LRRK2 kinase inhibition protects against Parkinson's disease-associated environmental toxicants

Idiopathic Parkinson's disease (PD) is epidemiologically linked with exposure to toxicants such as pesticides and solvents, which comprise a wide array of chemicals that pollute our environment. While most are structurally distinct, a common cellular target for their toxicity is mitochondrial dysfunction, a key pathological trigger involved in the selective vulnerability of dopaminergic neurons. We and others have shown that environmental mitochondrial toxicants such as the pesticides rotenone and paraquat, and the organic solvent trichloroethylene (TCE) appear to be influenced by the protein LRRK2, a genetic risk factor for PD. As LRRK2 mediates vesicular trafficking and influences endolysosomal function, we postulated that LRRK2 kinase activity may inhibit the autophagic removal of toxicant damaged mitochondria, resulting in elevated oxidative stress. Conversely, we suspected that inhibition of LRRK2, which has been shown to be protective against dopaminergic neurodegeneration caused by mitochondrial toxicants, would reduce the intracellular production of reactive oxygen species (ROS) and prevent mitochondrial toxicity from inducing cell death. To do this, we tested in vitro if genetic or pharmacologic inhibition of LRRK2 (MLi2) protected against ROS caused by four toxicants associated with PD risk - rotenone, paraquat, TCE, and tetrachloroethylene (PERC). In parallel, we assessed if LRRK2 inhibition with MLi2 could protect against TCE-induced toxicity in vivo, in a follow up study from our observation that TCE elevated LRRK2 kinase activity in the nigrostriatal tract of rats prior to dopaminergic neurodegeneration. We found that LRRK2 inhibition blocked toxicant-induced ROS and promoted mitophagy in vitro, and protected against dopaminergic neurodegeneration, neuroinflammation, and mitochondrial damage caused by TCE in vivo. We also found that cells with the LRRK2 G2019S mutation displayed exacerbated levels of toxicant induced ROS, but this was ameliorated by LRRK2 inhibition with MLi2. Collectively, these data support a role for LRRK2 in toxicant-induced mitochondrial dysfunction linked to PD risk through oxidative stress and the autophagic removal of damaged mitochondria.

Neuroprotective potential of Mentha piperita extract prevents motor dysfunctions in mouse model of Parkinson's disease through anti-oxidant capacities

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world. Neurodegeneration of the substantia nigra (SN) and diminished release of dopamine are prominent causes of this progressive disease. The current study aims to evaluate the protective potential of ethanolic extract of Mentha piperita (EthMP) against rotenone-mediated PD features, dopaminergic neuronal degeneration, oxidative stress and neuronal survival in a mouse model. Swiss albino male mice were assigned to five groups: control (2.5% DMSO vehicle), PD (rotenone 2.5 mg/kg), EthMP and rotenone (200mg/kg and 2.5mg/kg, respectively), EthMP (200 mg/kg), and Sinemet, reference treatment containing levodopa and carbidopa (20 mg/kg and rotenone 2.5mg/kg). Behavioral tests for motor functional deficit analysis were performed. Anti-oxidant capacity was estimated using standard antioxidant markers. Histopathology of the mid-brain for neurodegeneration estimation was performed. HPLC based dopamine level analysis and modulation of gene expression using quantitative real-time polymerase chain reaction was performed for the selected genes. EthMP administration significantly prevented the rotenone-mediated motor dysfunctions compared to PD group as assessed through open field, beam walk, pole climb down, stepping, tail suspension, and stride length tests. EthMP administration modulated the lipid peroxidation (LPO), reduced glutathione (GSH), and superoxide dismutase (SOD) levels, as well as glutathione-s-transferase (GST) and catalase (CAT) activities in mouse brain. EthMP extract prevented neurodegeneration in the SN of mice and partially maintained dopamine levels. The expression of genes related to dopamine, anti-oxidant potential and synapses were modulated in M. piperita (MP) extract treated mice brains. Current data suggest therapeutic capacities of MP extract and neuroprotective capacities, possibly through antioxidant capacities. Therefore, it may have potential clinical applications for PD management.

Vitamin C, vitamin E, β-carotene and risk of Parkinson's disease: a systematic review and dose-response meta-analysis of observational studies

OBJECTIVE

This study aimed to explore the relationship between the intake of vitamin C, vitamin E and β-carotene, and the risk of Parkinson's disease (PD).

METHODS

Web of Science, Embase, PubMed, Cochrane library, CNKI, and WanFang databases were searched from inception to 29 August 2022 for observational studies reporting the odds ratios (ORs) or relative risks (RRs) or hazard ratios (HRs) and 95% confidence intervals (CIs) of PD by Vitamin C/Vitamin E/β-carotene intake. Random-effects models, publication bias assessment, subgroup, sensitivity and dose-response analyses were performed, using.Stata version 12.0.

RESULTS

A total of 13 studies were included. There was no significant association between high-dose vitamin C intake and the risk of PD compared with low-dose vitamin C intake (RR = 0.98, 95%CI:0.89,1.08). Compared with low-dose intake, high-dose intake of vitamin E can prevent the risk of PD (RR = 0.87, 95%CI:0.77,0.99). Compared with lower β-carotene intake, there was a borderline non-significant correlation between higher intake and PD risk (RR = 0.91, 95%CI:0.82,1.01), and high dose β-carotene intake was found to be associated with a lower risk of PD in women (RR = 0.78, 95%CI:0.64,0.96).

CONCLUSION

This study shows that vitamin E intake can reduce the risk of PD and play a preventive role.

Cost-effectiveness analysis of insecticide ban aimed at preventing Parkinson's disease in Central California

BACKGROUND

Our study assessed whether banning specific insecticides to reduce the PD burden in three Central California (CA) counties is cost-effective.

METHOD

We applied a cost-effectiveness analysis using a cohort-based Markov model to estimate the impact and costs of banning seven insecticides that were previously associated with PD in these counties as well as mixture exposures to some of these pesticides. We relied for our estimations on the cohort of 65- and 66-year-olds living in these counties who were unaffected by PD at baseline in 2020 and projected their incidence, costs, and reduction in quality-adjusted-life-years (QALY) loss due to developing PD over a 20-year period. We included a shiny app for modeling different scenarios (https://sherlockli.shinyapps.io/pesticide_pd_economics_part_2/).

RESULTS

According to our scenarios, banning insecticides to reduce the occurrence of PD in three Central CA counties was cost-effective relative to not banning insecticides. In the worst-case scenario of exposure to a single pesticide, methomyl, versus none would result in an estimated 205 (95 % CI: 75, 348) additional PD cases or 12 % (95 % CI: 4 %, 20 %) increase in PD cases over a 20-year period based on residential proximity to pesticide applications. The increase in PD cases due to methomyl would increase health-related costs by $72.0 million (95 % CI: $5.5 million, $187.4 million). Each additional PD patient due to methomyl exposure would incur $109,327 (95 % CI, $5554, $347,757) in costs per QALY loss due to PD. Exposure to methomyl based on workplace proximity to pesticide applications generated similar estimates. The highest PD burden and associated costs would be incurred from exposure to multiple pesticides simultaneously.

CONCLUSION

Our study provides an assessment of the cost-effectiveness of banning specific insecticides to reduce PD burden in terms of health-related QALYs and related costs. This information may help policymakers and stakeholders to make decisions concerning the regulation of pesticides.

