Myricetin attenuated MPP(+)-induced cytotoxicity by anti-oxidation and inhibition of MKK4 and JNK activation in MES23.5 cells

Cellular stress response and neuroprotection of flavonoids in neurodegenerative diseases: Clinical insights into targeted therapy and molecular signaling pathways

Neurodegenerative diseases (NDs) are caused by the gradual decline of neuronal structure and function, which presents significant challenges in treatment. Cellular stress responses significantly impact the pathophysiology of these disorders, often exacerbating neuronal damage. Plant-derived flavonoids have demonstrated potential as neuroprotective agents due to their potent anti-inflammatory, anti-apoptotic, and antioxidant properties. This review provides an in-depth analysis of the molecular processes and clinical insights that cause the neuroprotective properties of flavonoids in NDs. By controlling essential signaling pathways such as Nrf2/ARE, MAPK, and PI3K/Akt, flavonoids can lower cellular stress and improve neuronal survival. The study discusses the challenges of implementing these discoveries in clinical practice and emphasizes the therapeutic potential of specific flavonoids and their derivatives. Flavonoids are identified as potential therapeutic agents for NDs, potentially slowing progression by regulating cellular stress and improving neuroprotection despite their potential medicinal uses and clinical challenges. The study designed a strategy to identify literature published in prestigious journals, utilizing search results from PubMed, Scopus, and WOS. We selected and investigated original studies, review articles, and research reports published until 2024. It suggests future research and therapeutic approaches to effectively utilize the neuroprotective properties of flavonoids.

Network pharmacology combined with experimental validation show that apigenin as the active ingredient of Campsis grandiflora flower against Parkinson's disease by inhibiting the PI3K/AKT/NF-κB pathway

The exploration of novel natural products for Parkinson's disease (PD) is a focus of current research, as there are no definitive drugs to cure or stop the disease. Campsis grandiflora (Thunb.) K. Schum (Lingxiaohua) is a traditional Chinese medicine (TCM), and the exact active constituents and putative mechanisms for treating PD are unknown. Through data mining and network pharmacology, apigenin (APi) was identified as the main active ingredient of Lingxiaohua, and key targets (TNF, AKT1, INS, TP53, CASP3, JUN, BCL2, MMP9, FOS, and HIF1A) of Lingxiaohua for the treatment of PD were discovered. The primary routes implicated were identified as PI3K/AKT, Apoptosis, TNF, and NF-κB pathways. Subsequently, therapeutic potential of APi in PD and its underlying mechanism were experimentally evaluated. APi suppressed the release of mediators of inflammation and initiation of NF-κB pathways in MES23.5 cells induced by MPP+. APi suppressed caspase-3 activity and apoptosis and elevated p-AKT levels in MES23.5 cells. Pretreatment with LY294002, a PI3K inhibitor, resulted in APi treatment blocking the activation of NF-κB pathway and expression of inflammatory factors in MES23.5 cells by activating the PI3K/AKT pathway. In conclusion, APi protects dopaminergic neurons by controlling the PI3K/AKT/NF-κB pathway, giving novel insights into the pharmacological mechanism of Lingxiaohua in treating PD.

Polyphenols Targeting MAP Kinase Signaling Pathway in Neurological Diseases: Understanding Molecular Mechanisms and Therapeutic Targets

Polyphenols are a class of secondary metabolic products found in plants that have been extensively studied for how well they regulate biological processes, such as the proliferation of cells, autophagy, and apoptosis. The mitogen-activated protein kinase (MAPK)-mediated signaling cascade is currently identified as a crucial pro-inflammatory pathway that plays a significant role in the development of neuroinflammation. This process has been shown to contribute to the pathogenesis of several neurological conditions, such as Alzheimer's disease (AD), Parkinson's disease (PD), CNS damage, and cerebral ischemia. Getting enough polyphenols through eating habits has resulted in mitigating the effects of oxidative stress (OS) and lowering the susceptibility to associated neurodegenerative disorders, including but not limited to multiple sclerosis (MS), AD, stroke, and PD. Polyphenols possess significant promise in dealing with the root cause of neurological conditions by modulating multiple therapeutic targets simultaneously, thereby attenuating their complicated physiology. Several polyphenolic substances have demonstrated beneficial results in various studies and are presently undergoing clinical investigation to treat neurological diseases (NDs). The objective of this review is to provide a comprehensive summary of the different aspects of the MAPK pathway involved in neurological conditions, along with an appraisal of the progress made in using polyphenols to regulate the MAPK signaling system to facilitate the management of NDs.

Therapeutic Potential of Myricetin in the Treatment of Neurological, Neuropsychiatric, and Neurodegenerative Disorders

Myricetin (MC), 3,5,7,3',4',5'-hexahydroxyflavone, chemically belongs to a flavonoid category known to confer antioxidant, antimicrobial, antidiabetic, and neuroprotective effects. MC is known to suppress the generation of Reactive Oxygen Species (ROS), lipid peroxidation (MDA), and inflammatory markers. It has been reported to improve insulin function in the human brain and periphery. Besides this, it modulates several neurochemicals including glutamate, GABA, serotonin, etc. MC has been shown to reduce the expression of the enzyme Mono Amine Oxidase (MAO), which is responsible for the metabolism of monoamines. MC treatment reduces levels of plasma corticosterone and restores hippocampal BDNF (full form) protein in stressed animals. Further, MC has shown its protective effect against amyloid-beta, MPTP, rotenone, 6-OHDA, etc. suggesting its potential role against neurodegenerative disorders. The aim of the present review is to highlight the therapeutic potential of MC in the treatment of several neurological, neuropsychiatric, and neurodegenerative disorders.

Antiplatelet drugs: Potential therapeutic options for the management of neurodegenerative diseases

The blood platelet plays an important role but often remains under-recognized in several vascular complications and associated diseases. Surprisingly, platelet hyperactivity and hyperaggregability have often been considered the critical risk factors for developing vascular dysfunctions in several neurodegenerative diseases (NDDs) like Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis. In addition, platelet structural and functional impairments promote prothrombotic and proinflammatory environment that can aggravate the progression of several NDDs. These findings provide the rationale for using antiplatelet agents not only to prevent morbidity but also to reduce mortality caused by NDDs. Therefore, we thoroughly review the evidence supporting the potential pleiotropic effects of several novel classes of synthetic antiplatelet drugs, that is, cyclooxygenase inhibitors, adenosine diphosphate receptor antagonists, protease-activated receptor blockers, and glycoprotein IIb/IIIa receptor inhibitors in NDDs. Apart from this, the review also emphasizes the recent developments of selected natural antiplatelet phytochemicals belonging to key classes of plant-based bioactive compounds, including polyphenols, alkaloids, terpenoids, and flavonoids as potential therapeutic candidates in NDDs. We believe that the broad analysis of contemporary strategies and specific approaches for plausible therapeutic treatment for NDDs presented in this review could be helpful for further successful research in this area.

