Baicalein prevents 6-hydroxydopamine-induced mitochondrial dysfunction in SH-SY5Y cells via inhibition of mitochondrial oxidation and up-regulation of DJ-1 protein expression

Effectiveness of Flavonoid-Rich Diet in Alleviating Symptoms of Neurodegenerative Diseases

Over the past decades, there has been a significant increase in the burden of neurological diseases, including neurodegenerative disorders, on a global scale. This is linked to a widespread demographic trend in which developed societies are aging, leading to an increased proportion of elderly individuals and, concurrently, an increase in the number of those afflicted, posing one of the main public health challenges for the coming decades. The complex pathomechanisms of neurodegenerative diseases and resulting varied symptoms, which differ depending on the disease, environment, and lifestyle of the patients, make searching for therapies for this group of disorders a formidable challenge. Currently, most neurodegenerative diseases are considered incurable. An important aspect in the fight against and prevention of neurodegenerative diseases may be broadly understood lifestyle choices, and more specifically, what we will focus on in this review, a diet. One proposal that may help in the fight against the spread of neurodegenerative diseases is a diet rich in flavonoids. Flavonoids are compounds widely found in products considered healthy, such as fruits, vegetables, and herbs. Many studies indicated not only the neuroprotective effects of these compounds but also their ability to reverse changes occurring during the progression of diseases such as Alzheimer's, Parkinson's and amyotrophic lateral sclerosis. Here, we present the main groups of flavonoids, discussing their characteristics and mechanisms of action. The most widely described mechanisms point to neuroprotective functions due to strong antioxidant and anti-inflammatory effects, accompanied with their ability to penetrate the blood-brain barrier, as well as the ability to inhibit the formation of protein aggregates. The latter feature, together with promoting removal of the aggregates is especially important in neurodegenerative diseases. We discuss a therapeutic potential of selected flavonoids in the fight against neurodegenerative diseases, based on in vitro studies, and their impact when included in the diet of animals (laboratory research) and humans (population studies). Thus, this review summarizes flavonoids' actions and impacts on neurodegenerative diseases. Therapeutic use of these compounds in the future is potentially possible but depends on overcoming key challenges such as low bioavailability, determining the therapeutic dose, and defining what a flavonoid-rich diet is and determining its potential negative effects. This review also suggests further research directions to address these challenges.

The role of sphingosine-1-phosphate in the development and progression of Parkinson's disease

Parkinson's disease (PD) could be viewed as a proteinopathy caused by changes in lipids, whereby modifications in lipid metabolism may lead to protein alterations, such as the accumulation of alpha-synuclein (α-syn), ultimately resulting in neurodegeneration. Although the loss of dopaminergic neurons in the substantia nigra is the major clinical manifestation of PD, the etiology of it is largely unknown. Increasing evidence has highlighted the important role of lipids in the pathophysiology of PD. Sphingosine-1-phosphate (S1P), a signaling lipid, has been suggested to have a potential association with the advancement and worsening of PD. Therefore, better understanding the mechanisms and regulatory proteins is of high interest. Most interestingly, S1P appears to be an important target to offers a new strategy for the diagnosis and treatment of PD. In this review, we first introduce the basic situation of S1P structure, function and regulation, with a special focus on the several pathways. We then briefly describe the regulation of S1P signaling pathway on cells and make a special focused on the cell growth, proliferation and apoptosis, etc. Finally, we discuss the function of S1P as potential therapeutic target to improve the clinical symptoms of PD, and even prevent the progression of the PD. In the context of PD, the functions of S1P modulators have been extensively elucidated. In conclusion, S1P modulators represent a novel and promising therapeutic principle and therapeutic method for PD. However, more research is required before these drugs can be considered as a standard treatment option for PD.

Herbal and Natural Treatments for the Management of the Glaucoma: An Update

Glaucoma causes the degeneration of the retinal ganglion cells (RGCs) and their axons, inducing a tissue reshaping that affects both the retina and the optic nerve head. Glaucoma care especially focuses on reducing intraocular pressure, a significant risk factor for progressive damage to the optic nerve. The use of natural treatments, such as herbs, vitamins, and minerals, is becoming increasingly popular today. While plants are a rich source of novel biologically active compounds, only a small percentage of them have been phytochemically examined and evaluated for their medicinal potential. It is necessary for eye care professionals to inform their glaucoma patients about the therapy, protection, and efficacy of commonly used herbal medicines, considering the widespread use of herbal medicines. The purpose of this review is to examine evidence related to the most widely used herbal medicines for the management and treatment of glaucoma, to better understand the potential benefits of these natural compounds as supplementary therapy.

Citronellol Prevents 6-OHDA-Induced Oxidative Stress, Mitochondrial Dysfunction, and Apoptosis in Parkinson Disease Model of SH-SY5Y Cells via Modulating ROS-NO, MAPK/ERK, and PI3K/Akt Signaling Pathways

Parkinson disease is a neurodegenerative disorder distinguished by dopaminergic shortage in the striatum and the accumulation of α-synuclein neuronal aggregates in the brains of patients. Since, there is no accurate treatment available for Parkinson disease, researches are designed to alleviate the pathognomonic symptoms such as neuroinflammation, oxidative stress, mitochondrial dysfunction, and apoptosis. Accordingly, a number of compounds have been reported to inhibit these pathognomonic symptoms. In this study, we have assessed the neuroprotective potential of citronellol against 6-OHDA-induced neurotoxicity in SH-SY5Y cells. The results found that citronellol treatment effectively hindered the cell death caused by 6-OHDA and thereby maintaining the cell viability in SH-SY5Y cells at 50 µg/mL concentration. As expected, the citronellol treatment significantly reduced the 6-OHDA-induced secretion of inflammatory factors (IL-1β, IL-6, and TNF-α), which was obtained through ELISA technique. Similarly, citronellol hindered the 6-OHDA-induced oxidative stress by lowering the intracellular ROS and NO level and MDA leakage along with increased expression of SOD level in SH-SY5Y cells. The JC-1 staining showed that 6-OHDA increased the number of green fluorescent dots with ruptured mitochondrial membrane potential, while citronellol increased the amount of red fluorescent, showing the rescue potential against the 6-OHDA-induced mitochondrial dysfunction. Furthermore, citronellol hampered the 6-OHDA-induced apoptosis via the suppression of Bcl-2/Bax pathway. The western blotting results hypothesized that citronellol rescued SH-SY5Y cells from 6-OHDA-induced neurotoxicity via modulating ROS-NO, MAPK/ERK, and PI3K/Akt signaling pathways. However, further clinical trials are required to verify the anti-Parkinson efficacy.

