Quercetin hinders microglial activation to alleviate neurotoxicity via the interplay between NLRP3 inflammasome and mitophagy

Quercetin modulates the liver metabolic profile in a chronic unpredictable mild stress rat model based on metabolomics technology

Depression is the most prevalent psychiatric disease, and its pathogenesis is still unclear. Currently, studies on the pathogenesis of depression are mainly focused on the brain. The liver can modulate brain function via the liver-brain axis, indicating that the liver plays an important role in the development of depression. This study aims to explore the protective effect of quercetin against chronic unpredictable mild stress (CUMS)-induced metabolic changes and the corresponding mechanisms in the rat liver based on untargeted metabolomics technology. In this study, 96 male rats were divided into six groups: control, different doses of quercetin (10 mg per kg bw or 50 mg per kg bw), CUMS, and CUMS + different doses of quercetin. After 8 weeks of CUMS modeling, the liver samples were collected for metabolomics analysis. A total of 17 altered metabolites were identified, including D-glutamic acid, S-adenosylmethionine, lithocholylglycine, L-homocystine, prostaglandin PGE2, leukotriene E4, cholic acid, 5-methyltetrahydrofolic acid, taurochenodeoxycholic acid, S-adenosylhomocysteine, deoxycholic acid, folic acid, L-methionine, leukotriene C5, estriol-17-glucuronide, PE, and PC, indicating that methionine metabolism, bile acid metabolism, and phosphatidylcholine biosynthesis are the major pathways involved in CUMS-induced hepatic metabolic disorders. Hepatic methylation damage may play a role in the pathophysiology of depression, as evidenced by the first discovery of the abnormality of hepatic methionine metabolism. Abnormal changes in hepatic bile acids may provide stronger evidence for depression pathogenesis involving the microbiota-gut-brain axis, suggesting that the liver is involved in depression development and may be a treatment target. The quercetin treatment alleviated the CUMS-induced liver metabolism disorder, suggesting that quercetin may protect against depression by regulating liver metabolism.

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.

Neuroprotective Potentials of Flavonoids: Experimental Studies and Mechanisms of Action

Neurological and neurodegenerative diseases, particularly those related to aging, are on the rise, but drug therapies are rarely curative. Functional disorders and the organic degeneration of nervous tissue often have complex causes, in which phenomena of oxidative stress, inflammation and cytotoxicity are intertwined. For these reasons, the search for natural substances that can slow down or counteract these pathologies has increased rapidly over the last two decades. In this paper, studies on the neuroprotective effects of flavonoids (especially the two most widely used, hesperidin and quercetin) on animal models of depression, neurotoxicity, Alzheimer's disease (AD) and Parkinson's disease are reviewed. The literature on these topics amounts to a few hundred publications on in vitro and in vivo models (notably in rodents) and provides us with a very detailed picture of the action mechanisms and targets of these substances. These include the decrease in enzymes that produce reactive oxygen and ferroptosis, the inhibition of mono-amine oxidases, the stimulation of the Nrf2/ARE system, the induction of brain-derived neurotrophic factor production and, in the case of AD, the prevention of amyloid-beta aggregation. The inhibition of neuroinflammatory processes has been documented as a decrease in cytokine formation (mainly TNF-alpha and IL-1beta) by microglia and astrocytes, by modulating a number of regulatory proteins such as Nf-kB and NLRP3/inflammasome. Although clinical trials on humans are still scarce, preclinical studies allow us to consider hesperidin, quercetin, and other flavonoids as very interesting and safe dietary molecules to be further investigated as complementary treatments in order to prevent neurodegenerative diseases or to moderate their deleterious effects.

Comprehensive analysis of pyroptosis-related gene signatures for glioblastoma immune microenvironment and target therapy

Glioblastoma (GBM) is a malignant brain tumour, but its subtypes (mesenchymal, classical, and proneural) show different prognoses. Pyroptosis is a programmed cell death relating to tumour progression, but its association with GBM is poorly understood. In this work, we collected 73 GBM samples (the Xiangya GBM cohort) and reported that pyroptosis involves tumour-microglia interaction and tumour response to interferon-gamma. GBM samples were grouped into different subtypes, cluster 1 and cluster 2, based on pyroptosis-related genes. Cluster 1 samples manifested a worse prognosis and had a more complicated immune landscape than cluster 2 samples. Single-cell RNA-seq data analysis supported that cluster 1 samples respond to interferon-gamma more actively. Moreover, the machine learning algorithm screened several potential compounds, including nutlin-3, for cluster 1 samples as a novel treatment. In vitro experiments supported that cluster 1 cell line, T98G, is more sensitive to nutlin-3 than cluster 2 cell line, LN229. Nutlin-3 can trigger oxidative stress by increasing DHCR24 expression. Moreover, pyroptosis-resistant genes were upregulated in LN229, which may participate against nutlin-3. Therefore, we hypothesis that GBM may be able to upregulate pyroptosis resistant related genes to against nutlin-3-triggered cell death. In summary, we conclude that pyroptosis highly associates with GBM progression, tumour immune landscape, and tumour response to nutlin-3.

Mechanism of pyroptosis in neurodegenerative diseases and its therapeutic potential by traditional Chinese medicine

Neurodegenerative diseases (NDs) are disorders characterized by degenerative degeneration of neurons and loss of their function. NDs have a complicated pathophysiology, of which neuroinflammation and neuronal death are significant factors. The inflammatory process known as pyroptosis ("fiery death") is caused by a family of pore-forming proteins called Gasdermins (GSDMs), which appears downstream from the activation of the inflammasome. Clear evidence of enhanced pyroptosis-related proteins activity in common NDs has coincided with abnormal aggregation of pathological proteins (such as Aβ, tau, α-synuclein et al.), making pyroptosis an attractive direction for the recent study of NDs. The purpose of this review is to provide an overview of the molecular mechanisms driving pyroptosis, the mechanistic links between pyroptosis and NDs, and emerging therapeutic strategies in Traditional Chinese Medicine (TCM) to inhibit pyroptosis for the treatment of NDs.

Microglial autophagy in Alzheimer's disease and Parkinson's disease

Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common neurodegenerative diseases, characterized by gradual and selective loss of neurons in the central nervous system. They affect more than 50 million people worldwide, and their incidence increases with age. Although most cases of AD and PD are sporadic, some are caused by genetic mutations that are inherited. Both sporadic and familial cases display complex neuropathology and represent the most perplexing neurological disorders. Because of the undefined pathogenesis and complex clinical manifestations, there is still no effective treatment for both AD and PD. Understanding the pathogenesis of these important neurodegenerative diseases is important for developing successful therapies. Increasing evidence suggests that microglial autophagy is associated with the pathogenesis of AD and PD, and its dysfunction has been implicated in disease progression. In this review, we focus on the autophagy function in microglia and its dysfunction in AD and PD disease models in an attempt to help our understanding of the pathogenesis and identifying new therapeutic targets of AD and PD.

Influence of the Neuroprotective Properties of Quercetin on Regeneration and Functional Recovery of the Nervous System

Quercetin is a dietary flavonoid present in vegetables, fruits, and beverages, such as onions, apples, broccoli, berries, citrus fruits, tea, and red wine. Flavonoids have antioxidant and anti-inflammatory effects, acting in the prevention of several diseases. Quercetin also has neuroprotective properties and may exert a beneficial effect on nervous tissue. In this literature review, we compiled in vivo studies that investigated the effect of quercetin on regeneration and functional recovery of the central and peripheral nervous system. In spinal cord injuries (SCI), quercetin administration favored axonal regeneration and recovery of locomotor capacity, significantly improving electrophysiological parameters. Quercetin reduced edema, neutrophil infiltration, cystic cavity formation, reactive oxygen species production, and pro-inflammatory cytokine synthesis, while favoring an increase in levels of anti-inflammatory cytokines, minimizing tissue damage in SCI models. In addition, the association of quercetin with mesenchymal stromal cells transplantation had a synergistic neuroprotective effect on spinal cord injury. Similarly, in sciatic nerve injuries, quercetin favored and accelerated sensory and motor recovery, reducing muscle atrophy. In these models, quercetin significantly inhibited oxidative stress and cell apoptosis, favoring Schwann cell proliferation and nerve fiber remyelination, thus promoting a significant increase in the number and diameter of myelinated fibers. Although there is still a lack of clinical research, in vivo studies have shown that quercetin contributed to the recovery of neurological functions, exerting a beneficial effect on the regeneration of the central and peripheral nervous system.

