in patients with Alzheimer disease (AD). Galectin-3 (Gal-3) is closely related to microglial activation in the nervous system and can promote the aggregation of cancer cells in tumors. This study aimed to investigate the mechanism by which farnesylthiosalicylic acid (FTS) affects neuroinflammation in Aβ1-42 mice through Gal-3.

METHODS

We used the Morris water maze, reverse transcription-polymerase chain reaction (RT-PCR), Western blotting, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence to conduct our study.

RESULTS

FTS reduced the levels of proinflammatory factors and microglial activation in Aβ1-42 mice. FTS inhibited total and membrane expression levels of Gal-3 in Aβ1-42 mice, and the anti-inflammatory effect of FTS was reversed by Gal-3-adeno-associated viral (AAV). FTS reduced the expression levels of toll-like receptors (TLRs), effects that were reversed by Gal-3-AAV. Moreover, FTS ameliorated Aβ oligomerization and accumulation in Aβ1-42 mice, effects that were also reversed by Gal-3-AAV. FTS, through the inhibition of the Gal-3-c-Jun N-terminal kinase (JNK) pathway, reduced PS1 expression; in addition, inhibition of Gal-3 increased the Aβ-degrading enzymes in Aβ1-42 mice. FTS-induced improvements in cognition in Aβ1-42 mice were reversed by Gal-3-AAV.

CONCLUSION

FTS may through inhibiting Gal-3 reduce the expression of TLR4 and CD14 and alleviate Aβ pathology, downregulating Aβ-stimulated TLR2, TLR4, and CD14 expression, and thus alleviate neuroinflammation in Aβ1-42 mice.

The intricate interplay between microglia and adult neurogenesis in Alzheimer's disease

Microglia, the resident immune cells of the central nervous system, play a crucial role in regulating adult neurogenesis and contribute significantly to the pathogenesis of Alzheimer's disease (AD). Under physiological conditions, microglia support and modulate neurogenesis through the secretion of neurotrophic factors, phagocytosis of apoptotic cells, and synaptic pruning, thereby promoting the proliferation, differentiation, and survival of neural progenitor cells (NPCs). However, in AD, microglial function becomes dysregulated, leading to chronic neuroinflammation and impaired neurogenesis. This review explores the intricate interplay between microglia and adult neurogenesis in health and AD, synthesizing recent findings to provide a comprehensive overview of the current understanding of microglia-mediated regulation of adult neurogenesis. Furthermore, it highlights the potential of microglia-targeted therapies to modulate neurogenesis and offers insights into potential avenues for developing novel therapeutic interventions.

Dysregulated expression of miR-140 and miR-122 compromised microglial chemotaxis and led to reduced restriction of AD pathology

BACKGROUND

Deposition of amyloid β, which is produced by amyloidogenic cleavage of APP by β- and γ-secretase, is one of the primary hallmarks of AD pathology. APP can also be processed by α- and γ-secretase sequentially, to generate sAPPα, which has been shown to be neuroprotective by promoting neurite outgrowth and neuronal survival, etc. METHODS: The global expression profiles of miRNA in blood plasma samples taken from 11 AD patients as well as from 14 age and sex matched cognitively normal volunteers were analyzed using miRNA-seq. Then, overexpressed miR-140 and miR-122 both in vivo and in vitro, and knock-down of the endogenous expression of miR-140 and miR-122 in vitro. Used a combination of techniques, including molecular biology, immunohistochemistry, to detect the impact of miRNAs on AD pathology.

RESULTS

In this study, we identified that two miRNAs, miR-140-3p and miR-122-5p, both targeting ADAM10, the main α-secretase in CNS, were upregulated in the blood plasma of AD patients. Overexpression of these two miRNAs in mouse brains induced cognitive decline in wild type C57BL/6J mice as well as exacerbated dyscognition in APP/PS1 mice. Although significant changes in APP and total Aβ were not detected, significantly downregulated ADAM10 and its non-amyloidogenic product, sAPPα, were observed in the mouse brains overexpressing miR-140/miR-122. Immunohistology analysis revealed increased neurite dystrophy that correlated with the reduced microglial chemotaxis in the hippocampi of these mice, independent of the other two ADAM10 substrates (neuronal CX3CL1 and microglial TREM2) that were involved in regulating the microglial immunoactivity. Further in vitro analysis demonstrated that both the reduced neuritic outgrowth of mouse embryonic neuronal cells overexpressing miR-140/miR-122 and the reduced Aβ phagocytosis in microglia cells co-cultured with HT22 cells overexpressing miR-140/miR-122 could be rescued by overexpressing the specific inhibitory sequence of miR-140/miR-122 TuD as well as by addition of sAPPα, rendering these miRNAs as potential therapeutic targets.

CONCLUSIONS

Our results suggested that neuroprotective sAPPα was a key player in the neuropathological progression induced by dysregulated expression of miR-140 and miR-122. Targeting these miRNAs might serve as a promising therapeutic strategy in AD treatment.