Protective effect of sterubin against neurochemical and behavioral impairments in rotenone-induced Parkinson's disease

This study was conducted to evaluate how sterubin affects rotenone-induced Parkinson's disease (PD) in rats. A total of 24 rats were distributed into 4 equal groups: normal saline control and rotenone control were administered saline or rotenone (ROT), respectively, orally; sterubin 10 received ROT + sterubin 10 mg/kg po; and sterubin alone was administered to the test group (10 mg/kg). Rats of the normal saline and sterubin alone groups received sunflower oil injection (sc) daily, 1 h after receiving the treatments cited above, while rats of the other groups received rotenone injection (0.5 mg/kg, sc). The treatment was continued over the course of 28 days daily. On the 29th day, catalepsy and akinesia were assessed. The rats were then euthanized, and the brain was extracted for estimation of endogenous antioxidants (MDA: malondialdehyde, GSH: reduced glutathione, CAT: catalase, SOD: superoxide dismutase), nitrative (nitrite) stress markers, neuroinflammatory cytokines, and neurotransmitter levels and their metabolites (3,4-dihydroxyphenylacetic acid (DOPAC), dopamine (DA), norepinephrine (NE), serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), and homovanillic acid (HVA)). Akinesia and catatonia caused by ROT reduced the levels of endogenous antioxidants (GSH, CAT, and SOD), elevated the MDA level, and altered the levels of nitrites, neurotransmitters, and their metabolites. Sterubin restored the neurobehavioral deficits, oxidative stress, and metabolites of altered neurotransmitters caused by ROT. Results demonstrated the anti-Parkinson's activities of sterubin in ROT-treated rats.

U.S. Tax Credits to Promote Practical Proactive Preventative Care for Parkinson's Disease

Persons with Parkinson's disease (PD) and society at large can profit from a strategic investment into a forward leaning, practical, preventative, and proactive multidisciplinary care policy. The American healthcare system is not easily bent to accommodate this type of care, and thus a tax benefit is an attractive option. An individual federal income tax benefit of $6200 each year for every person residing in the US with a diagnosis of PD, could among other offerings provide monthly access to a licensed clinical social worker and access to mental health services. The implementation of more coordinated care has the potential reduce the burden of depression, anxiety, and demoralization. Personal training would also be covered and directed by physical and occupational therapists. The combination of home-based and telemedicine services would have the added benefit of improving access. The tax benefit would also provide access to a dietician. This type of care strategy could be designed to proactively identify early signs of aspiration and urinary tract infections to 'head off' significant morbidity. A $6200/year individual tax benefit for those diagnosed with PD will thus translate into more fall prevention, more care in the home setting, less hospitalizations, less depression, less anxiety, less demoralization, better diets, and less persons placed in nursing facilities. Additionally, this tax benefit will provide the potential for billions of dollars in savings to the healthcare system. A tax benefit for PD is a practical preventative and proactive strategy which can serve to advantage both this generation and the next.

Neuroprotective effect of dexpanthenol on rotenone-induced Parkinson's disease model in rats

Parkinson's disease (PD) is the second most common and progressive neurodegenerative disease. This experimental study was designed to investigate the neuroprotective effects of dexpanthenol on antioxidant and anti-inflammatory processes in a rotenone-induced Parkinson's disease model in rats. Twenty-one male rats were randomly divided into 2 groups. The rotenone group (n = 14) was administered rotenone by intrastriatal injection, and the vehicle group (n = 7) was administered DMSO with the same application route. All animals underwent rotational movement testing with apomorphine injection 10 days later. Those with Parkinson's disease model were randomly divided into 2 groups. While 1 ml/kg of saline was applied to the saline group (n = 7), 500 mg/kg was administered to the dexpanthenol group intraperitoneally for 28 days. After 28 days, all rats were euthanized and brain tissue was removed. While striatal areas were evaluated immunohistochemically, brain MDA, TNF-α, and HVA levels were measured to evaluate their anti-oxidative and anti-inflammatory effects. In the dexpanthenol group, the total count (p < 0.001) and intensity (p < 0.001) of dopaminergic neurons in the striatal areas increased compared to the saline group. It was revealed that MDA (nmol/g) (p < 0.001) and TNF-α (pg/g) (p < 0.001) levels decreased in the dexpanthenol group, while HVA (ng/mg) levels increased (p < 0.01). This study suggests that dexpanthenol may have a neuroprotective effect by reducing neuronal loss, oxidative damage, and neuroinflammation in the striatum in rats.

Perspectives of People At-Risk on Parkinson's Prevention Research

 The movement toward prevention trials in people at-risk for Parkinson's disease (PD) is rapidly becoming a reality. The authors of this article include a genetically at-risk advocate with the LRRK2 G2019 S variant and two patients with rapid eye movement sleep behavior disorder (RBD), one of whom has now been diagnosed with PD. These authors participated as speakers, panelists, and moderators in the "Planning for Prevention of Parkinson's: A Trial Design Forum" hosted by Massachusetts General Hospital in 2021 and 2022. Other authors include a young onset person with Parkinson's (PwP) and retired family physician, an expert in patient engagement in Parkinson's, and early career and veteran movement disorders clinician researchers. Several themes emerged from the at-risk participant voice concerning the importance of early intervention, the legitimacy of their input in decision-making, and the desire for transparent communication and feedback throughout the entire research study process. Challenges and opportunities in the current environment include lack of awareness among primary care physicians and general neurologists about PD risk, legal and psychological implications of risk disclosure, limited return of individual research study results, and undefined engagement and integration of individuals at-risk into the broader Parkinson's community. Incorporating the perspectives of individuals at-risk as well as those living with PD at this early stage of prevention trial development is crucial to success.

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.

[Risk factors for Parkinson's disease: possibilities for prevention and intervention]

Considering age to be the primary risk factor for developing Parkinson's disease and the observation that the Dutch population is rapidly aging, the parkinson prevalence is expected to increase over the coming years, as there is still no cure available for the disease. This has been confirmed by epidemiological data, which show a steady increase of the disease prevalence in the Netherlands for the period 2010-2021. Genetic risk factors only partially explain the disease pathogenesis. Environmental factors, such as exposure to pesticides and trichloroethylene are associated with a higher risk for developing Parkinson's disease. Lifestyle factors such as exercise, caffeine intake and the Mediterranean diet are associated with a lower risk for developing the disease and possibly delay the disease progression. Policy makers and healthcare providers should employ stricter regulations for pesticide use and should stimulate a healthy lifestyle to slow down the increasing prevalence.

Low and high doses of oral maslinic acid protect against Parkinson's disease via distinct gut microbiota-related mechanisms

The use of oral agents that can modify the gut microbiota (GM) could be a novel preventative or therapeutic option for Parkinson's disease (PD). Maslinic acid (MA), a pentacyclic triterpene acid with GM-dependent biological activities when it is taken orally, has not yet been reported to be effective against PD. The present study found both low and high dose MA treatment significantly prevented dopaminergic neuronal loss in a classical chronic PD mouse model by ameliorating motor functions and improving tyrosine hydroxylase expressions in the substantia nigra pars compacta (SNpc) and increasing dopamine and its metabolite homovanillic acid levels in the striatum. However, the effects of MA in PD mice were not dose-responsive, since similar beneficial effects for low and high doses of MA were observed. Further mechanism studies indicated that low dose MA administration favored probiotic bacterial growth in PD mice, which helped to increase striatal serotonin, 5-hydroxyindole acetic acid, and γ-aminobutyric acid levels. High dose MA treatment did not influence GM composition in PD mice but significantly inhibited neuroinflammation as indicated by reduced levels of tumor necrosis factor alpha and interleukin 1β in the SNpc; moreover, these effects were mainly mediated by microbially-derived acetic acid in the colon. In conclusion, oral MA at different doses protected against PD via distinct mechanisms related to GM. Nevertheless, our study lacked in-depth investigations of the underlying mechanisms involved; future studies will be designed to further delineate the signaling pathways involved in the interactive actions between different doses of MA and GM.

Glutathione-Mediated Neuroprotective Effect of Purine Derivatives

Numerous basic studies have reported on the neuroprotective properties of several purine derivatives such as caffeine and uric acid (UA). Epidemiological studies have also shown the inverse association of appropriate caffeine intake or serum urate levels with neurodegenerative diseases such as Alzheimer disease (AD) and Parkinson's disease (PD). The well-established neuroprotective mechanisms of caffeine and UA involve adenosine A2A receptor antagonism and antioxidant activity, respectively. Our recent study found that another purine derivative, paraxanthine, has neuroprotective effects similar to those of caffeine and UA. These purine derivatives can promote neuronal cysteine uptake through excitatory amino acid carrier protein 1 (EAAC1) to increase neuronal glutathione (GSH) levels in the brain. This review summarizes the GSH-mediated neuroprotective effects of purine derivatives. Considering the fact that GSH depletion is a manifestation in the brains of AD and PD patients, administration of purine derivatives may be a new therapeutic approach to prevent or delay the onset of these neurodegenerative diseases.

