The role of inflammatory and oxidative stress mechanisms in the pathogenesis of Parkinson's disease: focus on astrocytes

The High Costs of Low-Grade Inflammation: Persistent Fatigue as a Consequence of Reduced Cellular-Energy Availability and Non-adaptive Energy Expenditure

Chronic or persistent fatigue is a common, debilitating symptom of several diseases. Persistent fatigue has been associated with low-grade inflammation in several models of fatigue, including cancer-related fatigue and chronic fatigue syndrome. However, it is unclear how low-grade inflammation leads to the experience of fatigue. We here propose a model of an imbalance in energy availability and energy expenditure as a consequence of low-grade inflammation. In this narrative review, we discuss how chronic low-grade inflammation can lead to reduced cellular-energy availability. Low-grade inflammation induces a metabolic switch from energy-efficient oxidative phosphorylation to fast-acting, but less efficient, aerobic glycolytic energy production; increases reactive oxygen species; and reduces insulin sensitivity. These effects result in reduced glucose availability and, thereby, reduced cellular energy. In addition, emerging evidence suggests that chronic low-grade inflammation is associated with increased willingness to exert effort under specific circumstances. Circadian-rhythm changes and sleep disturbances might mediate the effects of inflammation on cellular-energy availability and non-adaptive energy expenditure. In the second part of the review, we present evidence for these metabolic pathways in models of persistent fatigue, focusing on chronic fatigue syndrome and cancer-related fatigue. Most evidence for reduced cellular-energy availability in relation to fatigue comes from studies on chronic fatigue syndrome. While the mechanistic evidence from the cancer-related fatigue literature is still limited, the sparse results point to reduced cellular-energy availability as well. There is also mounting evidence that behavioral-energy expenditure exceeds the reduced cellular-energy availability in patients with persistent fatigue. This suggests that an inability to adjust energy expenditure to available resources might be one mechanism underlying persistent fatigue.

Role of Plant-Derived Flavonoids and Their Mechanism in Attenuation of Alzheimer's and Parkinson's Diseases: An Update of Recent Data

Neurodegeneration is a progressive loss of neuronal cells in certain regions of the brain. Most of the neurodegenerative disorders (NDDs) share the communal characteristic such as damage or reduction of various cell types typically including astrocytes and microglial activity. Several compounds are being trialed to treat NDDs but they possess solitary symptomatic advantages along with copious side effects. The finding of more enthralling and captivating compounds to suspend and standstill the pathology of NDDs will be considered as a hallmark of present times. Phytochemicals possess the potential to alternate the synthetic line of therapy against NDDs. The present review explores the potential efficacy of plant-derived flavonoids against most common NDDs including Alzheimer's disease (AD) and Parkinson's disease (PD). Flavonoids are biologically active phytochemicals which possess potential pharmacological effects, including antiviral, anti-allergic, antiplatelet, anti-inflammatory, anti-tumor, anti-apoptotic and anti-oxidant effects and are able to attenuate the pathology of various NDDs through down-regulating the nitric oxide (NO) production, by reducing the tumor necrosis factor-α (TNF-α), by reducing the excitotoxicity of superoxide as well as acting as tyrosine kinase (TK) and monoamine oxidase (MAO) inhibiting enzyme.

Neuroprotection through flavonoid: Enhancement of the glyoxalase pathway

The glyoxalase pathway functions to detoxify reactive dicarbonyl compounds, most importantly methylglyoxal. The glyoxalase pathway is an antioxidant defense mechanism that is essential for neuroprotection. Excessive concentrations of methylglyoxal have deleterious effects on cells, leading to increased levels of inflammation and oxidative stress. Neurodegenerative diseases - including Alzheimer's, Parkinson's, Aging and Autism Spectrum Disorder - are often induced or exacerbated by accumulation of methylglyoxal. Antioxidant compounds possess several distinct mechanisms that enhance the glyoxalase pathway and function as neuroprotectants. Flavonoids are well-researched secondary plant metabolites that appear to be effective in reducing levels of oxidative stress and inflammation in neural cells. Novel flavonoids could be designed, synthesized and tested to protect against neurodegenerative diseases through regulating the glyoxalase pathway.

Proanthocyanidins against Oxidative Stress: From Molecular Mechanisms to Clinical Applications

Proanthocyanidins (PCs) are naturally occurring polyphenolic compounds abundant in many vegetables, plant skins (rind/bark), seeds, flowers, fruits, and nuts. Numerous in vitro and in vivo studies have demonstrated myriad effects potentially beneficial to human health, such as antioxidation, anti-inflammation, immunomodulation, DNA repair, and antitumor activity. Accumulation of prooxidants such as reactive oxygen species (ROS) exceeding cellular antioxidant capacity results in oxidative stress (OS), which can damage macromolecules (DNA, lipids, and proteins), organelles (membranes and mitochondria), and whole tissues. OS is implicated in the pathogenesis and exacerbation of many cardiovascular, neurodegenerative, dermatological, and metabolic diseases, both through direct molecular damage and secondary activation of stress-associated signaling pathways. PCs are promising natural agents to safely prevent acute damage and control chronic diseases at relatively low cost. In this review, we summarize the molecules and signaling pathways involved in OS and the corresponding therapeutic mechanisms of PCs.

Metabolic Disturbances in the Striatum and Substantia Nigra in the Onset and Progression of MPTP-Induced Parkinsonism Model

Metabolic confusion has been linked to the pathogenesis of Parkinson's disease (PD), while the dynamic changes associated with the onset and progression of PD remain unclear. Herein, dynamic changes in metabolites were detected from the initiation to the development of 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) -induced Parkinsonism model to elucidate its potential metabolic mechanism. Ex vivo¹H nuclear magnetic resonance (NMR) spectroscopy was used to measure metabolite changes in the striatum and substantia nigra (SN) of mice at 1, 7, and 21 days after injection of MPTP. Metabolomic analysis revealed a clear separation of the overall metabolites between PD and control mice at different time points. Glutamate (Glu) in the striatum was significantly elevated at induction PD day 1 mice, which persisted to day 21. N-acetylaspartate (NAA) increased in the striatum of induction PD mice on days 1 and 7, but no significant difference was found in striatum on day 21. Myo-Inositol (mI) and taurine (Tau) were also disturbed in the striatum in induction PD day 1 mice. Additionally, key enzymes in the glutamate-glutamine cycle were significantly increased in PD mice. These findings suggest that neuron loss and motor function impairment in induction PD mice may be linked to overactive glutamate-glutamine cycle and altered membrane metabolism.

