Quercetin promotes learning and memory performance concomitantly with neural stem/progenitor cell proliferation and neurogenesis in the adult rat dentate gyrus

Low emotional contagious behavior induces PTSD susceptibility in observers and is related to the regulation of oxytocin receptor in mice

BACKGROUND

Post-traumatic stress disorder (PTSD) is a serious psychiatric disorder that occurs after an individual has witnessed or experienced a major traumatic event. Emotional contagion seems to play an important role in witnessing trauma, highlighting the importance of understanding the neurobiological consequences of psychological or emotional stress and its impact on the individual's mental health. Therefore, understanding the relationship between emotional contagion and PTSD susceptibility and the abnormal neurobiological and behavioral changes behind it could help find effective molecular treatment targets.

METHODS

The formalin pain test was used to distinguish the level of emotional contagion in observer mice, dividing them into quartiles according to their pain response. The upper and lower quartiles were the emotional contagion-prone (ECP) and -resistant (ECR) groups, respectively. The vicarious social defeat stress (VSDS) procedure was used to establish PTSD models in mice with various emotional contagion levels when witnessing stress. Open field, elevated plus maze, social interaction test, and forced swimming test were used to examine PTSD-like symptoms. Changes in the medial prefrontal cortex (mPFC) mRNA expression of brain-derived neurotrophic factor (BDNF) and oxytocin receptor (OTR) were detected by qPCR, and their protein levels were analyzed by Western blot and immunofluorescence staining.

RESULTS

The formalin pain test induced emotional contagion behaviors in mice between the ECP and ECR levels. The VSDS procedure resulted in PTSD symptoms in mice; mice in the lowest quartile were characterized by high levels of anxiety, depression, and social avoidance behaviors, such as decreased autonomous activity and residence time in the open field test or open arms position and increased immobility time and social avoidance behavior. These were accompanied by reduced OTR and BDNF protein expression levels and fluorescence intensity, as well as reduced OTR and BDNF mRNA levels in the mPFC.

CONCLUSIONS

Emotional contagion can induce PTSD-like behavior in mice that witnessed stress. Low emotional contagion behavior increased PTSD susceptibility in the observer mice and might be related to the regulation of their oxytocin receptors.

Role of Flavonoids in Mitigating the Pathological Complexities and Treatment Hurdles in Alzheimer's Disease

With the passage of time, people step toward old age and become more prone to several diseases associated with the age. One such is Alzheimer's disease (AD) which results into neuronal damage and dementia with the progression of age. The existing therapeutics has been hindered by various enkindles like less eminent between remote populations, affordability issues and toxicity profiles. Moreover, lack of suitable therapeutic option further worsens the quality of life in older population. Developing an efficient therapeutic intervention to cure AD is still a challenge for medical fraternity. Recently, alternative approaches attain the attention of researchers to focus on plant-based therapy in mitigating AD. In this context, flavonoids gained centrality as a feasible treatment in modifying various neurological deficits. This review mainly focuses on the pathological facets and economic burden of AD. Furthermore, we have explored the possible mechanism of flavonoids with the preclinical and clinical aspects for curing AD. Flavonoids being potential therapeutic, target the pathogenic factors of AD such as oxidative stress, inflammation, metal toxicity, Aβ accumulation, modulate neurotransmission and insulin signaling. In this review, we emphasized on potential neuroprotective effects of flavonoids in AD pathology, with focus on both experimental and clinical findings. While preclinical studies suggest promising therapeutic benefits, clinical data remains limited and inconclusive. Thus, further high-quality clinical trials are necessary to validate the efficacy of flavonoids in AD. The study aim is to promote the plant-based therapies and encourage people to add flavonoids to regular diet to avail the beneficial effects in preventive therapy for AD.

Effects of Quercetin against fluoride-induced neurotoxicity in the medial prefrontal cortex of rats: A stereological, histochemical and behavioral study

BACKGROUND

Exposure to high levels of fluoride leads to brain developmental and functional damage. Motor performance deficits, learning and memory dysfunctions are related to fluoride neurotoxicity in human and rodent studies.

MATERIALS AND METHODS

Here, we evaluated the effects of Quercetin treatment (25 mg/kg) against sodium fluoride-induced neurotoxicity (NaF, 200 ppm) in the medial prefrontal cortex (mPFC) of male adult rats based on oxidative markers, behavioral performances, mRNA expressions, and stereological parameters. After a 4-week experimental period, the brains of rats were collected and used for molecular and histological analysis.

RESULTS

We found that 4 weeks of NaF exposure decreased body weight, working memory, Brain-derived neurotrophic factor (BDNF) mRNA expression, total volume of mPFC, number of neurons and non-neuronal cells in the mPFC, and anti-oxidative markers (CAT, SOD, and GSH-Px), while increased lipid peroxidation, P53 mRNA expression and anxiety. Quercetin treatment could significantly reverse the neurotoxic effect of NaF in the mPFC.

CONCLUSIONS

In summary, Quercetin could decrease the detrimental effects of NaF in the mPFC of adult rats by improving antioxidant potency and consequently decreasing neuronal and non-neuronal apoptosis.

Mechanistic and Therapeutic Insights into Flavonoid-Based Inhibition of Acetylcholinesterase: Implications for Neurodegenerative Diseases

Flavonoids are naturally occurring polyphenolic compounds known for their extensive range of biological activities. This review focuses on the inhibitory effects of flavonoids on acetylcholinesterase (AChE) and their potential as therapeutic agents for cognitive dysfunction. AChE, a serine hydrolase that plays a crucial role in cholinergic neurotransmission, is a key target in the treatment of cognitive impairments due to its function in acetylcholine hydrolysis. Natural polyphenolic compounds, particularly flavonoids, have demonstrated significant inhibition of AChE, positioning them as promising alternatives or adjuncts in neuropharmacology. This study specifically examines flavonoids such as quercetin, apigenin, kaempferol, and naringenin, investigating their inhibitory efficacy, binding mechanisms, and additional neuroprotective properties, including their antioxidant and anti-inflammatory effects. In vitro, in vivo, and in silico analyses reveal that these flavonoids effectively interact with both the active and peripheral anionic sites of AChE, resulting in increased acetylcholine levels and the stabilization of cholinergic signaling. Their mechanisms of action extend beyond mere enzymatic inhibition, as they also exhibit antioxidant and anti-amyloidogenic properties, thereby offering a multifaceted approach to neuroprotection. Given these findings, flavonoids hold considerable therapeutic potential as modulators of AChE, with implications for enhancing cognitive function and treating neurodegenerative diseases. Future studies should prioritize the enhancement of flavonoid bioavailability, evaluate their efficacy in clinical settings, and explore their potential synergistic effects when combined with established therapies to fully harness their potential as neurotherapeutic agents.

Unveiling the impact of aging on BBB and Alzheimer's disease: Factors and therapeutic implications

Alzheimer's disease (AD) is a highly prevalent neurodegenerative condition that has devastating effects on individuals, often resulting in dementia. AD is primarily defined by the presence of extracellular plaques containing insoluble β-amyloid peptide (Aβ) and neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau protein (P-tau). In addition, individuals afflicted by these age-related illnesses experience a diminished state of health, which places significant financial strain on their loved ones. Several risk factors play a significant role in the development of AD. These factors include genetics, diet, smoking, certain diseases (such as cerebrovascular diseases, obesity, hypertension, and dyslipidemia), age, and alcohol consumption. Age-related factors are key contributors to the development of vascular-based neurodegenerative diseases such as AD. In general, the process of aging can lead to changes in the immune system's responses and can also initiate inflammation in the brain. The chronic inflammation and the inflammatory mediators found in the brain play a crucial role in the dysfunction of the blood-brain barrier (BBB). Furthermore, maintaining BBB integrity is of utmost importance in preventing a wide range of neurological disorders. Therefore, in this review, we discussed the role of age and its related factors in the breakdown of the blood-brain barrier and the development of AD. We also discussed the importance of different compounds, such as those with anti-aging properties, and other compounds that can help maintain the integrity of the blood-brain barrier in the prevention of AD. This review builds a strong correlation between age-related factors, degradation of the BBB, and its impact on AD.