β-carotene-loaded nanoparticles protect against neuromotor damage, oxidative stress, and dopamine deficits in a model of Parkinson's disease in Drosophila melanogaster

β-carotene-loaded nanoparticles improves absorption by increasing bioavailability. The Drosophila melanogaster model of Parkinson's disease must be helpful in investigating potential neuroprotective effects. Four groups of four-day-old flies were exposed to: (1) control; (2) diet containing rotenone (500 μM); (3) β-carotene-loaded nanoparticles (20 μM); (4) β-carotene-loaded nanoparticles and rotenone for 7 days. Then, the percentage of survival, geotaxis tests, open field, aversive phototaxis and food consumption were evaluated. At the end of the behaviors, the analyses of the levels of reactive species (ROS), thiobarbituric acid reactive substances (TBARS), catalase (CAT) and superoxide dismutase (SOD) activity was carried out, as well as an evaluation of the levels of dopamine and acetylcholinesterase (AChE) activity, in the head of flies. Nanoparticles loaded with β-carotene were able to improve motor function, memory, survival and also restored the oxidative stress indicators (CAT, SOD, ROS and TBARS), dopamine levels, AChE activity after exposure to rotenone. Overall, nanoparticles loaded with β-carotene showed significant neuroprotective effect against damage induced by the Parkinson-like disease model, emerging as a possible treatment. Overall, β-carotene-loaded nanoparticles presented significant neuroprotective effect against damage induced by model of Parkinson-like disease, emerging as a possible treatment.

Predicting structural features of selected flavonoids responsible for neuroprotection in a Drosophila model of Parkinson's disease

Nature-derived bioactive compounds have emerged as promising candidates for the prevention and treatment of diverse chronic illnesses, including neurodegenerative diseases. However, the exact molecular mechanisms underlying their neuroprotective effects remain unclear. Most studies focus solely on the antioxidant activities of natural products which translate to poor outcome in clinical trials. Current therapies against neurodegeneration only provide symptomatic relief, thereby underscoring the need for novel strategies to combat disease onset and progression. We have employed an environmental toxin-induced Drosophila Parkinson's disease (PD) model as an inexpensive in vivo screening platform to explore the neuroprotective potential of selected dietary flavonoids. We have identified a specific group of flavonoids known as flavones displaying protection against paraquat (PQ)-induced neurodegenerative phenotypes involving reduced survival, mobility defects, and enhanced oxidative stress. Interestingly, the other groups of investigated flavonoids, namely, the flavonones and flavonols failed to provide protection indicating a requirement of specific structural features that confer protection against PQ-mediated neurotoxicity in Drosophila. Based on our screen, the neuroprotective flavones lack a functional group substitution at the C3 and contain α,β-unsaturated carbonyl group. Furthermore, flavones-mediated neuroprotection is not solely dependent on antioxidant properties through nuclear factor erythroid 2-related factor 2 (Nrf2) but also requires regulation of the immune deficiency (IMD) pathway involving NFκB and the negative regulator poor Imd response upon knock-in (Pirk). Our data have identified specific structural features of selected flavonoids that provide neuroprotection against environmental toxin-induced PD pathogenesis that can be explored for novel therapeutic interventions.

HR LC-MS/MS metabolomic profiling of Yucca aloifolia fruit and the potential neuroprotective effect on rotenone-induced Parkinson's disease in rats

Yucca aloifolia L. fruit (Yucca or Spanish bayonet, family Asparagaceae) is recognized for its purplish red color reflecting its anthocyanin content, which has a powerful antioxidant activity. This study aimed to investigate yucca (YA) fruit extract's protective effect on Parkinson's disease (PD). In vitro study, the anti-inflammatory activity of yucca fruit extracts was explored by measuring tumor necrosis factor receptor 2 (TNF-R2) and nuclear factor kappa B (NF-KB) to choose the most effective extract. Afterward, a detailed in vivo investigation of the protective effect of the most active extract on rotenone-induced PD was performed on male albino Wister rats. First, the safety of the extract in two different doses (50 and 100 mg/kg in 0.9% saline orally) was confirmed by a toxicological study. The rats were divided into four groups: 1) normal control (NC); 2) rotenone group; and third and fourth groups received 50 and 100 mg/kg yucca extract, respectively. The neurobehavioral and locomotor activities of the rats were tested by rotarod, open field, and forced swim tests. Striatal dopamine, renal and liver functions, and oxidative stress markers were assessed. Western blot analysis of brain tissue samples was performed for p-AMPK, Wnt3a, and β-catenin. Histopathological examination of striatal tissue samples was performed by light and electron microscopy (EM). The metabolites of the active extract were characterized using high-resolution LC-MS/MS, and the results showed the prevalence of anthocyanins, saponins, phenolics, and choline. Biochemical and histopathological tests revealed a dose-dependent improvement with oral Yucca extract. The current study suggests a possible neuroprotective effect of the acidified 50% ethanol extract (YA-C) of the edible Yucca fruit, making it a promising therapeutic target for PD.

Hispidin in the Medicinal Fungus Protects Dopaminergic Neurons from JNK Activation-Regulated Mitochondrial-Dependent Apoptosis in an MPP+-Induced In Vitro Model of Parkinson's Disease

Degenerative diseases of the brain include Parkinson's disease (PD), which is associated with moveable signs and is still incurable. Hispidin belongs to polyphenol and originates primarily from the medicinal fungi Inonotus and Phellinus, with distinct biological effects. In the study, MES23.5 cells were induced by 1-methyl-4-phenylpyridinium (MPP⁺) to build a cell model of PD in order to detect the protective effect of hispdin and to specify the underlying mechanism. Pretreatment of MES23.5 cells with 1 h of hispdin at appropriate concentrations, followed by incubation of 24 h with 2 μmol/L MPP⁺ to induce cell damage. MPP⁺ resulted in reactive oxygen species production that diminished cell viability and dopamine content. Mitochondrial dysfunction in MS23.5 cells exposed to MPP⁺ was observed, indicated by inhibition of activity in the mitochondrial respiratory chain complex I, the collapse of potential in mitochondrial transmembrane, and the liberation of mitochondrial cytochrome c. Enabling C-Jun N-terminal kinase (JNK), reducing Bcl-2/Bax, and enhancing caspase-9/caspase-3/PARP cleavage were also seen by MPP⁺ induction associated with increased DNA fragmentation. All of the events mentioned above associated with MPP⁺-mediated mitochondrial-dependent caspases cascades were attenuated under cells pretreatment with hispidin (20 µmol/L); similar results were obtained during cell pretreatment with pan-JNK inhibitor JNK-IN-8 (1 µmol/L) or JNK3 inhibitor SR3576 (25 µmol/L). The findings show that hispidin has neuroprotection against MPP⁺-induced mitochondrial dysfunction and cellular apoptosis and suggest that hispidin can be seen as an assist in preventing PD.

Neuroprotective Effects of Bifidobacterium breve CCFM1067 in MPTP-Induced Mouse Models of Parkinson's Disease

There is mounting evidence that the microbiota-gut-brain axis (MGBA) is critical in the pathogenesis and progression of Parkinson's disease (PD), suggesting that probiotic therapy restoring gut microecology may slow down disease progression. In this study, we examined the disease-alleviating effects of Bifidobacterium breve CCFM1067, orally administered for 5 weeks in a PD mouse model. Our study shows that supplementation with the probiotic B. breve CCFM1067 protected dopaminergic neurons and suppressed glial cell hyperactivation and neuroinflammation in PD mice. In addition, the antioxidant capacity of the central nervous system was enhanced and oxidative stress was alleviated. Moreover, B. breve CCFM1067 protected the blood-brain and intestinal barriers from damage in the MPTP-induced mouse model. The results of fecal microbiota analysis showed that B. breve CCFM1067 intervention could act on the MPTP-induced microecological imbalance in the intestinal microbiota, suppressing the number of pathogenic bacteria (Escherichia-Shigella) while increasing the number of beneficial bacteria (Bifidobacterium and Akkermansia) in PD mice. In addition, the increase in short chain fatty acids (acetic and butyric acids) may explain the anti-inflammatory action of B. breve CCFM1067 in the gut or brain of the MPTP-induced PD mouse model. In conclusion, we demonstrated that the probiotic B. breve CCFM1067, which can prevent or treat PD by modulating the gut-brain axis, can be utilized as a possible new oral supplement for PD therapy.