Astrocytes as targets for drug discovery

Recent studies have illuminated the crucial role of astrocytes in maintaining proper neuronal health and function. Abnormalities in astrocytic functions have now been implicated in the pathogenesis of neurodegenerative diseases, including Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), and amyotrophic lateral sclerosis (ALS). Historically, drug development programs for neurodegenerative diseases generally target only neurons, overlooking the contributions of astrocytes. Therefore, targeting both disease neurons and astrocytes offers a new approach for drug development for the treatment of neurological diseases. Looking forward, the co-culturing of human neurons with astrocytes could be the next evolutionary step in drug discovery for neurodegenerative diseases.

Neuroprotective effect of arctigenin against neuroinflammation and oxidative stress induced by rotenone

Background: the present study was to investigate the neuroprotective effect of arctigenin, the major active component of a traditional Chinese medicine “Arctii Fructus”, against PD in a rat model induced by rotenone. Materials and methods: in the present study, rotenone was injected subcutaneously in the backs of rats to mimic the progressive neurodegenerative nature of PD and arctigenin was administered. Behavioral analyses including a grid test, bar test and open-field test were used to evaluate motor activities and behavioral movement abilities. Energy metabolism indexes including oxygen consumption, carbon dioxide production, heat production and energy expenditure were measured via a TSE phenoMaster/LabMaster animal monitoring system. Immunohistochemistry was performed to detect the staining of TH and the expression of α-synuclein in substantia nigra (SN). The effect of arctigenin on oxidative stress was evaluated by the levels of GSH and MDA, and activities of SOD and GSH-Px. The levels of pro-inflammatory cytokines such as IL-6, IL-1β, TNF-α, IFN-γ and PGE2, the expression of Iba-1 and GFAP, and the impression of inflammatory mediators such as COX-2 and NF-κB in the SN were measured to evaluate the effect on the inflammation of SN area induced by rotenone. Results: compared with the ROT group, the deadlock time of rats treated with arctigenin was significantly shortened and the score of locomotor activity increased in the behavioral test; the number of TH⁺ positive DA neurons of the arctigenin treated group was increased and α-synuclein immunopositive was decreased; the level of GSH and activities of SOD and GSH-Px in the arctigenin-treated group were significantly increased; arctigenin administration induced a significant decrease in the MDA level; arctigenin also significantly decreased the levels of IL-6, IL-1β, TNF-α, IFN-γ and PGE2 and reduced the impression of COX-2 and NF-κB in SN; treatment with arctigenin decreased microglia and astrocyte activation evidenced by the reduced expression of Iba-1 and GFAP. Conclusion: the findings demonstrated that arctigenin can improve the behavior changes of PD rats and the damage of DA neurons. The oxidative stress and inflammation involved in the pathogenesis of PD and arctigenin may protect DA neurons through its potent antioxidant and anti-inflammatory activities.

The present study was to investigate the neuroprotective effect of arctigenin, the major active component of a traditional Chinese medicine “Arctii Fructus”, against PD in a rat model induced by rotenone.

High glucose-induced defective thrombospondin-1 release from astrocytes via TLR9 activation contributes to the synaptic protein loss

Diabetes, characterized by chronic hyperglycemia, is known to induce synaptic degeneration in the brain, thereby resulting in cognitive dysfunction. Thrombospondin-1(TSP-1), the secreted protein produced by astrocytes, plays a crucial role in promoting synapse formation. Toll-like receptor 9 (TLR9) has been widely known to initiate the innate immune response. We recently reported TLR9 activation in neurons results in tau hyperphosphorylation induced by HG in vitro. Its activation has been also considered to mediate oxidative stress and astrocytic dysfunction under pathological circumstance. However, whether astrocytic TSP-1 alteration plays a role in synaptic protein loss under high glucose condition and whether TLR9 activation is involved in this process have not been reported. In this study, we found that primary mouse astrocytes incubated in high glucose (30mM) induced a significant decreased TSP-1 secretion and increased intracellular contents of TSP-1 without affecting transcription level. Addition of conditioned medium from high glucose (30mM) treated astrocytes to the primary neurons exhibited reduced synaptic proteins expression, which was attenuated by treatment with exogenous rTSP-1. In addition, we demonstrated that TLR9 activation along with reactive oxygen species (ROS) generation in astrocytes was induced by high glucose (30mM). Furthermore, we explored the relationship between TLR9 activation and TSP-1 production. Both TLR9 deficiency and the antioxidant N-acetyl-L-cysteine treatment improved altered intra- and extracellular TSP-1 levels under high glucose condition. Together, our findings suggest that high glucose (30mM) impairs TSP-1 secretion from astrocytes, which depends on astrocytic dysfunction associated with TLR9 activation mediated ROS signaling, ultimately contributing to the synaptic proteins loss.

Heat shock protein 70 suppresses neuroinflammation induced by α-synuclein in astrocytes

Neuroinflammation triggered by activation of glial cells plays an important role in the pathophysiology of several neurodegenerative diseases including Parkinson's disease (PD). Besides microglia, astrocytes are also critical in initiating and perpetuating inflammatory process associated with PD. Heat shock protein 70 (Hsp70) is originally described as intracellular chaperone, however, recent study revealed that it had anti-inflammatory effects as well. The present study is designed to investigate whether Hsp70 mediates neuroinflammation in astrocytes. By employing α-synuclein (α-Syn) (A53T) aggregates on primary cultured astrocytes of rats, we found that astrocytes were activated and neuroinflammatory response was triggered, as indicated by over-expression of glial fibrillary acidic protein (GFAP), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), increased production of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). The data also showed that the neuroinflammatory response accompanied up-regulated Hsp70 expression. Moreover, over-expression of Hsp70 through transfection of Hsp70 cDNA plasmids could significantly reduce the production of TNF-α, IL-1β, and the expression of GFAP, COX-2 as well as iNOS. While inhibition of Hsp70 by VER155008 exacerbated neuroinflammatory response in astrocytes challenged by α-Syn aggregates. Further mechanistic study indicated that c-Jun N-terminal kinase (JNK) and nuclear factor-κB (NF-κB) signalings were responsible for the neuroinflammation, which was also regulated by Hsp70. These findings demonstrated that Hsp70 was an important modulator in astrocytes induced inflammation, and up-regulation of Hsp70 might be a potential regulating approach for neuroinflammation-related neurodegenerative diseases, such as PD.

