Neuroprotective effect of quercetin against rotenone-induced neuroinflammation and alterations in mice behavior

Neuroprotective Roles of Daidzein Through Extracellular Signal-Regulated Kinases Dependent Pathway In Chronic Unpredictable Mild Stress Mouse Model

Depression is a stress-related neuropsychiatric disorder causing behavioural, biochemical, molecular dysfunctions and cognitive impairments. Previous studies suggested connection between neuropsychiatric diseases like depression with estrogen and estrogen receptors (ER). Daidzein is a phytoestrogen that functions as mammalian estrogen and regulates gene expressions through extracellular signal-regulated kinases (ERKs) dependent pathway by activating ERβ. ERβ modulates stress responses, physiological processes by activating protein kinases and plays a significant role in various neurological diseases like depression. However, significant roles of daidzein in depression involving ERK1/2, pERK1/2, and mTOR still unknown. Herein, we examined neuroprotective role of daidzein in chronic unpredictable mild stress (CUMS) mouse model. CUMS model was prepared, and placed in six groups namely, control, CUMS, CUMS vehicle, CUMS DZ (Daidzein 1 mg/kgbw, orally), CUMS PHTPP (ERβ blocker, 0.3 mg/kgbw, i..p.) and CUMS Untreated. Supplementation of daidzein to CUMS mice exhibits decrease depressive and anxiety-like behaviour, improved motor coordination and memory. Further, immunofluorescence results showed daidzein improved ERK1/2, pERK1/2 and mTOR expressions in the cortex, hippocampus and medulla of stressed mice. SOD, catalase and acetylcholinesterase levels were also improved. Blocking of ERβ with PHTPP stressed mice showed deficits in behaviour, low expression of ERK1/2, pERK1/2 and mTOR, and no significant changes in SOD, catalase and acetylcholinesterase level. Collectively, this study suggests that daidzein may ameliorate depressive and anxiety-like behaviour through ERK downregulating pathway by activating ERβ through ERK1/2, pERK1/2 and mTOR. Such study may be useful to understand daidzein dependent neuroprotection through ERβ in depression.

Exploring the Role of Reactive Oxygen Species in the Pathogenesis and Pathophysiology of Alzheimer's and Parkinson's Disease and the Efficacy of Antioxidant Treatment

Alzheimer's (AD) and Parkinson's Disease (PD) are life-altering diseases that are characterised by progressive memory loss and motor dysfunction. The prevalence of AD and PD is predicted to continuously increase. Symptoms of AD and PD are primarily mediated by progressive neuron death and dysfunction in the hippocampus and substantia nigra. Central features that drive neurodegeneration are caspase activation, DNA fragmentation, lipid peroxidation, protein carbonylation, amyloid-β, and/or α-synuclein formation. Reactive oxygen species (ROS) increase these central features. Currently, there are limited therapeutic options targeting these mechanisms. Antioxidants reduce ROS levels by the induction of antioxidant proteins and direct neutralisation of ROS. This review aims to assess the effectiveness of antioxidants in reducing ROS and neurodegeneration. Antioxidants enhance major endogenous defences against ROS including superoxide dismutase, catalase, and glutathione. Direct neutralisation of ROS by antioxidants protects against ROS-induced cytotoxicity. The combination of Indirect and direct protective mechanisms prevents ROS-induced α-synuclein and/or amyloid-β formation. Antioxidants ameliorate ROS-mediated oxidative stress and subsequent deleterious downstream effects that promote apoptosis. As a result, downstream harmful events including neuron death, dysfunction, and protein aggregation are decreased. The protective effects of antioxidants in human models have yet to directly replicate the success seen in cell and animal models. However, the lack of diversity in antioxidants for clinical trials prevents a definitive answer if antioxidants are protective. Taken together, antioxidant treatment is a promising avenue in neurodegenerative disease therapy and subsequent clinical trials are needed to provide a definitive answer on the protective effects of antioxidants. No current treatment strategies have significant impact in treating advanced AD and PD, but new mimetics of endogenous mitochondrial antioxidant enzymes (Avasopasem Manganese, GC4419 AVA) may be a promising innovative option for decelerating neurodegenerative progress in the future at the mitochondrial level of OS.