Phenylboronic Ester-Bridged Chitosan/Myricetin Nanomicelle for Penetrating the Endothelial Barrier and Regulating Macrophage Polarization and Inflammation against Ischemic Diseases

The brain and liver are more susceptible to ischemia and reperfusion (IR) injury (IRI), which triggers the reactive oxygen species (ROS) burst and inflammatory cascade and results in severe neuronal damage or hepatic injury. Moreover, the damaged endothelial barrier contributes to proinflammatory activity and limits the delivery of therapeutic agents such as some macromolecules and nanomedicine despite the integrity being disrupted after IRI. Herein, we constructed a phenylboronic-decorated chitosan-based nanoplatform to deliver myricetin, a multifunctional polyphenol molecule for the treatment of cerebral and hepatic ischemia. The chitosan-based nanostructures are widely studied cationic carriers for endothelium penetration such as the blood-brain barrier (BBB) and sinusoidal endothelial barrier (SEB). The phenylboronic ester was chosen as the ROS-responsive bridging segment for conjugation and selective release of myricetin molecules, which meanwhile scavenged the overexpressed ROS in the inflammatory environment. The released myricetin molecules fulfill a variety of roles including antioxidation through multiple phenolic hydroxyl groups, inhibition of the inflammatory cascade by regulation of the macrophage polarization from M1 to M2, and endothelial injury repairment. Taken together, our present study provides valuable insight into the development of efficient antioxidant and anti-inflammatory platforms for potential application against ischemic disease.

Antiparkinsonian Effects of Polyphenols: A Narrative Review with a Focus on the Modulation of the Gut-brain Axis

Polyphenols, which are naturally occurring bioactive compounds in fruits and vegetables, are emerging as potential therapeutics for neurological disorders such as Parkinson's disease (PD). Polyphenols have diverse biological activities, such as anti-oxidative, anti-inflammatory, anti-apoptotic, and α-synuclein aggregation inhibitory effects, which could ameliorate PD pathogenesis. Studies have shown that polyphenols are capable of regulating the gut microbiota (GM) and its metabolites; in turn, polyphenols are extensively metabolized by the GM, resulting in the generation of bioactive secondary metabolites. These metabolites may regulate various physiological processes, including inflammatory responses, energy metabolism, intercellular communication, and host immunity. With increasing recognition of the importance of the microbiota-gut-brain axis (MGBA) in PD etiology, polyphenols have attracted growing attention as MGBA regulators. In order to address the potential therapeutic role of polyphenolic compounds in PD, we focused on MGBA. DATA AVAILABILITY: Data will be made available on request.

Myricetin improves apoptosis after ischemic stroke via inhibiting MAPK-ERK pathway

BACKGROUND

Neuronal apoptosis is the main cause for the disabilities and deaths of patients suffered with stroke. Neuroprotectants are clinically used to reduce neuronal apoptosis in ischemic stroke. However, the current neuroprotectants have multiple limitations. Myricetin is beneficial for multiple neurodegenerative diseases, but the role of myricetin as a neuroprotective agent in ischemic stroke is still not fully understood.

METHODS AND RESULTS

Middle cerebral artery occlusion, Terminal deoxynucleotidyl transferase dUTP nick-end labeling staining and Western blots were used to explore the anti-apoptotic effects of myricetin in vivo. Flow cytometry, Western blots and Ca²⁺ staining were used to study the neuroprotective effects of myricetin in vitro. In this study, we first demonstrated that myricetin reduced neuronal apoptosis after ischemia in vivo and in vitro. And, among the factors of apoptosis after ischemic stroke, excitotoxicity, oxidative stress and inflammation-induced apoptosis can be alleviated by myricetin. Moreover, we further demonstrated that myricetin was able to improve neuronal intrinsic apoptosis by inhibiting the phosphorylation of extracellular signal-regulated kinase in the oxygen and glucose deprivation in vitro.

CONCLUSIONS

Summarily, our results support myricetin as a novel neuroprotectant for the prevention or treatment of ischemic stroke via MAPK-ERK signaling pathway.

Investigating the effect of myricetin against arsenic-induced cardiac toxicity in rats

Arsenic intoxication is a serious health hazard worldwide. Its toxicity is associated with several disorders and health problems in humans. Recent studies revealed that myricetin has various biological effects, including anti-oxidation. The aim of this study is to investigate the protective effect of myricetin against arsenic-induced cardiotoxicity in rats. Rats were randomized to one of the following groups: control, myricetin (2 mg/kg), arsenic (5 mg/kg), myricetin (1 mg/kg) + arsenic, and myricetin (2 mg/kg) + arsenic. Myricetin was given intraperitoneally 30 min before arsenic administration (5 mg/kg for 10 days). After treatments, the activity of lactate dehydrogenase (LDH) and the levels of aspartate aminotransferase (AST), creatine kinase myocardial band (CK-MB), lipid peroxidation (LPO), total antioxidant capacity (TAC), and total thiol molecules (TTM) were determined in serum samples and cardiac tissues. Also, histological changes in cardiac tissue were evaluated. Myricetin pretreatment inhibited arsenic-induced increase in LDH, AST, CK-MB, and LPO levels. Pretreatment with myricetin also enhanced the decreased TAC and TTM levels. In addition, myricetin improved histopathological alterations in arsenic-treated rats. In conclusion, the results of the present study demonstrated that treatment with myricetin prevented arsenic-induced cardiac toxicity at least in part by decreasing oxidative stress and restoring the antioxidant system.

The Neuroprotective Potentiality of Flavonoids on Alzheimer's Disease

Alzheimer's disease (AD), due to its spread, has become a global health priority, and is characterized by senile dementia and progressive disability. The main cause of AD and other neurodegenerations (Huntington, Parkinson, Amyotrophic Lateral Sclerosis) are aggregated protein accumulation and oxidative damage. Recent research on secondary metabolites of plants such as polyphenols demonstrated that they may slow the progression of AD. The flavonoids' mechanism of action in AD involved the inhibition of acetylcholinesterase, butyrylcholinesterase, Tau protein aggregation, β-secretase, oxidative stress, inflammation, and apoptosis through modulation of signaling pathways which are implicated in cognitive and neuroprotective functions, such as ERK, PI3-kinase/Akt, NFKB, MAPKs, and endogenous antioxidant enzymatic systems. This review focuses on flavonoids and their role in AD, in terms of therapeutic potentiality for human health, antioxidant potential, and specific AD molecular targets.

MKK4 Knockdown Plays a Protective Role in Hemorrhagic Shock-Induced Liver Injury through the JNK Pathway

Hemorrhagic shock (HS) triggers tissue hypoxia and organ failure during severe blood loss, and the liver is sensitive to HS. Mitogen-activated protein kinase kinase 4 (MKK4) activates the c-Jun NH2-terminal kinase (JNK) pathway, and its expression is upregulated in the serum of HS patients and mouse livers at 1 h post-HS. However, the function of MKK4 in HS-induced liver injury is unclear. The role of MKK4 was investigated in vivo using rat models of HS. Before HS, lentivirus harboring shRNA against MKK4 was injected into rats via the tail vein to knock down MKK4 expression. HS was induced by bloodletting via intubation of the femoral artery followed by resuscitation. The results showed that MKK4 knockdown reduced HS-induced apoptosis in the liver by decreasing Bax expression and the cleavage of caspase 3 and promoting Bcl-2 expression. Moreover, the generation of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) in the liver was promoted, while superoxide dismutase (SOD) activity was inhibited by HS. However, the effect of HS on oxidative stress was abrogated by MKK4 knockdown. Furthermore, MKK4 knockdown restored MMP and complex I and complex III activities and promoted ATP production, suggesting that HS-induced mitochondrial dysfunction in the liver was ameliorated by MKK4 knockdown. The inhibitory effect of MKK4 knockdown on the phosphorylation and activation of the JNK/c-Jun pathway was confirmed. Overall, MKK4 knockdown may suppress oxidative stress and subsequent apoptosis and improve mitochondrial function in the liver upon HS by inhibiting the JNK pathway. The MKK4/JNK axis was shown to be a therapeutic target for HS-induced liver injury in this study.