Neurochemical and Behavior Deficits in Rats with Iron and Rotenone Co-treatment: Role of Redox Imbalance and Neuroprotection by Biochanin A

Increasing evidences show that the etiology of Parkinson's disease (PD) is multifactorial. Studying the combined effect of several factors is becoming a hot topic in PD research. On one hand, iron is one of the essential trace metals for human body; on the other hand, iron may be involved in the etiopathogenesis of PD. In our present study, the rats with increased neonatal iron (120 μg/g bodyweight) supplementation were treated with rotenone (0.5 mg/kg) when they were aged to 14 weeks. We observed that iron and rotenone co-treatment induced significant behavior deficits (time-dependent) and striatal dopamine depletion in the male and female rats, while they did not do so when they were used alone. No significant change in striatal 5-hydroxytryptamine content was observed in the male and female rats with iron and rotenone co-treatment. Also, iron and rotenone co-treatment significantly decreased substantia nigra TH expression in the male rats. Furthermore, co-treatment with iron and rotenone significantly induced malondialdehyde increase and glutathione decrease in the substantia nigra of male and female rats. There was no significant change in cerebellar malondialdehyde and glutathione content of the rats co-treated with iron and rotenone. Interestingly, biochanin A significantly attenuated striatal dopamine depletion and improved behavior deficits (dose-dependently) in the male and female rats with iron and rotenone co-treatment. Biochanin A treatment also significantly alleviated substantia nigra TH expression reduction in the male rats co-treated with iron and rotenone. Finally, biochanin A significantly decreased malondialdehyde content and increased glutathione content in the substantia nigra of male and female rats with iron and rotenone co-treatment. Our results indicate that iron and rotenone co-treatment may result in aggravated neurochemical and behavior deficits through inducing redox imbalance and increased neonatal iron supplementation may participate in the etiopathogenesis of PD. Moreover, biochanin A may exert dopaminergic neuroprotection by maintaining redox balance.

Epigenetic regulation of astrocyte function in neuroinflammation and neurodegeneration

Epigenetic mechanisms control various functions throughout the body, from cell fate determination in development to immune responses and inflammation. Neuroinflammation is one of the prime contributors to the initiation and progression of neurodegeneration in a variety of diseases, including Alzheimer's and Parkinson's diseases. Because astrocytes are the largest population of glial cells, they represent an important regulator of CNS function, both in health and disease. Only recently have studies begun to identify the epigenetic mechanisms regulating astrocyte responses in neurodegenerative diseases. These epigenetic mechanisms, along with the epigenetic marks involved in astrocyte development, could elucidate novel pathways to potentially modulate astrocyte-mediated neuroinflammation and neurotoxicity. This review examines the known epigenetic mechanisms involved in regulation of astrocyte function, from development to neurodegeneration, and links these mechanisms to potential astrocyte-specific roles in neurodegenerative disease with a focus on potential opportunities for therapeutic intervention.

PARKIN overexpression in human mesenchymal stromal cells from Wharton's jelly suppresses 6-hydroxydopamine-induced apoptosis: Potential therapeutic strategy in Parkinson's disease

BACKGROUND AIMS

Stem cell transplantation is an excellent option for regenerative or replacement therapy. However, deleterious microenvironmental and endogenous factors (e.g., oxidative stress) compromise ongoing graft survival and longevity. Therefore, (transient or stable) genetically modified cells may be reasonably thought to resist oxidative stress-induced damage. Genetic engineering of mesenchymal stromal cells (MSCs) obtained from Wharton's jelly tissue may offer some therapeutic potential. PARKIN is a multifunctional ubiquitin ligase able to protect dopaminergic cells against stress-related signaling. We, therefore, evaluated the effect of the neurotoxicant 6-hydroxydopamine (6-OHDA) on regulated cell death signaling in MSCs and investigated whether overexpression of PARKIN in MSCs was capable of modulating the effect of 6-OHDA.

METHODS

We transiently transfected Wharton's jelly-derived MSCs with an mCherry-PARKIN vector using the Lipofectamine LTX method. Naïve MSCs and MSCs overexpressing PARKIN were exposed to increasing concentrations of 6-OHDA. We used light and fluorescence microscopy, flow cytometry, immunocytochemistry staining, in-cell Western and Western blot analysis.

RESULTS

After 12-24 h of 6-OHDA exposure, we detected dichlorofluorescein (DCF)-positive cells (80%) indicative of reactive oxygen species (H2O2) production, reduced cell viability (40-50%), decreased mitochondrial membrane potential (ΔΨm, ~35-45%), DNA fragmentation (18-30%), and G1-arrested cell cycle in the MSCs. 6-OHDA exposure increased the expression of the transcription factor c-JUN, increased the expression of the mitochondria maintenance Phosphatase and tensin homologue-induced putative kinase 1 (PINK1) protein and increased the expression of pro-apoptotic PUMA, caspase-3 and apoptosis-inducing factor (AIF). 6-OHDA exposure also significantly augmented the oxidation of the oxidative stress sensor, DJ-1. Overexpression of PARKIN in MSCs not only significantly reduced the expression of cell death and oxidative stress markers but also significantly reduced DCF-positive cells (~50% reduction).

DISCUSSION

6-OHDA induced apoptosis in MSCs via generation of H2O2, activation of c-JUN and PUMA, mitochondrial depolarization and nuclei fragmentation. Our findings suggest that PARKIN protects MSCs against 6-OHDA toxicity by partly interacting with H2O2, reducing the expression of c-JUN, PUMA, AIF and caspase-3, and maintaining the mitochondrial ΔΨm.

Subcellular compartmentalisation of copper, iron, manganese, and zinc in the Parkinson's disease brain

Elevated iron and decreased copper levels are cardinal features of the degenerating substantia nigra pars compacta in the Parkinson's disease brain. Both of these redox-active metals, and fellow transition metals manganese and zinc, are found at high concentrations within the midbrain and participate in a range of unique biological reactions. We examined the total metal content and cellular compartmentalisation of manganese, iron, copper and zinc in the degenerating substantia nigra, disease-affected but non-degenerating fusiform gyrus, and unaffected occipital cortex in the post mortem Parkinson's disease brain compared with age-matched controls. An expected increase in iron and a decrease in copper concentration was isolated to the soluble cellular fraction, encompassing both interstitial and cytosolic metals and metal-binding proteins, rather than the membrane-associated or insoluble fractions. Manganese and zinc levels did not differ between experimental groups. Altered Fe and Cu levels were unrelated to Braak pathological staging in our cases of late-stage (Braak stage V and VI) disease. The data supports our hypothesis that regional alterations in Fe and Cu, and in proteins that utilise these metals, contribute to the regional selectively of neuronal vulnerability in this disorder.

A study on the modulation of alpha-synuclein fibrillation by Scutellaria pinnatifida extracts and its neuroprotective properties

Aggregation of alpha-synuclein (α-SN) is a key pathogenic event in Parkinson's disease (PD) leading to dopaminergic degeneration. The identification of natural compounds inhibiting α-SN aggregation may have a major role in treating PD. Different Scutellaria species are known as valuable medicinal plants, primarily due to their high flavonoid levels. Scutellaria pinnatifida (S. pinnatifida) is endemic to Iran; however, the knowledge of its pharmaceutical properties is limited. Here we report that S. pinnatifida extracts have an anti-fibrillation effect on α-SN aggregation and neuroprotective properties on PC12 and primary dopaminergic neurons. Treatment during α-SN fibril formation with S. pinnatifida extracts showed that the extractions performed with dichloromethane (DCMEx) and n-butanol (BuOHEx) strongly inhibited α-SN fibrillation. TLC-based analysis revealed that S. pinnatifida contains a great amount of flavonoids with high antioxidant properties as shown using a radical scavenging assay. Further analysis using HPLC and Mass spectroscopy on the DCMEx revealed the presence of baicalein in this extract. We then selected the more efficient extracts based on cell viability and ROS scavenging on PC12 cells and tested their neuroprotective properties on primary dopaminergic neurons. Our results showed the extracts strongly protected against α-SN oligomers. Surprisingly, they also neutralized the severe toxicity of paraquat. Therefore, S. pinnatifida may be a potential valuable medicinal herb for further studies related to the treatment of PD.