Quercetin promotes the proportion and maturation of NK cells by binding to MYH9 and improves cognitive functions in aged mice

BACKGROUND

Quercetin is a flavonol compound widely distributed in plants that possesses diverse biological properties, including antioxidative, anti-inflammatory, anticancer, neuroprotective and senescent cell-clearing activities. It has been shown to effectively alleviate neurodegenerative diseases and enhance cognitive functions in various models. The immune system has been implicated in the regulation of brain function and cognitive abilities. However, it remains unclear whether quercetin enhances cognitive functions by interacting with the immune system.

RESULTS

In this study, middle-aged female mice were administered quercetin via tail vein injection. Quercetin increased the proportion of NK cells, without affecting T or B cells, and improved cognitive performance. Depletion of NK cells significantly reduces cognitive ability in mice. RNA-seq analysis revealed that quercetin modulated the RNA profile of hippocampal tissues in aging animals towards a more youthful state. In vitro, quercetin significantly inhibited the differentiation of Lin-CD117+ hematopoietic stem cells into NK cells. Furthermore, quercetin promoted the proportion and maturation of NK cells by binding to the MYH9 protein.

CONCLUSIONS

In summary, our findings suggest that quercetin promotes the proportion and maturation of NK cells by binding to the MYH9 protein, thereby improving cognitive performance in middle-aged mice.

Nelumbo nucifera leaves extract ameliorated scopolamine-induced cognition impairment via enhanced adult hippocampus neurogenesis

In this presentation, we explored the molecular mechanisms of N. nucifera leaf water extracts (NLWEs) and polyphenol extract (NLPE) on scopolamine-induced cell apoptosis and cognition defects. The administration of NLWE and NLPE did not alter the body weight and serum biomarker rs and significantly ameliorated scopolamine-induced cognition impairment according to Y-maze test analysis. In mice, treatment with scopolamine disrupted normal histoarchitecture in the hippocampus, whereas the administration of NLWE and NLPE reversed the phenomenon. Western blot analysis revealed that scopolamine mitigated the expression of doublecortin (DCX), nestin, and NeuN, and cotreatment with NLWE or NLPE significantly recovered the expression of these proteins. NLWE and NLPE upregulated DCX and NeuN expression in the hippocampus region, as evidenced by immunohistochemical staining analysis of scopolamine-treated mice. NLWE and NLPE obviously elevated brain-derived neurotrophic factor (BDNF) and enhanced its downstream proteins activity. NLWE and NLPE attenuated scopolamine-induced apoptosis by reducing Bax and increased Bcl-2 expression. In addition, scopolamine also triggered apoptosis in human neuroblastoma SH-SY5Y cells whereas co-treatment with NLWE or quercetin-3-glucuronide (Q3G) reversed the phenomenon. NLWE or Q3G enhanced Bcl-2 and reduced Bax expression in the presence of scopolamine in SH-SY5Y cells. NLWE or Q3G recovered the inhibitory effects of scopolamine on neurogenesis and BDNF signals in SH-SY5Y cells. Overall, our results revealed that N. nucifera leaf extracts and Q3G promoted adult hippocampus neurogenesis and prevented apoptosis to mitigate scopolamine-induced cognition dysfunction through the regulation of BDNF signaling pathway.

Oxidative damage in neurodegeneration: roles in the pathogenesis and progression of Alzheimer disease

Alzheimer disease (AD) is associated with multiple etiologies and pathological mechanisms, among which oxidative stress (OS) appears as a major determinant. Intriguingly, OS arises in various pathways regulating brain functions, and it seems to link different hypotheses and mechanisms of AD neuropathology with high fidelity. The brain is particularly vulnerable to oxidative damage, mainly because of its unique lipid composition, resulting in an amplified cascade of redox reactions that target several cellular components/functions ultimately leading to neurodegeneration. The present review highlights the "OS hypothesis of AD," including amyloid beta-peptide-associated mechanisms, the role of lipid and protein oxidation unraveled by redox proteomics, and the antioxidant strategies that have been investigated to modulate the progression of AD. Collected studies from our groups and others have contributed to unraveling the close relationships between perturbation of redox homeostasis in the brain and AD neuropathology by elucidating redox-regulated events potentially involved in both the pathogenesis and progression of AD. However, the complexity of AD pathological mechanisms requires an in-depth understanding of several major intracellular pathways affecting redox homeostasis and relevant for brain functions. This understanding is crucial to developing pharmacological strategies targeting OS-mediated toxicity that may potentially contribute to slow AD progression as well as improve the quality of life of persons with this severe dementing disorder.

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.

Human Mesenchymal Stem Cell Transplantation Improved Functional Outcomes Following Spinal Cord Injury Concomitantly with Neuroblast Regeneration

Purpose

Spinal cord injury (SCI) is damage to the spinal cord that resulted in irreversible neuronal loss, glial scar formation and axonal injury. Herein, we used the human amniotic fluid mesenchymal stem cells (hAF-MSCs) and their conditioned medium (CM), to investigate their ability in neuroblast and astrocyte production as well as functional recovery following SCI.

Methods

Fifty-four adult rats were randomly divided into nine groups (n=6), included: Control, SCI, (SCI + DMEM), (SCI + CM), (SCI + MSCs), (SCI + Astrocyte), (SCI + Astrocyte + DMEM), (SCI + Astrocyte + CM) and (SCI + Astrocyte + MSCs). Following laminectomy and SCI induction, DMEM, CM, MSCs, and astrocytes were injected. Western blot was performed to explore the levels of the Sox2 protein in the MSCs-CM. The immunofluorescence staining against doublecortin (DCX) and glial fibrillary acidic protein (GFAP) was done. Finally, Basso-Beattie-Brenham (BBB) locomotor test was conducted to assess the neurological outcomes.

Results

Our results showed that the MSCs increased the number of endogenous DCX-positive cells and decreased the number of GFAP-positive cells by mediating juxtacrine and paracrine mechanisms (P<0.001). Transplanted human astrocytes were converted to neuroblasts rather than astrocytes under influence of MSCs and CM in the SCI. Moreover, functional recovery indexes were promoted in those groups that received MSCs and CM.

Conclusion

Taken together, our data indicate the MSCs via juxtacrine and paracrine pathways could direct the spinal cord endogenous neural stem cells (NSCs) to the neuroblasts lineage which indicates the capability of the MSCs in the increasing of the number of DCX-positive cells and astrocytes decline.

Flavonoids in Combination with Stem Cells for the Treatment of Neurological Disorders

Neurological disorders are the leading cause of disability and the world's second leading cause of death. Despite the availability of significant knowledge to reduce the burden of some neurological disorders, various studies are exploring more effective treatment options. While the human body can repair and regenerate damaged tissue through stem cell recruitment, nerve regeneration in case of injury is minimal due to the restriction on the location of nerve stem cells. Recently, different types of stem cells extracted from various tissues have been used in combination with natural stimuli to treat neurologic disorders in neuronal tissue engineering. Flavonoids are polyphenolic compounds that can induce the differentiation of stem cells into neurons and stimulate stem cell proliferation, migration, and survival. They can also increase the secretion of nutritional factors from stem cells. In addition to the effects that flavonoids can have on stem cells, they can also have beneficial therapeutic effects on the nervous system alone. Therefore, the simultaneous use of these compounds and stem cells can multiply the therapeutic effect. In this review, we first introduce flavonoid compounds and provide background information on stem cells. We then compile available reports on the effects of flavonoids on stem cells for the treatment of neurological disorders.

Comprehensive Review of Nutraceuticals against Cognitive Decline Associated with Alzheimer's Disease

Nowadays, nutraceuticals are being incorporated into functional foods or used as supplements with nonpharmacological approaches in the prevention and management of several illnesses, including age-related conditions and chronic neurodegenerative diseases. Nutraceuticals are apt for preventing and treating such disorders because of their nontoxic, non-habit-forming, and efficient bioactivities for promoting neurological well-being due to their ability to influence cellular processes such as neurogenesis, synaptogenesis, synaptic transmission, neuro-inflammation, oxidative stress, cell death modulation, and neuronal survival. The capacity of nutraceuticals to modify all of these processes reveals the potential to develop food-based strategies to aid brain development and enhance brain function, prevent and ameliorate neurodegeneration, and possibly reverse the cognitive impairment observed in Alzheimer's disease, the most predominant form of dementia in the elderly. The current review summarizes the experimental evidence of the neuroprotective capacity of nutraceuticals against Alzheimer's disease, describing their mechanisms of action and the in vitro and in vivo models applied to evaluate their neuroprotective potential.