A review: traditional herbs and remedies impacting pathogenesis of Parkinson's disease

Parkinson's disease (PD) is characterized by progressive degeneration of dopaminergic neurons, leading to misbalance and loss of coordination. Current therapies are claimed only for symptomatic relief, on long-term use, which causes alteration in basal ganglia, and give rise to various adverse effects like dyskinesia and extra pyramidal side effects, which is reversed and proved to be attenuated with the help of various herbal approaches. Therefore, in order to attenuate the dopaminergic complications, focus of current research has been shifted from dopaminergic to non-dopaminergic strategies. Herbs and herbal remedies seems to be a better option to overcome the complications associated with current dopaminergic therapies. In recent years, various herbs and herbal remedies based on Ayurveda, traditional Chinese and Korean remedies, have become the target of various researches. These herbs and their bioactive compound are being extensively used to treat PD in India, China, Japan, and Korea. The major focus of this current review is to analyze preclinical studies with reference to various herbs, bioactive compounds, and traditional remedies for the management of Parkinson disorder, which will give an insight towards clinical trials.

Myricetin: a Multifunctional Flavonol in Biomedicine

PURPOSE OF REVEIW

The root cause of many diseases like CVD, cancer, and aging is free radicals which exert their effect by interfering with different metabolic pathways. The sources of free radicals can be exogenous, like UV rays from sunlight, and endogenous due to different metabolic by-products.In our body, there are defense mechanisms present, such as antioxidant enzymes and antioxidant molecules to combat these free radicals, but if there is an overload of these free radicals in our body, the defense system may not be sufficient to neutralize these free radicals. In such situations, we are exposed to a chronic low dose of oxidants creating oxidative stress, which is responsible for eliciting different diseases.

RECENT FINDINGS

Pubmed and Google Scholar are the search engines used to sort out relevant papers on myricetin and its role in combating many diseases. Myricetin is present in many fruits and vegetables and is a known antioxidant. It can elevate the antioxidant enzyme levels; reduces the lipid peroxidation; and is known to protect against cancer. In the case of myocardial dysfunction, myricetin has been shown to suppress the inflammatory cytokines and reduced the mortality rate. Myricetin has also been found to reduce platelet aggregation and control the viral infections by interfering in the DNA replication pathways.

SUMMARY

In this paper, we have briefly reviewed about the different type and site of free radicals and the role of myricetin in addressing the ROS and different diseases.

The role of flavonoids in inhibiting IL-6 and inflammatory arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that primarily affects the synovial joints. RA has well-known clinical manifestations and can cause progressive disability and premature death along with socioeconomic burdens. Interleukin-6 (IL-6) has been implicated in the pathology of RA where it can stimulate pannus formation, osteoclastogenesis, and oxidative stress. Flavonoids are plant metabolites with beneficial pharmacological effects, including anti-inflammatory, antioxidant, antidiabetic, anticancer, and others. Flavonoids are polyphenolic compounds found in a variety of plants, vegetables, and fruits. Many flavonoids have demonstrated anti-arthritic activity mediated mainly through the suppression of pro-inflammatory cytokines. This review thoroughly discusses the accumulate data on the role of flavonoids on IL-6 in RA.

Pharmacological Actions of Myricetin in the Nervous System: A Comprehensive Review of Preclinical Studies in Animals and Cell Models

Myricetin is a natural flavonoid extracted from a variety of plants, such as medicinal herbs, vegetables, berries, and tea leaves. A growing body of evidence has reported that myricetin supplementation display therapeutic activities in a lot of nervous system disorders, such as cerebral ischemia, Alzheimer’s disease, Parkinson’s disease, epilepsy, and glioblastoma. Myricetin supplementation can also protect against pathological changes and behavioral impairment induced by multiple sclerosis and chronic stress. On the basis of these pharmacological actions, myricetin could be developed as a potential drug for the prevention and/or treatment of nervous system disorders. Mechanistic studies have shown that inhibition of oxidative stress, cellular apoptosis, and neuroinflammatory response are common mechanisms for the neuroprotective actions of myricetin. Other mechanisms, including the activation of the nuclear factor E2-related factor 2 (Nrf2), extracellular signal-regulated kinase 1/2 (ERK1/2), protein kinase B (Akt), cyclic adenosine monophosphate-response element binding protein (CREB), and brain-derived neurotrophic factor (BDNF) signaling, inhibition of intracellular Ca²⁺ increase, inhibition of c-Jun N-terminal kinase (JNK)-p38 activation, and suppression of mutant protein aggregation, may also mediate the neuroprotective effects of myricetin. Furthermore, myricetin treatment has been shown to promote the activation of the inhibitory neurons in the hypothalamic paraventricular nucleus, which subsequently produces anti-epilepsy effects. In this review, we make a comprehensive understanding about the pharmacological effects of myricetin in the nervous system, aiming to push the development of myricetin as a novel drug for the treatment of nervous system disorders.

Anti-Oxidative, Anti-Inflammatory and Anti-Apoptotic Effects of Flavonols: Targeting Nrf2, NF-κB and p53 Pathways in Neurodegeneration

Neurodegenerative diseases are one of the leading causes of disability and death worldwide. Intracellular transduction pathways that end in the activation of specific transcription factors are highly implicated in the onset and progression of pathological changes related to neurodegeneration, of which those related to oxidative stress (OS) and neuroinflammation are particularly important. Here, we provide a brief overview of the key concepts related to OS- and neuroinflammation-mediated neuropathological changes in neurodegeneration, together with the role of transcription factors nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-κB (NF-κB). This review is focused on the transcription factor p53 that coordinates the cellular response to diverse genotoxic stimuli, determining neuronal death or survival. As current pharmacological options in the treatment of neurodegenerative disease are only symptomatic, many research efforts are aimed at uncovering efficient disease-modifying agents. Natural polyphenolic compounds demonstrate powerful anti-oxidative, anti-inflammatory and anti-apoptotic effects, partially acting as modulators of signaling pathways. Herein, we review the current understanding of the therapeutic potential and limitations of flavonols in neuroprotection, with emphasis on their anti-oxidative, anti-inflammatory and anti-apoptotic effects along the Nrf2, NF-κB and p53 pathways. A better understanding of cellular and molecular mechanisms of their action may pave the way toward new treatments.

Natural products targeting mitochondria: emerging therapeutics for age-associated neurological disorders

Mitochondria are the primary source of energy production in the brain thereby supporting most of its activity. However, mitochondria become inefficient and dysfunctional with age and to a greater extent in neurological disorders. Thus, mitochondria represent an emerging drug target for many age-associated neurological disorders. This review summarizes recent advances (covering from 2010 to May 2020) in the use of natural products from plant, animal, and microbial sources as potential neuroprotective agents to restore mitochondrial function. Natural products from diverse classes of chemical structures are discussed and organized according to their mechanism of action on mitochondria in terms of modulation of biogenesis, dynamics, bioenergetics, calcium homeostasis, and membrane potential, as well as inhibition of the oxytosis/ferroptosis pathway. This analysis emphasizes the significant value of natural products for mitochondrial pharmacology as well as the opportunities and challenges for the discovery and development of future neurotherapeutics.