The Mechanisms of Traditional Chinese Medicine Underlying the Prevention and Treatment of Parkinson's Disease

Parkinson's disease (PD), characterized with bradykinesia, static tremor, rigidity and disturbances in balance, is the second most common neurodegenerative disorder. Along with the largely aging population in the world, the incidence is increasing year by year, which imposes the negative impacts on patients, their families and the whole society. Traditional Chinese medicine (TCM) has a positive prospect for the prevention and cure of PD due to its advantages of less side effects and multi-target effects. At present, the pathogenesis of PD is not yet fully discovered. This paper elaborates the mechanisms of TCM underlying the prevention and treatment of PD with regards to the inhibition of oxidative stress, the regulation of mitochondrial dysfunction, the reduction of toxic excitatory amino acids (EAA), the inhibition of neuroinflammation, the inhibition of neuronal apoptosis, and the inhibition of abnormal protein aggregation.

A New Treatment Strategy for Parkinson's Disease through the Gut-Brain Axis: The Glucagon-Like Peptide-1 Receptor Pathway

Molecular communications in the gut-brain axis, between the central nervous system and the gastrointestinal tract, are critical for maintaining healthy brain function, particularly in aging. Epidemiological analyses indicate type 2 diabetes mellitus (T2DM) is a risk factor for neurodegenerative disorders including Alzheimer's disease (AD) and Parkinson's diseases (PD) for which aging shows a major correlative association. Common pathophysiological features exist between T2DM, AD, and PD, including oxidative stress, inflammation, insulin resistance, abnormal protein processing, and cognitive decline, and suggest that effective drugs for T2DM that positively impact the gut-brain axis could provide an effective treatment option for neurodegenerative diseases. Glucagon-like peptide-1 (GLP-1)-based antidiabetic drugs have drawn particular attention as an effectual new strategy to not only regulate blood glucose but also decrease body weight by reducing appetite, which implies that GLP-1 could affect the gut-brain axis in normal and pathological conditions. The neurotrophic and neuroprotective effects of GLP-1 receptor (R) stimulation have been characterized in numerous in vitro and in vivo preclinical studies using GLP-1R agonists and dipeptidyl peptidase-4 inhibitors. Recently, the first open label clinical study of exenatide, a long-acting GLP-1 agonist, in the treatment of PD showed long-lasting improvements in motor and cognitive function. Several double-blind clinical trials of GLP-1R agonists including exenatide in PD and other neurodegenerative diseases are already underway or are about to be initiated. Herein, we review the physiological role of the GLP-1R pathway in the gut-brain axis and the therapeutic strategy of GLP-1R stimulation for the treatment of neurodegenerative diseases focused on PD, for which age is the major risk factor.

Functional single-walled carbon nanotubes 'CAR' for targeting dopamine delivery into the brain of parkinsonian mice

Current treatments for Parkinson's disease (PD) are limited, partly due to the difficulties posed by the blood brain barrier (BBB) when delivering drugs to the brain. Herein, we explore the feasibility and efficacy of functional single-walled carbon nanotubes 'CAR' (SWCNT-PEGs-Lf) which carry and target-deliver dopamine (DA) to the brain in PD mice for treatment. SWCNTs can penetrate the cell-membrane remarkably, with the characteristics including high drug-loading and pH-dependent therapeutic unloading capacities. It has been reported that polyethylene glycol (PEG)-coated SWCNTs could increase the circulation time and thus prolong the concentration gradient of SWCNTs to the brain. Besides, an obvious lactoferrin-nanoparticle (Lf-NP) accumulation in the striatum, wherein the pharmacological target site of PD has been reported, a dual modification of PEG and Lf onto SWCNTs was applied and thus a specific 'CAR' to carry DA. The results from in vitro studies demonstrate that with 20 mol L^-1 DA loaded onto SWCNT-polyethylene glycol (PEGs) in addition to 100 μmol L^-1 6-hydroxydopamine (6-OHDA), the activity of PC12 cells increases significantly (p < 0.05), and that the lactate dehydrogenase (LDH) levels and reactive oxygen species (ROS) content also significantly decrease (p < 0.01). Furthermore, the levels of oxidative stress, tumor necrosis factor (TNF)-α and interleukin (IL)-1β are all reduced significantly in PD mice and the CAR-25 mg kg^-1 DA group in comparison with that in 6-OHDA-lesioned mice with saline and 6-OHDA-lesioned mice, as well as the Tyrosine hydroxylase-immunoreactive (TH-ir) density increased (p < 0.01). The toxicity of CAR was in vitro and in vivo investigated, showing that the safe dose of SWCNT-PEG exposure to PC12 cells was 6.25 μg μl^-1 or lower with a higher metabolic activity in comparison with that in the control group and the safe dose of CAR in the mice experiments was 3.25 mg kg^-1 or less, given by intraperitoneal injection with a lower level of oxidative stress and inflammatory responses in comparison with that in the control group. This study suggests that 25 mg kg^-1 DA loaded onto 3.25 mg kg^-1 CAR can alleviate the oxidative stress and inflammatory responses in parkinsonian mice and increase the TH-ir density in the striatum.

Pharmacological stimulation of nuclear factor (erythroid-derived 2)-like 2 translation activates antioxidant responses

Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is the master regulator of the antioxidant response, and its function is tightly regulated at the transcriptional, translational, and post-translational levels. It is well-known that Nrf2 is regulated at the protein level by proteasomal degradation via Kelch-like ECH-associated protein 1 (Keap1), but how Nrf2 is regulated at the translational level is less clear. Here, we show that pharmacological stimulation increases Nrf2 levels by overcoming basal translational repression. We developed a novel reporter assay that enabled identification of natural compounds that induce Nrf2 translation by a mechanism independent of Keap1-mediated degradation. Apigenin, resveratrol, and piceatannol all induced Nrf2 translation. More importantly, the pharmacologically induced Nrf2 overcomes Keap1 regulation, translocates to the nucleus, and activates the antioxidant response. We conclude that translational regulation controls physiological levels of Nrf2, and this can be modulated by apigenin, resveratrol, and piceatannol. Also, targeting this mechanism with novel compounds could provide new insights into prevention and treatment of multiple diseases in which oxidative stress plays a significant role.

