Polyphenols in Parkinson's Disease: A Systematic Review of In Vivo Studies

Assessing the stability of polyphenol content in red rooibos herbal tea using traditional methods and high-resolution mass spectrometry: Implications for studying dietary interventions in preclinical rodent studies

Preclinical rodent models are used to examine the relationship between tea consumption and bone health, where tea is available for rodents and typically replaced weekly. However, the extent to which the tea polyphenols change over time remains uncertain, despite its importance in preparing tea during preclinical rodent trials. Using an untargeted molecular approach, we applied a liquid chromatography quadrupole-time-of-flight mass spectrometry (LC-QTOFMS) system to assess the molecular profile of red rooibos teas throughout a 6-day aging period. We found a significant, 3-fold decrease of polyphenols involved in bone metabolism, including m-coumaric acid, catechin derivatives and courmaroyl tartaric acid over 6 days, likely due to photochemical decomposition and autooxidation within tea extracts. Using a novel untargeted workflow for polyphenol characterization, our findings revealed the complexity of polyphenols in red rooibos teas that can inform the evidence-based decisions of how often to change teas during in vivo rodent trials.

Therapeutic Targeting of Krüppel-Like Factor 4 and Its Pharmacological Potential in Parkinson's Disease: a Comprehensive Review

Krüppel-like factor 4 (KLF4), a zinc finger transcription factor, is found in different human tissues and shows diverse regulatory activities in a cell-dependent manner. In the brain, KLF4 controls various neurophysiological and neuropathological processes, and its contribution to various neurological diseases has been widely reported. Parkinson's disease (PD) is an age-related neurodegenerative disease that might have a connection with KLF4. In this review, we discussed the potential implication of KLF4 in fundamental molecular mechanisms of PD, including aberrant proteostasis, neuroinflammation, apoptosis, oxidative stress, and iron overload. The evidence collected herein sheds new light on KLF4-mediated pathways, which manipulation appears to be a promising therapeutic target for PD management. However, there is a gap in the knowledge on this topic, and extended research is required to understand the translational value of the KLF4-oriented therapeutical approach in PD.

In vitro inhibition of α-Synuclein aggregation and disaggregation of preformed fibers by polyphenol hybrids with 2-conjugated benzothiazole

The misfolding and aggregation of α-Syn play a pivotal role in connecting diverse pathological pathways in Parkinson's disease (PD). Preserving α-Syn proteostasis and functionality by inhibiting its aggregation or disaggregating existing aggregates using suitable inhibitors represents a promising strategy for PD prevention and treatment. In this study, a series of benzothiazole-polyphenol hybrids was designed and synthesized. Three identified compounds exhibited notable inhibitory activities against α-Syn aggregation in vitro, with IC50 values in the low micromolar range. These inhibitors demonstrated sustained inhibitory effects throughout the entire aggregation process, stabilizing α-Syn proteostasis conformation. Moreover, the compounds effectively disintegrated preformed α-Syn oligomers and fibers, potentially by binding to specific domains within the fibers, inducing fibril instability, collapse, and ultimately resulting in smaller-sized aggregates and monomers. These findings offer valuable insights into the therapeutic potential of polyphenol hybrids with 2-conjugated benzothiazole targeting α-Syn aggregation in the treatment of PD.

Understanding the (epi)genetic dysregulation in Parkinson's disease through an integrative brain competitive endogenous RNA network

Parkinson's disease (PD) is a rapidly growing neurodegenerative disorder characterized by dopaminergic neuron loss in the substantia nigra pars compacta (SN) and aggregation of α-synuclein. Its aetiology involves a multifaceted interplay among genetic, environmental, and epigenetic factors. We integrated brain gene expression data from PD patients to construct a comprehensive regulatory network encompassing messenger RNAs (mRNAs), microRNAs (miRNAs), circular RNAs (circRNAs) and, for the first time, RNA binding proteins (RBPs). Expression data from the SN of PD patients and controls were systematically selected from public databases to identify combined differentially expressed genes (DEGs). Brain co-expression analysis revealed modules comprising significant DEGs that function cooperatively. The relationships among co-expressed DEGs, miRNAs, circRNAs, and RBPs revealed an intricate competitive endogenous RNA (ceRNA) network responsible for post-transcriptional dysregulation in PD. Many genes in the ceRNA network, including the TOMM20 and HMGCR genes, overlap with the most relevant genes in our previous Alzheimer's disease-associated ceRNA network, suggesting common underlying mechanisms between both conditions. Moreover, in the ceRNA subnetwork, the RBP Aly/REF export factor (ALYREF), which acts as an RNA 5-methylcytosine(m5C)-binding protein, stood out. Our data sheds new light on the potential role of brain ceRNA networks in PD pathogenesis.

Polyphenolic Nanoparticle Platforms (PARCELs) for In Vitro and In Vivo mRNA Delivery

Despite their successful implementation in the COVID-19 vaccines, lipid nanoparticles (LNPs) still face a central limitation in the delivery of mRNA payloads: endosomal trapping. Improving upon this inefficiency could afford improved drug delivery systems, paving the way toward safer and more effective mRNA-based medicines. Here, we present polyphenolic nanoparticle platforms (PARCELs) as effective mRNA delivery systems. In brief, our investigation begins with a computationally guided structural analysis of 1825 discrete polyphenolic structural data points across 73 diverse small molecule polyphenols and 25 molecular parameters. We then generate structurally diverse PARCELs, evaluating their in vitro mechanism and activity, ultimately highlighting the superior endosomal escape properties of PARCELs relative to analogous LNPs. Finally, we examine the in vivo biodistribution, protein expression, and therapeutic efficacy of PARCELs in mice. In undertaking this approach, the goal of this study is to establish PARCELs as viable delivery platforms for safe and effective mRNA delivery.

Therapeutic potential of berries in age-related neurological disorders

Aging significantly impacts several age-related neurological problems, such as stroke, brain tumors, oxidative stress, neurodegenerative diseases (Alzheimer's, Parkinson's, and dementia), neuroinflammation, and neurotoxicity. Current treatments for these conditions often come with side effects like hallucinations, dyskinesia, nausea, diarrhea, and gastrointestinal distress. Given the widespread availability and cultural acceptance of natural remedies, research is exploring the potential effectiveness of plants in common medicines. The ancient medical system used many botanical drugs and medicinal plants to treat a wide range of diseases, including age-related neurological problems. According to current clinical investigations, berries improve motor and cognitive functions and protect against age-related neurodegenerative diseases. Additionally, berries may influence signaling pathways critical to neurotransmission, cell survival, inflammation regulation, and neuroplasticity. The abundance of phytochemicals in berries is believed to contribute to these potentially neuroprotective effects. This review aimed to explore the potential benefits of berries as a source of natural neuroprotective agents for age-related neurological disorders.

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

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

Oleanolic acid-based therapeutics ameliorate rotenone-induced motor and depressive behaviors in parkinsonian male mice via controlling neuroinflammation and activating Nrf2-BDNF-dopaminergic signaling pathways

Parkinson's disease (PD) is often accompanied by depression, which may appear before motor signs. Oleanolic acid (OA), a pentacyclic triterpenoid substance, have many pharmacological properties. However, its efficacy in treating PD-related chronic unpredictable stress (CUS) is unknown. Our study used behavioral, biochemical, and immunohistochemical techniques to assess how OA affected PDrelated CUS. Rotenone (1 mg/kg i.p. for first 21 days) was used to induce Parkinsonism, and modest psychological & environmental stresses generated CUS (from day 22 to day 43) in animals. The study included daily i.p.administration of OA (5, 10, and 20 mg/kg) from day 1 to day 57 in male swiss albino mice. Animals were evaluated for behavioral, biochemical parameters, neurotransmitters, and immunohistochemical expression following the treatment. Results of the study revealed that treatment with OA at all doses alleviated the core symptoms of CUS linked to PD and improved motor and non-motor function. OA therapy significantly lowered IL-1β, TNF-α (p < 0.01, < 0.01, < 0.001), IL-6 (p < 0.05, < 0.01, < 0.001), oxidative stress (p < 0.05, < 0.01, < 0.01), and elevated norepinephrine (p < 0.05, < 0.01, < 0.01), dopamine, and serotonin (p < 0.05, < 0.01, < 0.001) levels. Moreover, OA therapy substantially reduced α-synuclein (p < 0.05, < 0.01, < 0.01) aggregation and increased BDNF (p < 0.05, < 0.01, < 0.001) & Nrf-2 (p < 0.05, < 0.01, < 0.01) levels, which boosts neuronal dopamine survival. The study's findings indicated that OA ameliorates depressive-like behavior persuaded by CUS in PD, decreases neuroinflammation, and improves neurotransmitter concentration via activating Nrf2-BDNF-dopaminergic pathway.