The Role of Diet and Dietary Patterns in Parkinson's Disease

Parkinson's Disease (PD) is a neurodegenerative disorder associated with diminished nutrition status and decreased quality of life. While the prevalence of PD is expected to increase, no preventative or curative therapy for PD exists at this time. Although nutrition and diet represent modifiable risk factors for reducing chronic disease risk, research on the impact of single nutrients on PD has yielded mixed results. As a result, this single-nutrient approach may be the driving force behind the inconsistency, and a holistic dietary approach may overcome this inconsistency by accounting for the interactions between nutrients. The following review aims to examine the impact of a generally healthy dietary pattern, the protein-restricted diet (PRD), the ketogenic diet (KD), the Mediterranean diet (MD), and the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet on PD risk, progression, and severity. While most of the included studies support the role of diet and dietary patterns in reducing the risk of PD or alleviating PD severity, the inconsistent results and need for further evidence necessitate more research being conducted before making dietary recommendations. Research on the potential beneficial effects of dietary patterns on PD should also investigate potential risks.

Dietary Restriction against Parkinson's Disease: What We Know So Far

Dietary restriction (DR) is defined as a moderate reduction in food intake while avoiding malnutrition. The beneficial effects of DR are being increasingly acknowledged in aging and in a series of age-related neurodegenerative disorders, for example, Parkinson's disease (PD). To date, the pathogenesis of PD remains elusive and there is no cure for it in spite of intensive research over decades. In this review, we summarize the current knowledge on the efficacy of DR on PD, focusing on the underlying mechanisms involving general metabolism, neuroendocrinolgy, neuroinflammation, gut microbiome, and so on. We anticipate that this review will provide future perspectives for PD prevention and treatment.

Vaccination Reduces Risk of Alzheimer's Disease, Parkinson's Disease and Other Neurodegenerative Disorders

Neurodegeneration is an increasing problem of aging. Alzheimer's Disease (AD) and Parkinson's Disease (PD) are the most frequent forms of age-related neurodegeneration. Infectious diseases, in general, confer a risk of AD. Influenza and pneumonia vaccinations reduce risk of AD. Being vaccinated against pneumonia between ages 65-75 is associated with a reduction in the risk of AD afterwards. Protection against bacterial and viral infection is beneficial to the brain since these infections may activate dormant herpes simplex type 1 (HSV-1) and herpes zoster virus (HZV). HSV-1 and HZV may interact to trigger AD. Shingles (HZV) vaccine Zostavax reduces risk of AD and PD. This finding is consistent with the link between viruses and neurodegeneration. Herpes virus-induced reactivation of embryologic pathways silenced at birth could be one of the pathologic processes in AD and PD. Once embryologic reactivation has occurred in the brain of an older person and AD or PD develops, this complex process relentlessly destroys the protective mechanism it created in utero. Unanswered question: Are the AD-risk-reducing effects of flu, pneumonia, and shingles vaccinations cumulative?

Planning for Prevention of Parkinson Disease: Now Is the Time

Parkinson disease (PD) is a chronic progressive neurodegenerative disease with increasing worldwide prevalence. Despite many trials of neuroprotective therapies in manifest PD, no disease-modifying therapy has been established. Over the past several decades, a series of breakthroughs have identified discrete populations at substantially increased risk of developing PD. Based on this knowledge, now is the time to design and implement PD prevention trials. This endeavor builds on experience gained from early prevention trials in Alzheimer disease and Huntington disease. This article first reviews prevention trial precedents in these other neurodegenerative diseases before focusing on the critical design elements for PD prevention trials, including whom to enroll for these trials, what therapeutics to test, and how to measure outcomes in prevention trials. Our perspective reflects progress and remaining challenges that motivated a 2021 conference, "Planning for Prevention of Parkinson: A Trial Design Symposium and Workshop."

What to Test in Parkinson Disease Prevention Trials? Repurposed, Low-Risk, and Gene-Targeted Drugs

Despite the sound epidemiologic and basic science rationales underpinning numerous "disease modification" trials in manifest Parkinson disease (PD), none has convincingly demonstrated that a treatment slows progression. Rapidly expanding knowledge of the genetic determinants and prodromal features of PD now allows realistic planning of prevention trials with initiation of putatively neuroprotective therapies earlier in the disease. In this article, we outline the principles of drug selection for PD prevention trials, focused on proof-of-concept opportunities that will help establish a methodological foundation for this fledgling field. We describe prototypical, relatively low-risk drug candidates for such trials (e.g., albuterol, ambroxol, caffeine, ibuprofen), tailored to specific at-risk populations ranging from pathogenic LRRK2 or GBA gene variant carriers to those defined by prodromal PD and α-synucleinopathy. Finally, we review gene-targeted approaches currently in development targeting clinically manifest PD for their potential in future prevention trials.

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.

A focus on natural products for preventing and cure of mitochondrial dysfunction in Parkinson's disease

Mitochondria are considered the only source of energy production within cells. This organelle is vital for neural function and survival by producing energy (adenosine triphosphate (ATP)) and regulating intracellular calcium. Mitochondrial dysfunction, which significantly contributes to both idiopathic and familial types of Parkinson's disease (PD), depletes cellular energy, disrupts homeostasis, and induces oxidative stress, leading to cell death. In recent years several natural products have been discovered to be protective against mitochondrial dysfunction. This review discusses the role of mitochondria in the progression of PD to define the path for using natural products to prevent and/or cure PD.

Molecular Hydrogen as a Novel Protective Agent against Pre-Symptomatic Diseases

Mibyou, or pre-symptomatic diseases, refers to state of health in which a disease is slowly developing within the body yet the symptoms are not apparent. Common examples of mibyou in modern medicine include inflammatory diseases that are caused by chronic inflammation. It is known that chronic inflammation is triggered by the uncontrolled release of proinflammatory cytokines by neutrophils and macrophages in the innate immune system. In a recent study, it was shown that molecular hydrogen (H2) has the ability to treat chronic inflammation by eliminating hydroxyl radicals (·OH), a mitochondrial reactive oxygen species (ROS). In doing so, H2 suppresses oxidative stress, which is implicated in several mechanisms at the root of chronic inflammation, including the activation of NLRP3 inflammasomes. This review explains these mechanisms by which H2 can suppress chronic inflammation and studies its applications as a protective agent against different inflammatory diseases in their pre-symptomatic state. While mibyou cannot be detected nor treated by modern medicine, H2 is able to suppress the pathogenesis of pre-symptomatic diseases, and thus exhibits prospects as a novel protective agent.