Pathogenic Upregulation of Glial Lipocalin-2 in the Parkinsonian Dopaminergic System

Lipocalin-2 (LCN2) is a member of the highly heterogeneous secretory protein family of lipocalins and increases in its levels can contribute to neurodegeneration in the adult brain. However, there are no reports on the role of LCN2 in Parkinson's disease (PD). Here, we report for the first time that LCN2 expression is increased in the substantia nigra (SN) of patients with PD. In mouse brains, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment for a neurotoxin model of PD significantly upregulated LCN2 expression, mainly in reactive astrocytes in both the SN and striatum. The increased LCN2 levels contributed to neurotoxicity and neuroinflammation, resulting in disruption of the nigrostriatal dopaminergic (DA) projection and abnormal locomotor behaviors, which were ameliorated in LCN2-deficient mice. Similar to the effects of MPTP treatment, LCN2-induced neurotoxicity was also observed in the 6-hydroxydopamine (6-OHDA)-treated animal model of PD. Moreover, treatment with the iron donor ferric citrate (FC) and the iron chelator deferoxamine mesylate (DFO) increased and decreased, respectively, the LCN2-induced neurotoxicity in vivo In addition to the in vivo results, 1-methyl-4-phenylpyridinium (MPP(+))-induced neurotoxicity in cocultures of mesencephalic neurons and astrocytes was reduced by LCN2 gene deficiency in the astrocytes and conditioned media derived from MPP(+)-treated SH-SY5Y neuronal enhanced glial expression of LCN2 in vitro Therefore, our results demonstrate that astrocytic LCN2 upregulation in the lesioned DA system may play a role as a potential pathogenic factor in PD and suggest that inhibition of LCN2 expression or activity may be useful in protecting the nigrostriatal DA system in the adult brain.

SIGNIFICANCE STATEMENT

Lipocalin-2 (LCN2), a member of the highly heterogeneous secretory protein family of lipocalins, may contribute to neuroinflammation and neurotoxicity in the brain. However, LCN2 expression and its role in Parkinson's disease (PD) are largely unknown. Here, we report that LCN2 is upregulated in the substantia nigra of patients with PD and neurotoxin-treated animal models of PD. Our results suggest that LCN2 upregulation might be a potential pathogenic mechanism of PD, which would result in disruption of the nigrostriatal dopaminergic system through neurotoxic iron accumulation and neuroinflammation. Therefore, inhibition of LCN2 expression or activity may be useful in protecting the nigrostriatal dopaminergic projection in PD.

The vicious circle of hypometabolism in neurodegenerative diseases: Ways and mechanisms of metabolic correction

Hypometabolism, characterized by decreased brain glucose consumption, is a common feature of many neurodegenerative diseases. Initial hypometabolic brain state, created by characteristic risk factors, may predispose the brain to acquired epilepsy and sporadic Alzheimer's and Parkinson's diseases, which are the focus of this review. Analysis of available data suggests that deficient glucose metabolism is likely a primary initiating factor for these diseases, and that resulting neuronal dysfunction further promotes the metabolic imbalance, establishing an effective positive feedback loop and a downward spiral of disease progression. Therefore, metabolic correction leading to the normalization of abnormalities in glucose metabolism may be an efficient tool to treat the neurological disorders by counteracting their primary pathological mechanisms. Published and preliminary experimental results on this approach for treating Alzheimer's disease and epilepsy models support the efficacy of metabolic correction, confirming the highly promising nature of the strategy. © 2017 Wiley Periodicals, Inc.

A MicroRNA124 Target Sequence Restores Astrocyte Specificity of gfaABC1D-Driven Transgene Expression in AAV-Mediated Gene Transfer

Experimentally restricting transgene expression exclusively to astrocytes has proven difficult. Using adeno-associated-virus-mediated gene transfer, we assessed two commonly used glial fibrillary acidic protein promoters: the full-length version gfa2 (2,210-bp human glial fibrillary acidic protein [GFAP] promoter) and the truncated variant gfaABC₁D (681-bp GFAP promoter). The capacity to drive efficient, but also cell-type specific, expression of the EGFP in astrocytes was tested both in vitro in rat primary cortical cultures as well as in vivo in the rat striatum. We observed an efficient, but not entirely astrocyte-specific, gfa2-driven reporter expression. gfaABC₁D exhibited a weaker activity, and most importantly, off-target, neuronal expression of the transgene occurred in a larger fraction of cells. Therefore, we explored the potential of a microRNA (miR)-specific target-sequence-based approach for abolishing off-target expression. When miR124 target sequences were incorporated into the 3′ UTR, neuronal gene expression was effectively silenced. However, unexpectedly, the insertion of an additional sequence in the 3′ UTR clearly diminished transgene expression. In conclusion, the gfaABC₁D promoter on its own is not sufficient to specifically target transgene expression to astrocytes and is not well suited for AAV-based gene targeting, even if short promoter sequences are required. The combination with a miR de-targeting sequence represents a promising experimental strategy that eliminates off-target, neuronal expression.

Investigation into experimental toxicological properties of plant protection products having a potential link to Parkinson's disease and childhood leukaemia

In 2013, EFSA published a literature review on epidemiological studies linking exposure to pesticides and human health outcome. As a follow up, the EFSA Panel on Plant Protection Products and their residues (PPR Panel) was requested to investigate the plausible involvement of pesticide exposure as a risk factor for Parkinson's disease (PD) and childhood leukaemia (CHL). A systematic literature review on PD and CHL and mode of actions for pesticides was published by EFSA in 2016 and used as background documentation. The Panel used the Adverse Outcome Pathway (AOP) conceptual framework to define the biological plausibility in relation to epidemiological studies by means of identification of specific symptoms of the diseases as AO. The AOP combines multiple information and provides knowledge of biological pathways, highlights species differences and similarities, identifies research needs and supports regulatory decisions. In this context, the AOP approach could help in organising the available experimental knowledge to assess biological plausibility by describing the link between a molecular initiating event (MIE) and the AO through a series of biologically plausible and essential key events (KEs). As the AOP is chemically agnostic, tool chemical compounds were selected to empirically support the response and temporal concordance of the key event relationships (KERs). Three qualitative and one putative AOP were developed by the Panel using the results obtained. The Panel supports the use of the AOP framework to scientifically and transparently explore the biological plausibility of the association between pesticide exposure and human health outcomes, identify data gaps, define a tailored testing strategy and suggests an AOP's informed Integrated Approach for Testing and Assessment (IATA).