Pyrazolamide derivatives inhibit α-Synuclein aggregation, disaggregate preformed fibers, and reduce inclusion formation in neuron cells

α-Syn fibers, the primary cause and central element of Lewy bodies (LB), play a pivotal role in the development of Parkinson's disease (PD). This research aims to identify more potent inhibitors of α-Syn aggregation. A series of N-aryl-3-aryl-pyrazole-5-carboxamide derivatives were designed and synthesized for this purpose. Among them, four candidate compounds, combining pyrazole and polyphenol blocks, were identified through screening, demonstrating good inhibitory effects with IC50 values in the low micromolar range (1.25-4.29 μM). Two candidates exhibited high permeability through the blood-brain barrier. Mechanistic studies using various methods revealed that the candidates preferentially bind to the aggregation-prone domains-proNAC or NAC domains of α-Syn. This binding hinders the conformational transition from random coil/α-helix to β-sheet, preserving α-Syn proteostasis. As a result, it interferes with α-Syn nuclei formation, prolongs the lag phase, decelerates the elongation phase, and ultimately impedes the formation of α-Syn fibrils. Additionally, the candidates demonstrated promising results in the disaggregation of preformed α-Syn fibers, potentially by binding to specific sites near the β-sheet domain within fibers. This reduces fiber stability, causing rapid collapse and yielding smaller aggregates and monomers. Crucially, the candidate compounds exhibited significant inhibitory efficacy against α-Syn aggregation within nerve cells with low cytotoxicity. This resulted in a notable inhibition of the formation of LB-like α-Syn inclusions. These compounds show considerable promise as potential therapeutic agents for the prevention and treatment of PD.

Aqueous extract of Swietenia macrophylla leaf exerts an anti-inflammatory effect in a murine model of Parkinson's disease induced by 6-OHDA

Introduction

Parkinson's disease affects 2% of the population aged over 65 years and is the second most common neurodegenerative disorder in the general population. The appearance of motor symptoms is associated with the degeneration of dopaminergic neurons in the nigrostriatal pathway. Clinically significant nonmotor symptoms are also important for severe disability with disease progression. Pharmacological treatment with levodopa, which involves dopamine restitution, results in a temporary improvement in motor symptoms. Among the mechanisms underlying the pathogenesis of the disease are exacerbated oxidative stress, mitochondrial dysfunction, and neuroinflammation. A phytochemical prospecting study showed that the aqueous extract of the leaves from Swietenia macrophylla (Melineaceae), known as mahogany, has polyphenols with antioxidant and anti-inflammatory capacity in a significantly higher percentage than leaf extracts from other Amazonian plants. Furthermore, the antioxidant and anti-inflammatory capacity of aqueous extract of mahogany leaf has already been demonstrated in an in vitro model. In this study, we hypothesized that the aqueous extract of mahogany leaf (AEML) has a neuroprotective effect in a murine model of Parkinson's disease induced by 6-hydroxidopamine (6-OHDA), due to antioxidant and anti-inflammatory properties of its phenolic compounds.

Methods

Mice were treated daily with the mahogany extract at a dose of 50 mg/kg, starting 7 days before 6-OHDA infusion until post-surgery day 7.

Results and discussion

The animals from the 6-OHDA/mahogany group, which corresponds to animals injected with the toxin and treated with aqueous extract of the mahogany leaf, presented distinct behavioral phenotypes after apomorphine challenge and were therefore subdivided into 2 groups, 6-OHDA/mahogany F1 and 6-OHDA/mahogany F2. The F1 group showed a significant increase in contralateral rotations, whereas the F2 group did not show rotations after the apomorphine stimulus. In the F1 group, there was an increase, although not significant, in motor performance in the open field and elevated plus maze tests, whereas in the F2 group, there was significant improvement, which may be related to the lesser degree of injury to the nigrostriatal dopaminergic pathway. The TH+ histopathological analysis, a dopaminergic neuron marker, confirmed that the lesion to the nigrostriatal dopaminergic pathway was more pronounced in 6-OHDA/mahogany F1 than in 6-OHDA/mahogany F2. Our main result consisted of signs of improvement in the inflammatory profile in both the F1 and F2 6-OHDA/mahogany groups, such as a lower number of IBA-1+ microglial cells in the ventral striatum and substantia nigra pars compacta and a reduction in GFAP+ expression, an astrocyte marker, in the dorsal striatum. In this study, several bioactive compounds in the aqueous extract of mahogany leaf may have contributed to the observed beneficial effects. Further studies are necessary to better characterize their applicability for treating chronic degenerative diseases with inflammatory and oxidative bases, such as Parkinson's disease.

What Can Inflammation Tell Us about Therapeutic Strategies for Parkinson's Disease?

Parkinson's disease (PD) is a common neurodegenerative disorder with a complicated etiology and pathogenesis. α-Synuclein aggregation, dopaminergic (DA) neuron loss, mitochondrial injury, oxidative stress, and inflammation are involved in the process of PD. Neuroinflammation has been recognized as a key element in the initiation and progression of PD. In this review, we summarize the inflammatory response and pathogenic mechanisms of PD. Additionally, we describe the potential anti-inflammatory therapies, including nod-like receptor pyrin domain containing protein 3 (NLRP3) inflammasome inhibition, nuclear factor κB (NF-κB) inhibition, microglia inhibition, astrocyte inhibition, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibition, the peroxisome proliferator-activated receptor γ (PPARγ) agonist, targeting the mitogen-activated protein kinase (MAPK) pathway, targeting the adenosine monophosphate-activated protein kinase (AMPK)-dependent pathway, targeting α-synuclein, targeting miRNA, acupuncture, and exercise. The review focuses on inflammation and will help in designing new prevention strategies for PD.

Effect of the Flavonoid Rutin on the Modulation of the Myenteric Plexuses in an Experimental Model of Parkinson's Disease

Recent discoveries have shown that enteric glial cells play an important role in different neurodegenerative disorders, such as Parkinson's disease (PD), which is characterized by motor dysfunctions caused by the progressive loss of dopaminergic neurons in the substance nigra pars compacta and non-motor symptoms including gastrointestinal dysfunction. In this study, we investigated the modulatory effects of the flavonoid rutin on the behavior and myenteric plexuses in a PD animal model and the response of enteric glia. Adult male Wistar rats were submitted to stereotaxic injection with 6-hydroxydopamine or saline, and they were untreated or treated with rutin (10 mg/kg) for 14 days. The ileum was collected to analyze tissue reactivity and immunohistochemistry for neurons (HuC/HuD) and enteric glial cells (S100β) in the myenteric plexuses. Behavioral tests demonstrated that treatment with rutin improved the motor capacity of parkinsonian animals and improved intestinal transit without interfering with the cell population; rutin treatment modulated the reactivity of the ileal musculature through muscarinic activation, reducing relaxation through the signaling pathway of nitric oxide donors, and increased the longitudinal contractility of the colon musculature in parkinsonian animals. Rutin revealed modulatory activities on the myenteric plexus, bringing relevant answers regarding the effect of the flavonoid in this system and the potential application of PD adjuvant treatment.

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

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

Dietary flavonoids may have a protective and therapeutic effect in Parkinson disease: A systematic review

Parkinson disease (PD) is characterized by the loss of dopaminergic neurons because of oxidative stress and neuroinflammation. Polyphenols in vegetables, known for their high antioxidant capacity, may prevent the onset, or delay the progression of the disease; among these, flavonoids are the most abundant class of polyphenols in foods. Clinical and cohort studies have evaluated the effect of polyphenol consumption on the risk of developing PD or of attenuating the symptoms after diagnosis; therefore, it is necessary to integrate the scientific evidence into making dietary recommendations. The objective of this study was to perform a systematic review of randomized controlled trials and cohort studies that have investigated the use of polyphenols in PD. The studies were identified through the PubMed, Science Direct, Scielo, and Web of Science databases. A total of 1100 studies were found; these were analyzed and filtered by 2 independent reviewers. After completion, 5 studies were included (3 randomized controlled trials and 2 cohort studies). The consumption of flavonoids, anthocyanins, or 2-5 servings/week of specific foods (apples, red wine, blueberries, and strawberries) reduces the risk of PD and associated mortality. Treatment with licorice, curcumin, or cocoa, which are rich in flavonoids and other polyphenols, improves motor function in PD patients. No statistically significant differences were found in quality of life, disease progression or nonmotor symptoms such as cognitive ability and mood. Although cohort studies suggest a neuroprotective effect, further clinical studies are urgently needed to evaluate the effect of specific flavonoids and other polyphenols in PD.