The NLRP3 inflammasome in depression: Potential mechanisms and therapies

Increasing evidence suggests that the failure of clinical antidepressants may be related with neuroinflammation. The NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome is an intracellular multiprotein complex, and has been considered as a key contributor to the development of neuroinflammation. Inhibition of NLRP3 inflammasome is an effective method for depression treatment. In this review, we summarized current researches highlighting the role of NLRP3 inflammasome in the pathology of depression. Firstly, we discussed NLRP3 inflammasome activation in patients with depression and animal models. Secondly, we outlined the possible mechanisms driving the activation of NLRP3 inflammasome. Thirdly, we discussed the pathogenetic role of NLRP3 inflammasome in depression. Finally, we overviewed the current and potential antidepressants targeting the NLRP3 inflammasome. Overall, the inhibition of NLRP3 inflammasome activation may be a potential therapeutic strategy for inflammation-related depression.

Functional Nutrition as Integrated Intervention for In- and Outpatient with Schizophrenia

Schizophrenia is a chronic and progressive disorder characterized by cognitive, emotional, and behavioral abnormalities associated with neuronal development and synaptic plasticity alterations. Genetic and epigenetic abnormalities in cortical parvalbumin-positive GABAergic interneurons and consequent alterations in glutamate-mediated excitatory neurotransmission during early neurodevelopment underlie schizophrenia manifestation and progression. Also, epigenetic alterations during pregnancy or early phases of postnatal life are associated with schizophrenia vulnerability and inflammatory processes, which are at the basis of brain pathology and a higher risk of comorbidities, including cardiovascular diseases and metabolic syndrome. In addition, schizophrenia patients adopt an unhealthy lifestyle and poor nutrition, leading to premature death. Here, I explored the role of functional nutrition as an integrated intervention for the long-term management of patients with schizophrenia. Several natural bioactive compounds in plant-based whole foods, including flavonoids, phytonutrients, vitamins, fatty acids, and minerals, modulate brain functioning by targeting neuroinflammation and improving cognitive decline. Although further clinical studies are needed, a functional diet rich in natural bioactive compounds might be effective in synergism with standard treatments to improve schizophrenia symptoms and reduce the risk of comorbidities.

Quercetin effectively improves LPS-induced intestinal inflammation, pyroptosis, and disruption of the barrier function through the TLR4/NF-κB/NLRP3 signaling pathway in vivo and in vitro

Background

Inflammatory bowel diseases are characterized by the alterations of the mucosa and gastrointestinal physiology, and the core of these alterations is endothelial cells. Quercetin is a flavonoid presents in some traditional Chinese medicine, plants, and fruits. Its protective effects in several gastrointestinal tumors have been demonstrated, but its effects on bacterial enteritis and pyroptosis-related diseases have rarely been studied.

Objective

This study aimed to evaluate the effect of quercetin on bacterial enteritis and pyroptosis.

Design

In vitro experiments were performed using rat intestinal microvascular endothelial cells divided into seven groups: control group (no treatment), model group (10 μg/mL lipopolysaccharide (LPS)+1 mM adenosine triphosphate [ATP]), LPS group (10 μg/mL LPS), ATP group (1 mM ATP), and treatment groups (10 μg/mL LPS+1 mM ATP and 5, 10, and 20 μM quercetin). The expression of pyroptosis-associated proteins, inflammatory factors, tight junction proteins, and the percentage of late apoptotic and necrotic cells were measured. In vivo analysis was performed using specific pathogen-free Kunming mice pretreated with quercetin and the water extract of Cacumen Platycladi for 2 weeks followed by 6 mg/kg LPS on day 15. Inflammation in the blood and intestinal pathological changes were evaluated.

Results

Quercetin used in vitro significantly reduced the expression of Toll-like receptor 4 (TLR4), NOD-like receptor 3 (NLRP3), caspase-1, gasdermin D, interleukin (IL)-1β, IL-18, IL-6, and tumor necrosis factor-α. It also inhibited phosphorylation of nuclear factor-kappa B (NF-κB) p65 and increased cell migration and the expression of zonula occludens 1 and claudins, while reduced the number of late apoptotic cells. The in vivo results showed that Cacumen Platycladi and quercetin significantly reduced inflammation, protected the structure of the colon and cecum, and prevent fecal occult blood induced by LPS.

Conclusions

These findings suggested the ability of quercetin to reduce inflammation induced by LPS and pyroptosis through TLR4/NF-κB/NLRP3 pathway.

Glucagon-like Peptide 1 Receptor Activation Inhibits Microglial Pyroptosis via Promoting Mitophagy to Alleviate Depression-like Behaviors in Diabetic Mice

Depression is a frequent and serious comorbidity associated with diabetes which adversely affects prognosis and quality of life. Glucagon-like peptide-1 receptor (GLP-1R) agonists, widely used in the treatment of diabetes, are reported to exert neuroprotective effects in the central nervous system. Thus, we aim to evaluate whether GLP-1R agonist exendin-4 (EX-4) could alleviate depression-like behaviors in diabetic mice and to explore its underlying mechanism. The antidepressant effects of EX-4 were evaluated using behavioral tests in db/db mice. The effects of EX-4 on microglial pyroptosis and neuroinflammation were assessed in N9 microglial cells. EX-4 administration alleviated depression-like behaviors in diabetic db/db mice. GLP-1R activation by EX-4 significantly suppressed microglial pyroptosis and neuroinflammation by downregulation of gasdermin D (GSDMD) and interleukin (IL)-1β in diabetic mice and lipopolysaccharide (LPS)-primed N9 microglia. Mechanistically, GLP-1R activation improved mitochondrial function and promoted mitophagy by decreasing the accumulation of mitochondrial reactive oxygen species (mtROS) and intracellular ROS production. EX-4 exhibits antidepressant effects in depression associated with diabetes in diabetic mice, which may be mediated by inhibiting microglial pyroptisis via promoting mitophagy. It is supposed that GLP-1R agonists may be a promising therapy in depression associated with diabetes.

Quercetin Is An Active Agent in Berries against Neurodegenerative Diseases Progression through Modulation of Nrf2/HO1

Berries are well-known fruits for their antioxidant effects due to their high content of flavonoids, and quercetin is one of the potent bioactive flavonoids. Although oxidative stress is an inevitable outcome in cells due to energy uptake and metabolism and other factors, excessive oxidative stress is considered a pivotal mediator for the cell death and leads to the progression of neurodegenerative diseases (NDDs). Furthermore, oxidative stress triggers inflammation that leads to neuronal cell loss. Alzheimer's, Parkinson's, Huntington's disease, amyotrophic lateral sclerosis, multiple sclerosis, and so on are the main neurodegenerative diseases. Hence, AD and PD are the most affected NDDs and cause the most lethality without any effective cure. Since AD and PD are the most common NDDs, therefore, in this study, we will describe the effect of oxidative stress on AD and PD. Targeting oxidative stress could be a very effective way to prevent and cure NDDs. Thus, the nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO1) are potent endogenous antioxidant modulatory pathways, which also show cytoprotective activities. Modulation of Nrf2/HO1 signaling pathways through a biological approach could be an effective way to treat with NDDs. Quercetin is a natural polyphenol, which protects neurodegeneration, remarkably by suppressing oxidative stress and inflammation. Thus, quercetin could be a very effective agent against NDDs. We will discuss the benefits and challenges of quercetin to treat against NDDs, focusing on molecular biology.

Aerobic exercise reverses the NF-κB/NLRP3 inflammasome/5-HT pathway by upregulating irisin to alleviate post-stroke depression

Background

Post-stroke depression (PSD) is one of the most common and serious sequelae of stroke. The pathogenesis of PSD involves both psychosocial and biological mechanisms, and aerobic exercise is a potential therapeutic target. We conducted an in-depth exploration of the protective mechanisms of aerobic exercise in a PSD mouse model.

Methods

In this study, C57BL/6 mice were used as the research objects, and a PSD mouse model was established by combining middle cerebral artery occlusion and chronic unpredictable mild stimulation. Real-time quantitative polymerase chain reaction, enzyme-linked immunosorbent assays, adeno-associated virus microinjection technology, co-immunoprecipitation, fluorescence in-situ hybridization, and western blotting were performed. A moderate-load treadmill exercise was used for aerobic exercise intervention. The moderate-intensity aerobic exercise training method adopted 0 slopes and treadmill adaptation training for 5 days. We verified the effects of aerobic exercise on the nuclear factor kappa B (NF-κB)/nucleotide-binding oligomerization domain--like receptor protein 3 (NLRP3) inflammasome/5-hydroxytryptamine (5-HT) pathway.