Natural Phytochemicals as Novel Therapeutic Strategies to Prevent and Treat Parkinson's Disease: Current Knowledge and Future Perspectives

Parkinson's disease (PD) is the second-most common neurodegenerative chronic disease affecting both cognitive performance and motor functions in aged people. Yet despite the prevalence of this disease, the current therapeutic options for the management of PD can only alleviate motor symptoms. Research has explored novel substances for naturally derived antioxidant phytochemicals with potential therapeutic benefits for PD patients through their neuroprotective mechanism, targeting oxidative stress, neuroinflammation, abnormal protein accumulation, mitochondrial dysfunction, endoplasmic reticulum stress, neurotrophic factor deficit, and apoptosis. The aim of the present study is to perform a comprehensive evaluation of naturally derived antioxidant phytochemicals with neuroprotective or therapeutic activities in PD, focusing on their neuropharmacological mechanisms, including modulation of antioxidant and anti-inflammatory activity, growth factor induction, neurotransmitter activity, direct regulation of mitochondrial apoptotic machinery, prevention of protein aggregation via modulation of protein folding, modification of cell signaling pathways, enhanced systemic immunity, autophagy, and proteasome activity. In addition, we provide data showing the relationship between nuclear factor E2-related factor 2 (Nrf2) and PD is supported by studies demonstrating that antiparkinsonian phytochemicals can activate the Nrf2/antioxidant response element (ARE) signaling pathway and Nrf2-dependent protein expression, preventing cellular oxidative damage and PD. Furthermore, we explore several experimental models that evaluated the potential neuroprotective efficacy of antioxidant phytochemical derivatives for their inhibitory effects on oxidative stress and neuroinflammation in the brain. Finally, we highlight recent developments in the nanodelivery of antioxidant phytochemicals and its neuroprotective application against pathological conditions associated with oxidative stress. In conclusion, naturally derived antioxidant phytochemicals can be considered as future pharmaceutical drug candidates to potentially alleviate symptoms or slow the progression of PD. However, further well-designed clinical studies are required to evaluate the protective and therapeutic benefits of phytochemicals as promising drugs in the management of PD.

pH-Responsive Redox Nanoparticles Protect SH-SY5Y Cells at Lowered pH in a Cellular Model of Parkinson's Disease

The damage to SH-SY5Y cells by 6-hydroxydopamine (6-OHDA) is an established cellular model of Parkinson's disease (PD). Redox nanoparticles are a promising tool for therapy, including neurodegenerative diseases. As pH of the brain tissue at sites affected by PD is lowered down to 6.5, we studied the effect of pH-responsive redox nanoparticles (poly(ethylene glycol)-b-poly[4-(2,2,6,6-tetramethylpiperidine-1-oxyl)aminomethylstyrene]), which change their structure in a pH-dependent manner and become active below pH 7 (NRNPs pH), on the viability of SH-SY5Y cells treated with 6-OHDA at pH 6.5 and 7.4. Pretreatment of the cells with NRNPs pH (15-75 μM) prior to the 6-OHDA treatment increased their survival in a concentration-dependent manner at pH 6.5, but not at pH 7.4. Among several parameters studied (ATP and GSH content, the level of reactive oxygen species, mitochondrial potential, mitochondrial mass), only the mitochondrial mass was dose-dependently protected by NRNPs pH at pH 6.5, but not at pH 7.4. These results indicate that the action of NRNPs pH on mitochondria underlies their protective effect in this cellular model of PD. These results may have potential importance for future applications of NRNPs pH in preclinical and perhaps clinical studies.

Early low-dose ghrelin intervention via miniosmotic pumps could protect against the progressive dopaminergic neuron loss in Parkinson's disease mice

Ghrelin has been identified as a multifunctional peptide that has a potential application for treating Parkinson's disease (PD). The objective of this study was to assess the effects of subcutaneous administration of low-dose ghrelin via miniosmotic pumps on PD progression. The decreased levels of total and active ghrelin in plasma were rescued by ghrelin administration in PD mice. Interestingly, ghrelin did not affect weight gain in wild-type mice but improved weight loss in PD mice. We observed the attenuation of dopaminergic neuron loss in substantia nigra and a low level of dopamine content in the striatum in PD mice with ghrelin treatment. Ghrelin administration could improve the microenvironment of dopaminergic neurons by inhibiting microglial proliferation and proinflammatory cytokine expression and could enhance cell survival by upregulating Bcl-2/Bax ratio and superoxide dismutase1 protein level in the substantia nigra of PD mice. Subcutaneous administration of low-dose ghrelin could prevent the onset of the progression of PD and also provide a possible method for ghrelin application to cure PD.

Does glitazone treatment have a role on the prevention of Parkinson's disease in adult diabetic population? A systematic review

Lately, focus on the relation between Parkinson's disease (PD) and Diabetes has risen greatly, as neuroprotective properties have been attributed to insulin use. Several studies have assessed the effect of glitazones, an insulin-sensitizing agent, in diabetic population on PD future risk. However, reports on the effect of their use have been heterogeneous. We aimed to synthesize the available scientific evidence which assesses the effect of glitazone use in type 2 diabetes patients on PD incidence. A systematic review was performed on multiple electronic databases. Considered for inclusion were studies that assessed the incidence of PD in type 2 diabetes glitazone users. Two reviewers worked independently and in duplicate to assess all studies, extract information and assess the methodological quality in each included study. Four high quality retrospective cohorts fulfilled inclusion criteria. Comparison groups varied across studies. In each study, incidence of PD was lower in glitazone-exposed patients compared to their respective comparison group. Pooled analysis showed lesser risk of PD in ever versus never glitazone users (RR 0.75 [95% C.I. 0.67-0.85; p < .0001; I² = 0]). Our pooled analysis showed lesser risk of PD in glitazone versus non glitazone users, however, we advise to take results with caution since results are non-adjusted to possible confounding variables, furthermore, different glitazone-exposure time, follow up and comparison groups are aspects that also need to be pointed out. More clinical research focused on glitazone use and its relation with PD is needed, as this could result in new potential treatment modalities.

Melatonin and Autophagy in Aging-Related Neurodegenerative Diseases

With aging, the nervous system gradually undergoes degeneration. Increased oxidative stress, endoplasmic reticulum stress, mitochondrial dysfunction, and cell death are considered to be common pathophysiological mechanisms of various neurodegenerative diseases (NDDs) such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), organophosphate-induced delayed neuropathy (OPIDN), and amyotrophic lateral sclerosis (ALS). Autophagy is a cellular basic metabolic process that degrades the aggregated or misfolded proteins and abnormal organelles in cells. The abnormal regulation of neuronal autophagy is accompanied by the accumulation and deposition of irregular proteins, leading to changes in neuron homeostasis and neurodegeneration. Autophagy exhibits both a protective mechanism and a damage pathway related to programmed cell death. Because of its "double-edged sword", autophagy plays an important role in neurological damage and NDDs including AD, PD, HD, OPIDN, and ALS. Melatonin is a neuroendocrine hormone mainly synthesized in the pineal gland and exhibits a wide range of biological functions, such as sleep control, regulating circadian rhythm, immune enhancement, metabolism regulation, antioxidant, anti-aging, and anti-tumor effects. It can prevent cell death, reduce inflammation, block calcium channels, etc. In this review, we briefly discuss the neuroprotective role of melatonin against various NDDs via regulating autophagy, which could be a new field for future translational research and clinical studies to discover preventive or therapeutic agents for many NDDs.

Puerarin suppresses MPP+/MPTP-induced oxidative stress through an Nrf2-dependent mechanism

In this study, we hypothesized that anti-parkinsonian effect of puerarin is attributable to its antioxidant properties via Nrf2-dependent glutathione (GSH) biosynthesis mechanism. Experimentally, we found that puerarin attenuated 1-methyl-4-phenylpyridinium (MPP⁺)-induced oxidative stress through elevating biosynthetic capacity of GSH in PC12 cells. Mechanistically, puerarin suppressed Fyn phosphorylation by GSK-3β-dependent mechanism in MPP⁺-challenged PC12 cells. Furthermore, puerarin induced accumulation of Nrf2 in the nucleus via inhibiting its nuclear exclusion. In parallel, puerarin up-regulated antioxidant response element (ARE)-driven catalytic subunits from glutamate cysteine ligase (GCLc) expression at levels of transcription and translation. Most interestingly, pharmacological inhibitor of GSK-3β or Fyn shRNA blocked puerarin-induced Nrf2 activation in MPP⁺-challenged PC12 cells. Concomitantly, puerarin ameliorated motor deficits and inhibited oxidative stress in the ventral midbrain in MPTP-intoxicated wild-type (WT) mice, but failed to attenuate MPTP neurotoxicity and up-regulate GCLc gene in Nrf2-knockout (Nrf2^-/-) mice, suggesting that anti-parkinsonian effect of puerarin was dependent on Nrf2. Additionally, puerarin regulated Fyn and GSK-3β phosphorylation in the ventral midbrain in MPTP-intoxicated WT mice. Collectively, the results of the study provide molecular insights into the potential therapeutic action of puerarin in Parkinson's disease, suggesting that puerarin may be a promising candidate for the treatment of Parkinson's disease.