Cellular, histological, and behavioral pathological alterations associated with the mouse model of photothrombotic ischemic stroke

BACKGROUND

Photothrombotic (PT) stroke model is a reliable method to induce ischemic stroke in the target site using the excitation of photosensitive agents such as Rose Bengal (RB) dye after light illumination. Here, we performed a PT-induced brain ischemic model using a green laser and photosensitive agent RB and confirmed its efficiency through cellular, histological, and neurobehavioral approaches.

METHODS

Mice were randomly allocated into RB; Laser irradiation; and RB + Laser irradiation groups. Mice were exposed to a green laser at a wavelength of 532 nm and intensity of 150 mW in a mouse model after injection of RB under stereotactic surgery. The pattern of Hemorrhagic and ischemic changes were evaluated throughout the study. The volume of the lesion site was calculated using unbiased stereological methods. For investigation of neurogenesis, we performed double - (BrdU/NeuN) immunofluorescence (IF) staining on day 28 following the last- BrdU injection. To assess the effect and quality of ischemic stroke on neurological behavior, the Modified neurological severity score (mNSS) test was done on days 1, 7, 14, and 28 days after stroke induction.

RESULTS

Laser irradiation plus RB induced hemorrhagic tissue and pale ischemic changes over the 5 days. In the next few days, microscopic staining revealed neural tissue degeneration, demarcated necrotic site, and neuronal injury. BrdU staining showed a significant number of proliferating cells in the periphery of the lesion site in the Laser irradiation plus RB group compared to the group (p < 0.05) while the percent of NeuN+ cells per BrdU- positive cells was reduced. Also, prominent astrogliosis was observed in the periphery of irradiated sites on day 28. Neurological deficits were detected in mice from Laser irradiation plus the RB group. No histological or functional deficits were detected in RB and Laser irradiation groups.

CONCLUSIONS

Taken together, our study showed cellular and histologic pathological changes which are associated with the PT induction model. Our findings indicated that the undesirable microenvironment and inflammatory conditions could affect neurogenesis concomitantly with functional deficits. Moreover, this research showed that this model is a focal, reproducible, noninvasive and accessible stroke model with a distinctive demarcation similar to human stroke conditions.

A short dasatinib and quercetin treatment is sufficient to reinstate potent adult neuroregenesis in the aged killifish

The young African turquoise killifish has a high regenerative capacity, but loses it with advancing age, adopting several aspects of the limited form of mammalian regeneration. We deployed a proteomic strategy to identify pathways that underpin the loss of regenerative power caused by aging. Cellular senescence stood out as a potential brake on successful neurorepair. We applied the senolytic cocktail Dasatinib and Quercetin (D + Q) to test clearance of chronic senescent cells from the aged killifish central nervous system (CNS) as well as rebooting the neurogenic output. Our results show that the entire aged killifish telencephalon holds a very high senescent cell burden, including the parenchyma and the neurogenic niches, which could be diminished by a short-term, late-onset D + Q treatment. Reactive proliferation of non-glial progenitors increased substantially and lead to restorative neurogenesis after traumatic brain injury. Our results provide a cellular mechanism for age-related regeneration resilience and a proof-of-concept of a potential therapy to revive the neurogenic potential in an already aged or diseased CNS.

The potential neuroprotective effects of stingless bee honey

Tropical Meliponini bees produce stingless bee honey (SBH). Studies have shown beneficial properties, including antibacterial, bacteriostatic, anti-inflammatory, neurotherapeutic, neuroprotective, wound, and sunburn healing capabilities. High phenolic acid and flavonoid concentrations offer SBH its benefits. SBH can include flavonoids, phenolic acids, ascorbic acid, tocopherol, organic acids, amino acids, and protein, depending on its botanical and geographic origins. Ursolic acid, p-coumaric acid, and gallic acid may diminish apoptotic signals in neuronal cells, such as nuclear morphological alterations and DNA fragmentation. Antioxidant activity minimizes reactive oxygen species (ROS) formation and lowers oxidative stress, inhibiting inflammation by decreasing enzymes generated during inflammation. Flavonoids in honey reduce neuroinflammation by decreasing proinflammatory cytokine and free radical production. Phytochemical components in honey, such as luteolin and phenylalanine, may aid neurological problems. A dietary amino acid, phenylalanine, may improve memory by functioning on brain-derived neurotrophic factor (BDNF) pathways. Neurotrophin BDNF binds to its major receptor, TrkB, and stimulates downstream signaling cascades, which are crucial for neurogenesis and synaptic plasticity. Through BDNF, SBH can stimulate synaptic plasticity and synaptogenesis, promoting learning and memory. Moreover, BDNF contributes to the adult brain's lasting structural and functional changes during limbic epileptogenesis by acting through the cognate receptor tyrosine receptor kinase B (TrkB). Given the higher antioxidants activity of SBH than the Apis sp. honey, it may be more therapeutically helpful. There is minimal research on SBH's neuroprotective effects, and the related pathways contribute to it is unclear. More research is needed to elucidate the underlying molecular process of SBH on BDNF/TrkB pathways in producing neuroprotective effects.

Zebrafish: A Model Deciphering the Impact of Flavonoids on Neurodegenerative Disorders

Over the past century, advances in biotechnology, biochemistry, and pharmacognosy have spotlighted flavonoids, polyphenolic secondary metabolites that have the ability to modulate many pathways involved in various biological mechanisms, including those involved in neuronal plasticity, learning, and memory. Moreover, flavonoids are known to impact the biological processes involved in developing neurodegenerative diseases, namely oxidative stress, neuroinflammation, and mitochondrial dysfunction. Thus, several flavonoids could be used as adjuvants to prevent and counteract neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Zebrafish is an interesting model organism that can offer new opportunities to study the beneficial effects of flavonoids on neurodegenerative diseases. Indeed, the high genome homology of 70% to humans, the brain organization largely similar to the human brain as well as the similar neuroanatomical and neurochemical processes, and the high neurogenic activity maintained in the adult brain makes zebrafish a valuable model for the study of human neurodegenerative diseases and deciphering the impact of flavonoids on those disorders.

Sex differences in hippocampal β-amyloid accumulation in the triple-transgenic mouse model of Alzheimer's disease and the potential role of local estrogens

Introduction

Epidemiological studies show that women have a higher prevalence of Alzheimer's disease (AD) than men. Peripheral estrogen reduction during aging in women is proposed to play a key role in this sex-associated prevalence, however, the underlying mechanism remains elusive. We previously found that transcription factor early growth response-1 (EGR1) significantly regulates cholinergic function. EGR1 stimulates acetylcholinesterase (AChE) gene expression and is involved in AD pathogenesis. We aimed to investigate whether the triple-transgenic AD (3xTg-AD) mice harboring PS1 ^M146V , APP ^Swe , and Tau ^P301L show sex differences in β-amyloid (Aβ) and hyperphosphorylated tau (p-Tau), the two primary AD hallmarks, and how local 17β-estradiol (E2) may regulate the expression of EGR1 and AChE.

Methods

We first sacrificed male and female 3xTg-AD mice at 3-4, 7-8, and 11-12 months and measured the levels of Aβ, p-Tau, EGR1, and AChE in the hippocampal complex. Second, we infected SH-SY5Y cells with lentivirus containing the amyloid precursor protein construct C99, cultured with or without E2 administration we measured the levels of extracellular Aβ and intracellular EGR1 and AChE.

Results

Female 3xTg-AD mice had higher levels of Aβ compared to males, while no p-Tau was found in either group. In SH-SY5Y cells infected with lentivirus containing the amyloid precursor protein construct C99, we observed significantly increased extracellular Aβ and decreased expression of intracellular EGR1 and AChE. By adding E2 to the culture medium, extracellular Aβ(l-42) was significantly decreased while intracellular EGR1 and AChE expression were elevated.

Discussion

This data shows that the 3xTg-AD mouse model can be useful for studying the human sex differences of AD, but only in regards to Ap. Furthermore, in vitro data shows local E2 may be protective for EGR1 and cholinergic functions in AD while suppressing soluble Aβ(1-42) levels. Altogether, this study provides further in vivo and in vitro data supporting the human epidemiological data indicating a higher prevalence of AD in women is related to changes in brain estrogen levels.