New insights into the ameliorative effects of ferulic acid in pathophysiological conditions

Ferulic acid, a natural phytochemical has gained importance as a potential therapeutic agent by virtue of its easy commercial availability, low cost and minimal side-effects. It is a derivative of curcumin and possesses the necessary pharmacokinetic properties to be retained in the general circulation for several hours. The therapeutic effects of ferulic acid are mediated through its antioxidant and anti-inflammatory properties. It exhibits different biological activities such as anti-inflammatory, anti-apoptotic, anti-carcinogenic, anti-diabetic, hepatoprotective, cardioprotective, neuroprotective actions, etc. The current review addresses its therapeutic effects under different pathophysiological conditions (eg. cancer, cardiomyopathy, skin disorders, brain disorders, viral infections, diabetes etc.).

Exploring Braak's Hypothesis of Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disorder for which there is no cure. Most patients suffer from sporadic PD, which is likely caused by a combination of genetic and environmental factors. Braak’s hypothesis states that sporadic PD is caused by a pathogen that enters the body via the nasal cavity, and subsequently is swallowed and reaches the gut, initiating Lewy pathology (LP) in the nose and the digestive tract. A staging system describing the spread of LP from the peripheral to the central nervous system was also postulated by the same research group. There has been criticism to Braak’s hypothesis, in part because not all patients follow the proposed staging system. Here, we review literature that either supports or criticizes Braak’s hypothesis, focused on the enteric route, digestive problems in patients, the spread of LP on a tissue and a cellular level, and the toxicity of the protein αSynuclein (αSyn), which is the major constituent of LP. We conclude that Braak’s hypothesis is supported by in vitro, in vivo, and clinical evidence. However, we also conclude that the staging system of Braak only describes a specific subset of patients with young onset and long duration of the disease.

Ketamine suppresses the substance P-induced production of IL-6 and IL-8 by human U373MG glioblastoma/astrocytoma cells

The neuropeptide substance P (SP) is an important mediator of neurogenic inflammation within the central and peripheral nervous systems. SP has been shown to induce the expression of pro-inflammatory cytokines implicated in the pathogenesis of several disorders of the human brain via the neurokinin-1 receptor (NK-1R). Ketamine, an intravenous anesthetic agent, functions as a competitive antagonist of the excitatory neurotransmission N-methyl-D‑aspartate (NMDA) receptor, and also antagonizes the NK-1R by interfering with the binding of SP. In the present study, we investigated the anti-inflammatory effects of ketamine on the SP-induced activation of a human astrocytoma cell line, U373MG, which expresses high levels of NK-1R. The results from our experiments indicated that ketamine suppressed the production of interleukin (IL)-6 and IL-8 by the U373MG cells. Furthermore, ketamine inhibited the SP-induced activation of extracellular signal‑regulated kinase (ERK)1/2, p38 mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB). Taken together, these observations suggest that ketamine may suppress the SP-induced activation (IL-6 and IL-8 production) of U373MG cells by inhibiting the phosphorylation of signaling molecules (namely ERK1/2, p38 MAPK and NF-κB), thereby exerting anti‑inflammatory effects. Thus, ketamine may modulate SP-induced inflammatory responses by NK-1R‑expressing cells through the suppression of signaling molecules (such as ERK1/2, p38 MAPK and NF-κB).

Destination Brain: the Past, Present, and Future of Therapeutic Gene Delivery

Neurological diseases and disorders (NDDs) present a significant societal burden and currently available drug- and biological-based therapeutic strategies have proven inadequate to alleviate it. Gene therapy is a suitable alternative to treat NDDs compared to conventional systems since it can be tailored to specifically alter select gene expression, reverse disease phenotype and restore normal function. The scope of gene therapy has broadened over the years with the advent of RNA interference and genome editing technologies. Consequently, encouraging results from central nervous system (CNS)-targeted gene delivery studies have led to their transition from preclinical to clinical trials. As we shift to an exciting gene therapy era, a retrospective of available literature on CNS-associated gene delivery is in order. This review is timely in this regard, since it analyzes key challenges and major findings from the last two decades and evaluates future prospects of brain gene delivery. We emphasize major areas consisting of physiological and pharmacological challenges in gene therapy, function-based selection of a ideal cellular target(s), available therapy modalities, and diversity of viral vectors and nanoparticles as vehicle systems. Further, we present plausible answers to key questions such as strategies to circumvent low blood-brain barrier permeability and most suitable CNS cell types for targeting. We compare and contrast pros and cons of the tested viral vectors in the context of delivery systems used in past and current clinical trials. Gene vector design challenges are also evaluated in the context of cell-specific promoters. Key challenges and findings reported for recent gene therapy clinical trials, assessing viral vectors and nanoparticles are discussed from the perspective of bench to bedside gene therapy translation. We conclude this review by tying together gene delivery challenges, available vehicle systems and comprehensive analyses of neuropathogenesis to outline future prospects of CNS-targeted gene therapies.

A Novel Immunosuppressor, (5R)-5-Hydroxytriptolide, Alleviates Movement Disorder and Neuroinflammation in a 6-OHDA Hemiparkinsonian Rat Model

Parkinson's disease (PD) is one of the most common age-related neurodegenerative diseases. Promising therapies for PD still need to be explored. Immune dysfunction has been found to be involved in PD pathogenesis. Here, a novel immunosuppressor, (5R)-5-hydroxytriptolide (LLDT8), was used to treat 6-hydroxydopamine (6-OHDA)-induced hemiparkinson rats. We found that oral administration of LLDT8 significantly alleviated apomorphine-induced rotations at a dose of 125 µg/kg, and improved performance in cylinder and rotarod tests at a lower dose of 31.25 µg/kg, in 6-OHDA hemiparkinsonian rats. Moreover, loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) of the 6-OHDA rat was attenuated in response to LLDT8 treatment in a dose-dependent manner. In addition, inflammatory factors IL-1β, IL-6 and TNF-α, were significantly inhibited in LLDT8-treated hemiparkisonian rats, compared with vehicle. Notably, the level of dopamine (DA) in the striatum of PD rats was restored by LLDT8 treatment. Furthermore, we also detected that the disequilibrium of peripheral lymphocytes was reversed by LLDT8 administration. Taken together, the results imply that the immunosuppressor, LLDT8, can rescue dopaminergic neurodegeneration in 6-OHDA hemiparkinsonian rats, thus providing a potential therapeutic strategy for PD.