Dual Target Ligands with 4-tert-Butylphenoxy Scaffold as Histamine H3 Receptor Antagonists and Monoamine Oxidase B Inhibitors

Dual target ligands are a promising concept for the treatment of Parkinson's disease (PD). A combination of monoamine oxidase B (MAO B) inhibition with histamine H₃ receptor (H₃R) antagonism could have positive effects on dopamine regulation. Thus, a series of twenty-seven 4-tert-butylphenoxyalkoxyamines were designed as potential dual-target ligands for PD based on the structure of 1-(3-(4-tert-butylphenoxy)propyl)piperidine (DL76). Probed modifications included the introduction of different cyclic amines and elongation of the alkyl chain. Synthesized compounds were investigated for human H₃R (hH₃R) affinity and human MAO B (hMAO B) inhibitory activity. Most compounds showed good hH₃R affinities with K_i values below 400 nM, and some of them showed potent inhibitory activity for hMAO B with IC₅₀ values below 50 nM. However, the most balanced activity against both biological targets showed DL76 (hH₃R: K_i = 38 nM and hMAO B: IC₅₀ = 48 nM). Thus, DL76 was chosen for further studies, revealing the nontoxic nature of DL76 in HEK293 and neuroblastoma SH-SY5Ycells. However, no neuroprotective effect was observed for DL76 in hydrogen peroxide-treated neuroblastoma SH-SY5Y cells. Furthermore, in vivo studies showed antiparkinsonian activity of DL76 in haloperidol-induced catalepsy (Cross Leg Position Test) at a dose of 50 mg/kg body weight.

Healthspan Maintenance and Prevention of Parkinson's-like Phenotypes with Hydroxytyrosol and Oleuropein Aglycone in C. elegans

Numerous studies highlighted the beneficial effects of the Mediterranean diet (MD) in maintaining health, especially during ageing. Even neurodegeneration, which is part of the natural ageing process, as well as the foundation of ageing-related neurodegenerative disorders like Alzheimer’s and Parkinson’s disease (PD), was successfully targeted by MD. In this regard, olive oil and its polyphenolic constituents have received increasing attention in the last years. Thus, this study focuses on two main olive oil polyphenols, hydroxytyrosol (HT) and oleuropein aglycone (OLE), and their effects on ageing symptoms with special attention to PD. In order to avoid long-lasting, expensive, and ethically controversial experiments, the established invertebrate model organism Caenorhabditis elegans was used to test HT and OLE treatments. Interestingly, both polyphenols were able to increase the survival after heat stress, but only HT could prolong the lifespan in unstressed conditions. Furthermore, in aged worms, HT and OLE caused improvements of locomotive behavior and the attenuation of autofluorescence as a marker for ageing. In addition, by using three different C. elegans PD models, HT and OLE were shown i) to enhance locomotion in worms suffering from α-synuclein-expression in muscles or rotenone exposure, ii) to reduce α-synuclein accumulation in muscles cells, and iii) to prevent neurodegeneration in α-synuclein-containing dopaminergic neurons. Hormesis, antioxidative capacities and an activity-boost of the proteasome & phase II detoxifying enzymes are discussed as potential underlying causes for these beneficial effects. Further biological and medical trials are indicated to assess the full potential of HT and OLE and to uncover their mode of action.

GIP has neuroprotective effects in Alzheimer and Parkinson's disease models

Glucose-dependent Insulinotropic polypeptide (GIP) is a peptide hormone of the incretin family. It has growth factor properties and can re-activate energy utilization. In progressive neurodegenerative disorders such as Alzheimer's and Parkinson's disease, energy utilization is much reduced, and GIP has the potential to reverse this. Furthermore, GIP can reduce the inflammation response in the brain and reduce levels of pro-inflammatory cytokines. Tests in animal models of Alzheimer's and Parkinson's disease show good neuroprotective effects. In Parkinson's disease models, motor activity is normalized, dopaminergic neurons are protected, synapse numbers and dopamine levels are maintained. Levels of growth factors that are essential for neuronal and synaptic function are increased and alpha-synuclein levels are reduced. The chronic inflammation response and mitochondrial damage is reduced. In Alzheimer's disease models, memory is rescued, synapse numbers and synaptic plasticity in the hippocampus is normalized, amyloid plaque load and the chronic inflammation is reduced. Similar protective effects have been previously reported with analogues of glucagon-like peptide 1 (GLP-1), the sister incretin hormone. First clinical trials show good protective effects in both diseases. Recently, novel dual GLP-1/GIP receptor agonists have been developed. The ability to cross the blood-brain barrier (BBB) is key to their neuroprotective effects. We have developed two dual GLP-1/GIP receptor agonist that have cell penetrating sequences added for better BBB penetration. In direct comparisons, these dual agonists show improved neuroprotection in a mouse model of Parkinson's disease. Therefore, such novel multiple receptor agonists hold great promise as potential treatments for Alzheimer's and Parkinson's disease.

A Curcumin Derivative Activates TFEB and Protects Against Parkinsonian Neurotoxicity in Vitro

TFEB (transcription factor EB), which is a master regulator of autophagy and lysosome biogenesis, is considered to be a new therapeutic target for Parkinson’s disease (PD). However, only several small-molecule TFEB activators have been discovered and their neuroprotective effects in PD are unclear. In this study, a curcumin derivative, named E4, was identified as a potent TFEB activator. Compound E4 promoted the translocation of TFEB from cytoplasm into nucleus, accompanied by enhanced autophagy and lysosomal biogenesis. Moreover, TFEB knockdown effectively attenuated E4-induced autophagy and lysosomal biogenesis. Mechanistically, E4-induced TFEB activation is mainly through AKT-MTORC1 inhibition. In the PD cell models, E4 promoted the degradation of α-synuclein and protected against the cytotoxicity of MPP⁺ (1-methyl-4-phenylpyridinium ion) in neuronal cells. Overall, the TFEB activator E4 deserves further study in animal models of neurodegenerative diseases, including PD.

Peripheral Delivery of Neural Precursor Cells Ameliorates Parkinson's Disease-Associated Pathology

: Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by loss of motor control due to a wide loss of dopaminergic neurons along the nigro-striatal pathway. Some of the mechanisms that contribute to this cell death are inflammation, oxidative stress, and misfolded alpha-synuclein-induced toxicity. Current treatments are effective at managing the early motor symptoms of the disease, but they become ineffective over time and lead to adverse effects. Previous research using intracerebral stem cell therapy for treatment of PD has provided promising results; however, this method is very invasive and is often associated with unacceptable side effects. In this study, we used an MPTP-injected mouse model of PD and intravenously administered neural precursors (NPs) obtained from mouse embryonic and mesenchymal stem cells. Clinical signs and neuropathology were assessed. Female mice treated with NPs had improved motor function and reduction in the neuroinflammatory response. In terms of safety, there were no tumorigenic formations or any detectable adverse effect after treatment. Our results suggest that peripheral administration of stem cell-derived NPs may be a promising and safe therapy for the recovery of impaired motor function and amelioration of brain pathology in PD.