Effect of Streblus asper Leaf Extract on Scopolamine-Induced Memory Deficits in Zebrafish: The Model of Alzheimer's Disease

Streblus asper (SA) is well known as a folk medicinal plant in Asian countries. The effect of SA extract on preventing memory impairment in zebrafish induced by scopolamine was investigated. Male zebrafish, Danio rerio, were divided into 6 groups including the control, scopolamine 200 μM (SCO), scopolamine plus rivastigmine 1.5 mg/kg (RV + SCO), and scopolamine plus SA extract at doses of 200, 400, and 800 mg/kg (SA200 + SCO, S400 + SCO, and SA800 + SCO), respectively. Spatial memory was evaluated by the colour-biased appetite conditioning T-maze test, while fear memory was measured by the inhibitory avoidance test. In the spatial memory test, results showed that the RV + SCO group had the best time spent ratio in the T-maze, followed by SA800 + SCO, SA400 + SCO, SA200 + SCO, control, and SCO group, respectively, but with no statistical significance. For the fear memory test, zebrafish that received SA at doses of 200, 400, and 800 mg/kg had significantly increased latency time as 21.75 ± 4.59, 23.75 ± 13.01, and 18.20 ± 18.84 min, respectively, when compared to the SCO group (9.80 ± 10.45 min). These results suggested that SA extract attenuated memory impairment in an inhibitory avoidance test related to fear memory. Our findings can be useful for further research to develop SA extract as a health product to ameliorate the symptoms of Alzheimer's disease.

Neurotoxic Effect of Flavonol Myricetin in the Presence of Excess Copper

Oxidative stress (OS) induced by the disturbed homeostasis of metal ions is one of the pivotal factors contributing to neurodegeneration. The aim of the present study was to investigate the effects of flavonoid myricetin on copper-induced toxicity in neuroblastoma SH-SY5Y cells. As determined by the MTT method, trypan blue exclusion assay and measurement of ATP production, myricetin heightened the toxic effects of copper and exacerbated cell death. It also increased copper-induced generation of reactive oxygen species, indicating the prooxidative nature of its action. Furthermore, myricetin provoked chromatin condensation and loss of membrane integrity without caspase-3 activation, suggesting the activation of both caspase-independent programmed cell death and necrosis. At the protein level, myricetin-induced upregulation of PARP-1 and decreased expression of Bcl-2, whereas copper-induced changes in the expression of p53, p73, Bax and NME1 were not further affected by myricetin. Inhibitors of ERK1/2 and JNK kinases, protein kinase A and L-type calcium channels exacerbated the toxic effects of myricetin, indicating the involvement of intracellular signaling pathways in cell death. We also employed atomic force microscopy (AFM) to evaluate the morphological and mechanical properties of SH-SY5Y cells at the nanoscale. Consistent with the cellular and molecular methods, this biophysical approach also revealed a myricetin-induced increase in cell surface roughness and reduced elasticity. Taken together, we demonstrated the adverse effects of myricetin, pointing out that caution is required when considering powerful antioxidants for adjuvant therapy in copper-related neurodegeneration.

Effects of myricetin against cadmium-induced neurotoxicity in PC12 cells

Cadmium (Cd) is one of the most prevalent toxic metals widely found in the environment. Cd induces toxicity and apoptosis in various organs and cells. The nervous system is one of the primary organs targeted by Cd. Cd toxicity is correlated with induction of severe oxidative stress. Myricetin, a natural product, has been found to exert protective effects against various disease conditions. The present study aimed to evaluate the potential protective effects of myricetin on Cd-induced neurotoxicity in PC12 cells. The cells were pretreated with myricetin in the absence and presence of Cd. The viability of cells was assessed using the MTT assay. Markers of oxidative stress were investigated by the lipid peroxidation (LPO), glutathione (GSH) content, and total antioxidant capacity (TAC). Moreover, activation of caspase 3 was examined by Western blot analysis. Myricetin could significantly enhance the viability of PC12 cells. Pretreatment of the cells with myricetin, prior to Cd exposure, showed a significant decrease in the levels of LPO whereas GSH and TAC levels were increased. In addition, the activity of caspase-3 was notably prevented by myricetin. These findings revealed that myricetin has protective effects on Cd-induced neurotoxicity in PC12 cells, which can be linked to its antioxidant potential, inhibition of LPO, and prevention of caspase-3 activation.

Myricetin reduces cytotoxicity by suppressing hepcidin expression in MES23.5 cells

Multiple studies implicate iron accumulation in the substantia nigra in the degeneration of dopaminergic neurons in Parkinson’s disease. Indeed, slowing of iron accumulation in cells has been identified as the key point for delaying and treating Parkinson’s disease. Myricetin reportedly plays an important role in anti-oxidation, anti-apoptosis, anti-inflammation, and iron chelation. However, the mechanism underlying its neuroprotection remains unclear. In the present study, MES23.5 cells were treated with 1 × 10^–6 M myricetin for 1 hour, followed by co-treatment with 400 nM rotenone for 24 hours to establish an in vitro cell model of Parkinson’s disease. Our results revealed that myricetin alleviated rotenone-induced decreases in cell viability, suppressed the production of intracellular reactive oxygen species, and restored mitochondrial transmembrane potential. In addition, myricetin significantly suppressed rotenone-induced hepcidin gene transcription and partly relieved rotenone-induced inhibition of ferroportin 1 mRNA and protein levels. Furthermore, myricetin inhibited rotenone-induced phosphorylation of STAT3 and SMAD1 in MES23.5 cells. These findings suggest that myricetin protected rotenone-treated MES23.5 cells by potently inhibiting hepcidin expression to prevent iron accumulation, and this effect was mediated by alteration of STAT3 and SMAD1 signaling pathways.

Apelin-13 Protects Dopaminergic Neurons against Rotenone-Induced Neurotoxicity through the AMPK/mTOR/ULK-1 Mediated Autophagy Activation

Parkinson’s disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Several brain–gut peptides are able to exert neuroprotective effects on the nigrostriatal dopaminergic system. Apelin-13 is a neuropeptide, conveying potential neuroprotective activities. However, whether, and how, apelin-13 could antagonize rotenone-induced neurotoxicity has not yet been elucidated. In the present study, rotenone-treated SH-SY5Y cells and rats were used to clarify whether apelin-13 has protective effects on dopaminergic neurons, both in vivo and in vitro. The results showed that apelin-13 could protect SH-SY5Y cells from rotenone-induced injury and apoptosis. Apelin-13 was able to activate autophagy, and restore rotenone induced autophagy impairment in SH-SY5Y cells, which could be blocked by the autophagy inhibitor 3-Methyladenine. Apelin-13 activated AMPK/mTOR/ULK-1 signaling, AMPKα inhibitor compound C, as well as apelin receptor blockage via siRNA, which could block apelin-13-induced signaling activation, autophagy activation, and protective effects, in rotenone-treated SH-SY5Y cells. These results indicated that apelin-13 exerted neuroprotective properties against rotenone by stimulating AMPK/mTOR/ULK-1 signaling-mediated autophagy via the apelin receptor. We also observed that intracerebroventricular injection of apelin-13 could alleviate nigrostriatal dopaminergic neuron degeneration in rotenone-treated rats. Our findings provide new insights into the mechanism by which apelin-13 might attenuate neurotoxicity in PD.

Myricetin bioactive effects: moving from preclinical evidence to potential clinical applications

Several flavonoids have been recognized as nutraceuticals, and myricetin is a good example. Myricetin is commonly found in plants and their antimicrobial and antioxidant activities is well demonstrated. One of its beneficial biological effects is the neuroprotective activity, showing preclinical activities on Alzheimer, Parkinson, and Huntington diseases, and even in amyotrophic lateral sclerosis. Also, myricetin has revealed other biological activities, among them as antidiabetic, anticancer, immunomodulatory, cardiovascular, analgesic and antihypertensive. However, few clinical trials have been performed using myricetin as nutraceutical. Thus, this review provides new insights on myricetin preclinical pharmacological activities, and role in selected clinical trials.