Subthalamic nucleus deep brain stimulation on motor-symptoms of Parkinson's disease: Focus on neurochemistry

Deep brain stimulation (DBS) has become a standard therapy for Parkinson's disease (PD) and it is also currently under investigation for other neurological and psychiatric disorders. Although many scientific, clinical and ethical issues are still unresolved, DBS delivered into the subthalamic nucleus (STN) has improved the quality of life of several thousands of patients. The mechanisms underlying STN-DBS have been debated extensively in several reviews; less investigated are the biochemical consequences, which are still under scrutiny. Crucial and only partially understood, for instance, are the complex interplays occurring between STN-DBS and levodopa (LD)-centred therapy in the post-surgery follow-up. The main goal of this review is to address the question of whether an improved motor control, based on STN-DBS therapy, is also achieved through the additional modulation of other neurotransmitters, such as noradrenaline (NA) and serotonin (5-HT). A critical issue is to understand not only acute DBS-mediated effects, but also chronic changes, such as those involving cyclic nucleotides, capable of modulating circuit plasticity. The present article will discuss the neurochemical changes promoted by STN-DBS and will document the main results obtained in microdialysis studies. Furthermore, we will also examine the preliminary achievements of voltammetry applied to humans, and discuss new hypothetical investigational routes, taking into account novel players such as glia, or subcortical regions such as the pedunculopontine (PPN) area. Our further understanding of specific changes in brain chemistry promoted by STN-DBS would further disseminate its utilisation, at any stage of disease, avoiding an irreversible lesioning approach.

The effect of α-synuclein on gliosis and IL-1α, TNFα, IFNγ, TGFβ expression in murine brain

BACKGROUND

Alpha - synuclein (ASN) is the principal component of Lewy pathology and strongly influences on the pathogenesis of Parkinson's disease (PD). The increased level of ASN protein causes microglial response. The reactive microglial cells may actively participate in the damaging of dopaminergic neurons. The data suggests that ASN accumulation in astrocytes might damage these cells in the substantia nigra pars compacta (SN) and promotes degeneration of dopaminergic neurons in SN. We examined the potential role of recombinant ASN monomers as a major pathogenic factor causing the inflammatory response in the central nervous system.

METHODS

Mice were bilaterally infused by human ASN monomers into the striatum (ST) or SN (single treatment was 4μg/structure, 8μg per brain) and decapitated after 1, 4 or 12 weeks post injection. The changes in the level of inflammatory factors in ST were evaluated using Real-Time PCR and Western Blot method. The analysis of morphological changes of glial cells was performed by immunohistochemical staining.

RESULTS

We observed a strong activation of microglia cells in ST and increased expression of striatal interleukin 1α, tumor necrosis factor alpha and interferon gamma after ASN injection into the ST. We noticed an increase in striatal glial fibrillary acidic protein mRNA level 4 weeks after ASN injection into the ST. Injection of ASN into the SN led to an increase of striatal transforming growth factor beta mRNA level and has no influence on striatal glial fibrillary acidic protein mRNA level.

CONCLUSION

Our results suggest that both the microglia activation and supressing astrocytes play a crucial role in ASN-related dopaminergic neurotoxicity.

The protective mechanism of docosahexaenoic acid in mouse model of Parkinson: The role of hemeoxygenase

Parkinson's disease (PD) is characterized by degeneration of the dopaminergic neurons in substantia nigra (SN). Its major clinical symptoms are tremor, rigidity, bradykinesia and postural instability. Docosahexaenoic acid (DHA) is an essential fatty acid for neural functions that resides within the neural membrane. A decline in fatty acid concentration is observed in case of neurodegenerative diseases such as PD. The present study aimed to explore the role of the heme oxygenase (HO) enzyme in protective effects of DHA administration in an experimental model of PD by using the neurotoxin 1-Methly-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Three-month old male C57BL/6 mice were randomly divided into 4 groups as Control, DHA-treated (DHA), MPTP-injected (MPTP) and DHA-treated + MPTP injected (DHA + MPTP). DHA was administered daily (36 mg kg-1  day-1) by gavage to DHA and DHA + MPTP groups for 30 days. On the 23rd day of DHA administration, MPTP was intraperitoneally injected at a dose of 4 × 20  mg kg-1 with 2-hr. intervals. Motor activities of mice were evaluated by pole test, locomotor activity and rotarod tests on the 7th day of the utilization of experimental Parkinson's model. Total brain tissues were used in immunohistochemical analysis of the tyrosine hydroxylase (TH) and Nuclear factor E2 related factor2 (Nrf2). SN tissues were extracted for biochemical analysis. HO-1 and HO-2 protein levels were detected by western blotting. Further, HO activity was measured by spectrophotometric assay. As an indicator of motor coordination and balance, the rotarod test at 40 rpm showed that MPTP-treated animals exhibited shorter time on the rotating rod mill, which was significantly increased by DHA treatment in DHA + MPTP group. The total locomotor activity, ambulatory movement and total distance were decreased in MPTP group, whereas they were improved upon DHA treatment. The results of the pole test indicating the intensity of the bradykinesia showed that the T-turn and T-total were increased in MPTP group, while DHA treatment significantly shortened both parameters. The number of TH-positive cells in SN was significantly reduced in MPTP group compared to the Control and DHA + MPTP groups. Also, immunoreactive Nrf2 levels were clearly increased in MPTP group compared to DHA + MPTP group. HO-1 expression level decreased in the DHA + MPTP group compared to MPTP group. The results of the present study indicated that DHA has protective effects on dopaminergic neurons in MPTP-induced experimental model of PD. In addition, the pathways of HO-1 and HO-2 might participate in this protective mechanism.

Auraptene and Other Prenyloxyphenylpropanoids Suppress Microglial Activation and Dopaminergic Neuronal Cell Death in a Lipopolysaccharide-Induced Model of Parkinson's Disease

In patients with Parkinson’s disease (PD), hyperactivated inflammation in the brain, particularly microglial hyperactivation in the substantia nigra (SN), is reported to be one of the triggers for the delayed loss of dopaminergic neurons and sequential motor functional impairments. We previously reported that (1) auraptene (AUR), a natural prenyloxycoumain, suppressed inflammatory responses including the hyperactivation of microglia in the ischemic brain and inflamed brain, thereby inhibiting neuronal cell death; (2) 7-isopentenyloxycoumarin (7-IP), another natural prenyloxycoumain, exerted anti-inflammatory and neuroprotective effects against excitotoxicity; and (3) 4′-geranyloxyferulic acid (GOFA), a natural prenyloxycinnamic acid, also exerted anti-inflammatory effects. In the present study, using an intranigral lipopolysaccharide (LPS)-induced PD-like mouse model, we investigated whether AUR, 7-IP, and GOFA suppress microglial activation and protect against dopaminergic neuronal cell death in the SN. We successfully showed that these prenyloxyphenylpropanoids exhibited these prospective abilities, suggesting the potential of these compounds as neuroprotective agents for patients with PD.