High lithium levels in tobacco may account for reduced incidences of both Parkinson's disease and melanoma in smokers through enhanced β-catenin-mediated activity

Parkinson's disease (PD) patients have higher rates of melanoma and vice versa, observations suggesting that the two conditions may share common pathogenic pathways. β-Catenin is a transcriptional cofactor that, when concentrated in the nucleus, upregulates the expression of canonical Wnt target genes, such as Nurr1, many of which are important for neuronal survival. β-Catenin-mediated activity is decreased in sporadic PD as well as in leucine-rich repeat kinase 2 (LRRK2) and β-glucosidase (GBA) mutation cellular models of PD, which is the most common genetic cause of and risk for PD, respectively. In addition, β-catenin expression is significantly decreased in more aggressive and metastatic melanoma. Multiple observational studies have shown smokers to have significantly lower rates of PD as well as melanoma implying that tobacco may contain one or more elements that protect against both conditions. In support, smoker's brains have significantly reduced levels of α-synuclein, a pathological intracellular protein found in PD brain and melanoma cells. Tobacco contains very high lithium levels compared to other plants. Lithium has a broad array of neuroprotective actions, including enhancing autophagy and reducing intracellular α-synuclein levels, and is effective in both neurotoxin and transgenic preclinical PD models. One of lithium's neuroprotective actions is enhancement of β-catenin-mediated activity leading to increased Nurr1 expression through its ability to inhibit glycogen synthase kinase-3 β (GSK-3β). Lithium also has anti-proliferative effects on melanoma cells and the clinical use of lithium is associated with a reduced incidence of melanoma as well as reduced melanoma-associated mortality. This is the first known report hypothesizing that inhaled lithium from smoking may account for the associated reduced rates of both PD and melanoma and that this protection may be mediated, in part, through lithium-induced GSK-3β inhibition and consequent enhanced β-catenin-mediated activity. This hypothesis could be directly tested in clinical trials assessing lithium therapy's ability to affect β-catenin-mediated activity and slow disease progression in patients with PD or melanoma.

G protein-coupled estrogen receptor is involved in the neuroprotective effect of IGF-1 against MPTP/MPP+-induced dopaminergic neuronal injury

Insulin-like growth factor-1 (IGF-1), an endogenous peptide, exerts important role in brain development, neurogenesis and neuroprotection. There are accumulating evidence for the interaction of IGF-1 and 17β-estradiol systems. IGF-1/IGF-1 receptor (IGF-1R) signaling has been reported to regulate G-protein estrogen receptor (GPER) expression in cancer cells. Whether GPER is involved in the neuroprotective effect of IGF-1 against MPTP/MPP⁺-induced dopaminergic neuronal injury remains unclear. We showed that IGF-1 could improve MPTP-induced motor deficits and ameliorate the decreased contents of DA and its metabolites in striatum as well as the loss of TH-IR neurons in the substantia nigra (SN). IGF-1 pretreatment also reversed the changes of Bcl-2 and Bax protein expressions in SN in MPTP mice. These effects were abolished by IGF-1 receptor (IGF-1R) antagonist JB-1 or GPER antagonist G15 except the inhibitory effect of G15 on Bax protein expression. Moreover, IGF-1 pretreatment enhanced cell survival against MPP⁺-induced neurotoxicity in SH-SY5Y cells. IGF-1 exerted anti-apoptotic effects by restoring MPP⁺-induced changes of Bcl-2 and Bax protein expressions as well as mitochondria membrane potential. Co-treatment with JB-1 or G15 could block these effects. Furthermore, IGF-1 regulated the protein expression of GPER through activation of phosphatidylinositol 3-kinase (PI3-K) and mitogen-activated protein kinase (MAPK) signaling pathways. Overall, we show for the first time that GPER may contribute to the neuroprotective effects of IGF-1 against MPTP/MPP⁺-induced dopaminergic neuronal injury.

Overexpression of human Atp13a2Isoform-1 protein protects cells against manganese and starvation-induced toxicity

Mutations in ATP13A2 cause Kufor-Rakeb syndrome (KRS), a juvenile form of Parkinson's disease (PD) with dementia. However, the mechanisms by which mutations in ATP13A2 cause KRS is not understood. The mutations lead to misfolding of the translated Atp13a2 protein and its premature degradation in the endoplasmic reticulum, never reaching the lysosome where the protein is thought to function. Atp13a2 is a P-type ATPase, a class of proteins that function in ion transport. Indeed, studies of human, mouse, and yeast Atp13a2 proteins suggest a possible involvement in regulation of heavy metal toxicity. Here we report on the cytoprotective function of Atp13a2 on HeLa cells and dopamine neurons of Caenorhabditis elegans (C. elegans). HeLa cells stably overexpressing V5- tagged Atp13a2Isoform-1 protein were more resistant to elevated manganese exposure and to starvation-induced cell death compared to cells not overexpressing the protein. Because PD is characterized by loss of dopamine neurons, we generated transgenic C. elegans expressing GFP-tagged human Atp13a2 protein in dopamine neurons. The transgenic animals exhibited higher resistance to dopamine neuron degeneration after acute exposure to manganese compared to nematodes that expressed GFP alone. The results suggest Atp13a2 Isoform-1 protein confers cytoprotection against toxic insults, including those that cause PD syndromes.

Gastrodin protects dopaminergic neurons via insulin-like pathway in a Parkinson's disease model

BACKGROUND

Recently, the use of traditional Chinese medicine (TCM) has become more generally accepted, including by the Food and Drug Administration. To expand the use of TCM worldwide, it is important to study the molecular mechanisms by which TCM and its active ingredients produce effects. Gastrodin is an active ingredient from Gastrodia elata Blume. It is reported that gastrodin has neuroprotective function in Parkinson's disease. But its mechanisms of neuroprotection remain not clear in PD. Here, we build two C. elegans PD model using 6-OHDA and transgenic animal to observe the changes of PD worms treated with or without gastrodin to confirm the function of gastrodin, then utilize mutant worms to investigate DAF-2/DAF-16 signaling pathway, and finally verify the mechanism of gastrodin in PD.

RESULTS

Gastrodin attenuates the accumulation of α-synuclein and the injury of dopaminergic neurons, improves chemotaxis behavior in Parkinson's disease models, then recovers chemotaxis behavior by insulin-like pathway. DAF-2/DAF-16 is required for neuroprotective effect of dopamine neuron in PD.

CONCLUSIONS

Our study demonstrated that gastrodin rescued dopaminergic neurons and reduced accumulation of α-synuclein protein, and the activity of gastrodin against Parkinson's disease depended on the insulin-like DAF-2/DAF-16 signaling pathway. Our findings revealed that this insulin-like pathway mediates neuroprotection of gastrodin in a Parkinson's disease model.

5-(3,4-Difluorophenyl)-3-(6-methylpyridin-3-yl)-1,2,4-oxadiazole (DDO-7263), a novel Nrf2 activator targeting brain tissue, protects against MPTP-induced subacute Parkinson's disease in mice by inhibiting the NLRP3 inflammasome and protects PC12 cells against oxidative stress

Parkinson's disease (PD) is the second most common aging-related neurodegenerative disease worldwide. Oxidative stress and neuroinflammation are critical events in the degeneration of dopaminergic neurons in PD. In this study, we found that DDO-7263, a novel Nrf2-ARE activator reported by us, has ideal therapeutic effects on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease in mice. DDO-7263 improved the behavioral abnormalities induced by MPTP in mice, significantly attenuated chemically induced dopaminergic neuron loss of tyrosine hydroxylase (TH) in the substantia nigra (SN) and striatum of the mouse brain and inhibited the secretion of inflammatory factors. In addition, DDO-7263 protected PC12 neurons from H₂O₂-induced oxidative damage. The neuroprotective effects of DDO-7263 were confirmed both in vitro and in vivo models. Further studies showed that the neuroprotective effect of DDO-7263 was mediated by the activation of Nrf2-ARE signaling pathway and the inhibition of NLRP3 inflammasome activation. DDO-7263 induced NLRP3 inflammasome inhibition is dependent on Nrf2 activation. This conclusion was also verified in THP-1-derived macrophages (THP-Ms). DDO-7263 significantly inhibited NLRP3 activation, cleaved caspase-1 production and IL-1β protein expression in ATP-LPS-exposed THP-Ms cells. The pharmacokinetic parameters and tissue distribution results indicated that DDO-7263 has a brain tissue targeting function. All these lines of evidence show that DDO-7263 has ideal therapeutic effects on neurodegenerative diseases such as PD.