The potential of Rhein's aromatic amines for Parkinson's disease prevention and treatment: α-Synuclein aggregation inhibition and disaggregation of preformed fibers

The aggregation of α-Syn is a pivotal mechanism in Parkinson's disease (PD). Effectively maintaining α-Syn proteostasis involves both inhibiting its aggregation and promoting disaggregation. In this study, we developed a series of aromatic amide derivatives based on Rhein. Two of these compounds, 4,5-dihydroxy-N-(3-hydroxyphenyl)-9,10-dioxo-9,10-dihydroanthracene-2-carboxamide (a5) and 4,5-dihydroxy-N-(2-hydroxy-4-chlorophenyl)-9,10-dioxo-9,10-dihydroanthracene-2-carboxamide (a8), exhibited good binding affinities to α-Syn residues, demonstrating promising inhibitory activity against α-Syn aggregation in vitro, with low IC50 values (1.35 and 1.08 μM, respectivly). These inhibitors acted throughout the entire aggregation process by stabilizing α-Syn's conformation and preventing the formation of β-sheet aggregates. They also effectively disassembled preformed α-Syn oligomers and fibrils. Preliminary mechanistic insights indicated that they bound to the specific domain within fibrils, inducing fibril instability, collapse, and the formation of smaller aggregates and monomeric α-Syn units. This research underscores the therapeutic potential of Rhein's aromatic amides in targeting α-Syn aggregation for PD treatment and suggests broader applications in managing and preventing neurodegenerative diseases.

Amelioration of Motor Performance and Nigrostriatal Dopamine Cell Volume Using a Novel Far-Infrared Ceramic Blanket in an A53T Alpha-Synuclein Transgenic Parkinson's Disease Mouse Model

We had attended a Parkinson's Disease (PD) patient for a non-healing wound who reported a marked decrease in his hand tremor and freezing of gait when his wound was exposed to a ceramic far-field infrared (cFIR) blanket. PD is the most frequent motor disorder and the second most frequent neurodegenerative disease after Alzheimer's Disease (AD). The tremor, rigidity, and slowness of movement associated with Parkinson's disease (PD) affect up to 10 million people throughout the world, and the major contributing factor to the pathogenesis of PD is the accumulation and propagation of pathological α-synuclein (α-Syn) and the death of dopaminergic cells in the Nigrostriatal system. Efforts to slow or stop its spreading have resulted in the development and use of dopaminergic drug replacement therapy. Unfortunately, there is a loss of about 70-80% of substantia nigral dopaminergic neurons in patients by the time they are diagnosed with PD, and various dopaminergic drugs provide only temporary relief of their motor symptoms. There are limitations in treating PD with many conventional medications, necessitating a combination of pharmaceutical and non-pharmacological therapy as an essential adjunct to better address the health and welfare of PD patients. We used male adult A53T alpha-synuclein transgenic mice exposed to a ceramic far-infrared blanket. Motor activity was assessed using the rotarod apparatus, and mouse brains were examined to quantify the fluorescence intensities of the immunostained samples. A53T alpha-synuclein transgenic mice had a significantly shorter time stay on the rotating bar than the wild-type mice (B6C3H). The rotarod performance was significantly improved in A53T alpha-synuclein transgenic mice exposed to cFIR as well as B6C3H healthy wild mice exposed to cFIR. There was a significant statistical and substantive increase in the cellular composition of the Striatum and substantia nigra of cFIR-treated mice. Improvement in motor performance is seen in PD mice and wild mice and is associated with increases in cell volume in the substantia nigra and striatum after treatment.

Bioavailable Phenolic Compounds from Olive Pomace Present Anti-Neuroinflammatory Potential on Microglia Cells

The neuroinflammatory process is considered one of the main characteristics of central nervous system diseases, where a pro-inflammatory response results in oxidative stress through the generation of reactive oxygen and nitrogen species (ROS and RNS). Olive (Olea europaea L.) pomace is a by-product of olive oil production that is rich in phenolic compounds (PCs), known for their antioxidant and anti-inflammatory properties. This work looked at the antioxidant and anti-neuroinflammatory effects of the bioavailable PC from olive pomace in cell-free models and microglia cells. The bioavailable PC of olive pomace was obtained through the process of in vitro gastrointestinal digestion of fractionated olive pomace (OPF, particles size < 2 mm) and micronized olive pomace (OPM, particles size < 20 µm). The profile of the PC that is present in the bioavailable fraction as well as its in vitro antioxidant capacity were determined. The anti-neuroinflammatory capacity of the bioavailable PC from olive pomace (0.03-3 mg L-1) was evaluated in BV-2 cells activated by lipopolysaccharide (LPS) for 24 h. The total bioavailable PC concentration and antioxidant activity against peroxyl radical were higher in the OPM than those observed in the OPF sample. The activation of BV-2 cells by LPS resulted in increased levels of ROS and nitric oxide (NO). The bioavailable PCs from both OPF and OPM, at their lowest concentrations, were able to reduce the ROS generation in activated BV-2 cells. In contrast, the highest PC concentration of OPF and OPM was able to reduce the NO levels in activated microglial cells. Our results demonstrate that bioavailable PCs from olive pomace can act as anti-neuroinflammatory agents in vitro, independent of particle size. Moreover, studies approaching ways to increase the bioavailability of PCs from olive pomace, as well as any possible toxic effects, are needed before a final statement on its nutritional use is made.

Anti-Neurodegenerating Activity: Structure-Activity Relationship Analysis of Flavonoids

An anti-neurodegeneration activity study was carried out for 80 flavonoid compounds. The structure-activity analysis of the structures was carried out by performing three different anti-neurodegeneration screening tests, showing that in these structures, the presence of a hydroxy substituent group at position C3' as well as C5' of ring B and a methoxy substituent group at the C7 position of ring A play a vital role in neuroprotective and antioxidant as well as anti-inflammatory activity. Further, we found structure (5) was the top-performing active structure out of 80 structures. Subsequently, a molecular docking study was carried out for the 3 lead flavonoid compounds (4), (5), and (23) and 21 similar hypothetical proposed structures to estimate the binding strength between the tested compounds and proteins potentially involved in disease causation. Ligand-based pharmacophores were generated to guide future drug design studies.

Punicalagin's Protective Effects on Parkinson's Progression in Socially Isolated and Socialized Rats: Insights into Multifaceted Pathway

Parkinson's disease (PD) is a gradual deterioration of dopaminergic neurons, leading to motor impairments. Social isolation (SI), a recognized stressor, has recently gained attention as a potential influencing factor in the progress of neurodegenerative illnesses. We aimed to investigate the intricate relationship between SI and PD progression, both independently and in the presence of manganese chloride (MnCl2), while evaluating the punicalagin (PUN) therapeutic effects, a natural compound established for its cytoprotective, anti-inflammatory, and anti-apoptotic activities. In this five-week experiment, seven groups of male albino rats were organized: G1 (normal control), G2 (SI), G3 (MnCl2), G4 (SI + MnCl2), G5 (SI + PUN), G6 (MnCl2 + PUN), and G7 (SI + PUN + MnCl2). The results revealed significant changes in behavior, biochemistry, and histopathology in rats exposed to SI and/or MnCl2, with the most pronounced effects detected in the SI rats concurrently exposed to MnCl2. These effects were associated with augmented oxidative stress biomarkers and reduced antioxidant activity of the Nrf2/HO-1 pathway. Additionally, inflammatory pathways (HMGB1/RAGE/TLR4/NF-ᴋB/NLRP3/Caspase-1 and JAK-2/STAT-3) were upregulated, while dysregulation of signaling pathways (PI3K/AKT/GSK-3β/CREB), sustained endoplasmic reticulum stress by activation PERK/CHOP/Bcl-2, and impaired autophagy (AMPK/SIRT-1/Beclin-1 axis) were observed. Apoptosis induction and a decrease in monoamine levels were also noted. Remarkably, treatment with PUN effectively alleviated behaviour, histopathological changes, and biochemical alterations induced by SI and/or MnCl2. These findings emphasize the role of SI in PD progress and propose PUN as a potential therapeutic intervention to mitigate PD. PUN's mechanisms of action involve modulation of pathways such as HMGB1/RAGE/TLR4/NF-ᴋB/NLRP3/Caspase-1, JAK-2/STAT-3, PI3K/AKT/GSK-3β/CREB, AMPK/SIRT-1, Nrf2/HO-1, and PERK/CHOP/Bcl-2.

[The exposome in the context of preventive measures for Alzheimer's and Parkinson's diseases]

BACKGROUND

Preventive measures addressing the exposome can counteract neurodegenerative diseases.