Results

Aerobic exercise effectively alleviated the neurological damage caused by PSD (P<0.01). The results from the PSD mouse model in vivo were consistent with those of the cell experiments. Moreover, overexpression of irisin improves depression-like behavior in PSD mice. We confirmed that aerobic exercise is involved in PSD through 5-HT, which inhibits NF-κB/NLRP3 inflammasome initiation through irisin and alleviates mitochondrial damage under stress by reducing calcium overload, thereby inhibiting NLRP3 inflammasome activation.

Conclusions

Aerobic exercise reversed the NF-κB/NLRP3 inflammasome/5-HT pathway by upregulating irisin expression to alleviate PSD.

Pyroptosis in spinal cord injury

Spinal cord injury (SCI) often brings devastating consequences to patients and their families. Pathophysiologically, the primary insult causes irreversible damage to neurons and glial cells and initiates the secondary damage cascade, further leading to inflammation, ischemia, and cells death. In SCI, the release of various inflammatory mediators aggravates nerve injury. Pyroptosis is a new pro-inflammatory pattern of regulated cell death (RCD), mainly mediated by caspase-1 or caspase-11/4/5. Gasdermins family are pore-forming proteins known as the executor of pyroptosis and the gasdermin D (GSDMD) is best characterized. Pyroptosis occurs in multiple central nervous system (CNS) cell types, especially plays a vital role in the development of SCI. We review here the evidence for pyroptosis in SCI, and focus on the pyroptosis of different cells and the crosstalk between them. In addition, we discuss the interaction between pyroptosis and other forms of RCD in SCI. We also summarize the therapeutic strategies for pyroptosis inhibition, so as to provide novel ideas for improving outcomes following SCI.

The Emerging Role of Quercetin in the Treatment of Chronic Pain

Despite much research efforts being devoted to designing alternative pharmacological interventions, chronic pain remains to be an unresolved clinical problem. Quercetin, a compound that belongs to the flavonoids family, is abundantly found in fruits and vegetables. Emerging evidence indicates that quercetin possesses anti-nociceptive effects in different rodent models of chronic pain, including inflammatory pain, neuropathic pain and cancer pain. In this review, we summarize the mechanisms underlying the analgesic effect of quercetin in preclinical studies. These studies showed that quercetin exerts potent analgesic effects against chronic pain via suppressing neuroinflammation and oxidative stress as well as modulation of synaptic plasticity, GABAergic system, and opioidergic system. Considering that the safety of quercetin is well established, it has great potential for clinical use in pain treatment.

Mitochondrial glutamine transporter SLC1A5_var, a potential target to suppress astrocyte reactivity in Parkinson's Disease

SLC1A5 variant (SLC1A5_var) is identified as a mitochondrial glutamine transporter in cancer cells recently. However, the role of SLC1A5_var in Parkinson's disease (PD) is completely unknown. Here, we found the significant downregulation of SLC1A5_var in astrocytes and midbrain of mice treated with MPTP/MPP⁺ and LPS. Importantly, overexpression of SLC1A5_var ameliorated but knockdown of SLC1A5_var exacerbated MPTP/MPP⁺- and LPS-induced mitochondrial dysfunction. Consequently, SLC1A5_var provided beneficial effects on PD pathology including improvement of PD-like motor symptoms and rescue of dopaminergic (DA) neuron degeneration through maintaining mitochondrial energy metabolism. Moreover, SLC1A5_var reduced astrocyte reactivity via inhibition of A1 astrocyte conversion. Further investigation demonstrated that SLC1A5_var restrained the secretion of astrocytic pro-inflammatory cytokines by blunting TLR4-mediated downstream pathways. This is the first study to prove that astrocytic SLC1A5_var inhibits neuroinflammation, and rescues the loss of DA neurons and motor symptoms involved in PD progression, which provides a novel target for PD treatment.

Beneficial effects of natural flavonoids on neuroinflammation

Neuroinflammation is the fundamental immune response against multiple factors in the central nervous system and is characterized by the production of inflammatory mediators, activated microglia and astrocytes, and the recruitment of innate and adaptive immune cells to inflammatory sites, that contributes to the pathological process of related brain diseases, such as Alzheimer’s disease, Parkinson’s disease, depression, and stroke. Flavonoids, as a species of important natural compounds, have been widely revealed to alleviate neuroinflammation by inhibiting the production of pro-inflammatory mediators, elevating the secretion of anti-inflammatory factors, and modulating the polarization of microglia and astrocyte, mainly via suppressing the activation of NLRP3 inflammasome, as well as NF-κB, MAPK, and JAK/STAT pathways, promoting Nrf2, AMPK, BDNF/CREB, Wnt/β-Catenin, PI3k/Akt signals and SIRT1-mediated HMGB1 deacetylation. This review will provide the latest and comprehensive knowledge on the therapeutic benefits and mechanisms of natural flavonoids in neuroinflammation, and the natural flavonoids might be developed into food supplements or lead compounds for neuroinflammation-associated brain disorders.

Neuroprotective role of coconut oil for the prevention and treatment of Parkinson's disease: potential mechanisms of action

Neurodegenerative disease (ND) is a clinical condition in which neurons degenerate with a consequent loss of functions in the affected brain region. Parkinson's disease (PD) is the second most progressive ND after Alzheimer's disease (AD), which affects the motor system and is characterized by the loss of dopaminergic neurons from the nigrostriatal pathway in the midbrain, leading to bradykinesia, rigidity, resting tremor, postural instability and non-motor symptoms such as cognitive declines, psychiatric disturbances, autonomic failures, sleep difficulties, and pain syndrome. Coconut oil (CO) is an edible oil obtained from the meat of Cocos nucifera fruit that belongs to the palm family and contains 92% saturated fatty acids. CO has been shown to mediate oxidative stress, neuroinflammation, mitochondrial dysfunction, apoptosis and excitotoxicity-induced effects in PD in various in vitro and in vivo models as a multi-target bioagent. CO intake through diet has also been linked to a decreased incidence of PD in people. During digestion, CO is broken down into smaller molecules, like ketone bodies (KBs). The KBs then penetrate the blood-brain barrier (BBB) and are used as a source of energy its ability to cross BBB made this an important class of natural remedies for the treatment of ND. The current review describes the probable neuroprotective potential pathways of CO in PD, either prophylactic or therapeutic. In addition, we briefly addressed the important pathogenic pathways that might be considered to investigate the possible use of CO in neurodegeneration such as AD and PD.

Mitochondrial dysfunction in microglia: a novel perspective for pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease in the elderly globally. Emerging evidence has demonstrated microglia-driven neuroinflammation as a key contributor to the onset and progression of AD, however, the mechanisms that mediate neuroinflammation remain largely unknown. Recent studies have suggested mitochondrial dysfunction including mitochondrial DNA (mtDNA) damage, metabolic defects, and quality control (QC) disorders precedes microglial activation and subsequent neuroinflammation. Therefore, an in-depth understanding of the relationship between mitochondrial dysfunction and microglial activation in AD is important to unveil the pathogenesis of AD and develop effective approaches for early AD diagnosis and treatment. In this review, we summarized current progress in the roles of mtDNA, mitochondrial metabolism, mitochondrial QC changes in microglial activation in AD, and provide comprehensive thoughts for targeting microglial mitochondria as potential therapeutic strategies of AD.

Muscone with Attenuation of Neuroinflammation and Oxidative Stress Exerts Antidepressant-Like Effect in Mouse Model of Chronic Restraint Stress

Major depressive disorder (MDD) is a common mental disorder with high morbidity. Stress negatively affects for MDD development, whereby transport of stress-induced inflammatory mediators to the central nervous system (CNS) is associated with the etiology of mood disorders. Muscone is a pharmacologically active ingredient isolated from musk, with anti-inflammatory and neuroprotective effects. We hypothesized that muscone may ameliorate depression-like behavior by regulating inflammatory responses. To test this hypothesis, we used the chronic restraint stress (CRS) depression model, and CRS mice were treated with muscone (10 mg/kg, i.g., respectively) for 14 days. The effects of the drug on depressive-like behaviors were evaluated via the open field test (OFT), novelty-suppressed feeding test (NSFT), tail suspension test (TST), and forced swimming test (FST). Quantitative reverse transcription-PCR (qRT-PCR) was utilized to assess levels of proinflammatory cytokines (IL-6, TNF-α, COX2, and IL-1) and the anti-inflammatory cytokines (IL-4 and IL-10). We also determined levels of oxidative stress factors (malondialdehyde, superoxide dismutase, and glutathione peroxidase), as well as doublecortin (DCX) expression by immunofluorescence. The results showed that depression-like behavior and inflammatory levels were improved after muscone treatment. Muscone also significantly improved neurogenesis in the CRS mouse hippocampus and decreased oxidative stress in both the central and peripheral nervous systems. In conclusion, this work is the first to demonstrate that muscone has an antidepressant effect using a CRS model. Oxidative stress, neurogenesis, and inflammatory pathways are key factors affected by the drug and may represent new therapeutic targets to treat MDD, in this impact. These results may represent a new therapeutic target for MDD.