Synthesis and evaluation of Maillard conjugates for encapsulation and controlled delivery of quercetin under simulated gastrointestinal tract conditions

Encapsulation of bioactive molecules for therapeutic use is gaining great interest in the scientific community. Several encapsulation methodologies have been evaluated, sacrificing, in some cases, either encapsulation efficiency or compound integrity. Our work developed Maillard conjugates (MCs) based on the whey protein (WP)-Maltodextrin (MD) interaction to encapsulate quercetin by freeze-drying. The WP:MD ratio used (1:2 or 1:3) yielded the formation of MCs, demonstrated by an increased browning index and changes in the protein secondary structure. Freeze-drying showed high encapsulation efficiency, reaching 87.65% and 84.72% in treatments loaded with 3.3 mg quercetin/g MCs. Quercetin-loaded MCs showed spherical-shape (4-10 μm) and a negative charge, suggesting colloidal stability. Moreover, in vitro tests demonstrated a sustained release of quercetin throughout the oral, gastric, and intestinal phases, highlighting the MCs efficacy as bioactive delivery systems. This work provides useful information to design bioactive compound delivery systems for food and pharmaceutical applications.

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.

Effects of quercetin in preclinical models of Parkinson's disease: A systematic review

Parkinson's disease (PD) is a neurodegenerative disease that affects dopaminergic neurons, thus impairing dopaminergic signalling. Quercetin (QUE) has antioxidant and neuroprotective properties that are promising for the treatment of PD. This systematic review aimed to investigate the therapeutic effects of QUE against PD in preclinical models. The systematic search was performed in PubMed, Scopus and Web of Science. At the final screening stage, 26 articles were selected according to pre-established criteria. Selected studies used different methods for PD induction, as well as animal models. Most studies used rats (73.08%) and mice (23.08%), with 6-OHDA as the main strategy for PD induction (38.6%), followed by rotenone (30.8%). QUE was tested immersed in oil, nanosystems or in free formulations, in varied routes of administration and doses, ranging from 10 to 400 mg/kg and from 5 to 200 mg/kg in oral and intraperitoneal administrations, respectively. Overall, evidence from published data suggests a potential use of QUE as a treatment for PD, mainly through the inhibition of oxidative stress, neuroinflammatory response and apoptotic pathways.

Quercetin Protects Blood-Brain Barrier Integrity via the PI3K/Akt/Erk Signaling Pathway in a Mouse Model of Meningitis Induced by Glaesserella parasuis

Glaesserella parasuis (G. parasuis) causes serious inflammation and meningitis in piglets. Quercetin has anti-inflammatory and anti-bacterial activities; however, whether quercetin can alleviate brain inflammation and provide protective effects during G. parasuis infection has not been studied. Here, we established a mouse model of G. parasuis infection in vivo and in vitro to investigate transcriptome changes in the mouse cerebrum and determine the protective effects of quercetin on brain inflammation and blood-brain barrier (BBB) integrity during G. parasuis infection. The results showed that G. parasuis induced brain inflammation, destroyed BBB integrity, and suppressed PI3K/Akt/Erk signaling-pathway activation in mice. Quercetin decreased the expression of inflammatory cytokines (Il-18, Il-6, Il-8, and Tnf-α) and BBB-permeability marker genes (Mmp9, Vegf, Ang-2, and Et-1), increased the expression of angiogenetic genes (Sema4D and PlexinB1), reduced G. parasuis-induced tight junction disruption, and reactivated G. parasuis-induced suppression of the PI3K/Akt/Erk signaling pathway in vitro. Thus, we concluded that quercetin may protect BBB integrity via the PI3K/Akt/Erk signaling pathway during G. parasuis infection. This was the first attempt to explore the protective effects of quercetin on brain inflammation and BBB integrity in a G. parasuis-infected mouse model. Our findings indicated that quercetin is a promising natural agent for the prevention and treatment of G. parasuis infection.

Progress in the Treatment of Central Nervous System Diseases Based on Nanosized Traditional Chinese Medicine

Traditional Chinese Medicine (TCM) is widely used in clinical practice to treat diseases related to central nervous system (CNS) damage. However, the blood-brain barrier (BBB) constitutes a significant impediment to the effective delivery of TCM, thus substantially diminishing its efficacy. Advances in nanotechnology and its applications in TCM (also known as nano-TCM) can deliver active ingredients or components of TCM across the BBB to the targeted brain region. This review provides an overview of the physiological and pathological mechanisms of the BBB and systematically classifies the common TCM used to treat CNS diseases and types of nanocarriers that effectively deliver TCM to the brain. Additionally, drug delivery strategies for nano-TCMs that utilize in vivo physiological properties or in vitro devices to bypass or cross the BBB are discussed. This review further focuses on the application of nano-TCMs in the treatment of various CNS diseases. Finally, this article anticipates a design strategy for nano-TCMs with higher delivery efficiency and probes their application potential in treating a wider range of CNS diseases.

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.