OBJECTIVE

This article gives an overview on the influence of general and individual exogenous factors (environmental influences and lifestyle changes) as well as endogenous factors (e.g. metabolic alterations) on the development and progression of Alzheimer's disease (AD) and Parkinson's disease (PD).

METHODS

Summary and evaluation of current scientific studies and evidence regarding the exposome and prevention of AD and PD.

RESULTS

Numerous studies could demonstrate a potential influence of environmental influences associated with industrialization (general exogenous factors), such as pesticides, solvents or air pollution on the development of AD and PD. Additionally, individually addressable changes of lifestyle (individual exogenous factors, e.g. physical activity, cognitive stimulation, nutrition and sleep) contribute to disease protection and modification and are becoming increasingly more important in light of still limited therapeutic interventions. Moreover, other exogenous factors (medication, noise pollution, head trauma and heavy metals) are discussed as risk factors for AD and/or PD. Endogenous factors (e.g., changes of the enteral microbiome, systemic inflammation and neuroinflammation, metabolic changes) can contribute to disease development by a higher potential for interacting with exogenous factors.

CONCLUSION

Despite the comprehensive scientific evidence confirming the significance of the exposome for the pathogenesis of AD and PD, the great potential of preventive measures has not yet been exploited. A clarification of the high potential of lifestyle changes should be a therapeutic standard not only for individuals with manifest PD/AD but also for individuals with a risk profile or with suspected prodromal disease. Further investigations on the influence of environmental factors and the implementation of preventive strategies to avoid exposure should be the focus of international efforts.

Urolithin A in Health and Diseases: Prospects for Parkinson's Disease Management

Parkinson's disease (PD) is a chronic and progressive neurodegenerative disorder characterized by a complex pathophysiology and a range of symptoms. The prevalence increases with age, putting the ageing population at risk. Disease management includes the improvement of symptoms, the comfort of the patient's life, and palliative care. As there is currently no cure, growing evidence points towards the beneficial role of polyphenols on neurodegeneration. Numerous studies indicate the health benefits of the family of urolithins, especially urolithin A (UA). UA is a bacterial metabolite produced by dietary ellagitannins and ellagic acid. An expanding body of literature explores the involvement of the compound in mitochondrial health, and its anti-inflammatory, anti-oxidant, and anti-apoptotic properties. The review organizes the existing knowledge on the role of UA in health and diseases, emphasizing neurodegenerative diseases, especially PD. We gathered data on the potential neuroprotective effect in in vivo and in vitro models. We discussed the possible mechanisms of action of the compound and related health benefits to give a broader perspective of potential applications of UA in neuroprotective strategies. Moreover, we projected the future directions of applying UA in PD management.

Mitochondrial dysfunction-targeting therapeutics of natural products in Parkinson's disease

Parkinson's disease (PD), the second most common neurodegenerative disease worldwide, often occurs in middle-aged and elderly individuals. The pathogenesis of PD is complex and includes mitochondrial dysfunction, and oxidative stress. Recently, natural products with multiple structures and their bioactive components have become one of the most important resources for small molecule PD drug research targeting mitochondrial dysfunction. Multiple lines of studies have proven that natural products display ameliorative benefits in PD treatment by regulating mitochondrial dysfunction. Therefore, a comprehensive search of recent published articles between 2012 and 2022 in PubMed, Web of Science, Elesvier, Wliey and Springer was carried out, focusing on original publications related to natural products against PD by restoring mitochondrial dysfunction. This paper presented the mechanisms of various kinds of natural products on PD-related mitochondrial dysfunction regulation and provided evidence that natural products are promising to be developed as drugs for PD therapeutics.

Targeting Nrf2 signaling pathway and oxidative stress by resveratrol for Parkinson's disease: an overview and update on new developments

Parkinson's disease (PD) as a prevalent neurodegenerative condition impairs motor function and is caused by the progressive deterioration of nigrostriatal dopaminergic (DAergic) neurons. The current therapy solutions for PD are ineffective because they could not inhibit the disease's progression and they even have adverse effects. Natural polyphenols, a group of phytochemicals, have been found to offer various health benefits, including neuroprotection against PD. Among these, resveratrol (RES) has neuroprotective properties owing to its capacity to protect mitochondria and act as an antioxidant. An increase in the formation of reactive oxygen species (ROS) leads to oxidative stress (OS), which is responsible for cellular damage resulting in lipid peroxidation, oxidative protein alteration, and DNA damage. In PD models, it's been discovered that RES pretreatment can diminish oxidative stress by boosting endogenous antioxidant status and directly scavenging ROS. Several studies have examined the involvement of RES in the modulation of the transcriptional factor Nrf2 in PD models because this protein recognizes oxidants and controls the antioxidant defense. In this review, we have examined the molecular mechanisms underlying the RES activity and reviewed its effects in both in vitro and in vivo models of PD. The gathered evidence herein showed that RES treatment provides neuroprotection against PD by reducing OS and upregulation of Nrf2. Moreover, in the present study, scientific proof of the neuroprotective properties of RES against PD and the mechanism supporting clinical development consideration has been described.

Swimming training and herbal nanoformulations as natural remedies to improve sensory-motor impairment in rat midbrain tumor models: system biology, behavioral test, and experimental validation

Motor impairment worsens health-related quality of life in patients with primary and metastatic midbrain tumors. Here, 56-male-Wistar rats were divided into eight groups: Normal group, Midbrain Tomur Model group, Model + Exe group, Model + Lipo, Model + Extract, Model + Lipo-Extract, Model + Extract-Exe, Model + Lipo-Extract + Exe. According to the aim, mid-brain tumor models were conducted by injections of the C6 glioma cell line (5 × 105 cell suspension) and stereotaxic techniques in the substantia nigra area. Furthermore, consumption of nanoformulation of herbals extract (100 mg/kg/day), crude extract (100 mg/kg/day), and swimming training (30 min, 3 days/week) as interventional protocols were performed for 6 weeks. In addition, we evaluated the effect of polyherbal nanoliposomes containing four plant extracts and swimming training on the GABArα1/TRKB/DRD2/DRD1a/TH network in the substantia nigra of the midbrain tumor rat model. Data emphasized that DRD2 might be a druggable protein with the network's highest significance cut-point effect that could modulate sensory-motor impairment. Furthermore, we found Quercetin, Ginsenosides, Curcumin, and Rutin, as bioactive compounds present in Ginseng, Matthiola incana, Turmeric, and Green-Tea extracts, could bind over the DRD2 protein with approved binding affinity scores. Based on our data, swimming training, and nanoliposome-enriched combined supplements could consider effective complementary medicine for motor impairment recovery induced by the midbrain tumor in the substantia nigra area. Hence, regular swimming training and natural medicines rich in polyphenolic bioactive components and antioxidative effects could modify and improve the dopamine receptors' function.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03574-3.

Marine Macroalgae Polyphenols as Potential Neuroprotective Antioxidants in Neurodegenerative Diseases

Polyphenols are beneficial natural compounds with antioxidant properties that have recently gain a lot of interest for their potential therapeutic applications. Marine polyphenols derived from marine macroalgae have been discovered to possess interesting antioxidant properties; therefore, these compounds can be included in several areas of drug development. Authors have considered the use of polyphenol extracts from seaweeds as neuroprotective antioxidants in neurodegenerative diseases. Marine polyphenols may slow the progression and limit neuronal cell loss due to their antioxidant activity; therefore, the use of these natural compounds would improve the quality of life for patients affected with neurodegenerative diseases. Marine polyphenols have distinct characteristics and potential. Among seaweeds, brown algae are the main sources of polyphenols, and present the highest antioxidant activity in comparison to red algae and green algae. The present paper collects the most recent in vitro and in vivo evidence from investigations regarding polyphenols extracted from seaweeds that exhibit neuroprotective antioxidant activity. Throughout the review, oxidative stress in neurodegeneration and the mechanism of action of marine polyphenol antioxidant activity are discussed to evidence the potential of algal polyphenols for future use in drug development to delay cell loss in patients with neurodegenerative disorders.