Flavonoids bridging the gut and the brain: intestinal metabolic fate, and direct or indirect effects of natural supporters against neuroinflammation and neurodegeneration

In recent years, experimental evidence suggested a possible role of the gut microbiota in the onset and development of several neurodegenerative disorders, such as AD and PD, MS and pain. Flavonoids, including anthocyanins, EGCG, the flavonol quercetin, and isoflavones, are plant polyphenolic secondary metabolites that have shown therapeutic potential for the treatment of various pathological conditions, including neurodegenerative diseases. This is due to their antioxidant and anti-inflammatory properties, despite their low bioavailability which often limits their use in clinical practice. In more recent years it has been demonstrated that flavonoids are metabolized by specific bacterial strains in the gut to produce their active metabolites. On the other way round, both naturally-occurring flavonoids and their metabolites promote or limit the proliferation of specific bacterial strains, thus profoundly affecting the composition of the gut microbiota which in turn modifies its ability to further metabolize flavonoids. Thus, understanding the best way of acting on this virtuous circle is of utmost importance to develop innovative approaches to many brain disorders. In this review, we summarize some of the most recent advances in preclinical and clinical research on the neuroinflammatory and neuroprotective effects of flavonoids on AD, PD, MS and pain, with a specific focus on their mechanisms of action including possible interactions with the gut microbiota, to emphasize the potential exploitation of dietary flavonoids as adjuvants in the treatment of these pathological conditions.

Quercetin Supplement to Aspirin Attenuates Lipopolysaccharide-Induced Pre-eclampsia-Like Impairments in Rats Through the NLRP3 Inflammasome

BACKGROUND AND OBJECTIVES

Aspirin is a common drug for the treatment of pre-eclampsia. We aimed to explore whether quercetin as a supplement to aspirin could enhance the therapeutic outcome in pre-eclampsia rat models. We further aimed to evaluate the nucleotide-binding oligomerization domain-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome as a potential pre-eclampsia-related molecular mechanism, which can be affected by quercetin treatment.

METHODS

Rat pre-eclampsia models were established using an intravenous lipopolysaccharide injection after gestation. Rats were treated with aspirin and quercetin at 6-18 days after pregnancy. On day 20, blood, fetus, and placenta were harvested. Blood pressure and the level of proteinuria were measured every 4 days. Fetal outcomes were analyzed by pup body weight. Serum soluble Fms-like tyrosine kinase-1, PIGF, interleukin-6, and interleukin-10 levels were measured using the enzyme-linked immunosorbent assay. Caspase-1, NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain, and p-caspase-1 levels in the placenta were assessed using western blot or quantitative real-time polymerase chain reaction analyses.

RESULTS

Pre-eclampsia rat models showed a pronounced increase in systolic blood pressure and proteinuria after 4 days of pregnancy, while aspirin, quercetin, and aspirin/quercetin combinatory treatment significantly attenuated the blood pressure and proteinuria abnormalities. Notably, the aspirin/quercetin combinatory treatment showed the highest efficacy in attenuating pre-eclampsia-like symptoms. Placental caspase-1 and NLRP3 levels also showed the greatest attenuation in pre-eclampsia rats after aspirin/quercetin treatment.

CONCLUSIONS

Our data suggested that quercetin supplementation to aspirin is more effective in attenuating symptoms of pre-eclampsia and improving pregnancy outcomes compared with quercetin or aspirin alone. Quercetin can ameliorate placental NLRP3 inflammasome activation, which might serve as an underlying mechanism for its therapeutic efficacies in pre-eclampsia.

Potential therapeutic effects of natural compounds targeting autophagy to alleviate podocyte injury in glomerular diseases

Podocyte injury is a common cause of proteinuric kidney diseases. Uncontrollable progressive podocyte loss accelerates glomerulosclerosis and increases the risk of end-stage renal disease. To date, owing to the complex pathological mechanism, effective therapies for podocyte injury have been limited. Accumulating evidence supports the indispensable role of autophagy in the maintenance of podocyte homeostasis. A variety of natural compounds and their derivatives have been found to regulate autophagy through multiple targets, including promotes nuclear transfer of transcription factor EB and lysosomal repair. Here, we reviewed the recent studies on the use of natural compounds and their derivatives as autophagy regulators and discussed their potential applications in ameliorating podocyte injury. Several known natural compounds with autophagy-regulatory properties, such as quercetin, silibinin, kaempferol, and artemisinin, and their medical uses were also discussed. This review will help in improving the understanding of the podocyte protective mechanism of natural compounds and promote their development for clinical use.

Quercetin Protects against MPP+/MPTP-Induced Dopaminergic Neuron Death in Parkinson's Disease by Inhibiting Ferroptosis

Ferroptosis, a novel form of regulated cell death, is caused by accumulation of lipid peroxides and excessive iron deposition. This process has been linked to the death of dopaminergic neurons in substantia nigra compacta (SNc) of Parkinson's disease (PD) patients. Quercetin (QCT), a natural flavonoid, has multiple pharmacological activities. However, it has not been established whether QCT can protect against dopaminergic neuron death by inhibiting ferroptosis. In this study, we investigated the potential antiferroptotic effects of QCT in cellular models established using specific ferroptosis inducers (Erastin and RSL-3) and MPP+. The effects were also explored using MPTP-induced PD mouse models. The cell counting kit-8 (CCK-8) assay was performed to assess cell viability. Variations in mitochondrial morphology were evaluated by transmission electron microscopy (TEM) while the mitochondrial membrane potential, mass, and ROS were measured by fluorescent probes. Lipid peroxidation levels were assayed through measurement of lipid ROS, MDA, GSH, and SOD levels. The effects of QCT on MPTP-induced behavioral disorders were examined by rotarod and open field tests. In vitro and in vivo, QCT significantly inhibited ferroptosis by activating the nuclear factor erythroid 2-related factor 2 (Nrf2) protein. Additionally, QCT ameliorated motor behavioral impairments and protected against the loss of dopaminergic neurons in MPTP-induced PD models. Interestingly, Nrf2 knockdown alleviated the protective effects of QCT against ferroptosis. In conclusion, these results demonstrate that ferroptosis is involved in MPP+/MPTP-induced PD, and QCT inhibits ferroptosis by activating the Nrf2 protein. Therefore, QCT is a potential agent for preventing the loss of dopaminergic neurons by targeting ferroptosis.

Autophagy in health and disease: From molecular mechanisms to therapeutic target

Macroautophagy/autophagy is an evolutionally conserved catabolic process in which cytosolic contents, such as aggregated proteins, dysfunctional organelle, or invading pathogens, are sequestered by the double-membrane structure termed autophagosome and delivered to lysosome for degradation. Over the past two decades, autophagy has been extensively studied, from the molecular mechanisms, biological functions, implications in various human diseases, to development of autophagy-related therapeutics. This review will focus on the latest development of autophagy research, covering molecular mechanisms in control of autophagosome biogenesis and autophagosome-lysosome fusion, and the upstream regulatory pathways including the AMPK and MTORC1 pathways. We will also provide a systematic discussion on the implication of autophagy in various human diseases, including cancer, neurodegenerative disorders (Alzheimer disease, Parkinson disease, Huntington's disease, and Amyotrophic lateral sclerosis), metabolic diseases (obesity and diabetes), viral infection especially SARS-Cov-2 and COVID-19, cardiovascular diseases (cardiac ischemia/reperfusion and cardiomyopathy), and aging. Finally, we will also summarize the development of pharmacological agents that have therapeutic potential for clinical applications via targeting the autophagy pathway. It is believed that decades of hard work on autophagy research is eventually to bring real and tangible benefits for improvement of human health and control of human diseases.

Network pharmacology identify intersection genes of quercetin and Alzheimer’s disease as potential therapeutic targets

Background

Currently, there are no efficient therapies for Alzheimer’s disease (AD) among the elderly, although it is the most common etiology of dementia among the elderly. Quercetin, which has a variety of therapeutic properties, may pave the way for novel approaches to AD treatment. In the AD patients’ frontal cortex, current study aims to identify the potential mechanisms of quercetin’s pharmacological targets.