Mechanistic Effects of Baicalein on Aqueous Humor Drainage and Intraocular Pressure

Elevated intraocular pressure (IOP) is a major risk factor for glaucoma that results from impeded fluid drainage. The increase in outflow resistance is caused by trabecular meshwork (TM) cell dysfunction and excessive extracellular matrix (ECM) deposition. Baicalein (Ba) is a natural flavonoid and has been shown to regulate cell contraction, fluid secretion, and ECM remodeling in various cell types, suggesting the potential significance of regulating outflow resistance and IOP. We demonstrated that Ba significantly lowered the IOP by about 5 mmHg in living mice. Consistent with that, Ba increased the outflow facility by up to 90% in enucleated mouse eyes. The effects of Ba on cell volume regulation and contractility were examined in primary human TM (hTM) cells. We found that Ba (1–100 µM) had no effect on cell volume under iso-osmotic conditions but inhibited the regulatory volume decrease (RVD) by up to 70% under hypotonic challenge. In addition, Ba relaxed hTM cells via reduced myosin light chain (MLC) phosphorylation. Using iTRAQ-based quantitative proteomics, 47 proteins were significantly regulated in hTM cells after a 3-h Ba treatment. Ba significantly increased the expression of cathepsin B by 1.51-fold and downregulated the expression of D-dopachrome decarboxylase and pre-B-cell leukemia transcription factor-interacting protein 1 with a fold-change of 0.58 and 0.40, respectively. We suggest that a Ba-mediated increase in outflow facility is triggered by cell relaxation via MLC phosphorylation along with inhibiting RVD in hTM cells. The Ba-mediated changes in protein expression support the notion of altered ECM homeostasis, potentially contributing to a reduction of outflow resistance and thereby IOP.

Scutellaria baicalensis and its constituents baicalin and baicalein as antidotes or protective agents against chemical toxicities: a comprehensive review

Scutellaria baicalensis (SB), also known as the Chinese skullcap, has a long history of being used in Chinese medicine to treat a variety of conditions ranging from microbial infections to metabolic syndrome and malignancies. Numerous studies have reported that treatment with total SB extract or two main flavonoids found in its root and leaves, baicalin (BA) and baicalein (BE), can prevent or alleviate the detrimental toxic effects of exposure to various chemical compounds. It has been shown that BA and BE are generally behind the protective effects of SB against toxicants. This paper aimed to review the protective and therapeutic effects of SB and its main components BA and BE against chemical compounds that can cause intoxication after acute or chronic exposure and seriously affect different vital organs including the brain, heart, liver, and kidneys. In this review paper, we had a look into a total of 221 in vitro and in vivo studies from 1995 to 2021 from the scientific databases PubMed, Scopus, and Web of Science which reported protective or therapeutic effects of BA, BE, or SB against drugs and chemicals that one might be exposed to on a professional or accidental basis and compounds that are primarily used to simulate disease models. In conclusion, the protective effects of SB and its flavonoids can be mainly attributed to increase in antioxidants enzymes, inhibition of lipid peroxidation, reduction of inflammatory cytokines, and suppression of apoptosis pathway.

The Protective Effect of a Unique Mix of Polyphenols and Micronutrients against Neurodegeneration Induced by an In Vitro Model of Parkinson’s Disease

Parkinson’s disease (PD) is second-most common disabling neurological disorder worldwide, and unfortunately, there is not yet a definitive way to prevent it. Polyphenols have been widely shown protective efficacy against various PD symptoms. However, data on their effect on physio-pathological mechanisms underlying this disease are still lacking. In the present work, we evaluated the activity of a mixture of polyphenols and micronutrients, named A5⁺, in the murine neuroblastoma cell line N1E115 treated with 6-Hydroxydopamine (6-OHDA), an established neurotoxic stimulus used to induce an in vitro PD model. We demonstrate that a pretreatment of these cells with A5⁺ causes significant reduction of inflammation, resulting in a decrease in pro-inflammatory cytokines (IFN-γ, IL-6, TNF-α, and CXCL1), a reduction in ROS production and activation of extracellular signal-regulated kinases (ERK)1/2, and a decrease in apoptotic mechanisms with the related increase in cell viability. Intriguingly, A5⁺ treatment promoted cellular differentiation into dopaminergic neurons, as evident by the enhancement in the expression of tyrosine hydroxylase, a well-established dopaminergic neuronal marker. Overall, these results demonstrate the synergic and innovative efficacy of A5⁺ mixture against PD cellular pathological processes, although further studies are needed to clarify the mechanisms underlying its beneficial effect.