Beneficial Role of Vitexin in Parkinson's Disease

Today, Parkinson's disease (PD) is the foremost neurological disorder all across the globe. In the quest for a novel therapeutic agent for PD with a multimodal mechanism of action and relatively better safety profile, natural flavonoids are now receiving greater attention as a potential source of neuroprotection. Vitexin have been shown to exhibit diverse biological benefits in various disease conditions, including PD. It exerts its anti-oxidative property in PD patients by either directly scavenging reactive oxygen species (ROS) or by upregulating the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and enhancing the activities of antioxidant enzymes. Also, vitexin activates the ERK1/1 and phosphatidyl inositol-3 kinase/Akt (PI3K/Akt) pro-survival signalling pathway, which upregulates the release of anti-apoptotic proteins and downregulates the expression of pro-apoptotic proteins. It could be antagonistic to protein misfolding and aggregation. Studies have shown that it can also act as an inhibitor of monoamine oxidase B (MAO-B) enzyme, thereby increasing striatal dopamine levels, and hence, restoring the behavioural deficit in experimental PD models. Such promising pharmacological potential of vitexin could be a game-changer in devising novel therapeutic strategies against PD. This review discusses the chemistry, properties, sources, bioavailability and safety profile of vitexin. The possible molecular mechanisms underlying the neuroprotective action of vitexin in the pathogenesis of PD alongside its therapeutic potential is also discussed.

Blood-Brain Barrier Permeable Photoacoustic Probe for High-Resolution Imaging of Nitric Oxide in the Living Mouse Brain

Alternations in the brain nitric oxide (NO) homeostasis are associated with a variety of neurodegeneration diseases; therefore, high-resolution imaging of NO in the brain is essential for understanding pathophysiological processes. However, currently available NO probes are unsuitable for this purpose due to their poor ability to cross the blood-brain barrier (BBB) or to image in deep tissues with spatial resolution. Herein, we developed a photoacoustic (PA) probe with BBB crossing ability to overcome this obstacle. The probe shows a highly selective ratiometric response toward NO, which enables the probe to image NO with micron resolution in the whole brain of living mice. Using three-dimensional PA imaging, we demonstrated that the probe could be used to visualize the detailed NO distribution in varying depth cross-sections (0-8 mm) of the living Parkinson's disease (PD) mouse brain. We also investigated the therapeutic properties of natural polyphenols in the PD mouse brain using the probe as an imaging agent and suggested the potential of the probe for screening therapeutic agents. This study provides a promising imaging agent for imaging of NO in the mouse brain with high resolution. We anticipate that these findings may open up new possibilities for understanding the biological functions of NO in the brain and the development of new imaging agents for the diagnosis and treatment of brain diseases.

Development of Small Molecules Targeting α-Synuclein Aggregation: A Promising Strategy to Treat Parkinson’s Disease

Parkinson’s disease, the second most common neurodegenerative disorder worldwide, is characterized by the accumulation of protein deposits in the dopaminergic neurons. These deposits are primarily composed of aggregated forms of α-Synuclein (α-Syn). Despite the extensive research on this disease, only symptomatic treatments are currently available. However, in recent years, several compounds, mainly of an aromatic character, targeting α-Syn self-assembly and amyloid formation have been identified. These compounds, discovered by different approaches, are chemically diverse and exhibit a plethora of mechanisms of action. This work aims to provide a historical overview of the physiopathology and molecular aspects associated with Parkinson’s disease and the current trends in small compound development to target α-Syn aggregation. Although these molecules are still under development, they constitute an important step toward discovering effective anti-aggregational therapies for Parkinson’s disease.

Current Treatments and New, Tentative Therapies for Parkinson’s Disease

Parkinson’s disease (PD) is a neurodegenerative pathology, the origin of which is associated with the death of neuronal cells involved in the production of dopamine. The prevalence of PD has increased exponentially. The aim of this review was to describe the novel treatments for PD that are currently under investigation and study and the possible therapeutic targets. The pathophysiology of this disease is based on the formation of alpha-synuclein folds that generate Lewy bodies, which are cytotoxic and reduce dopamine levels. Most pharmacological treatments for PD target alpha-synuclein to reduce the symptoms. These include treatments aimed at reducing the accumulation of alpha-synuclein (epigallocatechin), reducing its clearance via immunotherapy, inhibiting LRRK2, and upregulating cerebrosidase (ambroxol). Parkinson’s disease continues to be a pathology of unknown origin that generates a significant social cost for the patients who suffer from it. Although there is still no definitive cure for this disease at present, there are numerous treatments available aimed at reducing the symptomatology of PD in addition to other therapeutic alternatives that are still under investigation. However, the therapeutic approach to this pathology should include a combination of pharmacological and non-pharmacological strategies to maximise outcomes and improve symptomatological control in these patients. It is therefore necessary to delve deeper into the pathophysiology of the disease in order to improve these treatments and therefore the quality of life of the patients.

Effects of the Polyphenols Delphinidin and Rosmarinic Acid on the Inducible Intra-cellular Aggregation of Alpha-Synuclein in Model Neuron Cells

Intracellular aggregation of α-synuclein is a major pathological feature of Parkinson's disease. In this study, we show that the polyphenols delphinidin and rosmarinic acid suppress intracellular aggregation of α-synuclein in a mouse neuron cell model when added under oxidative stress conditions. To enhance the detection threshold of this preventive effect of the two polyphenols, we generated a new strain of "aggregation prone model cells" that tended to show prominent α-synuclein aggregation even under normal conditions. Using this new highly sensitive cell line, we demonstrate that addition of delphinidin to model cell cultures effectively suppresses the formation of intracellular α-synuclein aggregates. Flow cytometric analysis shows that adding delphinidin decreases the fraction of "dying cells," cells that were alive but in a damaged state. Our findings suggest the possibility of using polyphenols to prevent and treat the symptoms correlated with the onset of Parkinson's disease. Additionally, our aggregation-prone cell model may be used in future studies to probe numerous neurodegenerative diseases with high sensitivity.

Small molecules to perform big roles: The search for Parkinson's and Huntington's disease therapeutics

Neurological motor disorders (NMDs) such as Parkinson's disease and Huntington's disease are characterized by the accumulation and aggregation of misfolded proteins that trigger cell death of specific neuronal populations in the central nervous system. Differential neuronal loss initiates the impaired motor control and cognitive function in the affected patients. Although major advances have been carried out to understand the molecular basis of these diseases, to date there are no treatments that can prevent, cure, or significantly delay the progression of the disease. In this context, strategies such as gene editing, cellular therapy, among others, have gained attention as they effectively reduce the load of toxic protein aggregates in different models of neurodegeneration. Nevertheless, these strategies are expensive and difficult to deliver into the patients' nervous system. Thus, small molecules and natural products that reduce protein aggregation levels are highly sought after. Numerous drug discovery efforts have analyzed large libraries of synthetic compounds for the treatment of different NMDs, with a few candidates reaching clinical trials. Moreover, the recognition of new druggable targets for NMDs has allowed the discovery of new small molecules that have demonstrated their efficacy in pre-clinical studies. It is also important to recognize the contribution of natural products to the discovery of new candidates that can prevent or cure NMDs. Additionally, the repurposing of drugs for the treatment of NMDs has gained huge attention as they have already been through clinical trials confirming their safety in humans, which can accelerate the development of new treatment. In this review, we will focus on the new advances in the discovery of small molecules for the treatment of Parkinson's and Huntington's disease. We will begin by discussing the available pharmacological treatments to modulate the progression of neurodegeneration and to alleviate the motor symptoms in these diseases. Then, we will analyze those small molecules that have reached or are currently under clinical trials, including natural products and repurposed drugs.

Neuroprotective Effect of Phloretin in Rotenone-Induced Mice Model of Parkinson's Disease: Modulating mTOR-NRF2-p62 Mediated Autophagy-Oxidative Stress Crosstalk

BACKGROUND

Parkinson's disease (PD) is an age-related progressive multifactorial, neurodegenerative disease. The autophagy and Keap1-Nrf2 axis system are both implicated in the oxidative-stress response, metabolic stress, and innate immunity, and their dysregulation is associated with pathogenic processes in PD. Phloretin (PLT) is a phenolic compound reported possessing anti-inflammatory and antioxidant activities.

OBJECTIVE

To evaluate the neuroprotective potential of PLT in PD via modulating the autophagy-antioxidant axisMethods:The neuroprotective effect of PLT was evaluated in vitro using rotenone (ROT) exposed SH-SY5Y cell line and in vivo using ROT administered C57BL/6 mice. Mice were administered with PLT (50 and 100 mg/kg, p.o.) concomitantly with ROT (1 mg/kg, i.p) for 3 weeks. Locomotive activity and anxiety behaviors were assessed using rotarod and open field tests respectively. Further apoptosis (Cytochrome-C, Bax), α-Synuclein (α-SYN), tyrosine hydroxylase (TH), antioxidant proteins (nuclear factor erythroid 2-related factor 2 (NRF2), heme oxygenase-1 (HO-1) and autophagic (mTOR, Atg5,7, p62, Beclin,LC3B-I/II) protein activity were evaluated both in in vitro and in vivo.