Neuroimmunomodulatory and Neuroprotective Effects of the Flavonoid Apigenin in in vitro Models of Neuroinflammation Associated With Alzheimer's Disease

Neurodegenerative disorders (ND) are characterized by the progressive and irreversible loss of neurons. Alzheimer’s Disease (AD) is the most incident age-related ND, in which the presence of a chronic inflammatory compound seems to be related to its pathogenesis. Different stimuli in the central nervous system (CNS) can induce activation, proliferation, and changes in phenotype and glial function, which can be modulated by anti-inflammatory agents. Apigenin (4,5,7–trihydroxyflavone) is a flavonoid found in abundance in many fruits and vegetables, that has shown important effects upon controlling the inflammatory response. This study evaluated the neuroprotective and neuroimmunomodulatory potential of apigenin using in vitro models of neuroinflammation associated with AD. Co-cultures of neurons and glial cells were obtained from the cortex of newborn and embryonic Wistar rats. After 26 days in vitro, cultures were exposed to lipopolysaccharide (LPS; 1 μg/ml), or IL-1β (10 ng/ml) for 24 h, or to Aβ oligomers (500 nM) for 4 h, and then treated with apigenin (1 μM) for further 24 h. It was observed that the treatment with apigenin preserved neurons and astrocytes integrity, determined by Rosenfeld’s staining and immunocytochemistry for β-tubulin III and GFAP, respectively. Moreover, it was observed by Fluoro-Jade-B and caspase-3 immunostaining that apigenin was not neurotoxic and has a neuroprotective effect against inflammatory damage. Additionally, apigenin reduced microglial activation, characterized by inhibition of proliferation (BrdU+ cells) and modulation of microglia morphology (Iba-1 + cells), and decreased the expression of the M1 inflammatory marker CD68. Moreover, as determined by RT-qPCR, inflammatory stimuli induced by IL-1β increased the mRNA expression of IL-6, IL-1β, and CCL5, and decreased the mRNA expression of IL-10. Contrary, after treatment with apigenin in inflammatory stimuli (IL-1β or LPS) there was a modulation of the mRNA expression of inflammatory cytokines, and reduced expression of OX42, IL-6 and gp130. Moreover, apigenin alone and after an inflammatory stimulus with IL-1β also induced the increase in the expression of brain-derived neurotrophic factor (BDNF), an effect that may be associated with anti-inflammatory and neuroprotective effects. Together these data demonstrate that apigenin presents neuroprotective and anti-inflammatory effects in vitro and might represent an important neuroimmunomodulatory agent for the treatment of neurodegenerative conditions.

Possible Epigenetic Role of Vitexin in Regulating Neuroinflammation in Alzheimer's Disease

Alzheimer's disease (AD) has been clinically characterized by a progressive degeneration of neurons which resulted in a gradual and irreversible cognitive impairment. The accumulation of Aβ and τ proteins in the brain contribute to the severity of the disease. Recently, vitexin compound has been the talk amongst researchers due to its pharmacological properties as anti-inflammation and anti-AD. However, the epigenetic mechanism of the compound in regulating the neuroinflammation activity is yet to be fully elucidated. Hence, this review discusses the potential of vitexin compound to have the pharmacoepigenetic property in regulating the neuroinflammation activity in relation to AD. It is with hope that the review would unveil the potential of vitexin as the candidate in treating AD.

Inhibitory Effects of Myricetin on Lipopolysaccharide-Induced Neuroinflammation

Microglial activation elicits an immune response by producing proinflammatory modulators and cytokines that cause neurodegeneration. Therefore, a plausible strategy to prevent neurodegeneration is to inhibit neuroinflammation caused by microglial activation. Myricetin, a natural flavanol, induces neuroprotective effects by inhibiting inflammation and oxidative stress. However, whether myricetin inhibits lipopolysaccharide (LPS)-induced neuroinflammation in hippocampus and cortex regions is not known. To test this, we examined the effects of myricetin on LPS-induced neuroinflammation in a microglial BV2 cell line. We found that myricetin significantly downregulated several markers of the neuroinflammatory response in LPS-induced activated microglia, including inducible nitric oxide (NO) synthase (iNOS), cyclooxygenase-2 (COX-2), and proinflammatory modulators and cytokines such as prostaglandin E2 (PGE₂), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α). Moreover, myricetin suppressed the expression of c-Jun NH2-terminal kinase (JNK), p38 MAPK, and extracellular signal-regulated kinase (ERK), which are components of the mitogen-activated protein kinase (MAPK) signaling pathway. Furthermore, myricetin inhibited LPS-induced macrophages and microglial activation in the hippocampus and cortex of mice. Based on our results, we suggest that myricetin inhibits neuroinflammation in BV2 microglia by inhibiting the MAPK signaling pathway and the production of proinflammatory modulators and cytokines. Therefore, this could potentially be used for the treatment of neuroinflammatory diseases.

Natural Flavonol, Myricetin, Enhances the Function and Survival of Cryopreserved Hepatocytes In Vitro and In Vivo

To improve the therapeutic potential of hepatocyte transplantation, the effects of the mitogen-activated protein kinase kinase 4 (MKK4) inhibitor, myricetin (3,3′,4′,5,5′,7-hexahydroxylflavone) were examined using porcine and human hepatocytes in vitro and in vivo. Hepatocytes were cultured, showing the typical morphology of hepatic parenchymal cell under 1–10 µmol/L of myricetin, keeping hepatocyte specific gene expression, and ammonia removal activity. After injecting the hepatocytes into neonatal Severe combined immunodeficiency (SCID) mouse livers, cell colony formation was found at 10–15 weeks after transplantation. The human albumin levels in the sera of engrafted mice were significantly higher in the recipients of myricetin-treated cells than non-treated cells, corresponding to the size of the colonies. In terms of therapeutic efficacy, the injection of myricetin-treated hepatocytes significantly prolonged the survival of ornithine transcarbamylase-deficient SCID mice from 32 days (non-transplant control) to 54 days. Biochemically, the phosphorylation of MKK4 was inhibited in the myricetin-treated hepatocytes. These findings suggest that myricetin has a potentially therapeutic benefit that regulates hepatocyte function and survival, thereby treating liver failure.

Myricetin ameliorates high glucose-induced endothelial dysfunction in human umbilical vein endothelial cells

Endothelial dysfunction is recognized as the initial detectable stage of cardiovascular disease, a serious complication of diabetes. In this study, we evaluated effects of myricetin on high glucose (HG)-elicited oxidative damage in human umbilical vein endothelial cells (HUVECs). The cells were pre-incubated with myricetin and then treated with HG to induce apoptosis. The effect of myricetin on viability was investigated by MTT assay. The levels of lipid peroxidation (LPO) were determined by thiobarbituric acid (TBA) method. The protein expression of Bax, Bcl-2 and caspase-3 was measured by western blot analysis. Moreover, the effect of myricetin on total antioxidant capacity (TAC) and total thiol molecules was also determined. Our results showed that myricetin was able to markedly restore the viability of endothelial cells under oxidative stress. Myricetin reduced HG-caused increase in LPO levels. Also, TAC and total thiol molecules were notably elevated by myricetin. Incubation with myricetin decreased the protein expression levels of Bax, whereas it increased the expression levels of the Bcl-2, compared with HG treatment alone. Furthermore, myricetin significantly decreased cleaved caspase-3 protein expression. It is concluded that myricetin may protect HUVECs from oxidative stress induced by HG via increasing cell TAC and reducing Bax/Bcl-2 protein ratio, and caspase-3 expression.

