Quercetin protects human brain microvascular endothelial cells from fibrillar β-amyloid1-40-induced toxicity

Synaptic plasticity and neuroprotection: The molecular impact of flavonoids on neurodegenerative disease progression

Flavonoids are a broad family of polyphenolic chemicals that are present in a wide variety of fruits, vegetables, and medicinal plants. Because of their neuroprotective qualities, flavonoids have attracted a lot of interest. The potential of flavonoids to control synaptic plasticity-a crucial process underlying memory, learning, and cognitive function-is becoming more and more clear. Dysregulation of synaptic plasticity is a feature of neurodegenerative diseases such as amyotrophic lateral sclerosis (0.4 %), Parkinson's (1-2 %), Alzheimer's (5-7 %), and Huntington's ((0.2 %)). This review discusses the molecular mechanisms via which flavonoids influence synaptic plasticity as well as their therapeutic potential in neurodegenerative diseases. Flavonoids modulate key signaling pathways such as MAPK/ERK and PI3K/Akt/mTOR to support neuroprotection, synaptic plasticity, and neuronal health, while also influencing neurotrophic factors (BDNF, NGF) and their receptors (TrkB, TrkA). They regulate neurotransmitter receptors like GABA, AMPA, and NMDA to balance excitatory and inhibitory transmission, and exert antioxidant effects via the Nrf2-ARE pathway and anti-inflammatory actions by inhibiting NF-κB signaling, highlighting their potential for treating neurodegenerative diseases. These varied reactions support the preservation of synapse function and neuronal integrity in the face of neurodegenerative insults. Flavonoids can reduce the symptoms of neurodegeneration, prevent synaptic loss, and enhance cognitive function, according to experimental studies. However, there are still obstacles to using these findings in clinical settings, such as limited bioavailability and the need for consistent dose. The focus of future research should be on improving flavonoid delivery systems and combining them with conventional medications.

Much More than Nutrients: The Protective Effects of Nutraceuticals on the Blood-Brain Barrier in Diseases

The dysfunction of the blood-brain barrier (BBB) is well described in several diseases, and is considered a pathological factor in many neurological disorders. This review summarizes the most important groups of natural compounds, including alkaloids, flavonoids, anthocyanidines, carotenoids, lipids, and vitamins that were investigated for their potential protective effects on brain endothelium. The brain penetration of these compounds and their interaction with BBB efflux transporters and solute carriers are discussed. The cerebrovascular endothelium is considered a therapeutic target for natural compounds in diseases. In preclinical studies modeling systemic and central nervous system diseases, nutraceuticals exerted beneficial effects on the BBB. In vivo, they decreased BBB permeability, brain edema, astrocyte swelling, and morphological changes in the vessel structure and basal lamina. At the level of brain endothelial cells, nutraceuticals increased cell survival and decreased apoptosis. From the general endothelial functions, decreased angiogenesis and increased levels of vasodilating agents were demonstrated. From the BBB functions, elevated barrier integrity by tightened intercellular junctions, and increased expression and activity of BBB transporters, such as efflux pumps, solute carriers, and metabolic enzymes, were shown. Nutraceuticals enhanced the antioxidative defense and exerted anti-inflammatory effects at the BBB. The most important signaling changes mediating the increased cell survival and BBB stability were the activation of the WNT, PI3K-AKT, and NRF2 pathways, and inhibition of the MAPK, JNK, ERK, and NF-κB pathways. Nutraceuticals represent a valuable source of new potentially therapeutic molecules to treat brain diseases by protecting the BBB.

Investigating the neuroprotective effects of Dracocephalum moldavica extract and its effect on metabolomic profile of rat model of sporadic Alzheimer's disease

Alzheimer's disease (AD) is a progressive condition marked by multiple underlying mechanisms. Therefore, the investigation of natural products that can target multiple pathways presents a potential gate for the understanding and management of AD. This study aimed to assess the neuroprotective effects of the hydroalcoholic extract of Dracocephalum moldavica (DM) on cognitive impairment, biomarker changes, and putative metabolic pathways in a rat model of AD induced by intracerebroventricular streptozotocin (ICV-STZ). The DM extract was standardized and quantified based on examining total phenolic, total flavonoid, rosmarinic acid, and quercetin contents using colorimetry and high-performance liquid chromatography (HPLC) methods. The antioxidant potential of the extract was evaluated by 2,2-Diphenyl-1-picrylhydrazyl and nitric oxide radical scavenging assays. Male Wistar rats were injected with STZ (3 mg/kg, single dose, bilateral ICV) to induce a sporadic AD (sAD) model. Following model induction, rats were orally administered with DM extract (100, 200, and 400 mg/kg/day) or donepezil (5 mg/kg/day) for 21 days. Cognitive function was assessed using the radial arm water maze behavioral test. The histopathological evaluations were conducted in the cortex and hippocampus regions. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) was used to assess metabolite changes in various brain regions. DM extract significantly attenuated cognitive dysfunction induced by ICV-STZ according to behavioral and histopathological investigations. Thirty-two discriminating metabolites related to the amino acid metabolism; the glutamate/gamma-aminobutyric acid/glutamine cycle; nucleotide metabolism; lipid metabolism (glycerophospholipids, sphingomyelins, ceramides, phosphatidylserines, and prostaglandins), and glucose metabolic pathways were identified in the brains of rats with sAD simultaneously for the first time in this model. Polyphenols in DM extract may contribute to the regulation of these pathways. After treatment with DM extract, 10 metabolites from the 32 identified ones were altered in the brain tissue of a rat model of sAD, most commonly at doses of 200 and 400 mg/kg. In conclusion, this study demonstrates the neuroprotective potential of DM by upregulation/downregulation of various pathophysiological biomarkers such as adenine, glycerophosphoglycerol, inosine, prostaglandins, and sphingomyelin induced by ICV-STZ in sAD. These findings are consistent with cognitive behavioral results and histopathological outcomes.

Quercetin, the Potential Powerful Flavonoid for Human and Food: A Review

Flavonoids occur naturally in different types of fruits and vegetables, including tea, cabbage, cauliflower, elderberries, cranberries, red apples, lettuce, pears, spinach, green hot peppers, white and red onions, kale, blueberries, and nuts. Among these flavonoids is quercetin, a potent natural antioxidant and cytotoxic substance with a number of therapeutic functions. Nowadays, quercetin is a common ingredient in many nutraceutical and cosmeceutical products due to its antioxidant properties. Its antibacterial effects and possible action mechanisms have been explored in many studies. From these, it has been established that quercetin stops the activity of numerous Gram-negative and -positive bacteria, fungi, and viruses. This review clarifies the plant sources and extraction methods of quercetin, as well as its medicinal applications as an antibacterial, antifungal, antiviral, and antioxidant agent, with a particular emphasis on the underlying mechanisms of its biological activity. The mechanism of its antimicrobial effect involves damaging the cell membrane-e.g., by changing its permeability, preventing biofilm formation, reducing the mitochondrial expression of virulence factors, and inhibiting protein and nucleic-acid synthesis. Moreover, quercetin has been shown to impede the activity of a variety of drug-resistant bacterial strains, pointing to the possibility of using it as a strong antimicrobial substance against such strains. In addition, it has occasionally been demonstrated that specific structural alterations to quercetin can increase its antibacterial action in comparison to the parent molecule. Overall, this review synthesizes our understanding of the mode of action of quercetin and its prospects for use as a therapeutic material.

Quercetin ameliorates neuroinflammatory and neurodegenerative biomarkers in the brain and improves neurobehavioral parameters in a repeated intranasal amyloid-beta exposed model of Alzheimer's disease

Objectives: The aim of the present study was to study the potential therapeutic effects of quercetin in protection against repeated intranasal exposure of an amyloid-beta-induced mouse model. Methods: Mice received intranasal Aβ1-42 (5 μg/10 μL) exposure once daily for seven consecutive days. Quercetin was orally administered to them at 30 mg kg-1 and 100 mg kg-1 doses for one week starting from day five following Aβ1-42 peptide administration. Following this, the animals were evaluated for neurobehavioral parameters using a Morris water maze test and a novel object recognition test. Further to this, the biomarkers for neuroinflammation and neurodegeneration were evaluated in the hippocampus and cortex regions of the brain in these animals. Results: Multiple exposures to intranasal Aβ led to a significant decline in the learning and cognitive memory of the animals, whereas oral treatment with quercetin at dosages of 30 and 100 mg kg-1 alleviated Aβ-induced effects. Quercetin treatment significantly reduced Aβ accumulation, oxidative stress and proinflammatory cytokine biomarkers in the brain. In addition, it also alleviated the activation of astrocytic biomarkers, amyloid precursor protein and phosphorylated-tau proteins in the brain. Conclusion: Quercetin was found to be a potent antioxidant, anti-inflammatory compound with protection against neurodegenerative damage and improved learning and cognitive memory in a repeated Aβ-exposure model of AD.