Nicotine protects against manganese and iron-induced toxicity in SH-SY5Y cells: Implication for Parkinson's disease

Manganese (Mn) and iron (Fe) are trace elements that are essential for proper growth and physiological functions as both play critical role in a variety of enzymatic reactions. At high concentrations, however, they can be toxic and cause neurodegenerative disorders, particularly Parkinson-like syndromes. Nicotine, on the other hand, has been shown to have neuroprotective effects against various endogenous or exogenous toxins that selectively damage the dopaminergic cells. These cells include neuroblastoma-derived SH-SY5Y cells which express significant dopaminergic activity. However, practically no information on possible neuroprotective effects of nicotine against toxicity induced by trace elements is available. Therefore, in this study we investigated the effects of nicotine on toxicity induced by manganese or iron in these cells. Exposure of SH-SY5Y cells for 24 h to manganese (20 μM) or iron (20 μM) resulted in approximately 30% and 35% toxicity, respectively. Pretreatment with nicotine (1 μM) completely blocked the toxicities of Mn and Fe. The effects of nicotine, in turn, were blocked by selective nicotinic receptor antagonists. Thus, dihydro-beta erythroidine (DHBE), a selective alpha 4-beta 2 subtype antagonist and methyllycaconitine (MLA), a selective alpha7 antagonist, as well as mecamylamine, a non-selective nicotinic antagonist all dose-dependently blocked the protective effects of nicotine against both Mn and Fe. These findings provide further support for the potential utility of nicotine or nicotinic agonists in Parkinson's disease-like neurodegenerative disorders, including those that might be precipitated by trace elements, such as Fe and Mn. Moreover, both alpha4-beta2 and alpha7 nicotinic receptor subtypes appear to mediate the neuroprotective effects of nicotine against toxicity induced by these two trace metals.

Role of Ketogenic Diets in Neurodegenerative Diseases (Alzheimer's Disease and Parkinson's Disease)

The goal of this review was to assess the effectiveness of ketogenic diets on the therapy of neurodegenerative diseases. The ketogenic diet is a low-carbohydrate and fat-rich diet. Its implementation has a fasting-like effect, which brings the body into a state of ketosis. The ketogenic diet has, for almost 100 years, been used in the therapy of drug-resistant epilepsy, but current studies indicate possible neuroprotective effects. Thus far, only a few studies have evaluated the role of the ketogenic diet in the prevention of Parkinson’s disease (PD) and Alzheimer’s disease (AD). Single studies with human participants have demonstrated a reduction of disease symptoms after application. The application of the ketogenic diet to elderly people, however, raises certain concerns. Persons with neurodegenerative diseases are at risk of malnutrition, while food intake reduction is associated with disease symptoms. In turn, the ketogenic diet leads to a reduced appetite; it is not attractive from an organoleptic point of view, and may be accompanied by side effects of the gastrointestinal system. All this may lead to further lowering of consumed food portions by elderly persons with neurodegenerative diseases and, in consequence, to further reduction in the supply of nutrients provided by the diet. Neither data on the long-term application of the ketogenic diet in patients with neurodegenerative disease or data on its effects on disease symptoms are available. Further research is needed to evaluate the suitability of the ketogenic diet in the therapy of AD- or PD-affected persons.

The Potential Use of Plant Natural Products and Plant Extracts with Antioxidant Properties for the Prevention/Treatment of Neurodegenerative Diseases: In Vitro, In Vivo and Clinical Trials

Neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease and Huntington's disease, present a major health issue and financial burden for health care systems around the world. The impact of these diseases will further increase over the next decades due to increasing life expectancies. No cure is currently available for the treatment of these conditions; only drugs, which merely alleviate the symptoms. Oxidative stress has long been associated with neurodegeneration, whether as a cause or as part of the downstream results caused by other factors. Thus, the use of antioxidants to counter cellular oxidative stress within the nervous system has been suggested as a potential treatment option for neurological disorders. Over the last decade, significant research has focused on the potential use of natural antioxidants to target oxidative stress. However, clinical trial results have lacked success for the treatment of patients with neurological disorders. The knowledge that natural extracts show other positive molecular activities in addition to antioxidant activity, however, has led to further research of natural extracts for their potential use as prevention or treatment/management of neurodegenerative diseases. This review will cover several in vitro and in vivo research studies, as well as clinical trials, and highlight the potential of natural antioxidants.

Polydatin Prevents Lipopolysaccharide (LPS)-Induced Parkinson's Disease via Regulation of the AKT/GSK3β-Nrf2/NF-κB Signaling Axis

Parkinson's disease (PD) is a common neurodegenerative disease characterized by selective loss of dopaminergic neurons in the substantia nigra (SN). Neuroinflammation induced by over-activation of microglia leads to the death of dopaminergic neurons in the pathogenesis of PD. Therefore, downregulation of microglial activation may aid in the treatment of PD. Polydatin (PLD) has been reported to pass through the blood-brain barrier and protect against motor degeneration in the SN. However, the molecular mechanisms underlying the effects of PLD in the treatment of PD remain unclear. The present study aimed to determine whether PLD protects against dopaminergic neurodegeneration by inhibiting the activation of microglia in a rat model of lipopolysaccharide (LPS)-induced PD. Our findings indicated that PLD treatment protected dopaminergic neurons and ameliorated motor dysfunction by inhibiting microglial activation and the release of pro-inflammatory mediators. Furthermore, PLD treatment significantly increased levels of p-AKT, p-GSK-3βSer9, and Nrf2, and suppressed the activation of NF-κB in the SN of rats with LPS-induced PD. To further explore the neuroprotective mechanism of PLD, we investigated the effect of PLD on activated microglial BV-2 cells. Our findings indicated that PLD inhibited the production of pro-inflammatory mediators and the activation of NF-κB pathways in LPS-induced BV-2 cells. Moreover, our results indicated that PLD enhanced levels of p-AKT, p-GSK-3βSer9, and Nrf2 in BV-2 cells. After BV-2 cells were pretreated with MK2206 (an inhibitor of AKT), NP-12 (an inhibitor of GSK-3β), or Brusatol (BT; an inhibitor of Nrf2), treatment with PLD suppressed the activation of NF-κB signaling pathways and the release of pro-inflammatory mediators in activated BV-2 cells via activation of the AKT/GSK3β-Nrf2 signaling axis. Taken together, our results are the first to demonstrate that PLD prevents dopaminergic neurodegeneration due to microglial activation via regulation of the AKT/GSK3β-Nrf2/NF-κB signaling axis.

Chinese herbal medicine reduced the risk of stroke in patients with Parkinson's disease: A population-based retrospective cohort study from Taiwan

Parkinson’s disease (PD) is associated with a significantly increased risk of stroke. Traditional Chinese medicine (TCM) has long been used in Asia to treat stroke, but there are no large-scale clinical data to confirm its efficacy in protecting PD patients against stroke. Herein, we analyzed a cohort of 1,000,000 records from Taiwan’s National Health Insurance Research Database for the period 1997–2011, and identified 1,882 patients with new-onset PD. We matched 290 patients who received Chinese herbal medicine (CHM) by age, sex, year of CHM prescription, and year of PD diagnosis with 290 patients who did not use CHM as control. Both cohorts were followed until the end of 2013 for the incidence of new-onset stroke. In a multivariable Cox proportional hazard model adjusted for potential comorbidities, the incidence of stroke was lower among PD patients using CHM compared with non-CHM users (11.10 per 100 person-years vs 23.15 per 100 person-years; Hazard ratio: 0.56; 95% confidence interval:  0.44 to 0.72). The probability curve generated from our follow-up data showed that PD patients receiving CHM treatment had a decreased risk of stroke compared with those not receiving CHM treatment (P <0.001). The analysis on the prescription pattern of CHM revealed that Danshen is the most common single herb and Ma Zi Ren Wan is the most common herbal formula. Although the analysis are limited by a lack of analytic information regarding lifestyle patterns, biochemical profiles, and levels of PD severity in database, this population-based study suggest that CHM may be an complementary therapy to reduce the risk of stroke in PD patients.