Amelioration of Mitochondrial Quality Control and Proteostasis by Natural Compounds in Parkinson's Disease Models

Parkinson’s disease (PD) is a well-known age-related neurodegenerative disorder associated with longer lifespans and rapidly aging populations. The pathophysiological mechanism is a complex progress involving cellular damage such as mitochondrial dysfunction and protein homeostasis. Age-mediated degenerative neurological disorders can reduce the quality of life and also impose economic burdens. Currently, the common treatment is replacement with levodopa to address low dopamine levels; however, this does not halt the progression of PD and is associated with adverse effects, including dyskinesis. In addition, elderly patients can react negatively to treatment with synthetic neuroprotection agents. Recently, natural compounds such as phytochemicals with fewer side effects have been reported as candidate treatments of age-related neurodegenerative diseases. This review focuses on mitochondrial dysfunction, oxidative stress, hormesis, proteostasis, the ubiquitin‒proteasome system, and autophagy (mitophagy) to explain the neuroprotective effects of using natural products as a therapeutic strategy. We also summarize the efforts to use natural extracts to develop novel pharmacological candidates for treatment of age-related PD.

Dietary myricetin intake is inversely associated with the prevalence of type 2 diabetes mellitus in a Chinese population

Myricetin is a natural plant-derived inhibitor for α-glucosidase and α-amylase and possesses strong antioxidant activity. Myricetin is reported to be effective in treating many symptoms that are associated with type 2 diabetes mellitus (T2DM), therefore, we hypothesized that myricetin plays a preventive role in the development of T2DM. To test this hypothesis, we designed a cross-sectional population study, which included 24 138 subjects, with 1357 of them diagnosed with T2DM. A validated 100-item food frequency questionnaire was used to collect dietary information. Daily intakes of myricetin and nutrients were calculated, based on the Chinese food composition tables. Multiple logistic regression analysis models were used to analyze the relationship between the quartiles of myricetin intake and the prevalence of T2DM. We found that, in this Chinese population, the daily intake of myricetin was 120.5 ± 95.7 mg, with apple, peach, orange, pineapple, and sweet potato being the main food sources. Significant inverse trends were observed between intakes of myricetin and prevalence of T2DM in multivariable models (all p-trend <0.0001). The odds ratios (95% CI) for T2DM across the ascending quartiles of myricetin intake were: 1.00 (reference), 0.73 (0.61, 0.87), 0.61 (0.50, 0.75), and 0.51 (0.40, 0.64). This study showed that myricetin intake was inversely related to the prevalence of T2DM in this Chinese population, suggesting a protective effect of myricetin in the development of T2DM.

Regulation of Toll-Like Receptor (TLR) Signaling Pathway by Polyphenols in the Treatment of Age-Linked Neurodegenerative Diseases: Focus on TLR4 Signaling

Neuronal dysfunction initiates several intracellular signaling cascades to release different proinflammatory cytokines and chemokines, as well as various reactive oxygen species. In addition to neurons, microglia, and astrocytes are also affected by this signaling cascade. This release can either be helpful, neutral or detrimental for cell survival. Toll-like receptors (TLRs) activate and signal their downstream pathway to activate NF-κB and pro-IL-1β, both of which are responsible for neuroinflammation and linked to the pathogenesis of different age-related neurological conditions. However, herein, recent aspects of polyphenols in the treatment of neurodegenerative diseases are assessed, with a focus on TLR regulation by polyphenols. Different polyphenol classes, including flavonoids, phenolic acids, phenolic alcohols, stilbenes, and lignans can potentially target TLR signaling in a distinct pathway. Further, some polyphenols can suppress overexpression of inflammatory mediators through TLR4/NF-κB/STAT signaling intervention, while others can reduce neuronal apoptosis via modulating the TLR4/MyD88/NF-κB-pathway in microglia/macrophages. Indeed, neurodegeneration etiology is complex and yet to be completely understood, it may be that targeting TLRs could reveal a number of molecular and pharmacological aspects related to neurodegenerative diseases. Thus, activating TLR signaling modulation via natural resources could provide new therapeutic potentiality in the treatment of neurodegeneration.

Myricetin Protects Against High Glucose-Induced β-Cell Apoptosis by Attenuating Endoplasmic Reticulum Stress via Inactivation of Cyclin-Dependent Kinase 5

BACKGROUND

Chronic hyperglycemia has deleterious effects on pancreatic β-cell function and turnover. Recent studies support the view that cyclin-dependent kinase 5 (CDK5) plays a role in β-cell failure under hyperglycemic conditions. However, little is known about how CDK5 impair β-cell function. Myricetin, a natural flavonoid, has therapeutic potential for the treatment of type 2 diabetes mellitus. In this study, we examined the effect of myricetin on high glucose (HG)-induced β-cell apoptosis and explored the relationship between myricetin and CDK5.

METHODS

To address this question, we subjected INS-1 cells and isolated rat islets to HG conditions (30 mM) in the presence or absence of myricetin. Docking studies were conducted to validate the interaction between myricetin and CDK5. Gene expression and protein levels of endoplasmic reticulum (ER) stress markers were measured by real-time reverse transcription polymerase chain reaction and Western blot analysis.

RESULTS

Activation of CDK5 in response to HG coupled with the induction of ER stress via the down regulation of sarcoendoplasmic reticulum calcium ATPase 2b (SERCA2b) gene expression and reduced the nuclear accumulation of pancreatic duodenal homeobox 1 (PDX1) leads to β-cell apoptosis. Docking study predicts that myricetin inhibit CDK5 activation by direct binding in the ATP-binding pocket. Myricetin counteracted the decrease in the levels of PDX1 and SERCA2b by HG. Moreover, myricetin attenuated HG-induced apoptosis in INS-1 cells and rat islets and reduce the mitochondrial dysfunction by decreasing reactive oxygen species production and mitochondrial membrane potential (ΔΨm) loss.

CONCLUSION

Myricetin protects the β-cells against HG-induced apoptosis by inhibiting ER stress, possibly through inactivation of CDK5 and consequent upregulation of PDX1 and SERCA2b.

RNAi-mediated knockdown of DJ-1 leads to mitochondrial dysfunction via Akt/GSK-3ß and JNK signaling pathways in dopaminergic neuron-like cells

Deletions or some mutations in the gene encoding the multifunctional protein, DJ-1, have been considered to be linked with autosomal recessive early onset Parkinson's disease (PD). Current emerging evidence suggests that DJ-1 is involved in the protection against oxidative stress-induced mitochondrial damage. However, the exact molecular mechanisms underlying this are not completely clear. The aim of this study was to investigate the effects of DJ-1 on the Akt pathway, nuclear factor erythroid 2-related factor (Nrf2), and c-Jun N-terminal kinase (JNK) with regard to modulating mitochondrial function. Here we showed that knockdown of DJ-1 resulted in mitochondrial dysfunction, including a decrease in active mitochondrial mass, complex I deficits, and inhibition of cellular adenosine 5'-triphosphate (ATP) content in the dopaminergic neuron-like cells PC12 and SH-SY5Y. Additionally, loss of DJ-1 impaired Akt signaling, and reduced nuclear translocation of Nrf2, thereby inhibiting activity of Nrf2-regulated downstream antioxidant enzymes such as heme oxygenase-1 and NAD(P)H quinone oxidoreductase 1. Moreover, DJ-1 knockdown also led to a significant increase in the mitochondrial reactive oxygen species, and then promoted the activation of JNK pathways. Furthermore, oxidative stress and mitochondrial dysfunction induced by knockdown of DJ-1 were blocked by a JNK inhibitor, which confirmed the important role of JNK activation in mitochondrial dysfunction. In conclusion, the present study indicates that DJ-1 knockdown leads to mitochondrial dysfunction in dopaminergic neuron-like cells, at least in part, through suppressing the Akt/GSK3β pathway and impairing the oxidative stress response, as well as through the subsequent increased JNK activation in dopaminergic neuron-like cells.