Natural Polyphenols-Resveratrol, Quercetin, Magnolol, and β-Catechin-Block Certain Aspects of Heroin Addiction and Modulate Striatal IL-6 and TNF-α

We have examined the effects of four different polyphenols in attenuating heroin addiction using a conditioned place preference (CPP) paradigm. Adult male Sprague Dawley rats received heroin (alternating with saline) in escalating doses starting from 10 mg/kg, i.p. up to 80 mg/kg/d for 14 consecutive days. The rats were treated with distilled water (1 mL), quercetin (50 mg/kg/d), β-catechin (100 mg/kg/d), resveratrol (30 mg/kg/d), or magnolol (50 mg/kg/d) through oral gavage for 7 consecutive days, 30 min before heroin administration, starting on day 8. Heroin withdrawal manifestations were assessed 24 h post last heroin administration following the administration of naloxone (1 mg/kg i.p). Heroin CPP reinstatement was tested following a single dose of heroin (10 mg/kg i.p.) administration. Striatal interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) were quantified (ELISA) after naloxone-precipitated heroin withdrawal. Compared to the vehicle, the heroin-administered rats spent significantly more time in the heroin-paired chamber (p < 0.0001). Concomitant administration of resveratrol and quercetin prevented the acquisition of heroin CPP, while resveratrol, quercetin, and magnolol blocked heroin-triggered reinstatement. Magnolol, quercetin, and β-catechin blocked naloxone-precipitated heroin withdrawal and increased striatal IL-6 concentration (p < 0.01). Resveratrol administration was associated with significantly higher withdrawal scores compared to those of the control animals (p < 0.0001). The results of this study show that different polyphenols target specific behavioral domains of heroin addiction in a CPP model and modulate the increase in striatal inflammatory cytokines TNF-α and IL-6 observed during naloxone-precipitated heroin withdrawal. Further research is needed to study the clinical utility of polyphenols and to investigate the intriguing finding that resveratrol enhances, rather than attenuates naloxone-precipitated heroin withdrawal.

The Potential Benefits of Quercetin for Brain Health: A Review of Anti-Inflammatory and Neuroprotective Mechanisms

Neuroinflammation is a critical factor in developing and progressing numerous brain diseases, including neurodegenerative diseases. Chronic or excessive neuroinflammation can lead to neurotoxicity, causing brain damage and contributing to the onset and progression of various brain diseases. Therefore, understanding neuroinflammation mechanisms and developing strategies to control them is crucial for treating brain diseases. Studies have shown that neuroinflammation plays a vital role in the progression of neurodegenerative diseases, such as Alzheimer's (AD) and Parkinson's (PD), and stroke. Additionally, the effects of PM2.5 pollution on the brain, including neuroinflammation and neurotoxicity, are well-documented. Quercetin is a flavonoid, a plant pigment in many fruits, vegetables, and grains. Quercetin has been studied for its potential health benefits, including its anti-inflammatory, antioxidant, and anti-cancer properties. Quercetin may also have a positive impact on immune function and allergy symptoms. In addition, quercetin has been shown to have anti-inflammatory and neuroprotective properties and can activate AMP-activated protein kinase (AMPK), a cellular energy sensor that modulates inflammation and oxidative stress. By reducing inflammation and protecting against neuroinflammatory toxicity, quercetin holds promise as a safe and effective adjunctive therapy for treating neurodegenerative diseases and other brain disorders. Understanding and controlling the mechanisms of NF-κB and NLRP3 inflammasome pathways are crucial for preventing and treating conditions, and quercetin may be a promising tool in this effort. This review article aims to discuss the role of neuroinflammation in the development and progression of various brain disorders, including neurodegenerative diseases and stroke, and the impact of PM2.5 pollution on the brain. The paper also highlights quercetin's potential health benefits and anti-inflammatory and neuroprotective properties.

The Potential of Flavonoids and Flavonoid Metabolites in the Treatment of Neurodegenerative Pathology in Disorders of Cognitive Decline