Materials and methods

The pharmacological targets of quercetin have been studied from DrugBank and SwissTarget. In order to distinguish AD-associated genes targeted by quercetin (Q-ADGs), we utilized an integrated intersection of gene expressions of the frontal cortex in combination with transcriptome analysis. To detect cortex-related Q-ADGs and immune-related Q-ADGs, a drug screening database and the immune infiltration analysis was utilized. The Q-ADGs were then linked with the AD severity scores (MMSE scores) to find severity-associated Q-ADGs. In addition, the miRNA-seq datasets were examined to identify severity-associated Q-ADG-miRNAs. Twelve genes, more frequently related to AD by previous studies among all the genes identified in the present study, were subjected to the verification of qRT-PCR in AD cell model.

Results

In the frontal lobe of AD, 207 Q-ADGs were discovered and found that axonogenesis, glial differentiation, and other biological processes had been enriched. There were 155 immune-related Q-ADGs (e.g., COX2, NOS2, HMGB1) and 65 cortex-related Q-ADGs (e.g., FOXO1, CXCL16, NOTCH3). Sixteen Q-ADGs (e.g., STAT3, RORA, BCL6) and 28 miRNAs (e.g., miR-142-5p, miR-17-5p) were found to be related to MMSE scores. In the qRT-PCR results, six out of twelve genes were significantly regulated by quercetin. DYRK1A, FOXO1, NOS2, NGF, NQO1, and RORA genes were novel target of quercetin in AD. DYRK1A, NOS2, and NQO1 genes targeted by quercetin have benefits in the treatment of AD. However, FOXO1, NGF, and RORA genes targeted by quercetin might have a negative impact on AD.

Conclusion

The role of quercetin in AD appears to be multifaceted, and it can affect patients’ frontal cortex in a variety of pathways, such as axonogenesis, immune infiltration, and glial cell differentiation. DYRK1A, NOS2, and NQO1 might be potential novel effective drug targets for quercetin in AD.

Copper induces microglia-mediated neuroinflammation through ROS/NF-κB pathway and mitophagy disorder

The epidemiological correlation between copper exposure and higher risk of Parkinson disease (PD) has been recognized for a long time, and microglia-mediated neuroinflammation has reported to be an important component of the pathogenesis of PD. The present study aimed to investigate the role of microglial activation and neuroinflammation in copper neurotoxicity and the underlying mechanism of copper-induced activation of microglia. Based on the inflammatory changes in mouse brain tissues, the activation of microglia, the loss of dopaminergic neurons and the aggregation of α-syn were found in the substantia nigra. In this study we found that copper significantly caused inflammatory activation of BV2 cells. Importantly, copper increased the level of reactive oxygen species (ROS) in BV2 cells, and then activated the NF-κB pathway which acted as an early survival signal. Further study indicated that sustained copper accumulation in BV2 cells led to the decrease of mitochondrial membrane potential, reduction of Parkin and PINK1 expression, increase of P62 expression and LC3BⅡ/I ratio, as well as upregulation of NLRP3/caspase1/GSDMD axis proteins. In addition, the increased release of inflammatory factors was rescued by redox agent, NF-κB pathway inhibitor and mitophagy inducer. This work illustrated that copper exposure activates microglia to secrete inflammatory products, resulting in the pyroptosis of dopaminergic neurons, which was related to the early activation of ROS/NF-κB pathway and subsequent mitophagy disorder in BV2 cells.

Roles of microglial mitophagy in neurological disorders

Microglia are the resident innate immune cells in the central nervous system (CNS) that serve as the first line innate immunity in response to pathogen invasion, ischemia and other pathological stimuli. Once activated, they rapidly release a variety of inflammatory cytokines and phagocytose pathogens or cell debris (termed neuroinflammation), which is beneficial for maintaining brain homeostasis if appropriately activated. However, excessive or uncontrolled neuroinflammation may damage neurons and exacerbate the pathologies in neurological disorders. Microglia are highly dynamic cells, dependent on energy supply from mitochondria. Moreover, dysfunctional mitochondria can serve as a signaling platform to facilitate innate immune responses in microglia. Mitophagy is a means of clearing damaged or redundant mitochondria, playing a critical role in the quality control of mitochondrial homeostasis and turnover. Mounting evidence has shown that mitophagy not only limits the inflammatory response in microglia but also affects their phagocytosis, whereas mitochondria dysfunction and mitophagy defects are associated with aging and neurological disorders. Therefore, targeting microglial mitophagy is a promising therapeutic strategy for neurological disorders. This article reviews and highlights the role and regulation of mitophagy in microglia in neurological conditions, and the research progress in manipulating microglial mitophagy and future directions in this field are also discussed.

Study on the effect and mechanism of quercetin in treating gout arthritis

Quercetin is widely found in natural plants, especially Chinese herbal plants. It has been used to treat arthritis in China for thousands of years. However, the effects and mechanisms of quercetin in the treatment of gout arthritis (GA) remain unclear. We aimed to verify the treatment of GA with quercetin and investigate the underlying mechanism. A combination of network pharmacology and experiments was used to reveal the mechanism of quercetin in the treatment of GA. Potential targets of quercetin and gout were identified. Then, the protein-protein interaction network for the common targets between quercetin and gout was constructed and the core targets were identified. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses for the common targets were performed to elucidate the pharmacological functions and mechanisms associated with quercetin treatment in GA. Finally, a monosodium urate-induced GA rat model was used to validate the predicted mechanisms in network pharmacology. Seventy-two common targets were identified. KEGG analysis revealed that treatment of GA with quercetin predominantly involved the interleukin (IL)-17, tumor necrosis factor (TNF), mitogen-activated protein kinase, and phosphoinositide 3-kinase-Akt signaling pathways. In an experimental validation, quercetin attenuated ankle joint inflammation-induced bone destruction and histological lesions. It also diminished the expression of IL-6, IL-17A, and IL-17F in the IL-17 pathway, and regulated the release of RAR-related orphan receptor gamma t,IL-17E, IL-1β, IL-6, TNF-α, Foxp3, and transforming growth factor-beta 1. The collective findings implicate quercetin as a valuable alternative drug for the treatment of GA.

Cryopreservation of Pig Semen Using a Quercetin-Supplemented Freezing Extender

Reactive oxygen species (ROS) produced during freeze−thaw procedures cause oxidative damage to the sperm, reducing fertility. We aimed to improve the post-thaw quality of pig sperm by quercetin (QRN) supplementation to reduce the cryodamage associated with the freeze−thaw procedure. Four equal aliquots of pooled boar semen were diluted with a freezing extender supplemented with different concentrations of QRN (0, 25, 50, and 100 µM) and then were subjected to cryopreservation in liquid nitrogen. Semen analysis was performed following 7 days of cryopreservation. Results demonstrated that the semen samples supplemented with 50 µM QRN significantly improved the post-thaw sperm quality than those subjected to other supplementations (p < 0.05). Semen samples supplemented with 50 µM QRN showed significantly improved plasma membrane functional integrity (47.5 ± 1.4 vs. 43.1 ± 4.1, 45.3 ± 1.7, and 44.1 ± 1.4) and acrosome integrity (73.6 ± 3.4 vs. 66.3 ± 2.4, 66.7 ± 3.6, and 68.3 ± 32.9) as compared to the control, 25 µM, and 100 µM QRN groups, respectively. The mitochondrial activity of the 50 µM QRN group was greater than control and 25 µM QRN groups (43.0 ± 1.0 vs. 39.1 ± 0.9 and 41.9 ± 1.0) but showed no difference with the 100 µM QRN group. Moreover, the 50 µM QRN group showed a higher sperm number displaced to 1 cm and 3 cm points in the artificial mucus than other groups. Therefore, supplementing the freezing extender with QRN can serve as an effective tool to reduce the magnitude of oxidative damage associated with sperm freezing.