Cognitive Fitness: Harnessing the Strength of Exerkines for Aging and Metabolic Challenges

Addressing cognitive impairment (CI) represents a significant global challenge in health and social care. Evidence suggests that aging and metabolic disorders increase the risk of CI, yet promisingly, physical exercise has been identified as a potential ameliorative factor. Specifically, there is a growing understanding that exercise-induced cognitive improvement may be mediated by molecules known as exerkines. This review delves into the potential impact of aging and metabolic disorders on CI, elucidating the mechanisms through which various exerkines may bolster cognitive function in this context. Additionally, the discussion extends to the role of exerkines in facilitating stem cell mobilization, offering a potential avenue for improving cognitive impairment.

Alzheimer, Parkinson, dementia, and phytochemicals: insight review

Alzheimer's, Parkinson's, and dementia are the leading neurodegenerative diseases that threaten the world with the aging population. Although the pathophysiology of each disease is unique, the steps to be taken to prevent diseases are similar. One of the changes that a person can make alone is to gain the habit of an antioxidant-rich diet. Phytochemicals known for their antioxidant properties have been reported to prevent neurodegenerative diseases in various studies. Phytochemicals with similar chemical structures are grouped. Accordingly, there are two main groups of phytochemicals, flavonoid and non-flavonoid. Various in vitro and in vivo studies on phytochemicals have proven neuroprotective effects by increasing cognitive function with their anti-inflammatory and antioxidant mechanisms. The purpose of this review is to summarize the in vitro and in vivo studies on phytochemicals with neuroprotective effects and to provide insight.

In Silico Prediction of Quercetin Analogs for Targeting Death-Associated Protein Kinase 1 (DAPK1) Against Alzheimer's Disease

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder that greatly affects the health and life quality of the elderly population. Existing drugs mainly alleviate symptoms but fail to halt disease progression, underscoring the urgent need for the development of novel drugs. Based on the neuroprotective effects of flavonoid quercetin in AD, this study was designed to identify potential AD-related targets for quercetin and perform in silico prediction of promising analogs for the treatment of AD. Database mining suggested death-associated protein kinase 1 (DAPK1) as the most promising AD-related target for quercetin among seven protein candidates. To achieve better biological effects for the treatment of AD, we devised a series of quercetin analogs as ligands for DAPK1, and molecular docking analyses, absorption, distribution, metabolism, and excretion (ADME) predictions, as well as molecular dynamics (MD) simulations, were performed. The energy for drug-protein interaction was predicted and ranked. As a result, quercetin-A1a and quercetin-A1a1 out of 19 quercetin analogs exhibited the lowest interaction energy for binding to DAPK1 than quercetin, and they had similar dynamics performance with quercetin. In addition, quercetin-A1a and quercetin-A1a1 were predicted to have better water solubility. Thus, quercetin-A1a and quercetin-A1a1 could be promising agents for the treatment of AD. Our findings paved the way for further experimental studies and the development of novel drugs.

Therapeutic considerations of bioactive compounds in Alzheimer's disease and Parkinson's disease: Dissecting the molecular pathways

Leading neurodegenerative diseases Alzheimer's disease (AD) and Parkinson's disease (PD) are characterized by the impairment of memory and motor functions, respectively. Despite several breakthroughs, there exists a lack of disease-modifying treatment strategies for these diseases, as the available drugs provide symptomatic relief and bring along side effects. Bioactive compounds are reported to bear neuroprotective properties with minimal toxicity, however, a detailed elucidation of their modes of neuroprotection is lacking. The review elucidates the neuroprotective mechanism(s) of some of the major phyto-compounds in pre-clinical and clinical studies of AD and PD to understand their potential in combating these diseases. Curcumin, eugenol, resveratrol, baicalein, sesamol and so on have proved efficient in countering the pathological hallmarks of AD and PD. Curcumin, resveratrol, caffeine and so on have reached the clinical phases of these diseases, while aromadendrin, delphinidin, cyanidin and xanthohumol are yet to be extensively explored in pre-clinical phases. The review highlights the need for extensive investigation of these compounds in the clinical stages of these diseases so as to utilize their disease-modifying abilities in the real field of treatment. Moreover, poor pharmacokinetic properties of natural compounds are constraints to their therapeutic yields and this review suggests a plausible contribution of nanotechnology in overcoming these limitations.

Research Progress on Natural Plant Molecules in Regulating the Blood-Brain Barrier in Alzheimer's Disease

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder. With the aging population and the continuous development of risk factors associated with AD, it will impose a significant burden on individuals, families, and society. Currently, commonly used therapeutic drugs such as Cholinesterase inhibitors, N-methyl-D-aspartate antagonists, and multiple AD pathology removal drugs have been shown to have beneficial effects on certain pathological conditions of AD. However, their clinical efficacy is minimal and they are associated with certain adverse reactions. Furthermore, the underlying pathological mechanism of AD remains unclear, posing a challenge for drug development. In contrast, natural plant molecules, widely available, offer multiple targeting pathways and demonstrate inherent advantages in modifying the typical pathologic features of AD by influencing the blood-brain barrier (BBB). We provide a comprehensive review of recent in vivo and in vitro studies on natural plant molecules that impact the BBB in the treatment of AD. Additionally, we analyze their specific mechanisms to offer novel insights for the development of safe and effective targeted drugs as well as guidance for experimental research and the clinical application of drugs for the prevention and treatment of AD.

Exploitation of Quercetin's Antioxidative Properties in Potential Alternative Therapeutic Options for Neurodegenerative Diseases

Oxidative stress (OS) is a condition in which there is an excess of reactive oxygen species (ROS) in the body, which can lead to cell and tissue damage. This occurs when there is an overproduction of ROS or when the body's antioxidant defense systems are overwhelmed. Quercetin (Que) is part of a group of compounds called flavonoids. It is found in high concentrations in vegetables, fruits, and other foods. Over the past decade, a growing number of studies have highlighted the therapeutic potential of flavonoids to modulate neuronal function and prevent age-related neurodegeneration. Therefore, Que has been shown to have antioxidant, anticancer, and anti-inflammatory properties, both in vitro and in vivo. Due to its antioxidant character, Que alleviates oxidative stress, thus improving cognitive function, reducing the risk of neurodegenerative diseases. On the other hand, Que can also help support the body's natural antioxidant defense systems, thus being a potentially practical supplement for managing OS. This review focuses on experimental studies supporting the neuroprotective effects of Que in Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and epilepsy.

Targeting Protein Aggregates with Natural Products: An Optional Strategy for Neurodegenerative Diseases

Protein aggregation is one of the hallmarks of aging and aging-related diseases, especially for the neurodegenerative diseases (NDs) such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), Amyotrophic lateral sclerosis (ALS), and others. In these diseases, many pathogenic proteins, such as amyloid-β, tau, α-Syn, Htt, and FUS, form aggregates that disrupt the normal physiological function of cells and lead to associated neuronal lesions. Protein aggregates in NDs are widely recognized as one of the important targets for the treatment of these diseases. Natural products, with their diverse biological activities and rich medical history, represent a great treasure trove for the development of therapeutic strategies to combat disease. A number of in vitro and in vivo studies have shown that natural products, by virtue of their complex molecular scaffolds that specifically bind to pathogenic proteins and their aggregates, can inhibit the formation of aggregates, disrupt the structure of aggregates and destabilize them, thereby alleviating conditions associated with NDs. Here, we systematically reviewed studies using natural products to improve disease-related symptoms by reducing or inhibiting the formation of five pathogenic protein aggregates associated with NDs. This information should provide valuable insights into new directions and ideas for the treatment of neurodegenerative diseases.

Origanum majorana L. protects against neuroinflammation-mediated cognitive impairment: a phyto-pharmacological study

BACKGROUND

Neuroinflammation and oxidative stress are critical players in the pathogenesis of numerous neurodegenerative diseases, such as Alzheimer's disease (AD) which is responsible for most cases of dementia in the elderly. With the lack of curative treatments, natural phenolics are potential candidates to delay the onset and progression of such age-related disorders due to their potent antioxidant and anti-inflammatory effects. This study aims at assessing the phytochemical characteristics of Origanum majorana L. (OM) hydroalcohol extract and its neuroprotective activities in a murine neuroinflammatory model.