Gut brain interaction theory reveals gut microbiota mediated neurogenesis and traditional Chinese medicine research strategies

Adult neurogenesis is the process of differentiation of neural stem cells (NSCs) into neurons and glial cells in certain areas of the adult brain. Defects in neurogenesis can lead to neurodegenerative diseases, mental disorders, and other maladies. This process is directionally regulated by transcription factors, the Wnt and Notch pathway, the extracellular matrix, and various growth factors. External factors like stress, physical exercise, diet, medications, etc., affect neurogenesis and the gut microbiota. The gut microbiota may affect NSCs through vagal, immune and chemical pathways, and other pathways. Traditional Chinese medicine (TCM) has been proven to affect NSCs proliferation and differentiation and can regulate the abundance and metabolites produced by intestinal microorganisms. However, the underlying mechanisms by which these factors regulate neurogenesis through the gut microbiota are not fully understood. In this review, we describe the recent evidence on the role of the gut microbiota in neurogenesis. Moreover, we hypothesize on the characteristics of the microbiota-gut-brain axis based on bacterial phyla, including microbiota's metabolites, and neuronal and immune pathways while providing an outlook on TCM's potential effects on adult neurogenesis by regulating gut microbiota.

Microbiota-Gut-Brain Axis Regulation of Adult Hippocampal Neurogenesis

The birth, maturation, and integration of new neurons in the adult hippocampus regulates specific learning and memory processes, responses to stress, and antidepressant treatment efficacy. This process of adult hippocampal neurogenesis is sensitive to environmental stimuli, including peripheral signals from certain cytokines, hormones, and metabolites, which can promote or hinder the production and survival of new hippocampal neurons. The trillions of microorganisms resident to the gastrointestinal tract, collectively known as the gut microbiota, also demonstrate the ability to modulate adult hippocampal neurogenesis. In doing so, the microbiota-gut-brain axis can influence brain functions regulated by adult hippocampal neurogenesis. Unlike the hippocampus, the gut microbiota is highly accessible to direct interventions, such as prebiotics, probiotics, and antibiotics, and can be manipulated by lifestyle choices including diet. Therefore, understanding the pathways by which the gut microbiota shapes hippocampal neurogenesis may reveal novel targets for non-invasive therapeutics to treat disorders in which alterations in hippocampal neurogenesis have been implicated. This review first outlines the factors which influence both the gut microbiome and adult hippocampal neurogenesis, with cognizance that these effects might happen either independently or due to microbiota-driven mechanisms. We then highlight approaches for investigating the regulation of adult hippocampal neurogenesis by the microbiota-gut-brain axis. Finally, we summarize the current evidence demonstrating the gut microbiota's ability to influence adult hippocampal neurogenesis, including mechanisms driven through immune pathways, microbial metabolites, endocrine signalling, and the nervous system, and postulate implications for these effects in disease onset and treatment.

Forest Biomass as a Promising Source of Bioactive Essential Oil and Phenolic Compounds for Alzheimer's Disease Therapy

Alzheimer’s disease (AD) is the most common neurodegenerative disorder affecting elderly people worldwide. Currently, there are no effective treatments for AD able to prevent disease progression, highlighting the urgency of finding new therapeutic strategies to stop or delay this pathology. Several plants exhibit potential as source of safe and multi-target new therapeutic molecules for AD treatment. Meanwhile, Eucalyptus globulus extracts revealed important pharmacological activities, namely antioxidant and anti-inflammatory properties, which can contribute to the reported neuroprotective effects. This review summarizes the chemical composition of essential oil (EO) and phenolic extracts obtained from Eucalyptus globulus leaves, disclosing major compounds and their effects on AD-relevant pathological features, including deposition of amyloid-β (Aβ) in senile plaques and hyperphosphorylated tau in neurofibrillary tangles (NFTs), abnormalities in GABAergic, cholinergic and glutamatergic neurotransmission, inflammation, and oxidative stress. In general, 1,8-cineole is the major compound identified in EO, and ellagic acid, quercetin, and rutin were described as main compounds in phenolic extracts from Eucalyptus globulus leaves. EO and phenolic extracts, and especially their major compounds, were found to prevent several pathological cellular processes and to improve cognitive function in AD animal models. Therefore, Eucalyptus globulus leaves are a relevant source of biological active and safe molecules that could be used as raw material for nutraceuticals and plant-based medicinal products useful for AD prevention and treatment.

Luteolin Treatment Ameliorates Brain Development and Behavioral Performance in a Mouse Model of CDKL5 Deficiency Disorder

CDKL5 deficiency disorder (CDD), a rare and severe neurodevelopmental disease caused by mutations in the X-linked CDKL5 gene, is characterized by early-onset epilepsy, intellectual disability, and autistic features. Although pharmacotherapy has shown promise in the CDD mouse model, safe and effective clinical treatments are still far off. Recently, we found increased microglial activation in the brain of a mouse model of CDD, the Cdkl5 KO mouse, suggesting that a neuroinflammatory state, known to be involved in brain maturation and neuronal dysfunctions, may contribute to the pathophysiology of CDD. The present study aims to evaluate the possible beneficial effect of treatment with luteolin, a natural flavonoid known to have anti-inflammatory and neuroprotective activities, on brain development and behavior in a heterozygous Cdkl5 (+/−) female mouse, the mouse model of CDD that best resembles the genetic clinical condition. We found that inhibition of neuroinflammation by chronic luteolin treatment ameliorates motor stereotypies, hyperactive profile and memory ability in Cdkl5 +/− mice. Luteolin treatment also increases hippocampal neurogenesis and improves dendritic spine maturation and dendritic arborization of hippocampal and cortical neurons. These findings show that microglia overactivation exerts a harmful action in the Cdkl5 +/− brain, suggesting that treatments aimed at counteracting the neuroinflammatory process should be considered as a promising adjuvant therapy for CDD.

Neurotrophic factor-secreting cells restored endogenous hippocampal neurogenesis through the Wnt/β-catenin signaling pathway in AD model mice

Background

Impairment in neurogenesis correlates with memory and  cognitive dysfunction in AD patients. In the recent decade, therapies with stem cell bases are growing and proved to be efficient. This study is a preliminary attempt to explore the impact of NTF-SCs on hippocampal neurogenesis mediated by the Wnt/β-catenin signaling cascade in AD-like mouse brain parenchyma.

Methods

The BALB/c mice were divided into four groups: Control, AD +Vehicle, AD+ TF-SCs-CM and AD+NTF-SCs (n = 10). For AD induction, 100 µM Aβ_1-42 was injected into lateral ventricles. The AD-like model was confirmed via passive avoidance test and Thioflavin-S staining 21 days following Aβ injection. Next, NTF-SCs were differentiated from ADMSCs, and both NTF-SCs and supernatant (NTF-SCs-CM) were injected into the hippocampus after AD confirmation. Endogenous neural stem cells (NSCs) proliferation capacity was assessed after 50 mg/kbW BrdU injection for 4 days using immunofluorescence (IF) staining. The percent of BrdU/Nestin and BrdU/NeuN positive NSCs were calculated. Real-time RT-PCR was used to detect genes related to the Wnt/β-catenin signaling cascade. The spatial learning and memory alternation was evaluated using the Morris water maze (MWM).

Results

Data showed the reduction in escape latency over 5 days in the AD mice compared to the control group. The administration of NTF-SCs and NTF-SCs-CM increased this value compared to the AD-Vehicle group. Both NTF-SCs and NTF-SCs-CM were the potential to reduce the cumulative distance to the platform in AD mice compared to the AD-Vehicle group. The time spent in target quadrants was ameliorated following NTF-SCs and NTF-SCs-CM transplantation followed by an improved MWM performance. IF imaging revealed the increase in BrdU/Nestin⁺ and BrdU/NeuN⁺ in AD mice that received NTF-SCs and NTF-SCs-CM, indicating enhanced neurogenesis. Based on real-time PCR analysis, the expression of PI3K, Akt, MAPK, ERK, Wnt, and β-catenin was upregulated and coincided with the suppression of GSK-3β after injection of NTF-SCs-CM and NTF-SCs. In this study, NTF-SCs had superior effects in AD mice that received NTF-SCs compared to NTF-SCs-CM.

Conclusions

The activation of Wnt/β-catenin pathway via NTF-SCs can be touted as a possible therapeutic approach to restore neurogenesis in AD mice.