RESULTS

PLT improved locomotive activity and anxiety-like behavior in mice. Further PLT diminished apoptotic cell death, α-SYN expression and improved the expression of TH, antioxidant, and autophagic regulating protein.

CONCLUSION

Taken together, present data deciphers that the PLT effectively improves motor and non-motor symptoms via modulating the mTOR/NRF2/p62 pathway-mediated feedback loop. Hence, PLT could emerge as a prospective disease-modifying drug for PD management.

Analysis of phenolic compounds in Parkinson's disease: a bibliometric assessment of the 100 most cited papers

Objective

The aim of this study was to identify and characterize the 100 most cited articles on Parkinson's disease (PD) and phenolic compounds (PCs).

Methods

Articles were selected in the Web of Science Core Collection up to June 2022 based on predetermined inclusion criteria, and the following bibliometric parameters were extracted: the number of citations, title, keywords, authors, year, study design, tested PC and therapeutic target. MapChart was used to create worldwide networks, and VOSviewer software was used to create bibliometric networks. Descriptive statistical analysis was used to identify the most researched PCs and therapeutic targets in PD.

Results

The most cited article was also the oldest. The most recent article was published in 2020. Asia and China were the continent and the country with the most articles in the list (55 and 29%, respectively). In vitro studies were the most common experimental designs among the 100 most cited articles (46%). The most evaluated PC was epigallocatechin. Oxidative stress was the most studied therapeutic target.

Conclusion

Despite the demonstrations in laboratorial studies, the results obtained point to the need for clinical studies to better elucidate this association.

Protective Effects of Currants (Vitis vinifera) on Corticolimbic Serotoninergic Alterations and Anxiety-like Comorbidity in a Rat Model of Parkinson's Disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the loss of nigral dopaminergic neurons. Increasing evidence supports that PD is not simply a motor disorder but a systemic disease leading to motor and non-motor symptoms, including memory loss and neuropsychiatric conditions, with poor management of the non-motor deficits by the existing dopaminergic medication. Oxidative stress is considered a contributing factor for nigrostriatal degeneration, while antioxidant/anti-inflammatory properties of natural phyto-polyphenols have been suggested to have beneficial effects. The present study aimed to determine the contribution of monoaminergic neurotransmission on the anxiety-like phenotype in a rat rotenone PD model and evaluate the possible neuroprotective effects of black Corinthian currant, Vitis vinifera, consisting of antioxidant polyphenols. Rotenone-treated rats showed anxiety-like behavior and exploratory deficits, accompanied by changes in 5-HT, SERT and β₂-ARs expression in the prefrontal cortices, hippocampus and basolateral amygdala. Importantly, the motor and non-motor behavior, as well as 5-HT, SERT and β₂-ARs expression patterns of the PD-like phenotype were partially recovered by a supplementary diet with currants. Overall, our results suggest that the neuroprotective effects of Corinthian currants in rotenone-induced anxiety-like behavior may be mediated via corticolimbic serotonergic transmission.

Potential implications of polyphenolic compounds in neurodegenerative diseases

Neurodegenerative diseases are common chronic diseases related to progressive damage to the nervous system. Current neurodegenerative diseases present difficulties and despite extensive research efforts to develop new disease-modifying therapies, there is still no effective treatment for halting the neurodegenerative process. Polyphenols are biologically active organic compounds abundantly found in various plants. It has been reported that plant-derived dietary polyphenols may improve some disease states and promote health. Emerging pieces of evidence indicate that polyphenols are associated with neurodegenerative diseases. This review aims to overview the potential neuroprotective roles of polyphenols in most common neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, epilepsy, and ischemic stroke.

Neuroprotective Effects of Some Nutraceuticals against Manganese-Induced Parkinson's Disease in Rats: Possible Modulatory Effects on TLR4/NLRP3/NF-κB, GSK-3β, Nrf2/HO-1, and Apoptotic Pathways

Parkinson's disease (PD) is a progressive neurodegenerative disorder affecting the substantia nigra where functions controlling body movement take place. Manganese (Mn) overexposure is linked to a neurologic syndrome resembling PD. Sesamol, thymol, wheat grass (WG), and coenzyme Q10 (CoQ10) are potent antioxidants, anti-inflammatory, and anti-apoptotic nutraceuticals. We investigated the potential protective effects of these nutraceuticals alone or in combinations against MnCl₂-induced PD in rats. Seven groups of adult male Sprague Dawley rats were categorized as follows: group (I) was the control, while groups 2-7 received MnCl₂ either alone (Group II) or in conjunction with oral doses of sesamol (Group III), thymol (Group IV), CoQ10 (Group V), WG (Group VI), or their combination (Group VII). All rats were subjected to four behavioral tests (open-field, swimming, Y-maze, and catalepsy tests). Biochemical changes in brain levels of monoamines, ACHE, BDNF, GSK-3β, GABA/glutamate, as well as oxidative stress, and apoptotic and neuroinflammatory biomarkers were evaluated, together with histopathological examinations of different brain regions. Mn increased catalepsy scores, while decreasing neuromuscular co-ordination, and locomotor and exploratory activity. It also impaired vigilance, spatial memory, and decision making. Most behavioral impairments induced by Mn were improved by sesamol, thymol, WG, or CoQ10, with prominent effect by sesamol and thymol. Notably, the combination group showed more pronounced improvements, which were confirmed by biochemical, molecular, as well as histopathological findings. Sesamol or thymol showed better protection against neuronal degeneration and some behavioral impairments induced by Mn than WG or CoQ10, partly via interplay between Nrf2/HO-1, TLR4/NLRP3/NF-κB, GSK-3β and Bax/Bcl2 pathways.

Microbiome and Metabolome Insights into the Role of the Gastrointestinal-Brain Axis in Parkinson's and Alzheimer's Disease: Unveiling Potential Therapeutic Targets

Neurodegenerative diseases such as Parkinson's (PD) and Alzheimer's disease (AD), the prevalence of which is rapidly rising due to an aging world population and westernization of lifestyles, are expected to put a strong socioeconomic burden on health systems worldwide. Clinical trials of therapies against PD and AD have only shown limited success so far. Therefore, research has extended its scope to a systems medicine point of view, with a particular focus on the gastrointestinal-brain axis as a potential main actor in disease development and progression. Microbiome and metabolome studies have already revealed important insights into disease mechanisms. Both the microbiome and metabolome can be easily manipulated by dietary and lifestyle interventions, and might thus offer novel, readily available therapeutic options to prevent the onset as well as the progression of PD and AD. This review summarizes our current knowledge on the interplay between microbiota, metabolites, and neurodegeneration along the gastrointestinal-brain axis. We further illustrate state-of-the art methods of microbiome and metabolome research as well as metabolic modeling that facilitate the identification of disease pathomechanisms. We conclude with therapeutic options to modulate microbiome composition to prevent or delay neurodegeneration and illustrate potential future research directions to fight PD and AD.

P75 neurotrophin receptor as a therapeutic target for drug development to treat neurological diseases

The interaction of neurotrophins with their receptors is involved in the pathogenesis and progression of various neurological diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, spinal cord injury and acute and chronic cerebral damage. The p75 neurotrophin receptor (p75NTR) plays a pivotal role in the development of neurological dysfunctions as a result of its high expression, abnormal processing and signalling. Therefore, p75NTR represents as a vital therapeutic target for the treatment of neurodegeneration, neuropsychiatric disorders and cerebrovascular insufficiency. This review summarizes the current research progress on the p75NTR signalling in neurological deficits. We also summarize the present therapeutic approaches by genetically and pharmacologically targeting p75NTR for the attenuation of pathological changes. Based on the evolving knowledge, the role of p75NTR in the regulation of tau hyperphosphorylation, Aβ metabolism, the degeneration of motor neurons and dopaminergic neurons has been discussed. Its position as a biomarker to evaluate the severity of diseases and as a druggable target for drug development has also been elucidated. Several prototype small molecule compounds were introduced to be crucial in neuronal survival and functional recovery via targeting p75NTR. These small molecule compounds represent desirable agents in attenuating neurodegeneration and cell death as they abolish activation-induced neurotoxicity of neurotrophins via modulating p75NTR signalling. More comprehensive and in-depth investigations on p75NTR-based drug development are required to shed light on effective treatment of numerous neurological disorders.

QEEG indices are associated with inflammatory and metabolic risk factors in Parkinson's disease dementia: An observational study

BACKGROUND

Quantitative electroencephalography (QEEG) is a reliable and non-invasive diagnostic tool to quantify cortical synaptic injury or loss in the clinical assessment of neurodegenerative diseases, and may be able to differentiate various types of dementia. We investigated if QEEG indices can differentiate Parkinson's Disease (PD) with nondementia (PD-ND) from PD with dementia (PDD), and to determine if QEEG indices correlate with inflammation and lipid metabolism markers in PD.