METHODS

OM phytochemical analysis was done by HPLC/PDA/ESI-MSⁿ. Oxidative stress was induced in vitro by hydrogen peroxide and cell viability was measured using WST-1 assay. Swiss albino mice were injected intraperitoneally with OM extract at a dose of 100 mg/kg for 12 days and with 250 μg/kg LPS daily starting from day 6 to induce neuroinflammation. Cognitive functions were assessed by novel object recognition and Y-maze behavioral tests. Hematoxylin and eosin staining was used to assess the degree of neurodegeneration in the brain. Reactive astrogliosis and inflammation were assessed by immunohistochemistry using GFAP and COX-2 antibodies, respectively.

RESULTS

OM is rich in phenolics, with rosmarinic acid and its derivatives being major constituents. OM extract and rosmarinic acid significantly protected microglial cells against oxidative stress-induced cell death (p < 0.001). OM protected against the LPS-induced alteration of recognition and spatial memory in mice (p < 0.001) and (p < 0.05), respectively. Mice that received OM extract prior to the induction of neuroinflammation showed comparable histology to control brains, with no overt neurodegeneration. Furthermore, OM pre-treatment decreased the immunohistochemistry profiler score of GFAP from positive to low positive and COX-2 from low positive to negative in the brain tissue, compared to the LPS group.

CONCLUSION

These findings highlight the potential preventive effects of OM phenolics against neuroinflammation and pave the way toward drug discovery and development for neurodegenerative disorders.

Dietary Polyphenols as a Protection against Cognitive Decline: Evidence from Animal Experiments; Mechanisms and Limitations

Emerging evidence suggests that cognitive impairments may result from various factors, such as neuroinflammation, oxidative stress, mitochondrial damage, impaired neurogenesis, synaptic plasticity, blood-brain barrier (BBB) disruption, amyloid β protein (Aβ) deposition, and gut dysbiosis. Meanwhile, dietary polyphenol intake in a recommended dosage has been suggested to reverse cognitive dysfunction via various pathways. However, excessive intake of polyphenols could trigger unwanted adverse effects. Thus, this review aims to outline possible causes of cognitive impairments and how polyphenols alleviate memory loss via various pathways based on in vivo experimental studies. Thus, to identify potentially relevant articles, the keywords (1) nutritional polyphenol intervention NOT medicine AND neuron growth OR (2) dietary polyphenol AND neurogenesis AND memory impairment OR (3) polyphenol AND neuron regeneration AND memory deterioration (Boolean operators) were used in the Nature, PubMed, Scopus, and Wiley online libraries. Based on the inclusion and exclusion criteria, 36 research papers were selected to be further reviewed. The outcome of all the studies included supports the statement of appropriate dosage by taking into consideration gender differences, underlying conditions, lifestyle, and causative factors for cognitive decline, which will significantly boost memory power. Therefore, this review recapitulates the possible causes of cognitive decline, the mechanism of polyphenols involving various signaling pathways in modulating the memory, gut dysbiosis, endogenous antioxidants, bioavailability, dosage, and safety efficacy of polyphenols. Hence, this review is expected to provide a basic understanding of therapeutic development for cognitive impairments in the future.

Neurotherapeutic Effects of Quercetin and Its Metabolite Compounds on Cognitive Impairment and Parkinson's Disease: An In Silico Study

BACKGROUND AND OBJECTIVE

Little is known about the metabolomic profile of quercetin and its biological effects. This study aimed to determine the biological activities of quercetin and its metabolite products, as well as the molecular mechanisms of quercetin in cognitive impairment (CI) and Parkinson's disease (PD).

METHODS

Key methods used were MetaTox, PASS Online, ADMETlab 2.0, SwissADME, CTD MicroRNA MIENTURNE, AutoDock, and Cytoscape.

RESULTS

A total of 28 quercetin metabolite compounds were identified by phase I reactions (hydroxylation and hydrogenation reactions) and phase II reactions (methylation, O-glucuronidation, and O-sulfation reactions). Quercetin and its metabolites were found to inhibit cytochrome P450 (CYP) 1A, CYP1A1, and CYP1A2. The studied compounds demonstrated significant gastrointestinal absorption and satisfied Lipinsky's criterion. Due to their high blood-brain barrier permeability, P-glycoprotein inhibition, anticancer, anti-inflammatory, and antioxidant capabilities, quercetin and its metabolite products have been proposed as promising molecular targets for the therapy of CI and PD. By regulating the expression of crucial signaling pathways [mitogen-activated protein kinase (MAPK) signaling pathway, and neuroinflammation and glutamatergic signaling], genes [brain derived neurotrophic factor (BDNF), human insulin gene (INS), and dopamine receptor D2 (DRD2), miRNAs (hsa-miR-16-5p, hsa-miR-26b-5p, hsa-miR-30a-5p, hsa-miR-125b-5p, hsa-miR-203a-3p, and hsa-miR-335-5p], and transcription factors [specificity protein 1 (SP1), v-rel avian reticuloendotheliosis viral oncogene homolog A (RELA), and nuclear factor Kappa B subunit 1 (NFKB1)], quercetin exhibited its neurotherapeutic effects in CI and PD. In addition to inhibiting β-N-acetylhexosaminidase, quercetin also showed robust interactions and binding affinities with heme oxygenase 1 (HMOX1), superoxide dismutase 2 (SOD2), tumor necrosis factor (TNF), nitric oxide synthase 2 (NOS2), brain-derived neurotrophic factor (BDNF), INS, DRD2, and γ-aminobutyric acid type A (GABAa).

CONCLUSION

This study identified 28 quercetin metabolite products. The metabolites have similar characteristics to quercetin such as physicochemical properties, absorption, distribution, metabolism, and excretion (ADME), and biological activities. More research, especially clinical trials, is needed to find out how quercetin and its metabolites protect against CI and PD.

Protocatechuic acid and quercetin attenuate ETEC-caused IPEC-1 cell inflammation and injury associated with inhibition of necroptosis and pyroptosis signaling pathways

BACKGROUND

Necroptosis and pyroptosis are newly identified forms of programmed cell death, which play a vital role in development of many gastrointestinal disorders. Although plant polyphenols have been reported to protect intestinal health, it is still unclear whether there is a beneficial role of plant polyphenols in modulating necroptosis and pyroptosis in intestinal porcine epithelial cell line (IPEC-1) infected with enterotoxigenic Escherichia coli (ETEC) K88. This research was conducted to explore whether plant polyphenols including protocatechuic acid (PCA) and quercetin (Que), attenuated inflammation and injury of IPEC-1 caused by ETEC K88 through regulating necroptosis and pyroptosis signaling pathways.

METHODS

IPEC-1 cells were treated with PCA (40 μmol/L) or Que (10 μmol/L) in the presence or absence of ETEC K88.

RESULTS

PCA and Que decreased ETEC K88 adhesion and endotoxin level (P < 0.05) in cell supernatant. PCA and Que increased cell number (P < 0.001) and decreased lactate dehydrogenases (LDH) activity (P < 0.05) in cell supernatant after ETEC infection. PCA and Que improved transepithelial electrical resistance (TEER) (P < 0.001) and reduced fluorescein isothiocyanate-labeled dextran (FD4) flux (P < 0.001), and enhanced membrane protein abundance of occludin, claudin-1 and ZO-1 (P < 0.05), and rescued distribution of these tight junction proteins (P < 0.05) after ETEC infection. PCA and Que also declined cell necrosis ratio (P < 0.05). PCA and Que reduced mRNA abundance and concentration of tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-8 (P < 0.001), and down-regulated gene expression of toll-like receptors 4 (TLR4) and its downstream signals (P < 0.001) after ETEC infection. PCA and Que down-regulated protein abundance of total receptor interacting protein kinase 1 (t-RIP1), phosphorylated-RIP1 (p-RIP1), p-RIP1/t-RIP1, t-RIP3, p-RIP3, mixed lineage kinase domain-like protein (MLKL), p-MLKL, dynamin- related protein 1 (DRP1), phosphoglycerate mutase 5 (PGAM5) and high mobility group box 1 (HMGB1) (P < 0.05) after ETEC infection. Moreover, PCA and Que reduced protein abundance of nod-like receptor protein 3 (NLRP3), nod-like receptors family CARD domain-containing protein 4 (NLRC4), apoptosis-associated speck-like protein containing a CARD (ASC), gasdermin D (GSDMD) and caspase-1 (P < 0.05) after ETEC infection.