Microglia Pyroptosis: A Candidate Target for Neurological Diseases Treatment

In addition to its profound implications in the fight against cancer, pyroptosis have important role in the regulation of neuronal injury. Microglia are not only central members of the immune regulation of the central nervous system (CNS), but are also involved in the development and homeostatic maintenance of the nervous system. Under various pathological overstimulation, microglia pyroptosis contributes to the massive release of intracellular inflammatory mediators leading to neuroinflammation and ultimately to neuronal damages. In addition, microglia pyroptosis lead to further neurological damage by decreasing the ability to cleanse harmful substances. The pathogenic roles of microglia in a variety of CNS diseases such as neurodegenerative diseases, stroke, multiple sclerosis and depression, and many other neurological disorders have been gradually unveiled. In the context of different neurological disorders, inhibition of microglia pyroptosis by targeting NOD-like receptor family pyrin domain containing (NLRP) 3, caspase-1 and gasdermins (GSDMs) by various chemical agents as well as natural products significantly improve the symptoms or outcome in animal models. This study will provide new ideas for immunomodulatory treatment of CNS diseases.

Therapeutic application of quercetin in aging-related diseases: SIRT1 as a potential mechanism

Quercetin, a naturally non-toxic flavonoid within the safe dose range with antioxidant, anti-apoptotic and anti-inflammatory properties, plays an important role in the treatment of aging-related diseases. Sirtuin 1 (SIRT1), a member of NAD+-dependent deacetylase enzyme family, is extensively explored as a potential therapeutic target for attenuating aging-induced disorders. SIRT1 possess beneficial effects against aging-related diseases such as Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), Depression, Osteoporosis, Myocardial ischemia (M/I) and reperfusion (MI/R), Atherosclerosis (AS), and Diabetes. Previous studies have reported that aging increases tissue susceptibility, whereas, SIRT1 regulates cellular senescence and multiple aging-related cellular processes, including SIRT1/Keap1/Nrf2/HO-1 and SIRTI/PI3K/Akt/GSK-3β mediated oxidative stress, SIRT1/NF-κB and SIRT1/NLRP3 regulated inflammatory response, SIRT1/PGC1α/eIF2α/ATF4/CHOP and SIRT1/PKD1/CREB controlled phosphorylation, SIRT1-PINK1-Parkin mediated mitochondrial damage, SIRT1/FoxO mediated autophagy, and SIRT1/FoxG1/CREB/BDNF/Trkβ-catenin mediated neuroprotective effects. In this review, we summarized the role of SIRT1 in the improvement of the attenuation effect of quercetin on aging-related diseases and the relationship between relevant signaling pathways regulated by SIRT1. Moreover, the functional regulation of quercetin in aging-related markers such as oxidative stress, inflammatory response, mitochondrial function, autophagy and apoptosis through SIRT1 was discussed. Finally, the prospects of an extracellular vesicles (EVs) as quercetin loading and delivery, and SIRT1-mediated EVs as signal carriers for treating aging-related diseases, as well as discussed the ferroptosis alleviation effects of quercetin to protect against aging-related disease via activating SIRT1. Generally, SIRT1 may serve as a promising therapeutic target in the treatment of aging-related diseases via inhibiting oxidative stress, reducing inflammatory responses, and restoring mitochondrial dysfunction.

Huc-MSCs-derived exosomes attenuate inflammatory pain by regulating microglia pyroptosis and autophagy via the miR-146a-5p/TRAF6 axis

Background

Chronic inflammatory pain significantly reduces the quality of life and lacks effective interventions. In recent years, human umbilical cord mesenchymal stem cells (huc-MSCs)-derived exosomes have been used to relieve neuropathic pain and other inflammatory diseases as a promising cell-free therapeutic strategy. However, the therapeutic value of huc-MSCs-derived exosomes in complete Freund's adjuvant (CFA)-induced inflammatory pain remains to be confirmed. In this study, we investigated the therapeutic effect and related mechanisms of huc-MSCs-derived exosomes in a chronic inflammatory pain model.

Methods

C57BL/6J male mice were used to establish a CFA-induced inflammatory pain model, and huc-MSCs-derived exosomes were intrathecally injected for 4 consecutive days. BV2 microglia cells were stimulated with lipopolysaccharide (LPS) plus adenosine triphosphate (ATP) to investigate the effect of huc-MSCs-derived exosomes on pyroptosis and autophagy. Bioinformatic analysis and rescue experiments were used to demonstrate the role of miR-146a-5p/ TRAF6 in regulating pyroptosis and autophagy. Western blotting, RT-qPCR, small interfering RNA and Yo-Pro-1 dye staining were performed to investigate the related mechanisms.

Results

Huc-MSCs-derived exosomes alleviated mechanical allodynia and thermal hyperalgesia in CFA-induced inflammatory pain. Furthermore, huc-MSCs-derived exosomes attenuated neuroinflammation by increasing the expression of autophagy-related proteins (LC3-II and beclin1) and inhibiting the activation of NLRP3 inflammasomes in the spinal cord dorsal horn. In vitro, NLRP3 inflammasome components (NLRP3, caspase1-p20, ASC) and gasdermin D (GSDMD-F, GSDMD-N) were inhibited in BV2 cells pretreated with huc-MSCs-derived exosomes. Western blot and Yo-Pro-1 dye staining demonstrated that 3-MA, an autophagy inhibitor, weakened the protective effect of huc-MSCs-derived exosomes on BV2 cell pyroptosis. Importantly, huc-MSCs-derived exosomes transfected with miR-146a-5p mimic promoted autophagy and inhibited BV2 cell pyroptosis. TRAF6, as a target gene of miR-146a-5p, was knocked down via small-interfering RNA, which increased pyroptosis and inhibited autophagy.

Conclusion

Huc-MSCs-derived exosomes attenuated inflammatory pain via miR-146a-5p/TRAF6, which increased the level of autophagy and inhibited pyroptosis.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01522-6.

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

Various studies suggested that neuroinflammation leads to the development of several neurodegenerative disorders like Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease (HD). Rotenone is an organic pesticide and potent inhibitor of complex I of electron transport chain widely used to develop the PD model. Numerous studies reported rotenone toxicity in the dopaminergic system but very few studies are available on rotenone-induced glial cell activation and subsequent neurodegeneration and alterations in various types of behavior. Therefore, the present study was designed to explore the effect of rotenone on neuroinflammation and its deleterious effect on the behavior of mice, and also how these effects can be protected through quercetin. Quercetin, a natural flavonoid having strong antioxidant and anti-inflammatory properties, is found in vegetables and fruits. The finding of the study indicated that rotenone 5 mg/kg body weight for 60 days through oral gavage leads to the release of inflammatory markers in blood serum, astrocytes activation in substantia nigra and hippocampus, and subsequently decreased density of dopaminergic fibers in the striatum. Rotenone also altered the memory of the mice as indicated by decreased spontaneous alteration in Y-maze and T-maze tests and reduction in exploration time in novel object recognition, increased immobility time in the forced swim test and reduced muscular strength. Co-treatment of quercetin 30 mg/kg/day through oral gavage for 60 days along with rotenone significantly reversed all these adverse effects, suggesting that quercetin could reduce neuroinflammation, and improve memory, and cognitive function.

PINK1-Dependent Mitophagy Reduced Endothelial Hyperpermeability and Cell Migration Capacity Under Simulated Microgravity

The effect of cardiovascular dysfunction including orthostatic intolerance and disability on physical exercise is one of the health problems induced by long-term spaceflight astronauts face. As an important part of vascular structure, the vascular endothelium, uniquely sensitive to mechanical force, plays a pivotal role in coordinating vascular functions. Our study found that simulated microgravity induced PINK1-dependent mitophagy in human umbilical vein endothelial cells (HUVECs). Here, we explored the underlying mechanism of mitophagy induction. The ER stress induced by proteostasis failure in HUVECs promoted the Ca2+ transfer from ER to mitochondria, resulting in mitochondria Ca2+ overload, decreased mitochondrial membrane potential, mitochondria fission, and accumulation of Parkin and p62 in mitochondria and mitophagy under simulated microgravity. Moreover, we assumed that mitophagy played a vital role in functional changes in endothelial cells under simulated microgravity. Using mdivi-1 and PINK1 knockdown, we found that NLRP3 inflammasome activation was enhanced after mitophagy was inhibited. The NLRP3 inflammasome contributed to endothelial hyperpermeability and cellular migration by releasing IL-1β. Thus, mitophagy inhibited cell migration ability and hyperpermeability in HUVECs exposed to clinostat-simulated microgravity. Collectively, we here clarify the mechanism of mitophagy induction by simulated microgravity in vitro and demonstrate the relationship between mitophagy and vascular endothelial functional changes including cellular migration and permeability. This study deepens the understanding of vascular functional changes under microgravity.