Inhibitory Mechanism of Baicalein on Acetylcholinesterase: Inhibitory Interaction, Conformational Change, and Computational Simulation

Alzheimer’s disease (AD) is the most prevalent chronic neurodegenerative disease in elderly individuals, causing dementia. Acetylcholinesterase (AChE) is regarded as one of the most popular drug targets for AD. Herbal secondary metabolites are frequently cited as a major source of AChE inhibitors. In the current study, baicalein, a typical bioactive flavonoid, was found to inhibit AChE competitively, with an associated IC₅₀ value of 6.42 ± 0.07 µM, through a monophasic kinetic process. The AChE fluorescence quenching by baicalein was a static process. The binding constant between baicalein and AChE was an order of magnitude of 10⁴ L mol⁻¹, and hydrogen bonding and hydrophobic interaction were the major forces for forming the baicalein−AChE complex. Circular dichroism analysis revealed that baicalein caused the AChE structure to shrink and increased its surface hydrophobicity by increasing the α-helix and β-turn contents and decreasing the β-sheet and random coil structure content. Molecular docking revealed that baicalein predominated at the active site of AChE, likely tightening the gorge entrance and preventing the substrate from entering and binding with the enzyme, resulting in AChE inhibition. The preceding findings were confirmed by molecular dynamics simulation. The current study provides an insight into the molecular-level mechanism of baicalein interaction with AChE, which may offer new ideas for the research and development of anti-AD functional foods and drugs.

Inhibition of γH2AX, COX-2 and regulation of antioxidant enzymes in MPP+-exposed SH-SY5Y cells pre-treated with rutin

Many plant-derived bioactive compounds such as rutin are reportedly effective in attenuating neuronal death in most neurodegenerative disorders. Parkinson's disease (PD) is characterized by the gradual degeneration of dopaminergic neurons in the substantia nigra of the midbrain, and has previously been modelled in-vitro through the specific neurotoxic activity of 1-methyl-4-phenylpyridinium (MPP⁺) on dopaminergic neurons. Rutin is a bioflavonoid with multiple pharmacological effects, and this study investigated the neuroprotective effects of rutin in the human dopaminergic SH-SY5Y cell line using the neurotoxin MPP⁺. SH-SY5Y cells pretreated with rutin, were exposed to MPP⁺ and evaluated for cell viability, nitric oxide (NO), reactive oxygen species (ROS) and antioxidant enzymes activities. In addition, western blot techniques were used to determine the protein expression levels of γH2AX and COX-2. Rutin significantly attenuated MPP⁺-induced loss of cell viability, mitigated ROS and NO production and inhibited the disruption of antioxidant enzymes activity. It was also observed that rutin significantly reduced protein expression levels of γH2AX and COX-2 in SH-SY5Y cells treated with MPP⁺. Taken together, findings from this study tend to suggest that rutin is a promising neuroprotective compound for the treatment of PD through its effects on some of the mechanisms that characterize this neurodegenerative disease.

A novel yeast-based screening system for potential compounds that can alleviate human α-synuclein toxicity

Aims

This study aimed to establish a yeast‐based screening system for potential compounds that can alleviate the toxicity of α‐synuclein (α‐syn), a neuropathological hallmark of Parkinson’s disease, either inhibition of α‐syn aggregation or promotion of ubiquitin‐mediated degradation of α‐syn.

Methods and Results

A powerful yeast‐based screening assay using the rsp5^A401E‐mutant strain, which is hypersensitive to α‐syn aggregation, was established by two‐step gene replacement and further overexpressed the GFP‐fused α‐syn in the drug‐sensitive yeast strain with a galactose‐inducible multicopy plasmid. The rsp5^A401E‐mutant strain treated with baicalein, a known α‐syn aggregation inhibitor, showed better α‐syn toxicity alleviation than the same background wild type strain as accessed by comparison on the reduction kinetics of viable dye resazurin fluorometrically (λ_ex540/λ_em590 nm). The rsp5^A401E‐mutant yeast‐based assay system showed high sensitivity as it could detect as low as 3.13 µmol l⁻¹ baicalein, the concentration that lower than previously report detected by the in vitro assay.

Conclusions

Our yeast‐based system has been effective for screening potential compounds that can alleviate α‐syn toxicity with high sensitivity and specificity.

Significance and Impact of the Study

Yeast‐based assay system can be used to discover novel neuroprotective drug candidates which may be either efficiently suppress‐α‐syn aggregation or enhance ubiquitin‐dependent degradation.

Protective Activity of Aspirin Eugenol Ester on Paraquat-Induced Cell Damage in SH-SY5Y Cells

Aspirin eugenol ester (AEE) is a new pharmaceutical compound esterified by aspirin and eugenol, which has anti-inflammatory, antioxidant, and other pharmacological activities. The aim of this study was to investigate the protective effect of AEE on paraquat- (PQ-) induced cell damage of SH-SY5Y human neuroblastoma cells and its potential molecular mechanism. There was no significant change in cell viability when AEE was used alone. PQ treatment reduced cell viability in a concentration-dependent manner. However, AEE reduced the PQ-induced loss of cell viability. Flow cytometry, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), and 4′6-diamidino-2-phenylindole (DAPI) staining were used to evaluate cell apoptosis. Compared with the PQ group, AEE pretreatment could significantly inhibit PQ-induced cell damage. AEE pretreatment could reduce the cell damage of SH-SY5Y cells induced by PQ via reducing superoxide anion, intracellular reactive oxygen species (ROS), and mitochondrial ROS (mtROS) and increasing the levels of mitochondrial membrane potential (ΔΨm). At the same time, AEE could increase the activity of glutathione peroxidase (GSH-Px), catalase (CAT), and superoxide dismutase (SOD) and decrease the activity of malondialdehyde (MDA). The results showed that compared with the control group, the expression of p-PI3K, p-Akt, and Bcl-2 was significantly decreased, while the expression of caspase-3 and Bax was significantly increased in the PQ group. In the AEE group, AEE pretreatment could upregulate the expression of p-PI3K, p-Akt, and Bcl-2 and downregulate the expression of caspase-3 and Bax in SH-SY5Y cells. PI3K inhibitor LY294002 and the silencing of PI3K by shRNA could weaken the protective effect of AEE on PQ-induced SH-SY5Y cells. Therefore, AEE has a protective effect on PQ-induced SH-SY5Y cells by regulating the PI3K/Akt signal pathway to inhibit oxidative stress.