Antidepressant Potential of Quercetin and its Glycoside Derivatives: A Comprehensive Review and Update

Depression is a global health problem with growing prevalence rates and serious impacts on the daily life of patients. However, the side effects of currently used antidepressants greatly reduce the compliance of patients. Quercetin is a flavonol present in fruits, vegetables, and Traditional Chinese medicine (TCM) that has been proved to have various pharmacological effects such as anti-depressant, anti-cancer, antibacterial, antioxidant, anti-inflammatory, and neuroprotective. This review summarizes the evidence for the pharmacological application of quercetin to treat depression. We clarified the mechanisms of quercetin regulating the levels of neurotransmitters, promoting the regeneration of hippocampal neurons, improving hypothalamic-pituitary-adrenal (HPA) axis dysfunction, and reducing inflammatory states and anti-oxidative stress. We also summarized the antidepressant effects of some quercetin glycoside derivatives to provide a reference for further research and clinical application.

Protective effect of quercetin against the metabolic dysfunction of glucose and lipids and its associated learning and memory impairments in NAFLD rats

BACKGROUND

Quercetin (QUE) is a flavonol reported with anti-inflammatory and antioxidant activities, and previous results from the group of this study have demonstrated its neuroprotective effect against lipopolysaccharide-induced neuropsychiatric injuries. However, little is known about its potential effect on neuropsychiatric injuries induced or accompanied by metabolic dysfunction of glucose and lipids.

METHODS

A nonalcoholic fatty liver disease (NAFLD) rat model was induced via a high-fat diet (HFD), and glucolipid parameters and liver function were measured. Behavioral performance was observed via the open field test (OFT) and the Morris water maze (MWM). The plasma levels of triggering receptor expressed on myeloid cells-1 (TREM1) and TREM2 were measured via enzyme-linked immunosorbent assay (ELISA). The protein expression levels of Synapsin-1 (Syn-1), Synaptatogmin-1 (Syt-1), TREM1 and TREM2 in the hippocampus were detected using western blotting. Morphological changes in the liver and hippocampus were detected by HE and Oil red or silver staining.

RESULTS

Compared with the control rats, HFD-induced NAFLD model rats presented significant metabolic dysfunction, hepatocyte steatosis, and impaired learning and memory ability, as indicated by the increased plasma concentrations of total cholesterol (TC) and triglyceride (TG), the impaired glucose tolerance, the accumulated fat droplets and balloon-like changes in the liver, and the increased escaping latency but decreased duration in the target quadrant in the Morris water maze. All these changes were reversed in QUE-treated rats. Moreover, apart from improving the morphological injuries in the hippocampus, treatment with QUE could increase the decreased plasma concentration and hippocampal protein expression of TREM1 in NAFLD rats and increase the decreased expression of Syn-1 and Syt-1 in the hippocampus.

CONCLUSIONS

These results suggested the therapeutic potential of QUE against NAFLD-associated impairment of learning and memory, and the mechanism might involve regulating the metabolic dysfunction of glucose and lipids and balancing the protein expression of synaptic plasticity markers and TREM1/2 in the hippocampus.

Neuroprotective Potential of Mung Bean (Vigna radiata L.) Polyphenols in Alzheimer's Disease: A Review

Mung bean contains various neuroprotective polyphenols, so it might be a healthy food for Alzheimer's disease (AD) prevention. Totally, 19 major phenolic compounds were quantified in mung bean, including 10 phenolic acids and 9 flavonoids. After summarizing their contents and effective doses in rodent AD models, it was speculated that vitexin, isovitexin, sinapic acid, and ferulic acid might be the major bioactive compounds for mung bean-mediated neuroprotection. The mechanisms involved inhibition of β-amyloidogenesis, tau hyperphosphorylation, oxidative stress, and neuroinflammation, and promotion of autophagy and acetylcholinesterase enzyme activity. Notably, the neuroprotective phenolic profile in mung bean changed after germination, with decreased vitexin and isovitexin, and increased rutin, isoquercitrin, isorhamnetin, and caffeic acid detected. However, only studies of individual phenolic compounds in mung bean are published at present. Hence, further studies are needed to elucidate the neuroprotective activities and mechanisms of extractions of mung bean seeds and sprouts, and the synergism between different phenolic compounds.

The Restorative Effect of Human Amniotic Fluid Stem Cells on Spinal Cord Injury

Spinal cord injury (SCI) is a debilitating condition within the neural system which is clinically manifested by sensory-motor dysfunction, leading, in some cases, to neural paralysis for the rest of the patient’s life. In the current study, mesenchymal stem cells (MSCs) were isolated from the human amniotic fluid, in order to study their juxtacrine and paracrine activities. Flow cytometry analysis was performed to identify the MSCs. A conditioned medium (CM) was collected to measure the level of BDNF, IL-1β, and IL-6 proteins using the ELISA assay. Following the SCI induction, MSCs and CM were injected into the lesion site, and also CM was infused intraperitoneally in the different groups. Two weeks after SCI induction, the spinal cord samples were examined to evaluate the expression of the doublecortin (DCX) and glial fibrillary acid protein (GFAP) markers using immunofluorescence staining. The MSCs’ phenotype was confirmed upon the expression and un-expression of the related CD markers. Our results show that MSCs increased the expression level of the DCX and decreased the level of the GFAP relative to the injury group (p < 0.001). Additionally, the CM promoted the DCX expression rate (p < 0.001) and decreased the GFAP expression rate (p < 0.01) as compared with the injury group. Noteworthily, the restorative potential of the MSCs was higher than that of the CM (p < 0.01). Large-scale meta-analysis of transcriptomic data highlighted PAK5, ST8SIA3, and NRXN1 as positively coexpressed genes with DCX. These genes are involved in neuroactive ligand–receptor interaction. Overall, our data revealed that both therapeutic interventions could promote the regeneration and restoration of the damaged neural tissue by increasing the rate of neuroblasts and decreasing the astrocytes.

Long-term memory of configural learning is enhanced via CREB upregulation by the flavonoid quercetin in Lymnaea stagnalis

Animals respond to acute stressors by modifying their behaviour and physiology. The pond snail Lymnaea stagnalis exhibits configural learning (CL), a form of higher order associative learning. In CL snails develop a landscape of fear when they experience a predatory cue along with a taste of food. This experience results in a suppression of the food response; but the memory only persists for 3 h. Lymnaea has also been found to upregulate heat shock proteins (HSPs) as a result of acute heat stress, which leads to the enhancement of memory formation. A plant flavonoid quercetin blocks the upregulation of HSPs when experienced prior to heat stress. Here, we used this blocking mechanism to test the hypothesis that HSP upregulation plays a critical role in CL. Snails experienced quercetin prior to CL training and surprisingly instead of blocking memory formation it enhanced the memory such that it now persisted for at least 24 h. Quercetin exposure either prior to or after CL enhanced long-term memory (LTM) up to 48 h. We quantified mRNA levels of the transcription factor CREB1 in the Lymnaea central nervous system and found LymCREB1 to be upregulated following quercetin exposure. The enhanced LTM phenotype in L. stagnalis was most pronounced when quercetin was experienced during the consolidation phase. Additionally, quercetin exposure during the memory reconsolidation phase also led to memory enhancement. Thus, we found no support of our original hypothesis but found that quercetin exposure upregulated LymCREB1 leading to LTM formation for CL.

Brain-Derived Neurotrophic Factor Signaling in the Pathophysiology of Alzheimer's Disease: Beneficial Effects of Flavonoids for Neuroprotection

The function of the brain-derived neurotrophic factor (BDNF) via activation through its high-affinity receptor Tropomyosin receptor kinase B (TrkB) has a pivotal role in cell differentiation, cell survival, synaptic plasticity, and both embryonic and adult neurogenesis in central nervous system neurons. A number of studies have demonstrated the possible involvement of altered expression and action of the BDNF/TrkB signaling in the pathogenesis of neurodegenerative diseases, including Alzheimer’s disease (AD). In this review, we introduce an essential role of the BDNF and its downstream signaling in neural function. We also review the current evidence on the deregulated the BDNF signaling in the pathophysiology of AD at gene, mRNA, and protein levels. Further, we discuss a potential usefulness of small compounds, including flavonoids, which can stimulate BDNF-related signaling as a BDNF-targeting therapy.