CONCLUSIONS

In general, our data suggest that PCA and Que are capable of attenuating ETEC-caused intestinal inflammation and damage via inhibiting necroptosis and pyroptosis signaling pathways.

Neuropharmacological interventions of quercetin and its derivatives in neurological and psychological disorders

Quercetin is a naturally occurring bioactive flavonoid abundant in many plants and fruits. Quercetin and its derivatives have shown an array of pharmacological activities in preclinical tests against various illnesses and ailments. Owing to its protective role against oxidative stress and neuroinflammation, quercetin is a possible therapeutic choice for the treatment of neurological disorders. Quercetin and its derivatives can modulate a variety of signal transductions, including neuroreceptor, neuroinflammatory receptor, and redox signaling events. The research on quercetin and its derivatives in neurology-related illnesses mainly focused on the targets, such as redox stress, neuroinflammation, and signaling pathways; however, the function of quercetin and its derivatives on specific molecular targets, such as nuclear receptors and proinflammatory mediators are yet to be explored. Findings showed that various molecular targets of quercetin and its derivatives have therapeutic potential against psychological and neurodegenerative disorders.

β-Sitosterol & quercetin enhances brain development in iodine deficient rat models

BACKGROUND

Recently thyroid hormone studies on brain growth, development and activity are regaining popularity. Thyroid hormones have long been believed to play critical role in mammalian brain growth and maturation regulating facets of neuronal cell growth, proliferation and differentiation and further signaling and glial cell differentiation. Deficiency of these hormones in mother leads to mental retardation in the subsequent offspring's.

METHODS

In this presented study, brain development of iodine deficient rat models created through deficiency in feeding, mating and further selection. Young adult female wistar rats were induced with iodine deficiency and then mated with healthy male rats. These pregnant hypothyroid induced females were treated with β-sitosterol (150 mg/kg/day) and quercetin (150 mg/kg/day) alone and in combination for whole gestation period. Analysis were dealt with the genetic and histological studies of the pups brain. PCR based RNA analysis was also carried out. Histology was done using eosin and hematoxylin.

RESULTS

Positive impacts of the β-sitosterol and quercetin on the iodine deficient brain were observed upon histological and PCR analysis. Altogether, the analysis proves that combined doses of β-sitosterol and quercetin for normal brain development in iodine deficient infants hence can be potentially applied as therapeutics in iodine deficiency circumstances.

Effects of Natural Polyphenols on Oxidative Stress-Mediated Blood–Brain Barrier Dysfunction

The blood-brain barrier (BBB), which consists mainly of brain microvascular endothelial cells and astrocytes connected by tight junctions (TJs) and adhesion molecules (AMs), maintains the homeostatic balance between brain parenchyma and extracellular fluid. Accumulating evidence shows that BBB dysfunction is a common feature of neurodegenerative diseases, including stroke, traumatic brain injury, and Alzheimer’s disease. Among the various pathological pathways of BBB dysfunction, reactive oxygen species (ROS) are known to play a key role in inducing BBB disruption mediated via TJ modification, AM induction, cytoskeletal reorganization, and matrix metalloproteinase activation. Thus, antioxidants have been suggested to exert beneficial effects on BBB dysfunction-associated brain diseases. In this review, we summarized the sources of ROS production in multiple cells that constitute or surround the BBB, such as BBB endothelial cells, astrocytes, microglia, and neutrophils. We also reviewed various pathological mechanisms by which BBB disruption is caused by ROS in these cells. Finally, we summarized the effects of various natural polyphenols on BBB dysfunction to suggest a therapeutic strategy for BBB disruption-related brain diseases.

The close link between brain vascular pathological conditions and neurodegenerative diseases: Focus on some examples and potential treatments

A close relationship is emerging among the age-related neurodegenerative decline, and the age-related typical alterations, dysfunctions, and related diseases of the cerobro-and/or cardiovascular system, which contributes in a significative manner to the triggering and progressing of neurodegenerative diseases (NeuroDegD). Specifically, macroinfarcts, microinfarcts, micro-hemorrhages (and particularly their number), atherosclerosis, arteriolosclerosis and cerebral amyloid angiopathy have been documented to be significantly associated with the onset of the cognitive impairment. In addition, vascular alterations and dysfunctions resulting in a reduced cerebral blood flow, and anomalies in the brain blood barrier (BBB), have been also demonstrated to contribute to NeuroDegD pathophysiologic processes. At the same time, such vascular alterations are also observed in cognitively unimpaired subjects. Here, some of these aspects are described with a particular focus on some NeuroDegD, as well as potential strategies for delaying or stopping their onset and progression.

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.

Natural Small Molecules Targeting NF-κB Signaling in Glioblastoma

Nuclear factor-κB (NF-κB) is a transcription factor that regulates various genes that mediate various cellular activities, including propagation, differentiation, motility, and survival. Abnormal activation of NF-κB is a common incidence in several cancers. Glioblastoma multiforme (GBM) is the most aggressive brain cancer described by high cellular heterogeneity and almost unavoidable relapse following surgery and resistance to traditional therapy. In GBM, NF-κB is abnormally activated by various stimuli. Its function has been associated with different processes, including regulation of cancer cells with stem-like phenotypes, invasion of cancer cells, and radiotherapy resistance identification of mesenchymal cells. Even though multimodal therapeutic approaches such as surgery, radiation therapy, and chemotherapeutic drugs are used for treating GBM, however; the estimated mortality rate for GBM patients is around 1 year. Therefore, it is necessary to find out new therapeutic approaches for treating GBM. Many studies are focusing on therapeutics having less adverse effects owing to the failure of conventional chemotherapy and targeted agents. Several studies of compounds suggested the involvement of NF-κB signaling pathways in the growth and development of a tumor and GBM cell apoptosis. In this review, we highlight the involvement of NF-κB signaling in the molecular understanding of GBM and natural compounds targeting NF-κB signaling.

Quercetin: A Bioactive Compound Imparting Cardiovascular and Neuroprotective Benefits: Scope for Exploring Fresh Produce, Their Wastes, and By-Products

Quercetin, a bioactive secondary metabolite, holds incredible importance in terms of bioactivities, which has been proved by in vivo and in vitro studies. The treatment of cardiovascular and neurological diseases by quercetin has been extensively investigated over the past decade. Quercetin is present naturally in appreciable amounts in fresh produce (fruits and vegetables). However, today, corresponding to the growing population and global demand for fresh fruits and vegetables, a paradigm shift and focus is laid towards exploring industrial food wastes and/or byproducts as a new resource to obtain bioactive compounds such as quercetin. Based on the available research reports over the last decade, quercetin has been suggested as a reliable therapeutic candidate for either treating or alleviating health issues, mainly those of cardiovascular and neurological diseases. In the present review, we have summarized some of the critical findings and hypotheses of quercetin from the available databases foreseeing its future use as a potential therapeutic agent to treat cardiovascular and neurological diseases. It is anticipated that this review will be a potential reference material for future research activities to be undertaken on quercetin obtained from fresh produce as well as their respective processing wastes/byproducts that rely on the circular concept.

Chronic effects of different quercetin doses in penicillin-induced focal seizure model

AIM

The aim of the present study was to examine the effects of different quercetin pretreatment doses on focal epileptiform activity induced by penicillin in adult male rat cortex.

METHOD

Twenty-eight male Wistar rats weighing 200-235 g were randomly divided into four groups: control (only penicillin-injected group) and penicillin + 25, 50 or 100 mg/kg quercetin doses. All quercetin-treated rats had a daily single dose of 25, 50 or 100 mg/kg intraperitoneally administered quercetin for 21 days, and the last dose was given 30 min before the penicillin injection. Epileptiform activity was induced by a single intracortical (i.c.) microinjection of penicillin (500 units/2.5 μl) into left motor cortex. After penicillin injection ECoG was recorded for the following 180 min.

RESULTS

Quercetin pretreatments of 25, 50 and 100 mg/kg significantly increased the duration of latency (initial spike activity) and decreased spike frequency of the epileptiform activity compared to the control group (p < 0.05). Duration of latency was significantly longer in 25 mg/kg quercetin pretreatment group compared to 100 mg/kg group (p < 0.05). Spike amplitude of epileptiform activity was not different in the study groups (p > 0.05).