Flavonoids: Potential Candidates for the Treatment of Neurodegenerative Disorders

Neurodegenerative disorders, such as Parkinson's disease (PD), Alzheimer's disease (AD), Amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD), are the most concerning disorders due to the lack of effective therapy and dramatic rise in affected cases. Although these disorders have diverse clinical manifestations, they all share a common cellular stress response. These cellular stress responses including neuroinflammation, oxidative stress, proteotoxicity, and endoplasmic reticulum (ER)-stress, which combats with stress conditions. Environmental stress/toxicity weakened the cellular stress response which results in cell damage. Small molecules, such as flavonoids, could reduce cellular stress and have gained much attention in recent years. Evidence has shown the potential use of flavonoids in several ways, such as antioxidants, anti-inflammatory, and anti-apoptotic, yet their mechanism is still elusive. This review provides an insight into the potential role of flavonoids against cellular stress response that prevent the pathogenesis of neurodegenerative disorders.

The comprehensive study on the therapeutic effects of baicalein for the treatment of COVID-19 in vivo and in vitro

Baicalein is the main active compound of Scutellaria baicalensis Georgi, a medicinal herb with multiple pharmacological activities, including the broad anti-virus effects. In this paper, the preclinical study of baicalein on the treatment of COVID-19 was performed. Results showed that baicalein inhibited cell damage induced by SARS-CoV-2 and improved the morphology of Vero E6 cells at a concentration of 0.1 μM and above. The effective concentration could be reached after oral administration of 200 mg/kg crystal form β of baicalein in rats. Furthermore, baicalein significantly inhibited the body weight loss, the replication of the virus, and relieved the lesions of lung tissue in hACE2 transgenic mice infected with SARS-CoV-2. In LPS-induced acute lung injury of mice, baicalein improved the respiratory function, inhibited inflammatory cell infiltration in the lung, and decreased the levels of IL-1β and TNF-α in serum. In conclusion, oral administration of crystal form β of baicalein could reach its effective concentration against SARS-CoV-2. Baicalein could inhibit SARS-CoV-2-induced injury both in vitro and in vivo. Therefore, baicalein might be a promising therapeutic drug for the treatment of COVID-19.

The Role of Oxidative Stress in Parkinson's Disease

Parkinson’s disease (PD) is caused by progressive neurodegeneration of dopaminergic (DAergic) neurons with abnormal accumulation of α-synuclein in substantia nigra (SN). Studies have suggested the potential involvement of dopamine, iron, calcium, mitochondria and neuroinflammation in contributing to overwhelmed oxidative stress and neurodegeneration in PD. Function studies on PD-causative mutations of SNCA, PRKN, PINK1, DJ-1, LRRK2, FBXO7 and ATP13A2 further indicate the role of oxidative stress in the pathogenesis of PD. Therefore, it is reasonable that molecules involved in oxidative stress, such as DJ-1, coenzyme Q10, uric acid, 8-hydroxy-2’-deoxyguanosin, homocysteine, retinoic acid/carotenes, vitamin E, glutathione peroxidase, superoxide dismutase, xanthine oxidase and products of lipid peroxidation, could be candidate biomarkers for PD. Applications of antioxidants to modulate oxidative stress could be a strategy in treating PD. Although a number of antioxidants, such as creatine, vitamin E, coenzyme Q10, pioglitazone, melatonin and desferrioxamine, have been tested in clinical trials, none of them have demonstrated conclusive evidence to ameliorate the neurodegeneration in PD patients. Difficulties in clinical studies may be caused by the long-standing progression of neurodegeneration, lack of biomarkers for premotor stage of PD and inadequate drug delivery across blood–brain barrier. Solutions for these challenges will be warranted for future studies with novel antioxidative treatment in PD patients.

An Overview of Crucial Dietary Substances and Their Modes of Action for Prevention of Neurodegenerative Diseases

Neurodegenerative diseases, namely Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis, Huntington's disease, and multiple sclerosis are becoming one of the main health concerns due to the increasing aging of the world's population. These diseases often share the same biological mechanisms, including neuroinflammation, oxidative stress, and/or protein fibrillation. Recently, there have been many studies published pointing out the possibilities to reduce and postpone the clinical manifestation of these deadly diseases through lifelong consumption of some crucial dietary substances, among which phytochemicals (e.g., polyphenols) and endogenous substances (e.g., acetyl-L-carnitine, coenzyme Q10, n-3 poysaturated fatty acids) showed the most promising results. Another important issue that has been pointed out recently is the availability of these substances to the central nervous system, where they have to be present in high enough concentrations in order to exhibit their neuroprotective properties. As so, such the aim of this review is to summarize the recent findings regarding neuroprotective substances, their mechanisms of action, as well as to point out therapeutic considerations, including their bioavailability and safety for humans.

Current Therapeutic Strategies and Perspectives for Neuroprotection in Parkinson's Disease

Parkinson's disease is a progressive neurodegenerative disorder of dopaminergic striatal neurons in basal ganglia. Treatment of Parkinson's disease (PD) through dopamine replacement strategies may provide improvement in early stages and this treatment response is related to dopaminergic neuronal mass which decreases in advanced stages. This treatment failure was revealed by many studies and levodopa treatment became ineffective or toxic in chronic stages of PD. Early diagnosis and neuroprotective agents may be a suitable approach for the treatment of PD. The essentials required for early diagnosis are biomarkers. Characterising the striatal neurons, understanding the status of dopaminergic pathways in different PD stages may reveal the effects of the drugs used in the treatment. This review updates on characterisation of striatal neurons, electrophysiology of dopaminergic pathways in PD, biomarkers of PD, approaches for success of neuroprotective agents in clinical trials. The literature was collected from the articles in database of PubMed, MedLine and other available literature resources.