METHODS

This clinical study collected data between July 1, 2018 and July 1, 2021 in Zhujiang Hospital of Southern Medical University in China and data was analysed. A total of 125 individuals comprising of 31 PDD, 47 patients with PD-ND and 47 healthy controls were included. We calculated the absolute spectral power (ASP) of frequency bands and the slow-to-fast frequency ratios of specific brain regions. Plasma levels of hypersensitive C-reactive protein (Hs-CRP), superoxide dismutase (SOD), and high-density lipoprotein cholesterol (HDL-C) were measured and correlations with QEEG indices were examined.

FINDINGS

A significantly higher ASP of delta frequency especially in the frontal region was observed in patients with PDD compared to PD-ND (P=0.004) and controls (P=0.000). Decreased HDL-C (OR=0.186, P=0.030), and increased Hs-CRP (OR =2.856, P=0.015) were associated with PDD. Frontal-delta ASP was negatively correlated with plasma HDL-C (r=-0.353, P=0.000) and SOD (r=-0.322, P=0.001), and positively correlated with Hs-CRP (r=0.342, P=0.000).

INTERPRETATION

We highlight novel correlations between QEEG indices and inflammation and lipid metabolism markers in PD-ND and PDD. QEEG indices, HDL-C and Hs-CRP are potentially useful for the evaluation of PDD. Our current findings suggest that peripheral inflammation might contribute to the pathogenesis of cognitive impairment and EEG slowing in PDD. The mechanism underlying frontal-delta ASP and its correlation with neuro-inflammatory and metabolic markers in PDD should be further investigated.

FUNDING

The National Natural Science Foundation of China (NO: 81873777, 82071414); the Scientific Research Foundation of Guangzhou (NO: 202206010005); the Science and Technology Program of Guangdong of China (NO: 2020A0505100037); the High-level Hospital Construction Research Project of Maoming People's Hospital (NO: xz2020009); the Science and Technology Program of Maoming City (NO: 2021S0026). Dr EK Tan is supported by the National Medical Research Council, Singapore.

Epigallocatechin-3-gallate: A phytochemical as a promising drug candidate for the treatment of Parkinson’s disease

Epigallocatechin 3-gallate (EGCG), an abundant polyphenolic component derived from green tea extract, possesses versatile bioactivities that can combat many diseases. During the last decade, EGCG was shown to be effective in experimental models of Parkinson’s disease (PD). Several experimental studies have suggested that it has pleiotropic neuroprotective effects, which has enhanced the appeal of EGCG as a therapeutic strategy in PD. In this review, we compiled recent updates and knowledge of the molecular mechanisms underlying the neuroprotective effects of EGCG in PD. We focused on the effects of EGCG on apoptosis, oxidative stress, inflammation, ferroptosis, modulation of dopamine production, and the aggregation of α-synuclein. The review highlights the pharmacological features of EGCG and its therapeutic implications in PD. Taken together, the accumulated data indicate that EGCG is a promising neuroprotective compound for the treatment of PD.

Hybrids of polyphenolic acids and xanthone, the potential preventive and therapeutic effects on PD: Design, synthesis, in vitro anti-aggregation of α-synuclein, and disaggregation against the existed α-synuclein oligomer and fibril

The misfolding and aggregation of α-Syn are the central mechanism linking and facilitating the other pathological mechanisms of PD. Maintaining α-Syn proteostasis by suitable inhibitors is an effective means to prevent PD. Disintegrating the neurotoxic oligomers and fibrils into the normal functional α-Syn by inhibitors is a more efficient way for PD treatment. This work synthesized two series hybrids of polyphenolic acids and xanthone. The hybrids possess a sheet-like conjugated skeleton and higher binding energies with α-Syn residues. Some compounds present well α-Syn aggregation inhibitory activities in vitro (IC₅₀ down to 2.58 μM). The inhibitory action goes throughout the aggregation process from lag to the stationary phase by stabilizing α-Syn proteostasis conformation and preventing β-sheets aggregation. The candidate compounds with appropriate LogP values (2.02-3.11) present good disintegration abilities against the existed α-Syn oligomers and fibrils. The preliminary mechanism studies suggest that the inhibitors could quickly and randomly bind to the specific site closed to the β-sheet domain in the fibril, resulting in unstable and collapse of the protein fibril, yielding a complex system with aggregates of different sizes and monomers.

Apigenin alleviates neuroinflammation in a mouse model of Parkinson's disease

PURPOSE OF THE STUDY

The aim of this study is to evaluate the effect of apigenin on inflammatory response in brain tissue in Parkinson's mouse model.

MATERIALS AND METHODS

Parkinson's disease model was induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Sixty 8-10-weeks-old male C57BL/6 mice were randomly divided into four groups control, Parkinson, prophylaxis, and treatment. Control (0.9% NaCl 0.5 ml, 10 days, i.p.), Parkinson (25 mg/kg MPTP, 5 days, i.p.), prophylaxis (50 mg/kg apigenin, 5 days + 25 mg/kg MPTP, 5 days, i.p.), and treatment (25 mg/kg MPTP, 5 days + 50 mg/kg apigenin, 5 days). The expressions and protein levels of tumor necrosis factor-alpha (TNF-α), interleukin-1-beta (IL-1β), IL-6, IL-10, and transforming growth factor-beta (TGF-β) were determined using immunohistochemistry and enzyme-linked immunosorbent analysis.

RESULTS

Apigenin administration attenuated MPTP-induced histopathological changes in brain tissue. Furthermore, apigenin reversed the changes in expressions and concentrations of TNF-α, IL-1β, IL-6, IL-10, and TGF-β.

CONCLUSION

This study suggests that apigenin could be used as a neuroprotective option to attenuate neuroinflammation in Parkinson's disease.

Evidence for Oxidative Pathways in the Pathogenesis of PD: Are Antioxidants Candidate Drugs to Ameliorate Disease Progression?

Parkinson’s disease (PD) is a progressive neurodegenerative disorder that arises due to a complex and variable interplay between elements including age, genetic, and environmental risk factors that manifest as the loss of dopaminergic neurons. Contemporary treatments for PD do not prevent or reverse the extent of neurodegeneration that is characteristic of this disorder and accordingly, there is a strong need to develop new approaches which address the underlying disease process and provide benefit to patients with this debilitating disorder. Mitochondrial dysfunction, oxidative damage, and inflammation have been implicated as pathophysiological mechanisms underlying the selective loss of dopaminergic neurons seen in PD. However, results of studies aiming to inhibit these pathways have shown variable success, and outcomes from large-scale clinical trials are not available or report varying success for the interventions studied. Overall, the available data suggest that further development and testing of novel therapies are required to identify new potential therapies for combating PD. Herein, this review reports on the most recent development of antioxidant and anti-inflammatory approaches that have shown positive benefit in cell and animal models of disease with a focus on supplementation with natural product therapies and selected synthetic drugs.

The role of nutrition on Parkinson's disease: a systematic review

BACKGROUND

Parkinson's disease (PD) in elderly patients is the second most prevalent neurodegenerative disease. The pathogenesis of PD is associated with dopaminergic neuron degeneration of the substantia nigra in the basal ganglia, causing classic motor symptoms. Oxidative stress, mitochondrial dysfunction, and neuroinflammation have been identified as possible pathways in laboratory investigations. Nutrition, a potentially versatile factor from all environmental factors affecting PD, has received intense research scrutiny.

METHODS

A systematic search was conducted in the MEDLINE, EMBASE, and WEB OF SCIENCE databases from 2000 until the present. Only randomized clinical trials (RCTs), observational case-control studies, and follow-up studies were included.

RESULTS

We retrieved fifty-two studies that met the inclusion criteria. Most selected studies investigated the effects of malnutrition and the Mediterranean diet (MeDiet) on PD incidence and progression. Other investigations contributed evidence on the critical role of microbiota, vitamins, polyphenols, dairy products, coffee, and alcohol intake.

CONCLUSIONS

There are still many concerns regarding the association between PD and nutrition, possibly due to underlying genetic and environmental factors. However, there is a body of evidence revealing that correcting malnutrition, gut microbiota, and following the MeDiet reduced the onset of PD and reduced clinical progression. Other factors, such as polyphenols, polyunsaturated fatty acids, and coffee intake, can have a potential protective effect. Conversely, milk and its accessory products can increase PD risk. Nutritional intervention is essential for neurologists to improve clinical outcomes and reduce the disease progression of PD.