CONCLUSION

Quercetin had an anticonvulsant activity in penicillin-induced focal seizure model in the present study. In addition, lower quercetin doses had highest anticonvulsant effect in this model.

Quercetin alleviates acute kidney injury by inhibiting ferroptosis

INTRODUCTION

Ferroptosis is an iron-dependent regulated necrosis and has been proven to contribute to the progress of acute kidney injury (AKI). Quercetin (QCT), a natural flavonoid which is commonly found in numerous fruits and vegetables, has extensive pharmacological effects, such as anti-oxidant, anti-inflammatory and anti-senescence effects.

OBJECTIVES

This study aims to explain whether ferroptosis is a therapeutic strategy to AKI, and to explore the effect of QCT on AKI ferroptosis.

METHODS

NRK-52E cells and HK-2 cells were used for in vitro ferroptosis studies. Morphology of cells was detected by transmission electron microscopy. Lipid ROS was assayed using flow cytometry. In vivo, AKI was induced by ischemia-reperfusion (I/R) or folic acid (FA). To explore the molecular mechanisms, RNA-sequence analysis was performed. Transwell was used to detect macrophage migration.

RESULTS

We discovered that quercetin (QCT), a natural flavonoid, inhibited ferroptosis in renal proximal tubular epithelial cells. QCT blocked the typical morphologic changes of ferroptotic cells by reducing the levels of malondialdehyde (MDA) and lipid ROS and increasing the levels of glutathione (GSH). Moreover, QCT ameliorated AKI induced by I/R or FA. RNA-sequence analysis highlighted activation transcription factor 3 (ATF3), as it was the dominant one among all the 299 down-regulated genes by QCT. Knockdown of ATF3 could significantly increase the levels of SLC7A11, GPX4 and increased the cell viability. In addition, ferroptotic cells were found to be extremely pro-inflammatory by recruiting macrophages through CCL2, while QCT inhibited the chemotaxis of macrophages induced by ferroptosis in AKI.

CONCLUSIONS

Collectively, these results identify QCT as a ferroptosis inhibitor and provide new therapeutic strategies for diseases related to ferroptosis.

The effects of six months Persicaria minor extract supplement among older adults with mild cognitive impairment: a double-blinded, randomized, and placebo-controlled trial

BACKGROUND

Persicaria minor extract exhibits antioxidant and anti-inflammatory properties and has potential effects on cognitive function and mood. However, the effects of P.minor on brain activation and biomarkers have not been studied among older adults. This multicentre, randomized, double-blinded, placebo-controlled study aimed to investigate the effect of 6 months P.minor extract supplement (Biokesum®) on cognition, mood, biomarkers, and brain activation among older adults with Mild Cognitive Impairment (MCI).

METHOD

A total of 36 Malaysian community-dwelling older adults with MCI (60-75-year-old) were randomized into Biokesum® (n = 18) and placebo group (n = 18). Each subject consumed one capsule of Biokesum® (250 mg/capsule) or placebo (maltodextrin, 280 mg/capsule) twice daily for 6 months. Cognitive function and mood were assessed at baseline, 3rd, and 6th-month using neuropsychological tests (MMSE, Digit Span, RAVLT, Digit Symbol, and Visual Reproduction) and Profile of Mood State (POMS) questionnaire. Blood lipid profile, fasting blood glucose, and biomarkers (MDA, LPO, COX-2, iNOS, and BDNF) were measured at baseline and 6th month. By the end of the intervention, there were 30 compliers (Biokesum®: N = 15; Placebo: N = 15) and 6 dropouts. For brain activation assessment, 15 subsamples (Biokesum®: N = 8; Placebo: N = 7) completed N-back and Stroop tasks during fMRI scanning at baseline and 6th month. The dorsolateral prefrontal cortex (Brodmann's area 9 and 46) was identified as a region of interest (ROI) for brain activation analysis using SPM software.

RESULTS

Two-way mixed ANOVA analysis showed significant improvements in Visual Reproduction II (p = 0.012, partial η2 = 0.470), tension (p = 0.042, partial η2 = 0.147), anger (p = 0.010, partial η2 = 0.207), confusion (p = 0.041, partial η2 = 0.148), total negative subscales (p = 0.043, partial η2 = 0.145), BDNF (p = 0.020, partial η2 = 0.179) and triglyceride (p = 0.029, partial η2 = 0.237) following 6 months of Biokesum® supplementation. Preliminary finding also demonstrated significant improvement at 0-back task-induced right DLPFC activation (p = 0.028, partial η2 = 0.652) among subsamples in Biokesum® group. No adverse events were reported at the end of the study.

CONCLUSION

Six months Biokesum® supplementation potentially improved visual memory, negative mood, BDNF, and triglyceride levels among older adults with MCI. Significant findings on brain activation at the right DPLFC must be considered as preliminary.

TRIAL REGISTRATION

Retrospectively registered on 30th August 2019 [ ISRC TN12417552 ].

Modified magnetic core-shell mesoporous silica nano-formulations with encapsulated quercetin exhibit anti-amyloid and antioxidant activity

Targeted tissue drug delivery is a challenge in contemporary nanotechnologically driven therapeutic approaches, with the interplay interactions between nanohost and encapsulated drug shaping the ultimate properties of transport, release and efficacy of the drug at its destination. Prompted by the need to pursue the synthesis of such hybrid systems, a family of modified magnetic core-shell mesoporous silica nano-formulations was synthesized with encapsulated quercetin, a natural flavonoid with proven bioactivity. The new nanocarriers were produced via the sol-gel process, using tetraethoxysilane as a precursor and bearing a magnetic core of surface-modified monodispersed magnetite colloidal superparamagnetic nanoparticles, subsequently surface-modified with polyethylene glycol 3000 (PEG3k). The arising nano-formulations were evaluated for their textural and structural properties, exhibiting enhanced solubility and stability in physiological media, as evidenced by the loading capacity, entrapment efficiency results and in vitro release studies of their load. Guided by the increased bioavailability of quercetin in its encapsulated form, further evaluation of the biological activity of the magnetic as well as non-magnetic core-shell nanoparticles, pertaining to their anti-amyloid and antioxidant potential, revealed interference with the aggregation of β-amyloid peptide (Aβ) in Alzheimer's disease, reduction of Aβ cellular toxicity and minimization of Aβ-induced Reactive Oxygen Species (ROS) generation. The data indicate that the biological properties of released quercetin are maintained in the presence of the host nanocarriers. Collectively, the findings suggest that the emerging hybrid nano-formulations can function as efficient nanocarriers of hydrophobic natural flavonoids in the development of multifunctional nanomaterials toward therapeutic applications.

Neuroprotection: Targeting Multiple Pathways by Naturally Occurring Phytochemicals

With the increase in the expectancy of the life span of humans, neurodegenerative diseases (NDs) have imposed a considerable burden on the family, society, and nation. In defiance of the breakthroughs in the knowledge of the pathogenesis and underlying mechanisms of various NDs, very little success has been achieved in developing effective therapies. This review draws a bead on the availability of the nutraceuticals to date for various NDs (Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, Huntington's disease, vascular cognitive impairment, Prion disease, Spinocerebellar ataxia, Spinal muscular atrophy, Frontotemporal dementia, and Pick's disease) focusing on their various mechanisms of action in various in vivo and in vitro models of NDs. This review is distinctive in its compilation to critically review preclinical and clinical studies of the maximum phytochemicals in amelioration and prevention of almost all kinds of neurodegenerative diseases and address their possible mechanism of action. PubMed, Embase, and Cochrane Library searches were used for preclinical studies, while ClinicalTrials.gov and PubMed were searched for clinical updates. The results from preclinical studies demonstrate the efficacious effects of the phytochemicals in various NDs while clinical reports showing mixed results with promise for phytochemical use as an adjunct to the conventional treatment in various NDs. These studies together suggest that phytochemicals can significantly act upon different mechanisms of disease such as oxidative stress, inflammation, apoptotic pathways, and gene regulation. However, further clinical studies are needed that should include the appropriate biomarkers of NDs and the effect of phytochemicals on them as well as targeting the appropriate population.