Ginsenoside Re Mitigates 6-Hydroxydopamine-Induced Oxidative Stress through Upregulation of GPX4

Ginsenosides are active components found abundantly in ginseng which has been used as a medicinal herb to modify disease status for thousands of years. However, the pharmacological activity of ginsenoside Re in the neuronal system remains to be elucidated. Neuroprotective activity of ginsenoside Re was investigated in SH-SY5Y cells exposed to 6-hydroxydopamine (6-OHDA) to induce cellular injury. Ginsenoside Re significantly inhibited 6-OHDA-triggered cellular damage as judged by analysis of tetrazolium dye reduction and lactose dehydrogenase release. In addition, ginsenoside Re induced the expression of the antioxidant protein glutathione peroxidase 4 (GPX4) but not catalase, glutathione peroxidase 1, glutathione reductase, or superoxide dismutase-1. Furthermore, upregulation of GPX4 by ginsenoside Re was mediated by phosphoinositide 3-kinase and extracellular signal-regulated kinase but not by p38 mitogen-activated protein kinase or c-Jun N-terminal kinase. Ginsenoside Re also suppressed 6-OHDA-triggered cellular accumulation of reactive oxygen species and peroxidation of membrane lipids. The GPX4 inhibitor (1S,3R)-RSL3 reversed ginsenoside Re-mediated inhibition of cellular damage in SH-SY5Y cells exposed to 6-OHDA, indicating that the neuronal activity of ginsenoside Re is due to upregulation of GPX4. These findings suggest that ginsenoside Re-dependent upregulation of GPX4 reduces oxidative stress and thereby alleviates 6-OHDA-induced neuronal damage.

NF-κB-Mediated Neuroinflammation in Parkinson's Disease and Potential Therapeutic Effect of Polyphenols

Different animal and human studies from last two decades in the case of Parkinson's disease (PD) have concentrated on oxidative stress due to increased inflammation and cytokine-dependent neurotoxicity leading to induction of dopaminergic (DA) degeneration pathway in the nigrostriatal region. Chronic inflammation, the principle hallmark of PD, forms the basis of neurodegeneration. Aging in association with activation of glia due to neuronal injury, perhaps because of immune alterations and genetic predispositions, leads to deregulation of inflammatory pathways premising the onset of PD. A family of inducible transcription factors, nuclear factor-κB (NF-κB), is found to show expression in various cells and tissues, such as microglia, neurons, and astrocytes which play an important role in activation and regulation of inflammatory intermediates during inflammation. Both canonical and non-canonical NF-κB pathways are involved in the regulation of the stimulated cells. During the prodromal/asymptomatic stage of age-associated neurodegenerative diseases (i.e., PD and AD), chronic neuroinflammation may act silently as the driver of neuronal dysfunction. Though research has provided an insight over age-related neurodegeneration in PD, elaborative role of NF-κB in neuroinflammation is yet to be completely understood and thus requires more investigation. Polyphenols, a group of naturally occurring compound in medicinal plants, have gained attention because of their anti-oxidative and anti-neuroinflammatory properties in neurodegenerative diseases. In this aspect, this review highlights the role of NF-κB and the possible therapeutic roles of polyphenols in NF-κB-mediated neuroinflammation in PD.

Baicalin alleviates 6-hydroxydopamine-induced neurotoxicity in PC12 cells by down-regulation of microRNA-192-5p

Parkinson's disease (PD), which is caused by neurodegenerative disorder, has no effective treatment until now. Baicalin was reported to have neuroprotective effects. Hence, we investigated the effects of baicalin on PD in an in vitro cell model by using 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in rat pheochromocytoma PC12 cells. PC12 cells were stimulated by 6-OHDA and were treated with baicalin and/or transfected with miR-192-5p mimic or negative control (NC). Cell viability and apoptosis were examined by Cell Counting Kit-8 assay and Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) analysis, respectively. The expression of p62, ratio of light chain (LC)3-II/LC3-I, miR-192-5p was detected by qRT-PCR. All protein expression levels were analyzed by western blot. We found that 6-OHDA significantly inhibited cell viability, induced apoptosis and autophagy, while baicalin reversed the results led by 6-OHDA. Moreover, baicalin negatively regulated expression of miR-192-5p. Under baicalin treatment, transfection with miR-192-5p mimic decreased cell viability and induced apoptosis and autophagy in 6-OHDA-treated cells compared with NC. In addition, the phosphorylation of phosphatidylinositol 3'-kinase (PI3K) and protein kinase B (AKT) was statistically down-regulated by baicalin then thereafter reversed by miR-192-5p mimic. Baicalin reduced 6-OHDA-induced cell injury through down-regulation of miR-192-5p, as well as regulation of PI3K/AKT and MDM-2/p53 signal pathways.

A Litopenaeus vannamei Hemocyanin-Derived Antimicrobial Peptide (Peptide B11) Attenuates Cancer Cells' Proliferation

Antimicrobial peptides play important roles in the immune response to pathogens and tumor cells; for this reason, they are being exploited for therapeutic use. In this study, we describe a Litopenaeus vannamei hemocyanin-derived peptide, denoted B11, which shares similar features with other anticancer peptides and attenuates the proliferation of cancer cells. Cell viability assay revealed that B11 significantly inhibited the proliferation of human cervical (HeLa), human hepatocellular carcinoma (HepG2), and human esophageal cancer (EC109) cancer cell lines, but not normal liver cell lines (T-antigen-immortalized human liver epithelial (THLE) cells or THLE-3), by inducing morphological changes, nuclear condensation, and margination, features which are indicative of apoptosis. Besides, peptide B11-induced apoptosis was confirmed by isothiocyanate-labeled Annexin V/propidium iodide (Annexin V-FITC/PI) double staining of HeLa cells. Moreover, cell uptake studies, confocal microscopy, and Western blot analysis revealed that rhodamine-labeled B11 permeated HeLa cells and localized to the mitochondria, causing mitochondria dysfunction through lost mitochondrial membrane potential, which consequently triggered the induction of apoptosis. Increased expression levels of caspase-9, caspase-3, and Bax (Bcl-2-associated X) proteins, coupled with a decrease in Bcl-2 (B-cell lymphoma 2) protein, confirmed that peptide B11 induced apoptosis via the mitochondrial pathway. Thus, the hemocyanin-derived peptide, B11, inhibits the proliferation of cancer cells by causing mitochondrial dysfunction and inducing apoptotic cell death, for which reason it could be explored as an anticancer peptide.