Evaluation of the neuroprotective effects of Vitamin E on the rat substantia nigra neural cells exposed to electromagnetic field: An ultrastructural study

Electromagnetic fields (EMFs) could induce oxidative stress (OS) in human tissues. Lipid peroxidation (LPO) is the main hallmark of OS that harms neural cell components, primarily lipids in the myelin sheaths and membranes. Vitamin E is a lipophilic antioxidant that protects cells from OS-related damages and inhibits the LPO process. In this study, male rats were assigned into three groups of Control, EMF, and EMF+ Vitamin E. The EMF producer equipment produced an alternate current of 50 Hz, 3 Mili Tesla (mT). At the end of the experiment, half of the substantia nigra in every sample was used for measurement of the malondialdehyde (MDA) level as the end-product of the LPO and activity of superoxide dismutase (SOD) enzyme. The next half of the tissue was prepared for transmission electron microscopy (TEM). In the EMF group, MDA level was enhanced and SOD value decreased significantly compared to the control group, but Vitamin E could restore these changes. In rats undergone EMF, heterochromatic nucleus and destruction in some portions of the nuclear membrane were detected. The segmental separation or destruction of myelin sheath lamellae was observed in nerve fibers. In treated animals, the nucleus was round, less heterochromatic, with a regular membrane. Separation of myelin sheath lamellae in some nerve fibers was slighter than the radiation group. Considering the results, EMF exposure induces LPO and triggers ultrastructural changes in the cell membranes, nucleus, and myelin sheath of substantia nigra cells, but Vitamin E consumption weakens these neuropathological alterations.

Maternal Separation-Induced Histone Acetylation Correlates with BDNF-Programmed Synaptic Changes in an Animal Model of PTSD with Sex Differences

Maternal separation (MS) causes long-lasting epigenetic changes in the brain and increases vulnerability to traumatic events in adulthood. Of interest, there may be sex-specific differences in these epigenetic changes. In this study, the extent of histone acetylation in the hippocampus (HIP) and the expression of BDNF were measured to determine whether BDNF influences risk of PTSD following MS in early life. Rat offspring were separated from their dams (3 h/day or 6 h/day from PND2~PND14). Then, pups were treated with a single prolonged stress (SPS) procedure when they reached adulthood (PND80). In animals stressed with the SPS procedure in adulthood, those that had increased MS intensity in childhood demonstrated more significant changes in performance on tests of anxiety, depression, and contextual fear memory. Reduced levels of total BDNF mRNA and protein were observed after SPS treatment and further declined in groups with greater MS time in childhood. Interestingly, these changes were correlated with decreased H3K9ac levels and increased HDAC2 levels. Additional MS also led to more severe ultrastructural synaptic damage in rats that experienced the SPS procedure, particularly in the CA1 and CA3 region of the HIP, reflecting impaired synaptic plasticity in these regions. Interestingly, male rats in the MS3h-PTSD group showed decreased anxiety, but no similar changes were found in female rats, suggesting a degree of gender specificity in coping with stress after mild MS. In summary, this study suggests that the epigenetic signatures of the BDNF genes can be linked to HIP responses to stress, providing insights that may be relevant for people at risk of stress-related psychopathologies.

Flavonoids as an Intervention for Alzheimer's Disease: Progress and Hurdles Towards Defining a Mechanism of Action

Attempts to develop a disease modifying intervention for Alzheimer's disease (AD) through targeting amyloid β (Aβ) have so far been unsuccessful. There is, therefore, a need for novel therapeutics against alternative targets coupled with approaches which may be suitable for early and sustained use likely required for AD prevention. Numerous in vitro and in vivo studies have shown that flavonoids can act within processes and pathways relevant to AD, such as Aβ and tau pathology, increases in BDNF, inflammation, oxidative stress and neurogenesis. However, the therapeutic development of flavonoids has been hindered by an ongoing lack of clear mechanistic data that fully takes into consideration metabolism and bioavailability of flavonoids in vivo. With a focus on studies that incorporate these considerations into their experimental design, this review will evaluate the evidence for developing specific flavonoids as therapeutics for AD. Given the current lack of success of anti-Aβ targeting therapeutics, particular attention will be given to flavonoid-mediated regulation of tau phosphorylation and aggregation, where there is a comparable lack of study. Reflecting on this evidence, the obstacles that prevent therapeutic development of flavonoids will be examined. Finally, the significance of recent advances in flavonoid metabolomics, modifications and influence of the microbiome on the therapeutic capacity of flavonoids in AD are explored. By highlighting the potential of flavonoids to target multiple aspects of AD pathology, as well as considering the hurdles, this review aims to promote the efficient and effective identification of flavonoid-based approaches that have potential as therapeutic interventions for AD.

Molecular mechanisms of altered adult hippocampal neurogenesis in Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia globally. AD is a progressive neurodegenerative disorder, eventually manifesting as severe cognitive impairment. Adult hippocampal neurogenesis (AHN) occurs throughout adulthood and plays an important role in hippocampus-dependent learning and memory. The stages of AHN, predominantly comprising the proliferation, differentiation, survival, and maturation of newborn neurons, are affected to varying degrees in AD. However, the exact molecular mechanisms remain to be elucidated. Recent evidence suggests that the molecules involved in AD pathology contribute to the compromised AHN in AD. Notably, various interventions may have common signaling pathways that, once identified, could be harnessed to enhance adult neurogenesis. This in turn could putatively rescue cognitive deficits associated with impaired neurogenesis as observed in animal models of AD. In this manuscript, we review the current knowledge concerning AHN under normal physiological and AD pathological conditions and highlight the possible role of specific molecules in AHN alteration in AD. In addition, we summarize in vivo experiments with emphasis on the effect of the activation of certain key signalings on AHN in AD rodent models. We propose that these signaling targets and corresponding interventions should be considered when developing novel therapies for AD.

Short-term supplementation of DHA as phospholipids rather than triglycerides improve cognitive deficits induced by maternal omega-3 PUFA deficiency during the late postnatal stage

Cognitive deficiencies, which are caused by maternal omega-3 PUFA deficiency (O-3 Def), are likely to be more rapidly and easily reversed at younger ages with quicker DHA reversal. This study aims to compare the efficiency of short-term supplementation of DHA in the form of phospholipids (PL) and triglycerides (TG) and improve cognitive deficiency in the O-3 Def model during different periods of brain development (3-week and 7-week old). The animal's spatial task performance, brain PUFA concentration, histopathology, and expression of synapse-associated proteins in the hippocampus were then analyzed. We demonstrate here that DHA-PL shows improved efficiency in improving cognitive deficiency compared to DHA-TG, particularly for adult O-3 Def offspring. The superiority of DHA-PL also correlates with the specific elevation of synapse-associated proteins, including BDNF, DCX, GAP-43, Syn, and PSD95, except to higher brain DHA accretion. This work highlights the DHA-PL as a better DHA supplement for inferior brain development caused by maternal O-3 Def, especially regarding those who missed the optimal time window of neurodevelopment.

Effects of Melatonin on Neurobehavior and Cognition in a Cerebral Palsy Model of plppr5-/- Mice

Cerebral palsy (CP), a group of clinical syndromes caused by non-progressive brain damage in the developing fetus or infant, is one of the most common causes of lifelong physical disability in children in most countries. At present, many researchers believe that perinatal cerebral hypoxic ischemic injury or inflammatory injury are the main causes of cerebral palsy. Previous studies including our works confirmed that melatonin has a protective effect against convulsive brain damage during development and that it affects the expression of various molecules involved in processes such as metabolism, plasticity and signaling in the brain. Integral membrane protein plppr5 is a new member of the plasticity-related protein family, which is specifically expressed in brain and spinal cord, and induces filopodia formation as well as neurite growth. It is highly expressed in the brain, especially in areas of high plasticity, such as the hippocampus. The signals are slightly lower in the cortex, the cerebellum, and in striatum. Noteworthy, during development plppr5 mRNA is expressed in the spinal cord, i.e., in neuron rich regions such as in medial motor nuclei, suggesting that plppr5 plays an important role in the regulation of neurons. However, the existing literature only states that plppr5 is involved in the occurrence and stability of dendritic spines, and research on its possible involvement in neonatal ischemic hypoxic encephalopathy has not been previously reported. We used plppr5 knockout (plppr5-/-) mice and their wild-type littermates to establish a model of hypoxicischemic brain injury (HI) to further explore the effects of melatonin on brain injury and the role of plppr5 in this treatment in an HI model, which mainly focuses on cognition, exercise, learning, and memory. All the tests were performed at 3-4 weeks after HI. As for melatonin treatment, which was performed 5 min after HI injury and followed by every 24h. In these experiments, we found that there was a significant interaction between genotype and treatment in novel object recognition tests, surface righting reflex tests and forelimb suspension reflex tests, which represent learning and memory, motor function and coordination, and the forelimb grip of the mice, respectively. However, a significant main effect of genotype and treatment on performance in all behavioral tests were observed. Specifically, wild-type mice with HI injury performed better than plppr5-/- mice, regardless of treatment with melatonin or vehicle. Moreover, treatment with melatonin could improve behavior in the tests for wild-type mice with HI injury, but not for plppr5-/- mice. This study showed that plppr5 knockout aggravated HI damage and partially weakened the neuroprotection of melatonin in some aspects (such as novel object recognition test and partial nerve reflexes), which deserves further study.