A Brief Review on the Neuroprotective Mechanisms of Vitexin

The neural dysfunction is triggered by cellular and molecular events that provoke neurotoxicity and neural death. Currently, neurodegenerative diseases are increasingly common, and available treatments are focused on relieving symptoms. Based on the above, in this review we describe the participation of vitexin in the main events involved in the neurotoxicity and cell death process, as well as the use of vitexin as a therapeutic approach to suppress or attenuate neurodegenerative progress. Vitexin contributes to increasing neuroprotective factors and pathways and counteract the targets that induce neurodegeneration, such as redox imbalance, neuroinflammation, abnormal protein aggregation, and reduction of cognitive and/or motor impairment. The results obtained provide substantial evidence to support the scientific exploration of vitexin in these pathologies, since their effects are still little explored for this direction.

Synergistic antimetastatic effect of cotreatment with licochalcone A and sorafenib on human hepatocellular carcinoma cells through the inactivation of MKK4/JNK and uPA expression

To improve the clinical outcome of tumor chemotherapy, more effective combination treatments against tumor metastasis and recurrence are required. Licochalcone A (LicA) is the root of Glycyrrhiza inflata and has been reported to possess anti-inflammatory, antimicrobial, and antitumor effects. Sorafenib (Sor), a multikinase inhibitor, is used to treat patients with solid tumors such as advanced hepatocellular carcinoma (HCC). However, the synergistic effects of LicA and Sor on the metastasis of human HCC cells have not been reported. We found that LicA and Sor did not have cytotoxic effects or arrest growth in human SK-Hep-1 and Huh-7 cells. In addition, treatment with LicA or Sor alone inhibited migration and invasion in human SK-Hep-1 and Huh-7 HCC cells. Furthermore, cotreatment with LicA and Sor synergistically inhibited the migration and invasion of HCC cells and significantly inhibited uPA protein expression. Notably, cotreatment of LicA and Sor synergistically and significantly downregulated MKK4-JNK expression. Through tail vein injection in nude mice, the aforementioned cotreatment synergistically suppressed SK-Hep-1 cell-mediated lung metastasis. These findings first revealed the synergistic effects of LicA and Sor cotreatment against human HCC cells, further suggesting that beneficial effects on tumor regression could be confirmed through prospective clinical trials.

Effect of Zishenpingchan granule prepared from Chinese medicinal substances on the c-Jun N-terminal protein kinase pathway in mice with Parkinson's disease induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

OBJECTIVE

To investigate the regulatory mechanism of the c-Jun N-terminal protein kinase (JNK) signaling pathway in substantia nigra (SN) dopaminergic neurons inflammation and apoptosis, and the neuroprotective effect of Zishenpingchan granules in mice with Parkinson's disease (PD) induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP).

METHODS

PD model mice were established by intraperitoneally injecting MPTP. Sixty mice were divided into a model group, Traditional Chinese Medicine (TCM) group and control group. The mice of the TCM group were administered Zishenpingchan granules 7 days before PD induction. Seven days after PD induction, we examined locomotor activity, and performed the rotarod test and swimming test, to evaluate limb movement function. Furthermore, we used immunohistochemistry and western blotting to examine the expression of tyrosine hydroxylase (TH), cyclooxygenase-2 (Cox-2), caspase-3 and p-JNK. The terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method was used to examine neuron apoptosis in the SN.

RESULTS

Compared with the control group, the mean score of locomotor activity, rotarod test and swimming test was significantly lower in the model group (P < 0.05); the TH-positive neuron expression was significantly decreased in the SN pars compacta (SNpc); the protein expression levels of Cox-2, caspase-3 and p-JNK was obviously increased; and the number of TUNEL-positive neurons in the SN was increased (P < 0.01). Compared with the model group, the mean score of neurobehavioral tests in the TCM group was obviously higher, the loss of TH-positive neurons ignificantly decreased, the protein expression levels of Cox-2, caspase-3 and p-JNK obviously decreased, and the number of TUNEL- positive neurons in the SN clearly decreased (P < 0.01).

CONCLUSION

The JNK pathway plays an important role in the regulation of inflammation and apoptosis in nigral cells in PD mice. TCM can suppress the over-activation of the JNK pathway in the SN, and alleviate the inflammatory response in nigral cells and dopaminergic neuron apoptosis in PD mice.

Interleukin-6 regulates iron-related proteins through c-Jun N-terminal kinase activation in BV2 microglial cell lines

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the loss of dopaminergic (DA) neurons in the substantia nigra (SN) and subsequent DA depletion in the striatum. Microglia activation and nigral iron accumulation play important roles in the pathogenesis of PD. Activated microglia show increased iron deposits. However, the relationship between microglia activation and iron accumulation remains unclear. In the present study, we aimed to determine how iron levels affect interleukin-6 (IL-6) synthesis, and the effect of IL-6 on cellular iron metabolism in BV2 microglial cells.IL-6 mRNA was up-regulated after FAC treatment for 12 h in BV2 cells. Iron regulatory protein 1 (IRP1) and divalent metal transporter 1 (DMT1) were up-regulated and iron exporter ferroportin 1 (FPN1) was down-regulated in BV2 cells after 24 h of IL-6 treatment. Phosphorylated JNK increased significantly compared to the control after BV2 cells were treated with IL-6 for 1 h. Pretreatment with SP600125 attenuated the up-regulation of IRP1 and DMT1 and down-regulation of FPN1 (compared to IL-6-treated group). These results suggest that iron load could increase IL-6 mRNA expression in BV2 cells. Further, IL-6 likely up-regulates IRP1 and DMT1 expression and down-regulates FPN1 expression in BV2 microglial cells through JNK signaling pathways.

Effect of a Traditional Chinese Herbal Medicine Formulation on Cell Survival and Apoptosis of MPP+-Treated MES 23.5 Dopaminergic Cells

Progressive degeneration of dopaminergic neurons in the substantia nigra (SN) is implicated in Parkinson's disease (PD). The efficacy of these currently used drugs is limited while traditional Chinese medicine (TCM) has been used in the management of neurodegenerative diseases for many years. This study was designed to evaluate the effect of a modified traditional Chinese herbal medicine decoction, Cong Rong Jing (CRJ), on cell survival and apoptosis of 1-methyl-4-phenylpyridinium- (MPP⁺-) treated MES23.5 dopaminergic cells. CRJ was prepared as a decoction from three Chinese herbs, namely, Herba Cistanches, Herba Epimedii, and Rhizoma Polygonati. We reported here that CRJ significantly enhanced the cell survival of MES23.5 cells after the exposure of MPP⁺ and inhibited the production of intracellular reactive oxygen species (ROS) induced by MPP⁺. CRJ also prevented the MPP⁺-treated MES23.5 cells from apoptosis by reducing the externalization of phosphatidylserine and enhancing the Bcl-2/Bax protein expression ratio. Signaling proteins such as JAK2, STAT3, and ERK1/2 were also involved in the action of CRJ. Taken together, these results provide a preliminary mechanism to support clinical application of the TCM formulation in PD and possibly other neurodegenerative diseases associated with ROS injury and apoptosis.