Bioactive Polyphenols and Neuromodulation: Molecular Mechanisms in Neurodegeneration

The interest in dietary polyphenols in recent years has greatly increased due to their antioxidant bioactivity with preventive properties against chronic diseases. Polyphenols, by modulating different cellular functions, play an important role in neuroprotection and are able to neutralize the effects of oxidative stress, inflammation, and apoptosis. Interestingly, all these mechanisms are involved in neurodegeneration. Although polyphenols display differences in their effectiveness due to interindividual variability, recent studies indicated that bioactive polyphenols in food and beverages promote health and prevent age-related cognitive decline. Polyphenols have a poor bioavailability and their digestion by gut microbiota produces active metabolites. In fact, dietary bioactive polyphenols need to be modified by microbiota present in the intestine before being absorbed, and to exert health preventive effects by interacting with cellular signalling pathways. This literature review includes an evaluation of the literature in English up to December 2019 in PubMed and Web of Science databases. A total of 307 studies, consisting of research reports, review articles and articles were examined and 146 were included. The review highlights the role of bioactive polyphenols in neurodegeneration, with a particular emphasis on the cellular and molecular mechanisms that are modulated by polyphenols involved in protection from oxidative stress and apoptosis prevention.

Allium cepa exerts neuroprotective effect on retinal ganglion cells of pterygopalatine artery (PPA) ligated mice

Background

Repeated failure to rescue the damaged retinal ganglion cells (RGCs) by various drugs has warranted the need to screen common herbal compounds available in the form of various eye formulations for their efficacy.

Objective

We aimed to investigate the neuroprotective effect of pretreatment with aqueous extract of A. cepa in Ischemia/Reperfusion (I/R) induced retinal injury.

Methods

Ischemia was induced for 2 h by pterygopalatine artery (PPA) ligation in C57BL/6J mice, followed by reperfusion. The neuroprotective role of oral pretreatment with aqueous extract of A. cepa (300 mg/kg) was analyzed with respect to control and injury only group at 7, 14, and 28 day after the surgery for expression of different genes in the retina by Real-Time PCR.

Results

Molecular analysis at different time points showed increased expression of BCl-2, GDNF, GFAP, and Brn3b in the retina at 14 and 28 day after A. cepa treatment in comparison to the injury alone group. However, at shorter time point (7th day), the expression of these genes was pronounced in the injury only group in comparison to the injury and pretreated group.

Conclusion

Pretreatment with aqueous extract of A. cepa may protect from the neuronal damage in I/R-induced retinal injury in mice by altering the expression of neurotrophic factor.

Protective effects of ginsenoside Rb1 on H2O2-induced oxidative injury in human endothelial cell line (EA.hy926) via miR-210

Ginsenoside Rb1 (Rb1) possesses a cardioprotective effect via mediating microRNAs (miRs), while it is unexplored whether miR-210 is regulated by Rb1 in response to oxidative stress. Human endothelial EA.hy926 cells were stimulated with H₂O₂ before Rb1 treatment. After transfection, cell viability, apoptosis, migration, and invasion assays were conducted. Western blot was applied to quantify protein. BCL2/adenovirus E1B 19-kDa interacting protein 3 (BNIP3) and miR-210 were analyzed with quantitative reverse transcription polymerase chain reaction. Dual luciferase activity assay was performed. Rb1 elevated viability, migration, and invasion of H₂O₂-treated cells. H₂O₂-induced apoptosis was moderated by Rb1. miR-210 was augmented in H₂O₂-treated cells after Rb1 stimulation. miR-210 inhibitor abolished the positive effects of Rb1. BNIP3 was negatively modulated by miR-210 and implicated in modulating viability, apoptosis, and migration and invasion. In addition, BNIP3 modulated phosphorylation of regulators. Rb1 repressed oxidative injury via elevating miR-210. miR-210 negatively mediated BNIP3, which participated in oxidative damage via regulating mammalian targets of rapamycin (mTOR) and nuclear factor-κB (NF-κB).

Quercetin depletes intracellular Ca2+ stores and blunts ATP-triggered Ca2+ signaling in bEnd.3 endothelial cells

Quercetin is a flavonol polyphenol widely found in many vegetables, grains, and fruits. Quercetin has been shown to inhibit proliferation and invasion of various glioma cells and is regarded as a potential anticancer agent against glioma. However, whether and how this drug could affect brain blood vessels and endothelial cells (EC) are less understood. Further, there is hitherto no report on how quercetin affects brain EC Ca²⁺ homeostasis. In this report, we investigated the effects of quercetin on Ca²⁺ homeostasis in mouse brain bEnd.3 EC. We demonstrated that quercetin raised cytosolic Ca²⁺ level in a concentration-dependent manner. Quercetin-triggered Ca²⁺ signal composed of both internal Ca²⁺ release and extracellular Ca²⁺ influx. Quercetin caused Ca²⁺ release from the endoplasmic reticulum, and consistently, inhibition of inositol 1,4,5-trisphosphate receptor (IP3R) by xestospongin C (XeC) suppressed quercetin-triggered Ca²⁺ release. Quercetin also caused Ca²⁺ release from lysosomes, an observation in concordance with the inhibition of quercetin-triggered Ca²⁺ release by trans-Ned-19, a blocker of two-pore channels. As quercetin depleted intracellular Ca²⁺ storage, it suppressed ATP-induced Ca²⁺ release and thereby blunted ATP-triggered Ca²⁺ signaling. In addition, quercetin co-treatment significantly suppressed ATP-stimulated nitric oxide release. Our work therefore showed, for the first time, quercetin perturbed intracellular Ca²⁺ stores and strongly suppressed ATP-triggered response in bEnd.3 cells.

Natural products and their derivatives as multifunctional ligands against Alzheimer's disease

Alzheimer's disease (AD), a complex neurodegenerative disorder causing multiple cellular changes including impaired cholinergic system, beta-amyloid (βA) aggregation, tau hyperphosphorylation, metal dyshomeostasis, neuroinflammation, and many other pathways are involved in the pathogenesis of the disease. However, the exact cause of the disease is not known. Natural products such as flavonoids, alkaloids, resveratrol, and curcumin have multifunctional properties, and have drawn the attention of the researchers because these molecules are capable of interacting concurrently with the multiple targets of AD. Therefore, natural products and their derivatives with proven efficacy could be used in the management of the neurodegenerative disorders. This review focuses on the natural product based multitarget directed ligands like tacrine-coumarin, tacrine-huperzine A, harmine-isoxazoline, berberine-thiophenyl, galantamine-indole, pyridoxine-resveratrol, donepezil-curcumin and their mode of action.

JAX2, an ethanol extract of Hyssopus cuspidatus Boriss, can prevent bronchial asthma by inhibiting MAPK/NF-κB inflammatory signaling

BACKGROUND

Hyssopus cuspidatus Boriss has been used to treat bronchial asthma for many years in Uighur medicine. JAX2, an ethanol extract from this plant, has effectiveness against bronchial asthma. However, the molecular basis for the anti-inflammatory effects of JAX2 remains unclear.

PURPOSE

This study aimed to evaluate the mechanism of JAX2 against bronchial asthma.

METHODS

We established an asthma model in rats using ovalbumin (OVA), and an inflammatory model in RAW264.7 cells using lipopolysaccharide (LPS) stimulation. To evaluate the anti-inflammatory effects of JAX2, the concentrations of tumor necrosis factor (TNF)-α, interleukin (IL)-4, IL-6, IL-17, eotaxin and immunoglobulin (Ig)E were measured by enzyme-linked immunosorbent assay (ELISA). Cell viability was investigated by the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)2H-tetrazolium, inner salt (MTS) assay. Further, nitric oxide (NO) and reactive oxygen species (ROS) were determined using Griess reagent and 2,7-dichlorofluorescein diacetate. The phosphorylation of p-extracellular signal-regulated kinase (ERK), p-Jun-NH2-terminal kinase (JNK), p38 kinases (p38) and p-inhibitor of nuclear factor kappa-B kinase (IKK), and nuclear translocation of p-p65 kinases (p-p65) were determined by immunofluorescence to uncover the effects of JAX2 on the Mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathways.

RESULTS

After JAX2 administration to rats, Interferon (IFN)-γ concentrations in BALF increased significantly. Further, the concentrations of TNF-α, IL-4, IL-6, IL-17 and eotaxin in BALF, and IgE in serum decreased. JAX2 decreased TNF-α, IL-6 and NO in cell supernatant, and reduced ROS intracellularly. Concurrently, IFN-γ concentrations increased in cell supernatant significantly. In LPS-induced RAW264.7 cells, JAX2 inhibited phosphorylation of p-ERK, p-JNK and p-38 MAPK. The subsequent phosphorylation of p-IKK and nuclear translocation of the p-p65 subunit of NF-κB were also suppressed.