Autocrine VEGF drives neural stem cell proximity to the adult hippocampus vascular niche

The vasculature is a key component of adult brain neural stem cell (NSC) niches. In the adult mammalian hippocampus, NSCs reside in close contact with a dense capillary network. How this niche is maintained is unclear. We recently found that adult hippocampal NSCs express VEGF, a soluble factor with chemoattractive properties for vascular endothelia. Here, we show that global and NSC-specific VEGF loss led to dissociation of NSCs and their intermediate progenitor daughter cells from local vasculature. Surprisingly, though, we found no changes in local vascular density. Instead, we found that NSC-derived VEGF supports maintenance of gene expression programs in NSCs and their progeny related to cell migration and adhesion. In vitro assays revealed that blockade of VEGF receptor 2 impaired NSC motility and adhesion. Our findings suggest that NSCs maintain their own proximity to vasculature via self-stimulated VEGF signaling that supports their motility towards and/or adhesion to local blood vessels.

Curcumin Improves Neurogenesis in Alzheimer's Disease Mice via the Upregulation of Wnt/β-Catenin and BDNF

Adult neurogenesis in the dentate gyrus (DG) is impaired during Alzheimer's disease (AD) progression. Curcumin has been reported to reduce cell apoptosis and stimulate neurogenesis. This study aimed to investigate the influence of curcumin on adult neurogenesis in AD mice and its potential mechanism. Two-month-old male C57BL/6J mice were injected with soluble β-amyloid (Aβ1-42) using lateral ventricle stereolocalization to establish AD models. An immunofluorescence assay, including bromodeoxyuridine (BrdU), doublecortin (DCX), and neuron-specific nuclear antigen (NeuN), was used to detect hippocampal neurogenesis. Western blot and an enzyme-linked immunosorbent assay (ELISA) were used to test the expression of related proteins and the secretion of brain-derived neurotrophic factor (BDNF). A Morris water maze was used to detect the cognitive function of the mice. Our results showed that curcumin administration (100 mg/kg) rescued the impaired neurogenesis of Aβ1-42 mice, shown as enhanced BrdU+/DCX+ and BrdU+/NeuN+ cells in DG. In addition, curcumin regulated the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) -mediated glycogen synthase kinase-3β (GSK3β) /Wingless/Integrated (Wnt)/β-catenin pathway and cyclic adenosine monophosphate response element-binding protein (CREB)/BDNF in Aβ1-42 mice. Inhibiting Wnt/β-catenin and depriving BDNF could reverse both the upregulated neurogenesis and cognitive function of curcumin-treated Aβ1-42 mice. In conclusion, our study indicates that curcumin, through targeting PI3K/Akt, regulates GSK3β/Wnt/β-catenin and CREB/BDNF pathways, improving the adult neurogenesis of AD mice.

Adult Neurogenesis, Context Encoding, and Pattern Separation: A Pathway for Treating Overgeneralization

In mammals, the subgranular zone of the dentate gyrus is one of two brain regions (with the subventricular zone of the olfactory bulb) that continues to generate new neurons throughout adulthood, a phenomenon known as adult hippocampal neurogenesis (AHN) (Eriksson et al., Nat Med 4:1313-1317, 1998; García-Verdugo et al., J Neurobiol 36:234-248, 1998). The integration of these new neurons into the dentate gyrus (DG) has implications for memory encoding, with unique firing and wiring properties of immature neurons that affect how the hippocampal network encodes and stores attributes of memory. In this chapter, we will describe the process of AHN and properties of adult-born cells as they integrate into the hippocampal circuit and mature. Then, we will discuss some methodological considerations before we review evidence for the role of AHN in two major processes supporting memory that are performed by the DG. First, we will discuss encoding of contextual information for episodic memories and how this is facilitated by AHN. Second, will discuss pattern separation, a major role of the DG that reduces interference for the formation of new memories. Finally, we will review clinical and translational considerations, suggesting that stimulation of AHN may help decrease overgeneralization-a common endophenotype of mood, anxiety, trauma-related, and age-related disorders.

Neural stem cells persist to generate new neurons in the hippocampus of adult and aged human brain - Fiction or accurate?