Neuroprotective and anti-inflammatory effects of morin in a murine model of Parkinson's disease

Parkinson's disease (PD) is one of the most common neurodegenerative disorders and is characterized by loss of dopaminergic neurons in the substantia nigra (SN). Although the causes of PD are not understood, evidence suggests that oxidative stress, mitochondrial dysfunction, and inflammation are associated with its pathogenesis. Morin (3,5,7,2',4'-pentahydroxyflavone) is a flavonol found in wine and many herbs and fruits. Previous studies have suggested that morin prevents oxidative damage and inflammation and ameliorates mitochondrial dysfunction. The present study describes the neuroprotective effects of morin in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of PD, and we report the results of our investigation into its neuroprotective mechanism in primary neurons and astrocytes. In the mouse model, morin pretreatment ameliorated motor dysfunction, protected against dopaminergic neuronal losses in SN and striatum, and alleviated MPTP-induced astrocyte activation. In vitro studies revealed that morin protected primary cultured neurons against 1-methyl-4-phenylpyridine (MPP(+) )-mediated reactive oxygen species production and mitochondrial membrane potential (MMP) disruption. In addition, morin effectively reduced MPP(+) -induced astroglial activation and nuclear translocation of nuclear factor-κB in primary cultured astrocytes. These results indicate that morin acts via multiple neuroprotective mechanisms in our mouse model and suggest that morin be viewed as a potential treatment and preventative for PD. © 2016 Wiley Periodicals, Inc.

Flavonoid myricetin inhibits TNF-α-stimulated production of inflammatory mediators by suppressing the Akt, mTOR and NF-κB pathways in human keratinocytes

Flavonoid myricetin has been shown to exhibit anti-inflammatory and anti-oxidant effects. Nevertheless, the effect of myricetin on the TNF-α-stimulated production of inflammatory mediators in keratinocytes has not been studied. Using human keratinocytes, we examined the effect of myricetin on the TNF-α-stimulated production of inflammatory mediators in relation to the Akt, mTOR and NF-κB pathways, which regulate the transcription genes involved in immune and inflammatory responses. TNF-α stimulated production of the inflammatory mediators and reactive oxygen species in keratinocytes, and activation of the Akt, mTOR and NF-κB pathways in HaCaT cells and primary keratinocytes. Myricetin, Akt inhibitor, Bay 11-7085 (an inhibitor of NF-κB activation), rapamycin (mTOR inhibitor) and N-acetylcysteine attenuated TNF-α-induced activation of Akt, mTOR and NF-κB. Myricetin and N-acetylcysteine attenuated the TNF-α-stimulated production of cytokines and chemokines, and production of reactive oxygen species in keratinocytes. The results show that myricetin may reduce TNF-α-stimulated inflammatory mediator production in keratinocytes by suppressing the activation of the Akt, mTOR and NF-κB pathways. The effect of myricetin appears to be associated with inhibition of the production of reactive oxygen species. Further, myricetin appears to attenuate the proinflammatory mediator-induced inflammatory skin diseases.

Myricetin: A Dietary Molecule with Diverse Biological Activities

Myricetin is a common plant-derived flavonoid and is well recognised for its nutraceuticals value. It is one of the key ingredients of various foods and beverages. The compound exhibits a wide range of activities that include strong anti-oxidant, anticancer, antidiabetic and anti-inflammatory activities. It displays several activities that are related to the central nervous system and numerous studies have suggested that the compound may be beneficial to protect against diseases such as Parkinson's and Alzheimer's. The use of myricetin as a preserving agent to extend the shelf life of foods containing oils and fats is attributed to the compound's ability to protect lipids against oxidation. A detailed search of existing literature revealed that there is currently no comprehensive review available on this important molecule. Hence, the present work includes the history, synthesis, pharmaceutical applications and toxicity studies of myricetin. This report also highlights structure-activity relationships and mechanisms of action for various biological activities.

Protective Effects of Streblus asper Leaf Extract on H2O2-Induced ROS in SK-N-SH Cells and MPTP-Induced Parkinson's Disease-Like Symptoms in C57BL/6 Mouse

This study investigated the effects of Streblus asper leaf extract (SA) on reactive oxygen species (ROS) in SK-N-SH cell culture and on motor functions and behaviors in MPTP-treated C57BL/6 mice. SK-N-SH cell viability after incubation with SA for 24 h was measured by MTT assay. Intracellular ROS levels of SK-N-SH cells were quantified after pretreatment with SA (0, 200, 600, and 1000 µg/mL) in the presence of H2O2 (300 µM). Male C57BL/6 mice were force-fed with water or 200 mg/kg/day SA for 32 days. Intraperitoneal injection of MPTP was used to induce Parkinson's disease-like symptoms. Catalepsy, beam balance ability, olfactory discrimination, social recognition, and spontaneous locomotor activity were assessed on days 19, 21, 23, 26, and 32, respectively. In cell culture, SA at 200, 600, and 1000 µg/mL significantly decreased ROS levels in H2O2-treated SK-N-SH cells. MPTP-treated C57BL/6 mice showed a significant change in all parameters tested when compared to the control group. Pretreatment and concurrent treatment with 200 mg/kg/day SA could antagonize the motor and cognitive function deficits induced by MPTP. The results show that SA possesses anti-Parkinson effects in MPTP-treated C57BL/6 mice and that reduction in ROS levels might be one of the mechanisms.

Myricetin Attenuates Depressant-Like Behavior in Mice Subjected to Repeated Restraint Stress

Increasing evidence has shown that oxidative stress may be implicated in chronic stress-induced depression. Several flavonoids with anti-oxidative effects have been proved to be anti-depressive. Myricetin is a well-defined flavonoid with the anti-oxidative, anti-inflammatory, anti-apoptotic, and neuroprotective properties. The aim of the present study is to investigate the possible effects of chronic administration of myricetin on depressant-like behaviors in mice subjected to repeated restraint (4 h/day) for 21 days. Our results showed that myricetin administration specifically reduced the immobility time in mice exposed to chronic stress, as tested in both forced swimming test and tail suspension test. Myricetin treatment improved activities of glutathione peroxidase (GSH-PX) in the hippocampus of stressed mice. In addition, myricetin treatment decreased plasma corticosterone levels of those mice subjected to repeated restraint stress. The effects of myricetin on the brain-derived neurotrophic factor (BDNF) levels in hippocampus were also investigated. The results revealed that myricetin normalized the decreased BDNF levels in mice subjected to repeated restraint stress. These findings provided more evidence that chronic administration of myricetin improves helpless behaviors. The protective effects of myricetin might be partially mediated by an influence on BDNF levels and might be attributed to myricetin-mediated anti-oxidative stress in the hippocampus.

Protective Mechanisms of Flavonoids in Parkinson's Disease

Parkinson's disease is a chronic, debilitating neurodegenerative movement disorder characterized by progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta region in human midbrain. To date, oxidative stress is the well accepted concept in the etiology and progression of Parkinson's disease. Hence, the therapeutic agent is targeted against suppressing and alleviating the oxidative stress-induced cellular damage. Within the past decades, an explosion of research discoveries has reported on the protective mechanisms of flavonoids, which are plant-based polyphenols, in the treatment of neurodegenerative disease using both in vitro and in vivo models. In this paper, we have reviewed the literature on the neuroprotective mechanisms of flavonoids in protecting the dopaminergic neurons hence reducing the symptoms of this movement disorder. The mechanism reviewed includes effect of flavonoids in activation of endogenous antioxidant enzymes, suppressing the lipid peroxidation, inhibition of inflammatory mediators, flavonoids as a mitochondrial target therapy, and modulation of gene expression in neuronal cells.