Flavonoids are a biodiverse family of dietary compounds that have antioxidant, anti-inflammatory, antiviral, and antibacterial cell protective profiles. They have received considerable attention as potential therapeutic agents in biomedicine and have been widely used in traditional complimentary medicine for generations. Such complimentary medical herbal formulations are extremely complex mixtures of many pharmacologically active compounds that provide a therapeutic outcome through a network pharmacological effects of considerable complexity. Methods are emerging to determine the active components used in complimentary medicine and their therapeutic targets and to decipher the complexities of how network pharmacology provides such therapeutic effects. The gut microbiome has important roles to play in the generation of bioactive flavonoid metabolites retaining or exceeding the antioxidative and anti-inflammatory properties of the intact flavonoid and, in some cases, new antitumor and antineurodegenerative bioactivities. Certain food items have been identified with high prebiotic profiles suggesting that neutraceutical supplementation may be beneficially employed to preserve a healthy population of bacterial symbiont species and minimize the establishment of harmful pathogenic organisms. Gut health is an important consideration effecting the overall health and wellbeing of linked organ systems. Bioconversion of dietary flavonoid components in the gut generates therapeutic metabolites that can also be transported by the vagus nerve and systemic circulation to brain cell populations to exert a beneficial effect. This is particularly important in a number of neurological disorders (autism, bipolar disorder, AD, PD) characterized by effects on moods, resulting in depression and anxiety, impaired motor function, and long-term cognitive decline. Native flavonoids have many beneficial properties in the alleviation of inflammation in tissues, however, concerns have been raised that therapeutic levels of flavonoids may not be achieved, thus allowing them to display optimal therapeutic effects. Dietary manipulation and vagal stimulation have both yielded beneficial responses in the treatment of autism spectrum disorders, depression, and anxiety, establishing the vagal nerve as a route of communication in the gut-brain axis with established roles in disease intervention. While a number of native flavonoids are beneficial in the treatment of neurological disorders and are known to penetrate the blood–brain barrier, microbiome-generated flavonoid metabolites (e.g., protocatechuic acid, urolithins, γ-valerolactones), which retain the antioxidant and anti-inflammatory potency of the native flavonoid in addition to bioactive properties that promote mitochondrial health and cerebrovascular microcapillary function, should also be considered as potential biotherapeutic agents. Studies are warranted to experimentally examine the efficacy of flavonoid metabolites directly, as they emerge as novel therapeutic options.

Dietary Intervention with Quercetin Attenuates Diesel Exhaust Particle-Instilled Pulmonary Inflammation and Behavioral Abnormalities in Mice

Exposure to diesel exhaust particles (DEPs) is inevitable and closely linked with increased health hazards, causing pulmonary abnormalities by increasing inflammation, hypoxia, and so on. Moreover, long-term exposure to DEPs may trigger whole-body toxicity with behavioral alterations. Therefore, nutritional intervention with natural components may be desirable to prevent and/or ameliorate DEP-inducible pathophysiology in mammals. Quercetin has been demonstrated to reduce metabolic complications by possessing antioxidative, anti-inflammatory, and antimutagenic effects. In this study, we investigated the effects of quercetin on pulmonary inflammation and behavioral alteration in male C57BL/6 mice against DEP instillation. The experimental mice were separated into four treatment groups (n = 8 per group), which include: vehicle control, DEP instillation, dietary intervention with a low dose of quercetin (20 mg/kg) for 14 days with DEP instillation for 7 days, or dietary intervention with a high dose of quercetin (100 mg/kg) for 14 days with DEP instillation for 7 days. Compared with the DEP-instilled group, dietary intervention with quercetin significantly attenuated eosinophils in the bronchoalveolar lavage fluid analysis, pulmonary cytokine, and hypoxic mRNA expressions regardless of quercetin concentrations. DEP instillation triggered hyperactivities in the experimental mice, while quercetin pretreatment successfully normalized DEP-inducible abnormalities regardless of the dosage. Therefore, dietary intervention with quercetin may be an applicable means to prevent DEP-triggered pulmonary and behavioral abnormalities.

Non-Reproducibility of Oral Rotenone as a Model for Parkinson's Disease in Mice

Oral rotenone has been proposed as a model for Parkinson’s disease (PD) in mice. To establish the model in our lab and study complex behavior we followed a published treatment regimen. C57BL/6 mice received 30 mg/kg body weight of rotenone once daily via oral administration for 4 and 8 weeks. Motor functions were assessed by RotaRod running. Immunofluorescence studies were used to analyze the morphology of dopaminergic neurons, the expression of alpha-Synuclein (α-Syn), and inflammatory gliosis or infiltration in the substantia nigra. Rotenone-treated mice did not gain body weight during treatment compared with about 4 g in vehicle-treated mice, which was however the only robust manifestation of drug treatment and suggested local gut damage. Rotenone-treated mice had no deficits in motor behavior, no loss or sign of degeneration of dopaminergic neurons, no α-Syn accumulation, and only mild microgliosis, the latter likely an indirect remote effect of rotenone-evoked gut dysbiosis. Searching for explanations for the model failure, we analyzed rotenone plasma concentrations via LC-MS/MS 2 h after administration of the last dose to assess bioavailability. Rotenone was not detectable in plasma at a lower limit of quantification of 2 ng/mL (5 nM), showing that oral rotenone had insufficient bioavailability to achieve sustained systemic drug levels in mice. Hence, oral rotenone caused local gastrointestinal toxicity evident as lack of weight gain but failed to evoke behavioral or biological correlates of PD within 8 weeks.