Adult neurogenesis, comprising the generation, differentiation and integration of new neurons in the mature brain, has emerged as a dynamic area of research over decades. The discovery of adult neurogenesis was a paradigm shift to comprehend mechanisms underlying brain plasticity, cognitive function, and neurological disorders. This review deliberates significant findings from articles published over four decades on adult neurogenesis, highlighting key milestones, methodological advances, and controversies that have shaped our comprehension of the phenomenon of adult neurogenesis. Early skepticism gave way to a rich body of evidence via various reliable approaches. Studies on neurogenic niches, microenvironmental factors, molecular regulators, and functional implications have uncovered the involvement of adult neurogenesis in learning, memory, mood, and even neurological and neurodegenerative conditions. Despite significant progress, several questions still need to be answered, including the exact contributions of new neurons to brain function, their integration into existing circuits, and the impact of enhancing adult neurogenesis in the human hippocampus. While the existence of robust neurogenesis in the adult and aged human hippocampus is yet to be confirmed, this review highlights evidence from a significant number of studies supporting the persistence of hippocampal neurogenesis during adulthood and aging in humans, including in some neurological conditions, such as epilepsy and Alzheimer's disease. Nonetheless, additional large-scale studies using single cell-RNA-seq, single nucleus-RNA-seq, and spatial transcriptomics are critical to validate the presence and contribution of hippocampal neurogenesis in the pathophysiology of various neurological and neurodegenerative conditions at different stages of the disease. There is also a need to develop standardized protocols for analyzing postmortem hippocampal tissues for cellular and molecular analyses.

Advances in Amino Acid-Based Chemistry

Numerous applications of amino acid-based compounds and peptide derivatives in different biomedicine- and nanotechnology-related fields were described in the recent scientific literature [...].

Perspectives on Aging and Quality of Life

The aging of the world's population and the health problems accompanying it are becoming increasingly severe. Healthcare policies in developed countries focus on how to prevent and treat diseases associated with aging and how to maintain quality of life. Typical age-related diseases include deafness, cataracts, osteoarthritis, chronic obstructive pulmonary disease, diabetes mellitus, and dementia. Although the mechanisms by which these diseases develop differ, they are all caused by the accumulation of molecular and cellular damage over time. In addition, age-related diseases can cause a decline in physical and mental functions and the ability to perform activities of daily living, as well as the loss of roles in society and a sense of fulfillment in life. Therefore, there is a need for treatment and measures to accurately grasp and maintain quality of life. This review aims to introduce areas and representative papers expected to be contributed to the special issue of "Aging and Quality of Life".

The glymphatic system: a new perspective on brain diseases

The glymphatic system is a brain-wide perivascular pathway driven by aquaporin-4 on the endfeet of astrocytes, which can deliver nutrients and active substances to the brain parenchyma through periarterial cerebrospinal fluid (CSF) influx pathway and remove metabolic wastes through perivenous clearance routes. This paper summarizes the composition, overall fluid flow, solute transport, related diseases, affecting factors, and preclinical research methods of the glymphatic system. In doing so, we aim to provide direction and reference for more relevant researchers in the future.

Nicotinic acetylcholine receptors and learning and memory deficits in Neuroinflammatory diseases

Animal survival depends on cognitive abilities such as learning and memory to adapt to environmental changes. Memory functions require an enhanced activity and connectivity of a particular arrangement of engram neurons, supported by the concerted action of neurons, glia, and vascular cells. The deterioration of the cholinergic system is a common occurrence in neurological conditions exacerbated by aging such as traumatic brain injury (TBI), posttraumatic stress disorder (PTSD), Alzheimer's disease (AD), and Parkinson's disease (PD). Cotinine is a cholinergic modulator with neuroprotective, antidepressant, anti-inflammatory, antioxidant, and memory-enhancing effects. Current evidence suggests Cotinine's beneficial effects on cognition results from the positive modulation of the α7-nicotinic acetylcholine receptors (nAChRs) and the inhibition of the toll-like receptors (TLRs). The α7nAChR affects brain functions by modulating the function of neurons, glia, endothelial, immune, and dendritic cells and regulates inhibitory and excitatory neurotransmission throughout the GABA interneurons. In addition, Cotinine acting on the α7 nAChRs and TLR reduces neuroinflammation by inhibiting the release of pro-inflammatory cytokines by the immune cells. Also, α7nAChRs stimulate signaling pathways supporting structural, biochemical, electrochemical, and cellular changes in the Central nervous system during the cognitive processes, including Neurogenesis. Here, the mechanisms of memory formation as well as potential mechanisms of action of Cotinine on memory preservation in aging and neurological diseases are discussed.

Neural stem and progenitor cells support and protect adult hippocampal function via vascular endothelial growth factor secretion

Adult neural stem and progenitor cells (NSPCs) reside in the dentate gyrus (DG) of the hippocampus throughout the lifespan of most mammalian species. In addition to generating new neurons, NSPCs may alter their niche via secretion of growth factors and cytokines. We recently showed that adult DG NSPCs secrete vascular endothelial growth factor (VEGF), which is critical for maintaining adult neurogenesis. Here, we asked whether NSPC-derived VEGF alters hippocampal function independent of adult neurogenesis. We found that loss of NSPC-derived VEGF acutely impaired hippocampal memory, caused neuronal hyperexcitability and exacerbated excitotoxic injury. We also found that NSPCs generate substantial proportions of total DG VEGF and VEGF disperses broadly throughout the DG, both of which help explain how this anatomically-restricted cell population could modulate function broadly. These findings suggest that NSPCs actively support and protect DG function via secreted VEGF, thereby providing a non-neurogenic functional dimension to endogenous NSPCs.