Quercetin alleviates styrene oxide-induced cytotoxicity in cortical neurons in vitro via modulation of oxidative stress and apoptosis

Styrene 7,8-oxide (SO) is the principal metabolite of styrene, an industrial neurotoxic compound which causes various neurodegenerative disorders. The present study aimed to explore the mechanisms of SO cytotoxicity (0.5 - 4 mM) in primary cortical neurons and to evaluate the neuroprotective potential of quercetin (QUER). Our results showed that exposure to SO decreased viability of cortical neurons in a concentration-dependent manner. In the presence of QUER, cell viability was increased significantly. The neuroprotective effects of QUER were associated with the reduction of intracellular Reactive Oxygen Species (ROS), the decrease in calcium overload and the restoration of mitochondrial membrane depolarization caused by SO. Additionally, to evaluate neuronal death mechanisms triggered by SO, cells were incubated with Ac-DEVD-CHO, Calpeptin and Necrostatin-1, pharmacological inhibitors of caspase-3, calpains and necroptosis respectively. The data showed that the three inhibitors reduced cell death induced by SO and suggested the implication of apoptotic, necrotic and necroptotic pathways. However, western blot analysis showed that QUER attenuated the activation of caspase-3 but did not prevent calpain activity. Taken together, these data indicated that the cytotoxicity of SO was mediated by oxidative stress and apoptosis, necrosis and necroptosis mechanisms, while the neuroprotection provided by QUER against SO depended mainly on its anti-apoptotic activity.

Flavonoids as a Natural Enhancer of Neuroplasticity-An Overview of the Mechanism of Neurorestorative Action

Neuroplasticity is a complex physiological process occurring in the brain for its entire life. However, it is of particular importance in the case of central nervous system (CNS) disorders. Neurological recovery largely depends on the ability to reestablish the structural and functional organization of neurovascular networks, which must be pharmacologically supported. For this reason, new forms of therapy are constantly being sought. Including adjuvant therapies in standard treatment may support the enhancement of repair processes and restore impaired brain functions. The common hallmark of nerve tissue damage is increased by oxidative stress and inflammation. Thus, the studies on flavonoids with strong antioxidant and anti-inflammatory properties as a potential application in neuro intervention have been carried out for a long time. However, recent results have revealed another important property of these compounds in CNS therapy. Flavonoids possess neuroprotective activity, and promote synaptogenesis and neurogenesis, by, among other means, inhibiting oxidative stress and neuroinflammation. This paper presents an overview of the latest knowledge on the impact of flavonoids on the plasticity processes of the brain, taking into account the molecular basis of their activity.

Crosstalk between obesity, diabetes, and alzheimer's disease: Introducing quercetin as an effective triple herbal medicine

Obesity and diabetes are the most common metabolic disorders, which are strongly related to Alzheimer's disease (AD) in aging. Diabetes and obesity can lead to the accumulation of amyloid plaques, neurofibrillary tangles (NFTs), and other symptoms of AD through several pathways, including insulin resistance, hyperglycemia, hyperinsulinemia, chronic inflammation, oxidative stress, adipokines dysregulation, and vascular impairment. Currently, the use of polyphenols has been expanded in animal models and in-vitro studies because of their comparatively negligible adverse effects. Among them, quercetin (QT) is one of the most abundant polyphenolic flavonoids, which is present in fruits and vegetables and displays many biological, health-promoting effects in a wide range of diseases. The low bioavailability and poor solubility of QT have also led researchers to make various QT-involved nanoparticles (NPs) to overcome these limitations. In this paper, we review significant molecular mechanisms induced by diabetes and obesity that increase AD pathogenesis. Then, we summarize in vitro, in vivo, and clinical evidence regarding the anti-Alzheimer, anti-diabetic and anti-obesity effects of QT. Finally, QT in pure and combination form using NPs has been suggested as a promising therapeutic agent for future studies.

Neuroprotection of Tropical Fruit Juice Mixture via the Reduction of iNOS Expression and CRH Level in β-Amyloid-Induced Rats Model of Alzheimer's Disease

This study aimed to determine the effects of tropical fruit juice mixture (pomegranate, white guava, and Roselle) on biochemical, behavioral, and histopathological changes of β-amyloid- (Aβ-) induced rats. Formulation 8 (F8) of tropical fruit juice mixture was chosen for this present study due to its high phenolic content and antioxidant capacity. Forty Wistar male rats were divided into five groups: dPBS (sham-operated control), dAβ (Aβ control), JPBS (F8 and PBS), JAβ (F8 and Aβ), and IBFAβ (ibuprofen and Aβ). F8 (5 ml/kg BW), and ibuprofen (10 ml/kg BW) was given orally daily for four weeks before the intracerebroventricular infusion of Aβ for two weeks. Histological analysis and neuronal count of hippocampus tissue in the Cornu Ammonis (CA1) region showed that supplementation with F8 was able to prevent Aβ-induced tissue damage and neuronal shrinkage. However, no significant difference in locomotor activity and novel object recognition (NOR) percentage was detected among different groups at day 7 and day 14 following Aβ infusion. Only effect of time differences (main effect of day) was observed at day 7 as compared to day 14, where reduction in locomotor activity and NOR percentage was observed in all groups, with F (1, 7) = 6.940, p < 0.05 and F (1, 7) = 7.152, p < 0.05, respectively. Besides, the MDA level of the JAβ group was significantly lower (p < 0.01) than that of the dPBS group. However, no significant changes in SOD activity were detected among different groups. Significant reduction in plasma CRH level (p < 0.05) and iNOS expression (p < 0.01) in the brain was detected in the JAβ group as compared to the dAβ group. Hence, our current findings suggest that the tropical fruit juice mixture (F8) has the potential to protect the rats from Aβ-induced neurotoxicity in brain hippocampus tissue possibly via its antioxidant properties and the suppression of iNOS expression and CRH production.

The controlled design of electrospun PCL/silk/quercetin fibrous tubular scaffold using a modified wound coil collector and L-shaped ground design for neural repair

Asymmetrically porous and aligned fibrous tubular conduit with selective permeability as a biomimetic neural scaffold was manufactured using polycaprolactone (PCL), silk, and quercetin by a modified electrospinning method. The outer surface of the randomly oriented fibrous scaffold had microscale pores that could prevent fibrous tissue invasion (FTI), but could permeate neurotrophic factors, nutrients, and oxygen. The inner surface of the aligned fibrous scaffold can be favorable for neurite outgrowth, because of their superior neural cell attachment, migration, and directional growth. In vitro and in vivo studies have demonstrated the therapeutic effect of Quercetin, a ubiquitous flavonoid widely distributed in plants, on neuropathy, by modulating the expression of NRF-2-dependent antioxidant responsive elements. In this study, the controlled inner and outer surface geometry of the 0.5, 1.0, and 2.0 wt% quercetin-containing electrospun PCL/silk fibrous tubular scaffold fabricated via a modified wound coil collector and L-shaped ground design (WCC-LG) was characterized by FE-SEM, TEM, FFT, FT-IR, and XRD. In addition, two types of neural cell lines, PC12 and S42, were used to evaluate the cell proliferation rate of the different amount of quercetin-loaded PCL/silk tubular scaffolds.