Bis-chalcone polyphenols with potential preventive and therapeutic effects on PD: Design, synthesis and in vitro disaggregation activity against α-synuclein oligomers and fibrils

α-Syn fibrils, which are neurotoxic, play a key role in the development of PD. Maintaining α-Syn proteostasis by suitable molecule ligands is an effective approach to prevent aggregation. Disintegrating the existed oligomers and fibrils into individual α-Syn by small molecular compounds is a more efficient way to treat PD. This work designed and synthesized two series of bis-chalcone polyphenol compounds, which possess a sheet-like conjugated skeleton with stronger H-bonding, π-stacking, and hydrophobic interaction with α-Syn protein residues. Some compounds have shown high α-Syn aggregation inhibitory activities in vitro with IC₅₀ down to 0.64 μM. The inhibition goes throughout the aggregation process from the lag to the stationary phase by stabilizing α-Syn proteostasis conformation and preventing β-sheets aggregation, especially in the lag phase. In addition, the inhibitors present good disintegration abilities against the existed α-Syn oligomers and fibrils. The preliminary mechanism studies suggest that the inhibitors could quickly and randomly bind to the specific site closed to the β-sheet domain in the fibril, resulting in unstable and collapse of the protein fibril and yielding a complex system with aggregates of different sizes and monomers. The inhibitors, which could penetrate the blood-brain barrier, are expected to develop into the drug candidates for PD targeting α-Syn aggregation.

Astrocyte Reaction to Catechol-Induced Cytotoxicity Relies on the Contact with Microglia Before Isolation

Astrocytes preserve the brain microenvironment homeostasis in order to protect other brain cells, mainly neurons, against damages. Glial cells have specific functions that are important in the context of neuronal survival in different models of central nervous system (CNS) diseases. Microglia are among these cells, secreting several molecules that can modulate astrocyte functions. Although 1,2-dihydroxybenzene (catechol) is a neurotoxic monoaromatic compound of exogenous origin, several endogenous molecules also present the catechol group. This study compared two methods to obtain astrocyte-enriched cultures from newborn Wistar rats of both sexes. In the first technique (P1), microglial cells began to be removed early 48 h after primary mixed glial cultures were plated. In the second one (P2), microglial cells were late removed 7 to 10 days after plating. Both cultures were exposed to catechol for 72 h. Catechol was more cytotoxic to P1 cultures than to P2, decreasing cellularity and changing the cell morphology. Microglial-conditioned medium (MCM) protected P1 cultures and inhibited the catechol autoxidation. P2 cultures, as well as P1 in the presence of 20% MCM, presented long, dense, and fibrillary processes positive for glial fibrillary acidic protein, which retracted the cytoplasm when exposed to catechol. The Ngf and Il1beta transcription increased in P1, meanwhile astrocytes expressed more Il10 in P2. Catechol decreased Bdnf and Il10 in P2 cultures, and it decreased the expression of Il1beta in both conditions. A prolonged contact with microglia before isolation of astrocyte-enriched cultures modifies astrocyte functions and morphology, protecting these cells against catechol-induced cytotoxicity.

Urolithins: potential biomarkers of gut dysbiosis and disease stage in Parkinson's patients

Gut microbiota alteration (gut dysbiosis) occurs during the onset and progression of Parkinson's disease. Gut dysbiosis biomarkers could be relevant to prodromal disease. Urolithins, anti-inflammatory metabolites produced from some dietary polyphenols by specific gut microbial ecologies (urolithin metabotypes), have been proposed as biomarkers of gut microbiota composition and functionality. However, this has not been explored in Parkinson's disease patients. The current study aimed to assess associations between urolithin metabotypes, gut dysbiosis and disease severity in Parkinson's disease patients. Participants (52 patients and 117 healthy controls) provided stool samples for microbiota sequencing and urine samples for urolithin profiling before and after consuming 30 g of walnuts for three days. Data on demographics, medication, disease duration and Hoehn and Yahr disease stage were collected. We observed a significant gradual increase of urolithin non-producers (metabotype-0) as the disease severity increased. The gut microbiome of metabotype-0 patients and patients with the greatest severity was characterized by a more altered bacterial composition, i.e., increased pro-inflammatory Enterobacteriaceae and reduced protective bacteria against autoimmune and inflammatory processes, including butyrate and urolithin-producing bacteria (Lachnospiraceae members and Gordonibacter). Besides, their microbiome was characterized by predictive functions of lipopolysaccharide biosynthesis and metabolism of glutathione, cysteine and methionine that could indirectly reflect the gut pro-inflammatory status. Urolithin detection in urine is a feasible, non-invasive and fast approach that can reflect gut microbiome dysbiosis and intestinal inflammation in Parkinson's disease patients. Our current study could provide novel strategies for improving diagnostics, and for preventing and treating disease progression in microbiota-based interventions.

Brain polar phenol content, behavioural and neurochemical effects of Corinthian currant in a rotenone rat model of Parkinson's disease

OBJECTIVE

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the loss of nigral dopaminergic neurons, leading to reduced motor control. A contributing factor for the nigrostriatal degeneration is known to be oxidative stress, while antioxidant/anti-inflammatory properties of natural polyphenols have been suggested to show beneficial effects. The present study questioned the potential neuroprotective effects of supplementary diet with Corinthian currant, using a rat rotenone PD model.

METHODS

The alterations in motor activity, brain Corinthian currant polar phenols' accumulation, expression patterns of tyrosine hydroxylase (TH), dopamine transporter (DAT) and brain-derived neurotrophic factor (BDNF) in the nigrostriatal dopaminergic system were determined in rotenone-treated, currant-diet rats and matching controls.

RESULTS

Rotenone treatment resulted in motor deficits and TH expression decreases in the nigrostriatal pathway, exhibiting PD-like behavioural motor and neurochemical phenotypes. Interestingly, 38 days Corinthian currant consumption resulted in differential accumulation of polar phenols in mesencephalon and striatum and had a significant effect on attenuating motor deficits and dopaminergic cell loss in substantia nigra pars compacta. In addition, it induced up-regulation of BDNF expression in the nigrostriatal dopaminergic system.

DISCUSSION

Taken all together, evidence is provided for the potential neuroprotective influences of Corinthian currant consumption, involving the neurotrophic factor BDNF, in rescuing aspects of PD-like phenotype.

Therapeutic Potential of Polyscias fruticosa (L.) Harms Leaf Extract for Parkinson's Disease Treatment by Drosophila melanogaster Model

Parkinson's disease (PD) is characterized by progressive locomotive defects and loss of dopaminergic neurons. Polyscias fruticosa leaves are used by Vietnamese as herbal medicines to support the treatment of some diseases related to neurodegeneration such as Parkinson's and Alzheimer's diseases. However, recent scientific data have not provided sufficient evidence for the use of P. fruticosa leaves to treat PD or decelerate PD progression. In the present study, the capacity of P. fruticosa leaf extract for PD treatment on the dietary supplementation was investigated using dUCH-knockdown Drosophila model. The results indicated that P. fruticosa leaf extract decelerated dopaminergic neuron degeneration induced by dUCH knockdown in not only the larval stage but also the adult stage, which might result in the amelioration in locomotor ability of dUCH-knockdown larvae and flies. Furthermore, antioxidant activities and some key phytochemicals such as saponins, polyphenols, and flavonoids that might contribute to the effects of the P. fruticosa leaf extract were identified.

Neuroprotective Effects of Cranberry Juice Treatment in a Rat Model of Parkinson's Disease

Rich in polyphenols, cranberry juice (CJ) with high antioxidant activity is believed to contribute to various health benefits. However, our knowledge of the neuroprotective potential of cranberries is limited. Previously, we have demonstrated that CJ treatment controls oxidative stress in several organs, with the most evident effect in the brain. In this study, we examined the capability of CJ for protection against Parkinson's disease (PD) in a rotenone (ROT) rat model. Wistar rats were administered with CJ in a dose of 500 mg/kg b.w./day (i.g.) and subcutaneously injected with ROT (1.3 mg/kg b.w./day). The experiment lasted 45 days, including 10 days pre-treatment with CJ and 35 days combined treatment with CJ and ROT. We quantified the expression of α-synuclein and apoptosis markers in the midbrain, performed microscopic examination, and assessed postural instability to evaluate the CJ neuroprotective effect. Our results indicate that the juice treatment provided neuroprotection, as evidenced by declined α-synuclein accumulation, Bax and cleaved/active caspase-9 expression, and normalized cytochrome c level that was accompanied by the enhancement of neuronal activity survival and improved postural instability. Importantly, we also found that long-term administration of CJ alone in a relatively high dose may exert a deleterious effect on cell survival in the midbrain.