Methylglyoxal-induced neuroinflammatory response in in vitro astrocytic cultures and hippocampus of experimental animals

Diabetes mellitus is characterized by chronic hyperglycemia and its diverse complications. Hyperglycemia is associated with inflammatory responses in different organs and diabetic patients have a higher risk of developing neurodegenerative disorders. Methylglyoxal is a reactive advanced glycation end product precursor that accumulates in diabetic patients. It induces various stress responses in the central nervous system and causes neuronal dysfunction. Astrocytes are actively involved in maintaining neuronal homeostasis and possibly play a role in protecting the brain against neurodegeneration. However it is not clear whether methylglyoxal exerts any adverse effects towards these astrocytes. In the present study we investigated the effects of methylglyoxal in astrocytic cultures and hippocampi of experimental animals. The cells from the astrocytic line DITNC1 were treated with methylglyoxal for 1 to 24 h. For the in vivo model, 3 months old C57BL/6 mice were treated with methylglyoxal solution for 6 weeks by intraperitoneal injection. Following the treatment, both astrocytes and hippocampi were harvested for MTT assay, Western blot and real time PCR analyses. We found that methylglyoxal induced astrogliosis in DITNC1 astrocytic cultures and C57BL/6 mice. Further, activation of the pro-inflammatory JNK signaling pathway and its downstream effectors c-Jun were observed. Furthermore, increased gene expression of pro-inflammatory cytokines and astrocytic markers were observed from real time PCR analyses. In addition, inhibition of JNK activities resulted in down-regulation of TNF-α gene expression in methylglyoxal treated astrocytes. Our results suggest that methylglyoxal may contribute to the progression of diabetes related neurodegeneration through JNK pathway activation in astrocytes and the subsequent neuroinflammatory responses in the central nervous system.

The Chemical Molecule B355252 is Neuroprotective in an In Vitro Model of Parkinson's Disease

6-Hydroxydopamine (6-OHDA) is a neurotoxin frequently used to create in vitro and in vivo experimental models of Parkinson's disease (PD), a chronic neurodegenerative disorder largely resulting from damage to the nigrostriatal dopaminergic pathway. No effective drugs or therapies have been developed for this devastating disorder, and current regimens of symptomatic therapeutics only alleviate symptoms temporarily. Therefore, effective treatments that reverse or cure this disorder are urgently needed. The aim of the study described in this report was to investigate the therapeutic impact of B355252, an aryl thiophene sulfonamide chemical entity, in the widely recognized in vitro model of PD, and to characterize the molecular signaling pathways. We show here that 6-OHDA-induced cell death in HT22, a murine neuronal cell model, through a pathway that involves the mitochondria by increasing the levels of reactive oxygen species (ROS), raising intracellular calcium ([Ca(2+)]i), enhancing the release of cytochrome c to the cytosol, and promoting activation of stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK) signaling pathway. More importantly, we found that B355252 protected HT22 neurons against 6-OHDA toxin-induced neuronal cell death by significant attenuation of ROS production, blocking of mitochondrial depolarization, inhibition of cytochrome c release, sequestration of [Ca(2+)]i, modulation of JNK cascade, and strong inhibition of caspase 3/7 cleavage. Overall, this study demonstrates that death of neurons under toxic conditions characteristic of PD can be efficiently halted by B355252 and suggests that further development of the molecule could be potentially beneficial as a therapeutic prevention or treatment option for PD.

Biological functions of selenium and its potential influence on Parkinson's disease

Parkinson's disease is characterized by the death of dopaminergic neurons, mainly in the substantia nigra, and causes serious locomotor dysfunctions. It is likely that the oxidative damage to cellular biomolecules is among the leading causes of neurodegeneration that occurs in the disease. Selenium is an essential mineral for proper functioning of the brain, and mainly due to its antioxidant activity, it is possible to exert a special role in the prevention and in the nutritional management of Parkinson's disease. Currently, few researchers have investigated the effects of selenium on Parkinson´s disease. However, it is known that very high or very low body levels of selenium can (possibly) contribute to the pathogenesis of Parkinson's disease, because this imbalance results in increased levels of oxidative stress. Therefore, the aim of this work is to review and discuss studies that have addressed these topics and to finally associate the information obtained from them so that these data and associations serve as input to new research.

Therapeutic effects of paeonol on methyl-4-phenyl-1,2,3,6-tetrahydropyridine/probenecid-induced Parkinson's disease in mice

Paeonol is a major phenolic compound of the Chinese herb, Cortex Moutan, and is known for its antioxidant, anti-inflammatory and antitumor properties. The present study was designed to investigate the therapeutic potential and underlying mechanisms of paeonol on a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/probenecid (MPTP/p)-induced mouse model of Parkinson's disease (PD). MPTP (25 mg/kg), followed by probenecid (250 mg/kg), was administered via i.p. injection for five consecutive days to induce the mouse model of PD. Paeonol (20 mg/kg) was administrated orally for 21 days. Behavior was assessed using the rotarod performance and open-field tests. Additionally, the levels of tyrosine hydroxylase (TH), microglia, interleukin-1β (IL-1β), and brain-derived neurotrophic factor (BDNF) in the substantia nigra pars compacta (SNpc) were evaluated by immunohistochemical staining. MPTP/p-induced motor deficits were observed to be significantly improved following long-term treatment with paeonol. Paeonol treatment decreased MPTP/p-induced oxidative stress, as determined by evaluating the activity levels of superoxide dismutase, catalase and glutathione. Additionally, MPTP/p-induced neuroinflammation was assessed by examining the levels of microglia and IL-1β, which were significantly decreased following paeonol treatment. Paeonol treatment improved the MPTP/p-induced dopaminergic neurodegeneration, as measured by observing the increased TH level in the SNpc. Furthermore, the BDNF level was significantly elevated in the paeonol treatment group compared with mice treated with MPTP/p only. In conclusion, paeonol exerted therapeutic effects in the MPTP/p-induced mouse model of PD, possibly by decreasing the damage from oxidative stress and neuroinflammation, and by enhancing the neurotrophic effect on dopaminergic neurons. The results demonstrate paeonol as a potential novel treatment for PD.

Protective Effects of Costunolide against Hydrogen Peroxide-Induced Injury in PC12 Cells

Oxidative stress-mediated cellular injury has been considered as a major cause of neurodegenerative diseases including Alzheimer’s and Parkinson’s diseases. The scavenging of reactive oxygen species (ROS) mediated by antioxidants may be a potential strategy for retarding the diseases’ progression. Costunolide (CS) is a well-known sesquiterpene lactone, used as a popular herbal remedy, which possesses anti-inflammatory and antioxidant activity. This study aimed to investigate the protective role of CS against the cytotoxicity induced by hydrogen peroxide (H₂O₂) and to elucidate potential protective mechanisms in PC12 cells. The results showed that the treatment of PC12 cells with CS prior to H₂O₂ exposure effectively increased the cell viability. Furthermore, it decreased the intracellular ROS, stabilized the mitochondria membrane potential (MMP), and reduced apoptosis-related protein such as caspase 3. In addition, CS treatment attenuated the cell injury by H₂O₂ through the inhibition of phosphorylation of p38 and the extracellular signal-regulated kinase (ERK). These results demonstrated that CS is promising as a potential therapeutic candidate for neurodegenerative diseases resulting from oxidative damage and further research on this topic should be encouraged.