CONCLUSION

Based on these findings, we believe that JAX2 has both preventive and treatment effects in bronchial asthma. Furthermore, in the RAW264.7 cell inflammatory model, JAX2 also inhibited NF-κB and MAPK signaling pathways.

Molecular mechanisms underlying protective role of quercetin in attenuating Alzheimer's disease

Quercetin belongs to the flavonoids family, which is present in most of the plants including fruits, vegetables, green tea and even in red wine having antioxidant activities. It is available as a food supplement in the market and has physiological health effects. Quercetin has anti-inflammatory, anticancer and anti-prostate activities along with its beneficial effects on high cholesterol, kidney transplantation, asthma, diabetes, viral infections, pulmonary, schizophrenia and cardiovascular diseases. Quercetin possesses scavenging potential of hydroxyl radical (OH^-), hydrogen peroxide (H₂O₂), and superoxide anion (O₂^-). These reactive oxygen species (ROS) hampers lipid, protein, amino acids and deoxyribonucleic acid (DNA) processing leading to epigenetic alterations. Quercetin has the ability to combat these harmful effects. ROS plays a vital role in the progression of Alzheimer's disease (AD), and we propose that quercetin would be the best choice to overcome cellular and molecular signals in regulating normal physiological functions. However, data are not well documented regarding exact cellular mechanisms of quercetin. The neuroprotective effects of quercetin are mainly due to potential up- and/or down-regulation of cytokines via nuclear factor (erythroid-derived 2)-like 2 (Nrf2), Paraoxonase-2, c-Jun N-terminal kinase (JNK), Protein kinase C, Mitogen-activated protein kinase (MAPK) signalling cascades, and PI3K/Akt pathways. Therefore, the aim of the present review was to elaborate on the cellular and molecular mechanisms of the quercetin involved in the protection against AD.

Recent Expansions on Cellular Models to Uncover the Scientific Barriers Towards Drug Development for Alzheimer's Disease

Globally, the central nervous system (CNS) disorders appear as the most critical pathological threat with no proper cure. Alzheimer's disease (AD) is one such condition frequently observed with the aged population and sometimes in youth too. Most of the research utilizes different animal models for in vivo study of AD pathophysiology and to investigate the potency of the newly developed therapy. These in vivo models undoubtably provide a powerful investigation tool to study human brain. Although, it sometime fails to mimic the exact environment and responses as the human brain owing to the distinctive genetic and anatomical features of human and rodent brain. In such condition, the in vitro cell model derived from patient specific cell or human cell lines can recapitulate the human brain environment. In addition, the frequent use of animals in research increases the cost of study and creates various ethical issues. Instead, the use of in vitro cellular models along with animal models can enhance the translational values of in vivo models and represent a better and effective mean to investigate the potency of therapeutics. This strategy also limits the excessive use of laboratory animal during the drug development process. Generally, the in vitro cell lines are cultured from AD rat brain endothelial cells, the rodent models, human astrocytes, human brain capillary endothelial cells, patient derived iPSCs (induced pluripotent stem cells) and also from the non-neuronal cells. During the literature review process, we observed that there are very few reviews available which describe the significance and characteristics of in vitro cell lines, for AD investigation. Thus, in the present review article, we have compiled the various in vitro cell lines used in AD investigation including HBMEC, BCECs, SHSY-5Y, hCMEC/D3, PC-2 cell line, bEND3 cells, HEK293, hNPCs, RBE4 cells, SK-N-MC, BMVECs, CALU-3, 7W CHO, iPSCs and cerebral organoids cell lines and different types of culture media such as SCM, EMEM, DMEM/F12, RPMI, EBM and 3D-cell culture.

Inhibition of protein misfolding and aggregation by natural phenolic compounds

Protein misfolding and aggregation into fibrillar deposits is a common feature of a large group of degenerative diseases affecting the central nervous system or peripheral organs, termed protein misfolding disorders (PMDs). Despite their established toxic nature, clinical trials aiming to reduce misfolded aggregates have been unsuccessful in treating or curing PMDs. An interesting possibility for disease intervention is the regular intake of natural food or herbal extracts, which contain active molecules that inhibit aggregation or induce the disassembly of misfolded aggregates. Among natural compounds, phenolic molecules are of particular interest, since most have dual activity as amyloid aggregation inhibitors and antioxidants. In this article, we review many phenolic natural compounds which have been reported in diverse model systems to have the potential to delay or prevent the development of various PMDs, including Alzheimer's and Parkinson's diseases, prion diseases, amyotrophic lateral sclerosis, systemic amyloidosis, and type 2 diabetes. The lower toxicity of natural compounds compared to synthetic chemical molecules suggest that they could serve as a good starting point to discover protein misfolding inhibitors that might be useful for the treatment of various incurable diseases.

Asiaticoside Attenuates Cell Growth Inhibition and Apoptosis Induced by Aβ1-42 via Inhibiting the TLR4/NF-κB Signaling Pathway in Human Brain Microvascular Endothelial Cells

Alzheimer's disease (AD) is a very common progressive neurodegenerative disorder with the highest incidence in the world. Dysfunction of the blood-brain barrier (BBB) may be responsible for the pathogenesis and pathology of AD for abnormally transporting amyloid-β (Aβ, the main component of the senile plaques) from the sera into the central nervous system. Aβ peptides induce apoptosis in human brain microvascular endothelial cells (hBMECs), the main component of BBB. Apoptosis in neuronal cells plays a critical role in the pathogenesis of AD. Asiaticoside, a natural glycoside extracted from Centella asiatica (L.) Urban, has an anti-apoptotic effect on hBMECs but the molecule mechanism remains unclear. Therefore, we investigate the protective effect of asiaticoside on Aβ_1-42-induced cytotoxicity and apoptosis as well as associated mechanism in hBMECs with commonly used in vitro methods for clinical development of asiaticoside as a novel anti-AD agent. In the present study, we investigated the effects of asiaticoside on cytotoxicity by Cell Counting Kit-8 assay, mitochondrial membrane potential by JC-1 fluorescence analysis, anti-apoptosis by Hoechst 33258 staining and Annexin V-FITC (fluorescein isothiocyanate) and propidium iodide (PI) analyses, the expressions of TNF-α and IL-6 by enzyme-linked immunosorbent assay (ELISA) and TLR4, MyD88, TRAF6, p-NF-κB p65, and total NF-κB p65 by Western blotting, and nuclear translocation of NF-κB p65 by immunofluorescence analysis in hBMECs. The results showed that pretreatment of asiaticoside (25, 50, and 100 μM) for 12 h significantly attenuated cell growth inhibition and apoptosis, and restored declined mitochondrial membrane potential induced by Aβ_1-42 (50 μM) in hBMECs. Asiaticoside also significantly downregulated the elevated expressions of TNF-α, IL-6, TLR4, MyD88, TRAF6, and p-NF-κB p65, as well as inhibited NF-κB p65 translocation from cytoplasm to nucleus induced by Aβ_1-42 in hBMECs in a concentration-dependent manner. The possible underlying molecular mechanism of asiaticoside may be through inhibiting the TLR4/NF-κB signaling pathway. Therefore, asiaticoside may be developed as a novel agent for the prevention and/or treatment of AD clinically.

Quercetin inhibits okadaic acid-induced tau protein hyperphosphorylation through the Ca2+‑calpain‑p25‑CDK5 pathway in HT22 cells

Alzheimer's disease (AD) is a common neurodegenerative disorder characterized by aberrant tau protein hyperphosphorylation, which eventually leads to the formation of neurofibrillary tangles. Hyperphosphorylated tau protein is considered as a vital factor in the development of AD and is highly associated with cognitive impairment. Therefore, it is recognized to be a potential therapeutic target. Quercetin (QUE) is a naturally occurring flavonoid compound. In the present study, the inhibitory effect of QUE on okadaic acid (OA)-induced tau protein hyperphosphorylation in HT22 cells was explored. Western blotting results indicated that QUE significantly attenuated OA‑induced tau protein hyperphosphorylation at the Ser396, Ser199, Thr231 and Thr205 sites. Further experiments demonstrated that QUE inhibited the activity of cyclin‑dependent kinase 5 (CDK5), a key enzyme in the regulation of tau protein, and blocked the Ca2+‑calpain‑p25‑CDK5 signaling pathway. These observations indicate the ability of QUE to decrease tau protein hyperphosphorylation and thereby attenuate the associated neuropathology. In conclusion, these results support the potential of QUE as a therapeutic agent for AD and other neurodegenerative tauopathies.