The Effects of Yuan-Zhi Decoction and Its Active Ingredients in Both In Vivo and In Vitro Models of Chronic Cerebral Hypoperfusion by Regulating the Levels of Aβ and Autophagy

Chronic cerebral hypoperfusion (CCH) is closely related to the occurrence of Alzheimer's disease (AD) in the elderly. CCH can induce overactivation of autophagy, which increases the deposition of amyloid-β (Aβ) plaques in the brain, eventually impairing the cognitive function. Yuan-Zhi decoction (YZD) is a traditional Chinese medicine (TCM) formulation that is used to treat cognitive dysfunction in the elderly, but the specific mechanism is still unclear. In this study, we simulated CCH in a rat model through bilateral common carotid artery occlusion (BCCAO) and treated the animals with YZD. Standard neurological tests indicated that YZD significantly restored the impaired cognitive function after BCCAO in a dose-dependent manner. Furthermore, YZD also decreased the levels of Aβ aggregates and the autophagy-related proteins ATG5 and ATG12 in their hippocampus. An in vitro model of CCH was also established by exposing primary rat hippocampal neurons to hypoxia and hypoglycemia (H-H). YZD and its active ingredients increased the survival of these neurons and decreased the levels of Aβ1-40 and Aβ1-42, autophagy-related proteins Beclin-1 and LC3-II, and the APP secretases BACE1 and PS-1. Finally, both Aβ aggregates showed a positive statistical correlation with the expression levels of the above proteins. Taken together, YZD targets Aβ, autophagy, and APP-related secretases to protect the neurons from hypoxic-ischemic injury and restore cognitive function.

Quercetin in Animal Models of Alzheimer's Disease: A Systematic Review of Preclinical Studies

Alzheimer’s disease (AD) is the leading cause of dementia worldwide. It involves progressive impairment of cognitive function. A growing number of neuroprotective compounds have been identified with potential anti-AD properties through in vitro and in vivo models of AD. Quercetin, a natural flavonoid contained in a wide range of plant species, is repeatedly reported to exert neuroprotective effects in experimental animal AD models. However, a systematic analysis of methodological rigor and the comparison between different studies is still lacking. A systematic review uses a methodical approach to minimize the bias in each independent study, providing a less biased, comprehensive understanding of research findings and an objective judgement of the strength of evidence and the reliability of conclusions. In this review, we identified 14 studies describing the therapeutic efficacy of quercetin on animal AD models by electronic and manual retrieval. Some of the results of the studies included were meta-analyzed by forest plot, and the methodological quality of each preclinical trial was assessed with SYRCLE’s risk of bias tool. Our results demonstrated the consistent neuroprotective effects of quercetin on different AD models, and the pharmacological mechanisms of quercetin on AD models are summarized. This information eliminated the bias of each individual study, providing guidance for future tests and supporting evidence for further implementation of quercetin into clinical trials. However, the limitations of some studies, such as the absence of sample size calculations and low method quality, should also be noted.

Effects of mild intrauterine hypoperfusion in the second trimester on memory and learning function in rat offspring

Mild intrauterine hypoperfusion (MIUH) is a serious pathological event that affects the growth and development of fetuses and offspring. MIUH can lead to growth restriction, low birth weight, neurodevelopmental disorders, and other adverse clinical outcomes. To study the effects of MIUH on learning and memory function in offspring, a model of MIUH was established by placing a coil (length 2.5 mm, diameter 0.24 mm) on the uterine artery and ovarian uterine artery of Sprague-Dawley rats in the second trimester of pregnancy (day 17). Next, 120 mg/kg lithium chloride (the MIUH + Li group) or normal saline (the MIUH group) was injected intraperitoneally into these rats. In addition, 120 mg/kg lithium chloride (the Li group) or normal saline (the SHAM group) was injected intraperitoneally into pregnant rats without coil placement. The Morris water maze was used to detect changes in learning and memory ability in the offspring at 4 weeks after birth. In the MIUH group, the escape latency and journey length before reaching the platform were both increased, and the number of times that the platform was crossed and the activity time in the target quadrant within 90 seconds were both decreased compared with the SHAM group. Immunofluorescence double staining and western blot assays demonstrated that hippocampal nestin and Ki67 (both cell-proliferation-related proteins) expression was significantly downregulated in the MIUH group compared with the SHAM group. Furthermore, western blot assays were conducted to investigate changes in related signaling pathway proteins in the brains of offspring rats, and revealed that glycogen synthase kinase 3β (GSK3β) expression was upregulated and β-catenin expression was downregulated in the MIUH group compared with the SHAM group. In addition, compared with the MIUH group, the expression levels of p-GSK3β and β-catenin were upregulated in the MIUH + Li group. These results suggest that MIUH may affect learning and memory function in rat offspring by regulating the GSK3β signaling pathway. The experimental procedures were approved by Animal Ethics Committee of Shengjing Hospital of China Medical University (approval No. 2018PS07K) in June 2018.

Molecular Mechanism of Autophagy: Its Role in the Therapy of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder of progressive dementia that is characterized by the accumulation of beta-amyloid (Aβ)-containing neuritic plaques and intracellular Tau protein tangles. This distinctive pathology indicates that the protein quality control is compromised in AD. Autophagy functions as a "neuronal housekeeper" that eliminates aberrant protein aggregates by wrapping then into autophagosomes and delivering them to lysosomes for degradation. Several studies have suggested that autophagy deficits in autophagy participate in the accumulation and propagation of misfolded proteins (including Aβ and Tau). In this review, we summarize current knowledge of autophagy in the pathogenesis of AD, as well as some pathways targeting the restoration of autophagy. Moreover, we discuss how these aspects can contribute to the development of disease-modifying therapies in AD.

Transcriptional regulation of adult neural stem/progenitor cells: tales from the subventricular zone

In rodents, well characterized neurogenic niches of the adult brain, such as the subventricular zone of the lateral ventricles and the subgranular zone of the hippocampus, support the maintenance of neural/stem progenitor cells (NSPCs) and the production of new neurons throughout the lifespan. The adult neurogenic process is dependent on the intrinsic gene expression signatures of NSPCs that make them competent for self-renewal and neuronal differentiation. At the same time, it is receptive to regulation by various extracellular signals that allow the modulation of neuronal production and integration into brain circuitries by various physiological stimuli. A drawback of this plasticity is the sensitivity of adult neurogenesis to alterations of the niche environment that can occur due to aging, injury or disease. At the core of the molecular mechanisms regulating neurogenesis, several transcription factors have been identified that maintain NSPC identity and mediate NSPC response to extrinsic cues. Here, we focus on REST, Egr1 and Dbx2 and their roles in adult neurogenesis, especially in the subventricular zone. We review recent work from our and other laboratories implicating these transcription factors in the control of NSPC proliferation and differentiation and in the response of NSPCs to extrinsic influences from the niche. We also discuss how their altered regulation may affect the neurogenic process in the aged and in the diseased brain. Finally, we highlight key open questions that need to be addressed to foster our understanding of the transcriptional mechanisms controlling adult neurogenesis.

Enhancing the potential preclinical and clinical benefits of quercetin through novel drug delivery systems

Quercetin is reported to have numerous pharmacological actions, including antidiabetic, anti-inflammatory and anticancer activities. The main mechanism responsible for its pharmacological activities is its ability to quench reactive oxygen species (ROS) and, hence, decrease the oxidative stress responsible for the development of various diseases. Despite its proven therapeutic potential, the clinical use of quercetin remains limited because of its low aqueous solubility, bioavailability, and substantial first-pass metabolism. To overcome this, several novel formulations have been reported. In this review, we focus on the applications of quercetin extract as well as its novel formulations for treating different disorders. We also examine its proposed mechanism of action of quercetin.

Cognitive Function and Consumption of Fruit and Vegetable Polyphenols in a Young Population: Is There a Relationship?

Scientific evidence has shown the relationship between consumption of fruits and vegetables and their polyphenols with the prevention or treatment of diseases. The aim of this review was to find out whether the same relationship exists between fruits and vegetables and cognitive function, especially memory, in a young population. The mechanisms by which polyphenols of fruits and vegetables can exert cognitive benefits were also evaluated. These compounds act to improve neuronal plasticity through the protein CREB (Camp Response Element Binding) in the hippocampus, modulating pathways of signaling and transcription factors (ERK/Akt). In the same way, brain-derived neurotrophic factor (BDNF) is implicated in the maintenance, survival, growth, and differentiation of neurons. All these effects are produced by an increase of cerebral blood flow and an increase of the blood’s nitric oxide levels and oxygenation.