Natural Compounds for the Management of Parkinson's Disease and Attention-Deficit/Hyperactivity Disorder

Parkinson's disease (PD) is the second most common neurodegenerative disorder with an unknown aetiology. The pathogenic mechanisms include oxidative stress, mitochondrial dysfunction, protein dysfunction, inflammation, autophagy, apoptosis, and abnormal deposition of α-synuclein. Currently, the existing pharmacological treatments for PD cannot improve fundamentally the degenerative process of dopaminergic neurons and have numerous side effects. On the other hand, attention-deficit/hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder of childhood and is characterised by hyperactivity, impulsivity, and inattention. The aetiology of ADHD remains unknown, although it has been suggested that its pathophysiology involves abnormalities in several brain regions, disturbances of the catecholaminergic pathway, and oxidative stress. Psychostimulants and nonpsychostimulants are the drugs prescribed for the treatment of ADHD; however, they have been associated with increased risk of substance use and have several side effects. Today, there are very few tools available to prevent or to counteract the progression of such neurological disorders. Thus, therapeutic approaches with high efficiency and fewer side effects are needed. This review presents a brief overview of the two neurological disorders and their current treatments, followed by a discussion of the natural compounds which have been studied as therapeutic agents and the mechanisms underlying the beneficial effects, in particular, the decrease in oxidative stress.

Therapeutic effects of baicalein on rotenone-induced Parkinson's disease through protecting mitochondrial function and biogenesis

Mitochondrial dysfunction has been implicated in the pathogenesis of Parkinson’s disease (PD) for several decades, and disturbed mitochondrial biogenesis (mitobiogenesis) was recently found to be a common phenomenon in PD. Baicalein, a major bioactive flavone of Scutellaria baicalensis Georgi, exerted neuroprotective effects in several experimental PD models. However, the effects of baicalein in rotenone-induced PD rats and the possible mechanisms remain poorly understood. In this study, we evaluated the therapeutic effects of baicalein and explored its mechanism of action in rotenone-induced PD models. The results indicated that behavioural impairments and the depletion of dopaminergic neurons induced by rotenone were attenuated by baicalein. Furthermore, in rotenone-induced parkinsonian rats, baicalein treatment effectively restored mitochondrial function and improved mitobiogenesis, as determined by measuring the mitochondrial density and key regulators involved in mitobiogenesis. Additionally, we confirmed that baicalein enhanced mitobiogenesis through the cAMP-responsive element binding protein (CREB) and glycogen synthase kinase-3β (GSK-3β) pathways in rotenone-treated SH-SY5Y cells. Moreover, we demonstrated that the cytoprotective effects of baicalein could be attenuated by the mitobiogenesis inhibitor chloramphenicol as well as CREB siRNA transfection. Overall, our results suggested that baicalein partially enhanced mitobiogenesis to restore mitochondrial function, thus exerting therapeutic effects in rotenone-induced PD models.

Therapeutic potential of flavonoids in inflammatory bowel disease: A comprehensive review

The inflammatory process plays a central role in the development and progression of numerous pathological situations, such as inflammatory bowel disease (IBD), autoimmune and neurodegenerative diseases, metabolic syndrome, and cardiovascular disorders. IBDs involve inflammation of the gastrointestinal area and mainly comprise Crohn’s disease (CD) and ulcerative colitis (UC). Both pathological situations usually involve recurring or bloody diarrhea, pain, fatigue and weight loss. There is at present no pharmacological cure for CD or UC. However, surgery may be curative for UC patients. The prescribed treatment aims to ameliorate the symptoms and prevent and/or delay new painful episodes. Flavonoid compounds are a large family of hydroxylated polyphenolic molecules abundant in plants, including vegetables and fruits which are the major dietary sources of these compounds for humans, together with wine and tea. Flavonoids are becoming very popular because they have many health-promoting and disease-preventive effects. Most interest has been directed towards the antioxidant activity of flavonoids, evidencing a remarkable free-radical scavenging capacity. However, accumulating evidence suggests that flavonoids have many other biological properties, including anti-inflammatory, antiviral, anticancer, and neuroprotective activities through different mechanisms of action. The present review analyzes the available data about the different types of flavonoids and their potential effectiveness as adjuvant therapy of IBDs.

Baicalein induces CD4(+)Foxp3(+) T cells and enhances intestinal barrier function in a mouse model of food allergy

The incidence of food allergy, which is triggered by allergen permeation of the gastrointestinal tract followed by a T-helper (Th) 2-mediated immune response, has been increasing annually worldwide. We examined the effects of baicalein (5,6,7-trihydroxyflavone), a flavonoid from Scutellaria baicalensis used in oriental herbal medicine, on regulatory T (Treg) cell induction and intestinal barrier function through the regulation of tight junctions in a mouse model of food allergy. An allergic response was induced by oral challenge with ovalbumin, and the incidence of allergic symptoms and T cell-related activity in the mesenteric lymph nodes were analyzed with and without the presence of baicalein. Our results demonstrated that the administration of baicalein ameliorated the symptoms of food allergy and attenuated serum IgE and effector T cells. However, Treg-related factors were up-regulated by baicalein. Furthermore, baicalein was shown to enhance intestinal barrier function through the regulation of tight junctions. We also found that baicalein treatment induced the differentiation of Treg cells via aryl hydrocarbon receptors (AhRs). Thus, the action of baicalein as an agonist of AhR can induce Treg differentiation and enhance barrier function, suggesting that baicalein might serve as an effective immune regulator derived from foods for the treatment of food allergy.