Quercetin alleviated multi-walled carbon nanotubes-induced neurotoxicity in mice through inhibition of oxidation, inflammation, and pyroptosis

Recently, we reported that quercetin (Que) could alleviate immunotoxicity induced by pristine multi-walled carbon nanotubes (MWCNTs) in mice. In the present study, we explored whether Que could also relieve MWCNTs-induced neurotoxicity. MWCNTs injection induced a dose-dependent neurotoxic effect in mice as evidenced by increased oxidative stress, inflammation, and pyroptosis in the brain. However, treatment with Que ameliorated MWCNTs-induced neurotoxicity as revealed by 1) elevated acetylcholinesterase (AChE) activity, 2) reduced lipid peroxidation biomarker malondialdehyde (MDA), 3) improved antioxidant status as indicated by increased levels of reduced glutathione (GSH) and activities of superoxide dismutase (SOD), catalase (CAT), as well as upregulated expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) genes, 4) decreased levels and expression of inflammatory biomarkers [nitric oxide (NO), interleukin 1 beta (IL1ß), tumor necrosis factor-alpha (TNFα), and nuclear factor kappa B (NF-κB)], 5) downregulated expression of pyroptosis-related genes [nod-like receptor protein inflammasome 3 (Nlrp3) and caspase 1 (Casp1)] but with no effect on the apoptotic Casp3 gene, 6) minimized axonal degeneration and number of microglia in the cerebral medulla, and 7) diminished the number of degenerated neurons in hippocampus and cerebellum. Taken together, Que could ameliorate MWCNT-induced neurotoxicity through antioxidant, anti-inflammatory, and anti-pyroptotic mechanisms.

Engineered Nanoerythrocytes Alleviate Central Nervous System Inflammation by Regulating the Polarization of Inflammatory Microglia

Microglial polarization is one of the most promising therapeutic strategies for multiple central nervous system (CNS) disorders. However, safe, effective, and controllable microglial regulation still faces formidable challenges. Although some anti-inflammatory factors promote microglia polarization, their short half-life, high cost, unpredictable in vivo behavior, and complex delivery operations, hamper their clinical application. Here, inspired by the natural microhemorrhage cleaning mechanism, an MG1 peptide and RVG29 peptide engineered nanoerythrocyte (NEMR) that can reprogram microglia are developed from classical M1 toward alternative M2 by inducing heme oxygenase-1 (HO-1), stimulating Notch1/Hes1/Stat3 signaling, and further inhibiting NF-κB p65 translocation. Moreover, anti-inflammatory carbon monoxide (CO) and bilirubin produced by endogenous metabolism of heme further reinforces the anti-inflammatory effect. In middle cerebral artery occlusion and experimental autoimmune encephalomyelitis models, a satisfactory prognosis is achieved, with precise regulation of inflammatory microglia in lesion sites, increased expression of anti-inflammatory factors, reduced blood-brain barrier permeability, as well as promotion of neurogenesis and functional recovery. Furthermore, NEMR can be integrated with clinical therapeutic agents, which facilitates precise drug delivery to enhance therapeutic effects. Hence, the natural nanoerythrocytes, as a feasible, efficient, safe, and practical tool, provides a new strategy for rebalancing of the immune environment in the CNS disorders.

Activating cGAS-STING axis contributes to neuroinflammation in CVST mouse model and induces inflammasome activation and microglia pyroptosis

Background

Neuroinflammation-induced injury is intimately associated with poor prognosis in patients with cerebral venous sinus thrombosis (CVST). The cyclic GMP-AMP synthase–stimulator of interferon gene (cGAS–STING) axis is a cytoplasmic double-stranded DNA (dsDNA) sensing pathway has recently emerged as a crucial mediator of neuroinflammation in ischemic stroke. However, the role of the cGAS–STING pathway in modulating post-CVST inflammation and the underlying mechanisms involved remain unclear.

Methods

A CVST model was induced by ferric chloride in male C57BL/6J mice. The selective cGAS inhibitor RU.521, STING agonist 2′3′-cGAMP, and STING siRNA were delivered by intranasal administration or intraventricular injection. Post-CVST assessments included rotarod test, TUNEL staining, Fluoro-Jade C staining, dihydroethidium staining, western blotting, qPCR, immunofluorescence, immunohistochemistry, ELISA and flow cytometry.

Results

cGAS, STING, NLRP3 and GSDMD were significantly upregulated after CVST and mostly in the microglia of the mouse brain. CVST triggered the release of dsDNA into the cytoplasm and elicited an inflammatory response via activating the cGAS–STING axis. RU.521 decreased the levels of 2′3′-cGAMP, STING and downstream inflammatory cytokines, and suppressed the expressions of NLRP3 inflammasome and pyroptosis-pertinent components containing cleaved caspase-1, GSDMD, GSDMD-C, pro- and cleaved IL-1β, and cleaved IL-1β/pro-IL-1β. Besides, RU.521 treatment also reduced oxidative stress, lessened the numbers of microglia and neutrophils, and ameliorated neuronal apoptosis, degeneration along with neurological deficits post-CVST. 2′3'-cGAMP delivery enhanced the expressions of STING and related inflammatory mediators, NLRP3 inflammasome and pyroptosis-relevant proteins, whereas these alterations were significantly abrogated by the silencing of STING by siRNA.

Conclusions

Our data demonstrate that repression of the cGAS–STING pathway diminishes the neuroinflammatory burden of CVST and highlight this approach as a potential therapeutic tactic in CVST-mediated pathologies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02511-0.

Hibiscus, Rooibos, and Yerba Mate for Healthy Aging: A Review on the Attenuation of In Vitro and In Vivo Markers Related to Oxidative Stress, Glycoxidation, and Neurodegeneration

The world is currently undergoing a demographic change towards an increasing number of elderly citizens. Aging is characterized by a temporal decline in physiological capacity, and oxidative stress is a hallmark of aging and age-related disorders. Such an oxidative state is linked to a decrease in the effective mechanisms of cellular repair, the incidence of post-translational protein glycation, mitochondrial dysfunction, and neurodegeneration, just to name some of the markers contributing to the establishment of age-related reduction-oxidation, or redox, imbalance. Currently, there are no prescribed therapies to control oxidative stress; however, there are strategies to elevate antioxidant defenses and overcome related health challenges based on the adoption of nutritional therapies. It is well known that herbal teas such, as hibiscus, rooibos, and yerba mate, are important sources of antioxidants, able to prevent some oxidation-related stresses. These plants produce several bioactive metabolites, have a pleasant taste, and a long-lasting history as safe foods. This paper reviews the literature on hibiscus, rooibos, and yerba mate teas in the context of nutritional strategies for the attenuation of oxidative stress-related glycoxidation and neurodegeneration, and, here, Alzheimer’s Disease is approached as an example. The focus is given to mechanisms of glycation inhibition, as well as neuroprotective in vitro effects, and, in animal studies, to frame interest in these plants as nutraceutical agents related to current health concerns.

Salidroside attenuates high altitude hypobaric hypoxia-induced brain injury in mice via inhibiting NF-κB/NLRP3 pathway

Salidroside (Sal), an active ingredient from Rhodiola crenulate, has been reported to exert neuroprotection in cerebral injury from hypobaric hypoxia (HH) at high altitude. However, it remains to be understood whether its protective effects are related to inflammation suppression. In the present work, we aimed to reveal the mechanism of Sal attenuating HH-induced brain injury in mice caused by an animal hypobaric and hypoxic chamber. Our results provided that Sal could attenuate HH-evoked pathological injury and oxidative stress response by decreasing the content of ROS and MDA, and elevating the activities of SOD and GSH-Px. Sal treatment could partly enhance the energy metabolism, evidenced by increasing the activities of Na⁺-K⁺-ATPase, Ca²⁺-Mg²⁺-ATPase, ATP, SDH, HK and PK, while decreasing the release of LDH and LD. Meanwhile, Sal administration reversed the degradation of tight junction proteins ZO-1, Occludin and Claudin-5. Further, the increased levels of TNF-α, IL-1β and IL-6 were confined with Sal administration under the HH condition. Importantly, Sal could downregulate the proteins expression of p-NF-κB-p65, NLRP3, cleaved-Caspase-1 and ASC. Sal also decreased the protein expression of iNOS and COX2 with the increased CD206 and Arg1 expression. Taken together, these data provided that the inhibited NF-κB/NLRP3 pathway by Sal could attenuate HH-induced cerebral oxidative stress injury, inflammatory responses and the blood brain barrier (BBB) damage, attributing to the improved energy metabolism and the microglial phenotype of anti-inflammatory M2. The findings suggested that Sal was expected to be a promising anti-inflammatory agent for high altitude HH-induced brain injury.