Total flavonoid extract from Dracoephalum moldavica L. attenuates β-amyloid-induced toxicity through anti-amyloidogenesic and neurotrophic pathways

AIMS

Alzheimer's disease (AD) is an incurable neurodegenerative disorder characterized by global cognitive impairment that involves accumulation of amyloid-beta peptides (Aβ) in the brain. Herbal approaches can be used as alternative medicines to slow the progression of AD. This study aimed to determine the beneficial effects and potential underlying mechanisms of total flavonoid extract from Dracoephalum moldavica L. (TFDM) for attenuating Alzheimer-related deficits induced by Aβ.

MAIN METHODS

We used amyloid precursor protein (APP) and presenilin 1 (PS1) double transgenic mice and copper-injured APP Swedish mutation overexpressing SH-SY5Y cells to evaluate the beneficial effects of TFDM. Further, identifying the mechanisms of action was conducted on anti-amyloidogenic and neurotrophic transductions.

KEY FINDINGS

Our results indicated that TFDM treatment ameliorated cognitive impairments and neurodegeneration and improved the antioxidant defense system in APP/PS1 mice. TFDM also reduced Aβ burden by relieving Aβ deposition, decreasing insoluble Aβ levels, and inhibiting β-amyloidogenic processing pathway involving downregulation of β-secretase and β-C-terminal fragment in the brain. In the in vitro model of AD, TFDM treatment protected injured cells, and combined with the beneficial effects of decreasing APP levels, lowered Aβ_1-42 and regulated the redox imbalance. Moreover, TFDM preserved the extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor pathway both in vitro and in vivo.

SIGNIFICANCE

In conclusion, TFDM clearly demonstrated neuroprotective effects by restoring the anti-amyloidogenic and neurotrophic transductions in the context of AD-associated deficits. These findings indicate the potential use of herb-based substances as supplements or potential alternative supplements for attenuating the progression of AD.

Quercetin, Hyperin, and Chlorogenic Acid Improve Endothelial Function by Antioxidant, Antiinflammatory, and ACE Inhibitory Effects

In recent years, the blueberry cultivation and processing industry developed quickly because blueberries are super-fruit with healthy function. Blueberry leaves are byproducts of the blueberry industry, which are rich in bioactive phenolics, such as quercetin (Q), hyperin (H), and chlorogenic acid (C). This study investigated protective effects of 3 phenolics (Q, H, and C) from leaves of rabbiteye blueberry Vaccinium ashei on human umbilical vein endothelial cells. The results showed that all these 3 phenolics could improve endothelial function by inhibiting oxidative damage and proinflammatory cytokines caused by tumor necrosis factor-α (TNF-α). The cell vitalities of endothelial cells pretreated with Q, H, and C were higher than those stimulated with TNF-α only. These phenolics could decrease reactive oxygen species and xanthine oxidase-1 levels and increase superoxide dismutase and heme oxygenase-1 levels in endothelial cells. They also could decrease the protein expressions of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and monocyte chemotactic protein-1 induced by TNF-α. In addition, Q, H, and C also exhibited vasodilatory effect by reducing the angiotensin I-converting enzyme (ACE) protein levels in endothelial cells. Mostly 3 phenolics exhibited bioactivities as a function of concentration, but the effects not always depended on the concentration. The antioxidant and antiinflammatory effects of Q seemed to be more pronounced than H; however, H exhibited higher cell vitalities. The results indicated that phenolics from rabbiteye blueberry leaves could be potential antioxidants, inflammation and ACE inhibitors, and rabbiteye blueberry leaves provide a new resources of phytochemicals beneficial for cardiovascular health.

Luteolin Inhibits Fibrillary β-Amyloid1-40-Induced Inflammation in a Human Blood-Brain Barrier Model by Suppressing the p38 MAPK-Mediated NF-κB Signaling Pathways

Amyloid-β peptides (Aβ) exist in several forms and are known as key modulators of Alzheimer's disease (AD). Fibrillary Aβ (fAβ) has been found to disrupt the blood-brain barrier (BBB) by triggering and promoting inflammation. In this study, luteolin, a naturally occurring flavonoid that has shown beneficial properties in the central nervous system, was evaluated as a potential agent to preserve barrier function and inhibit inflammatory responses at the BBB that was injured by fAβ_1-40. We established an in vitro BBB model by co-culturing human brain microvascular endothelial cells (hBMECs) and human astrocytes (hAs) under fAβ_1-40-damaged conditions and investigated the effect of luteolin by analyzing cellular toxicity, barrier function, cytokine production and inflammation-related intracellular signaling pathways. Our results demonstrated that, in cells injured by fAβ_1-40, luteolin increased cell viability of hBMECs and hAs. The cytoprotection of the co-culture against the damage induced by fAβ_1-40 was also increased at both the apical and basolateral sides. Luteolin protected the barrier function by preserving transendothelial electrical resistance and relieving aggravated permeability in the human BBB model after being exposed to fAβ_1-40. Moreover, in both the apical and basolateral sides of the co-culture, luteolin reduced fAβ_1-40-induced inflammatory mediator and cytokine production, including cyclooxygenase-2 (COX-2), tumor necrosis factor α (TNF-α), interleukin 1 β (IL-1β), interleukin 6 (IL-6), and interleukin 8 (IL-8), however it did not show sufficient effects on scavenging intracellular reactive oxygen species (ROS) in hBMECs and hAs. The mechanism of BBB protection against fAβ_1-40-induced injury may be related to the regulation of inflammatory signal transduction, which involves inhibition of p38 mitogen-activated protein kinase (MAPK) activation, downregulation of phosphorylated inhibitory κB kinase (phosphor-IKK) levels, relief of inhibitory κB α (IκBα) degradation, blockage of nuclear factor κB (NF-κB) p65 nuclear translocation, and reduction of the release of inflammatory cytokines. Moreover, the employment of p38 MAPK and NF-κB inhibitors reversed luteolin-mediated barrier function and cytokine release. Taken together, luteolin may serve as a potential therapeutic agent for BBB protection by inhibiting inflammation following fAβ_1-40-induced injury.

Natural products against Alzheimer's disease: Pharmaco-therapeutics and biotechnological interventions

Alzheimer's disease (AD) is a severe, chronic and progressive neurodegenerative disease associated with memory and cognition impairment ultimately leading to death. It is the commonest reason of dementia in elderly populations mostly affecting beyond the age of 65. The pathogenesis is indicated by accumulation of the amyloid-beta (Aβ) plaques and neurofibrillary tangles (NFT) in brain tissues and hyperphosphorylation of tau protein in neurons. The main cause is considered to be the formation of reactive oxygen species (ROS) due to oxidative stress. The current treatment provides only symptomatic relief by offering temporary palliative therapy which declines the rate of cognitive impairment associated with AD. Inhibition of the enzyme acetylcholinesterase (AChE) is considered as one of the major therapeutic strategies offering only symptomatic relief and moderate disease-modifying effect. Other non-cholinergic therapeutic approaches include antioxidant and vitamin therapy, stem cell therapy, hormonal therapy, use of antihypertensive or lipid-lowering medications and selective phosphodiesterase (PDE) inhibitors, inhibition of β-secretase and γ-secretase and Aβ aggregation, inhibition of tau hyperphosphorylation and intracellular NFT, use of nonsteroidal anti-inflammatory drugs (NSAIDs), transition metal chelators, insulin resistance drugs, etanercept, brain-derived neurotrophic factor (BDNF) etc. Medicinal plants have been reported for possible anti-AD activity in a number of preclinical and clinical trials. Ethnobotany, being popular in China and in the Far East and possibly less emphasized in Europe, plays a substantial role in the discovery of anti-AD agents from botanicals. Chinese Material Medica (CMM) involving Chinese medicinal plants has been used traditionally in China in the treatment of AD. Ayurveda has already provided numerous lead compounds in drug discovery and many of these are also undergoing clinical investigations. A number of medicinal plants either in their crude forms or as isolated compounds have exhibited to reduce the pathological features associated with AD. In this present review, an attempt has been made to elucidate the molecular mode of action of various plant extracts, phytochemicals and traditional herbal formulations investigated against AD as reported in various preclinical and clinical tests. Herbal synergism often found in polyherbal formulations were found effective to combat disease heterogeneity as found in complex pathogenesis of AD. Finally a note has been added to describe biotechnological improvement, genetic and genomic resources and mathematical and statistical techniques for empirical model building associated with anti-AD plant secondary metabolites and their source botanicals.