Directed differentiation of postnatal hippocampal neural stem cells generates nuclear receptor related‑1 protein‑ and tyrosine hydroxylase‑expressing cells

Parkinson's disease (PD) is a severe neurodegenerative disorder. Although the detailed underlying molecular mechanism remains to be elucidated, the major pathological feature of PD is the loss of dopaminergic (DA) neurons of the substantia nigra. The use of donor stem cells to replace DA neurons may be a key breakthrough in the treatment of PD. In the present study, the growth kinetics of hippocampal neural stem cells (Hip-NSCs) isolated from postnatal mice and cultured in vitro were observed, specifically the generation of cells expressing DA neuronal markers nuclear receptor related-1 protein (Nurr1) and tyrosine hydroxylase (TH). It was revealed that Hip-NSCs differentiated primarily into astrocytes when cultured in serum-containing medium. However, in low serum conditions, the number of βIII tubulin-positive neurons increased markedly. The proportion of Nurr1-positive cells and TH-positive neurons, significantly increased with increasing duration of directed differentiation of Hip-NSCs (P=0.0187 and 0.0254, respectively). The results of the present study reveal that Hip-NSCs may be induced to differentiate in vitro into neurons expressing Nurr1 and TH, known to be critical regulators of DA neuronal fate. Additionally, their expression may be necessary to facilitate neuronal maturation in vitro. These data suggest that Hip-NSCs may serve as a source of DA neurons for cell therapy in patients diagnosed with PD.

DJ-1/PARK7, But Not Its L166P Mutant Linked to Autosomal Recessive Parkinsonism, Modulates the Transcriptional Activity of the Orphan Nuclear Receptor Nurr1 In Vitro and In Vivo

Although mutations of DJ-1 have been linked to autosomal recessive Parkinsonism for years, its physiological function and the pathological mechanism of its mutants are not well understood. We report for the first time that exogenous application of DJ-1, but not its L166P mutant, enhances the nuclear translocation and the transcriptional activity of Nurr1, a transcription factor essential for dopaminergic neuron development and maturation, both in vitro and in vivo. Knockdown of DJ-1 attenuates Nurr1 activity. Further investigation showed that signaling of Raf/MEK/ERK MAPKs is involved in this regulatory process and that activation induced by exogenous DJ-1 is antagonized by U0126, an ERK pathway inhibitor, indicating that DJ-1 modulates Nurr1 activity via the Raf/MEK/ERK pathway. Our findings shed light on the novel function of DJ-1 to enhance Nurr1 activity and provide the first insight into the molecular mechanism by which DJ-1 enhances Nurr1 activity.

Induction of intrinsic apoptotic pathway and cell cycle arrest via baicalein loaded iron oxide nanoparticles as a competent nano-mediated system for triple negative breast cancer therapy

Magnetic nanoparticles have shown an increasing number of applications in the field of molecular medicine.

Therapeutic potentials of human adipose-derived stem cells on the mouse model of Parkinson's disease

The treatment of Parkinson's disease (PD) using stem cells has long been the focus of many researchers, but the ideal therapeutic strategy has not yet been developed. The consistency and high reliability of the experimental results confirmed by animal models are considered to be a critical factor in the stability of stem cell transplantation for PD. Therefore, the aim of this study was to investigate the preventive and therapeutic potential of human adipose-derived stem cells (hASC) for PD and was to identify the related factors to this therapeutic effect. The hASC were intravenously injected into the tail vein of a PD mouse model induced by 6-hydroxydopamine. Consequently, the behavioral performances were significantly improved at 3 weeks after the injection of hASC. Additionally, dopaminergic neurons were rescued, the number of structure-modified mitochondria was decreased, and mitochondrial complex I activity was restored in the brains of the hASC-injected PD mouse model. Overall, this study underscores that intravenously transplanted hASC may have therapeutic potential for PD by recovering mitochondrial functions.

Mitochondria-Targeted Protective Compounds in Parkinson's and Alzheimer's Diseases

Mitochondria are cytoplasmic organelles that regulate both metabolic and apoptotic signaling pathways; their most highlighted functions include cellular energy generation in the form of adenosine triphosphate (ATP), regulation of cellular calcium homeostasis, balance between ROS production and detoxification, mediation of apoptosis cell death, and synthesis and metabolism of various key molecules. Consistent evidence suggests that mitochondrial failure is associated with early events in the pathogenesis of ageing-related neurodegenerative disorders including Parkinson's disease and Alzheimer's disease. Mitochondria-targeted protective compounds that prevent or minimize mitochondrial dysfunction constitute potential therapeutic strategies in the prevention and treatment of these central nervous system diseases. This paper provides an overview of the involvement of mitochondrial dysfunction in Parkinson's and Alzheimer's diseases, with particular attention to in vitro and in vivo studies on promising endogenous and exogenous mitochondria-targeted protective compounds.

Echinacoside Protects against 6-Hydroxydopamine-Induced Mitochondrial Dysfunction and Inflammatory Responses in PC12 Cells via Reducing ROS Production

Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive loss of dopaminergic (DA) neurons at the substantia nigra. Mitochondrial dysfunction and inflammatory responses are involved in the mechanism of cell damage in PD. 6-Hydroxydopamine (6-OHDA), a dopamine analog, specifically damages dopaminergic neurons. Echinacoside (ECH) is a phenylethanoid glycoside isolated from the stems of Cistanche salsa, showing a variety of neuroprotective effects in previous studies. The present study was to investigate its effect against 6-OHDA-induced neurotoxicity and possible mechanisms in PC12 cells. The results showed that 6-OHDA reduced cell viability, decreased oxidation-reduction activity, decreased mitochondrial membrane potential, and induced mitochondria-mediated apoptosis compared with untreated PC12 cells. However, echinacoside treatment significantly attenuated these changes induced by 6-OHDA. In addition, echinacoside also could significantly alleviate the inflammatory responses induced by 6-OHDA. Further research showed that echinacoside could reduce 6-OHDA-induced ROS production in PC12 cells. These results suggest that the underlying mechanism of echinacoside against 6-OHDA-induced neurotoxicity may be involve in attenuating mitochondrial dysfunction and inflammatory responses by reducing ROS production.