ACT001 attenuates microglia-mediated neuroinflammation after traumatic brain injury via inhibiting AKT/NFκB/NLRP3 pathway

Background

Microglia-mediated neuroinflammatory response following traumatic brain injury (TBI) is considered as a vital secondary injury factor, which drives trauma-induced neurodegeneration and is lack of efficient treatment. ACT001, a sesquiterpene lactone derivative, is reportedly involved in alleviation of inflammatory response. However, little is known regarding its function in regulating innate immune response of central nervous system (CNS) after TBI. This study aimed to investigate the role and underlying mechanism of ACT001 in TBI.

Methods

Controlled cortical impact (CCI) models were used to establish model of TBI. Cresyl violet staining, evans blue extravasation, neurobehavioral function assessments, immunofluorescence and transmission electron microscopy were used to evaluate therapeutic effects of ACT001 in vivo. Microglial depletion was induced by administering mice with colony stimulating factor 1 receptor (CSF1R) inhibitor, PLX5622. Cell-cell interaction models were established as co-culture system to simulate TBI conditions in vitro. Cytotoxic effect of ACT001 on cell viability was assessed by cell counting kit-8 and activation of microglia cells were induced by Lipopolysaccharides (LPS). Pro-inflammatory cytokines expression was determined by Real-time PCR and nitric oxide production. Apoptotic cells were detected by TUNEL and flow cytometry assays. Tube formation was performed to evaluate cellular angiogenic ability. ELISA and western blot experiments were used to determine proteins expression. Pull-down assay was used to analyze proteins that bound ACT001.

Results

ACT001 relieved the extent of blood-brain barrier integrity damage and alleviated motor function deficits after TBI via reducing trauma-induced activation of microglia cells. Delayed depletion of microglia with PLX5622 hindered therapeutic effect of ACT001. Furthermore, ACT001 alleviated LPS-induced activation in mouse and rat primary microglia cells. Besides, ACT001 was effective in suppressing LPS-induced pro-inflammatory cytokines production in BV2 cells, resulting in reduction of neuronal apoptosis in HT22 cells and improvement of tube formation in bEnd.3 cells. Mechanism by which ACT001 functioned was related to AKT/NFκB/NLRP3 pathway. ACT001 restrained NFκB nuclear translocation in microglia cells through inhibiting AKT phosphorylation, resulting in decrease of NLRP3 inflammasome activation, and finally down-regulated microglial neuroinflammatory response.

Conclusions

Our study indicated that ACT001 played critical role in microglia-mediated neuroinflammatory response and might be a novel potential chemotherapeutic drug for TBI.

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

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

Tert-butylhydroquinone prevents neuroinflammation and relieves depression via regulation of NLRP3 signaling in mice

Depression is a common psychiatric disorder, which seriously affects people's health and quality of life. Current treatments, which mainly focus on neurotransmitter levels, are not effective in many patients. Recent studies have shown that neuroinflammation has certain correlation with the pathogenesis of depression. Tert-butylhydroquinone (TBHQ) is an antioxidant with an anti-inflammatory effect. The present study evaluated the effects of TBHQ on the improvement of depression-like behaviors induced by lipopolysaccharide (LPS) in mice and its possible mechanism. Behavioral test results showed that TBHQ treatment could significantly improve the depression-like behaviors of mice. Western blot results showed that TBHQ treatment inhibited the protein expression of NLRP3, Caspase-1, IL-1β, and IL-18, which induced by LPS. Immunofluorescence staining results showed that TBHQ treatment inhibited the activation of microglia induced by LPS. These results suggested that, by inhibiting LPS-induced neuroinflammation and microglia activation, TBHQ could effectively improve LPS-induced inflammation-related depression-like behavior through modulating the NLRP3 signaling pathway.

Quercetin Alleviates Demyelination Through Regulating Microglial Phenotype Transformation to Mitigate Neuropsychiatric Symptoms in Mice with Vascular Dementia

Cerebral hypoperfusion plays a pivotal role in the ictus and development of vascular dementia (VaD) with neuropsychiatric symptoms. To date, few pharmacological interventions for neuropsychiatric symptoms are available in the VaD patients with neuropsychiatric impairments. Here, our results demonstrated that the extent of demyelination was dramatically deteriorated and the thickness of myelin sheath was evidently decreased in the presence of cerebral hypoperfusion, whereas Quercetin possessed the potential of abrogating these effects at least in part, then relieving anxiety and depression-like behavior when mice exposed to bilateral carotid artery stenosis (BCAS)/chronic restraint stress (CRS). The underlying mechanism was that Quercetin facilitated secretion of anti-inflammatory cytokines (IL-4 and IL-10) and in turn decreased production of pro-inflammatory factors (TNF-α and IL-1β) due to regulating microglial phenotype transformation, thereafter enhancing the microglial engulfment ability of myelin fragments in vitro and in vivo. Collectively, the results demonstrated that that Quercetin mediated microglial transformation into anti-inflammatory phenotype to reduce demyelination in ventral hippocampus (vHIP), thereafter mitigating neuropsychiatric deficits (including anxiety and depression). The present research broadens the therapeutic scope of Quercetin in central nervous system (CNS) disorders with presence of white matter damage and/or the insufficient activation of anti-inflammatory microglia, particularly for vascular dementia with/without neuropsychiatric symptoms.

Quercetin improves the apoptotic index and oxidative stress in post-thaw dog sperm

Freeze storage of ejaculated sperms is a crucial technique for the semen preservation of valuable pet animals such as dogs. The current study was conducted to investigate if quercetin (QRN) may ameliorate apoptosis and oxidative stress in post-thaw dog sperm. Herein, we evaluated the post-thaw apoptosis and oxidative stress after treatment with QRN (control, 25, 50, and 100 μM) in the freezing of dog semen. Reactive oxygen species levels were significantly affected (p < 0.05) between the various concentrations of QRN and the control (17.56 ± 1.02, 7.54 ± 0.48, 5.66 ± 0.80, and 10.41 ± 0.69), respectively. The apoptosis index was 9.1 ± 1.34, 6.66 ± 0.58, 6.77 ± 0.66, and 5.38 ± 0.86 in the control, and 25, 50, and 100 μM QRN treatment groups, respectively (p < 0.05). The effects of ameliorated cryo-induced damage by QRN on post-thaw sperm quality were also observed through improved structural and functional tests. Sperm treated with 50 μM QRN showed significantly higher motility (51.8 ± 2.1% vs. 43.1 ± 1.4%, P < 0.05), survival rates (46.9 ± 0.7% vs. 43.9 ± 0.4%, P < 0.05), and mucus penetration than control group, respectively. Results also indicated that higher concentrations of QRN (100 μM) were not effective on sperm quality and parameters when compared with the medium levels (50 μM). In conclusion, supplementation of freezing buffer with 50 μM QRN reduced oxidative damage and improved the quality of post-thaw dog sperm.

The Role of NLRP3 Inflammasome in Alzheimer’s Disease and Potential Therapeutic Targets

Alzheimer’s disease (AD) is a common age-related neurodegenerative disease characterized by progressive cognitive dysfunction and behavioral impairment. The typical pathological characteristics of AD are extracellular senile plaques composed of amyloid ß (Aβ) protein, intracellular neurofibrillary tangles formed by the hyperphosphorylation of the microtubule-associated protein tau, and neuron loss. In the past hundred years, although human beings have invested a lot of manpower, material and financial resources, there is no widely recognized drug for the effective prevention and clinical cure of AD in the world so far. Therefore, evaluating and exploring new drug targets for AD treatment is an important topic. At present, researchers have not stopped exploring the pathogenesis of AD, and the views on the pathogenic factors of AD are constantly changing. Multiple evidence have confirmed that chronic neuroinflammation plays a crucial role in the pathogenesis of AD. In the field of neuroinflammation, the nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is a key molecular link in the AD neuroinflammatory pathway. Under the stimulation of Aβ oligomers and tau aggregates, it can lead to the assembly and activation of NLRP3 inflammasome in microglia and astrocytes in the brain, thereby causing caspase-1 activation and the secretion of IL-1β and IL-18, which ultimately triggers the pathophysiological changes and cognitive decline of AD. In this review, we summarize current literatures on the activation of NLRP3 inflammasome and activation-related regulation mechanisms, and discuss its possible roles in the pathogenesis of AD. Moreover, focusing on the NLRP3 inflammasome and combining with the upstream and downstream signaling pathway-related molecules of NLRP3 inflammasome as targets, we review the pharmacologically related targets and various methods to alleviate neuroinflammation by regulating the activation of NLRP3 inflammasome, which provides new ideas for the treatment of AD.