Neurotoxin mechanisms and processes relevant to Parkinson's disease: an update

The molecular mechanism responsible for degenerative process in the nigrostriatal dopaminergic system in Parkinson's disease (PD) remains unknown. One major advance in this field has been the discovery of several genes associated to familial PD, including alpha synuclein, parkin, LRRK2, etc., thereby providing important insight toward basic research approaches. There is an consensus in neurodegenerative research that mitochon dria dysfunction, protein degradation dysfunction, aggregation of alpha synuclein to neurotoxic oligomers, oxidative and endoplasmic reticulum stress, and neuroinflammation are involved in degeneration of the neuromelanin-containing dopaminergic neurons that are lost in the disease. An update of the mechanisms relating to neurotoxins that are used to produce preclinical models of Parkinson´s disease is presented. 6-Hydroxydopamine, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, and rotenone have been the most wisely used neurotoxins to delve into mechanisms involved in the loss of dopaminergic neurons containing neuromelanin. Neurotoxins generated from dopamine oxidation during neuromelanin formation are likewise reviewed, as this pathway replicates neurotoxin-induced cellular oxidative stress, inactivation of key proteins related to mitochondria and protein degradation dysfunction, and formation of neurotoxic aggregates of alpha synuclein. This survey of neurotoxin modeling-highlighting newer technologies and implicating a variety of processes and pathways related to mechanisms attending PD-is focused on research studies from 2012 to 2014.

Pinocembrin attenuates 6-OHDA-induced neuronal cell death through Nrf2/ARE pathway in SH-SY5Y cells

Pinocembrin (PB), the most abundant flavonoid in propolis, has been known to display antioxidant activity. However, the mechanism as how PB can induce antioxidant activity remains elusive. The purpose of the present study was to investigate the potential neuroprotective role of PB and to delineate its mechanism of action against the Parkinson's disease-related neurotoxin 6-hydroxydopamine(6-OHDA)-induced cell death in neuroblastoma SH-SY5Y cells. Results indicate that pretreatment with PB for 4 h significantly reduced the 6-OHDA-induced cell viability loss, apoptotic rate and decreased Bcl-2/Bax ratio. In addition, PB inhibited 6-OHDA-induced oxidative stress as measured by the formation of reactive oxygen species, the level of malondialdehyde, mitochondrial membrane potential, and superoxide dismutase. Moreover, we have revealed the PB treatment resulted in an increase in nuclear factor E2-related factor 2 (Nrf2) protein levels and subsequent activation of antioxidant response element (ARE) pathway genes of heme oxygenase-1 (HO-1) and γ-glutamylcysteine synthetase (γ-GCS) in SH-SY5Y cells. Treatment of SH-SY5Y cells with Nrf2 small interference RNA abolished PB-induced HO-1 and γ-GCS expression and its protective effects. Taken together, these findings suggest that PB can protect the SH-SY5Y cells from 6-OHDA-induced oxidative cell death via Nrf2/ARE pathway. Thus, our study indicates that PB has a partial cytoprotective role in dopaminergic cell culture systems.

Chikusetsu saponin V attenuates MPP+-induced neurotoxicity in SH-SY5Y cells via regulation of Sirt1/Mn-SOD and GRP78/caspase-12 pathways

Studies have shown that saponins from Panax japonicus (SPJ) possess neuroprotective effects. However, whether Chikusetsu saponin V (CsV), the most abundant member of SPJ, can exert neuroprotective effects against 1-methyl-4-phenylpyridinium ion (MPP⁺)-induced cytotoxicity is not known. In this study, we aimed to investigate the neuroprotective effects of CsV on MPP⁺-induced cytotoxicity in human neuroblastoma SH-SY5Y cells and explore its possible mechanisms. Our results show that CsV attenuates MPP⁺-induced cytotoxicity, inhibits ROS accumulation, and increases mitochondrial membrane potential dose-dependently. We also found that levels of Sirt1 protein and Mn-SOD mRNA significantly decreased in MPP⁺-treated group but were restored with CsV treatment in a dose-dependent manner. Furthermore, GRP78 protein and Caspase-12 mRNA levels were elevated by MPP⁺ exposure but reversed by CsV treatment. CsV inhibited the MPP⁺-induced downregulation of Bcl-2 and up-regulation of Bax in a dose-dependent manner and, thus, increased the ratio of Bcl-2/Bax. Overall, these results suggest that Sirt1/Mn-SOD and GRP78/Caspase-12 pathways might be involved in the CsV-mediated neuroprotective effects.

Baicalein ameliorates cognitive deficits in epilepsy-like tremor rat

Baicalein has been shown to possess various pharmacological actions. The current work was designed to assess the neuroprotection of baicalein against cognitive deficits in epilepsy-like tremor rat (TRM). Epileptic characteristics and memory functions were assessed by electroencephalograms recording and Morris water maze test, respectively. The changes of oxidative indicators including malondialdehyde (MDA), catalase (CAT), Cu/Zn-superoxide dismutase (Cu/Zn-SOD), Mn-SOD, glutathione (GSH), glutathione peroxidase (GSH-PX) and 8-isoprostane were measured using corresponding commercial kits. Real-time RT-PCR and immunoassay were employed to detect activities of various inflammatory mediators such as NF-κB p65, TNF-α, IL-1β, IL-6 and IL-10. Western blot analysis was performed to determine heat shock protein (HSP) 70 and mitogen-activated protein kinases (MAPKs) (including ERK, JNK and p38) proteins. Our results illustrated that baicalein significantly ameliorated epileptiform activity and cognitive deficits in TRM. Besides, reduced oxidative stress and inflammatory responses were also found in TRM treated with baicalein. Furthermore, there were evident alterations of HSP70 and MAPK cascades at protein levels after 14-day pretreatment with baicalein. It was concluded that the neuroprotective effect of baicalein against cognitive dysfunction might be associated with suppressing oxidative stress, inhibiting inflammation and mediating HSP70 as well as MAPK cascades in absence-like TRM.