Parkinson disease: from pathology to molecular disease mechanisms

Inhibition of α-Synuclein Aggregation and Mature Fibril Disassembling With a Minimalistic Compound, ZPDm

Synucleinopathies are a group of disorders characterized by the accumulation of α-Synuclein amyloid inclusions in the brain. Preventing α-Synuclein aggregation is challenging because of the disordered nature of the protein and the stochastic nature of fibrillogenesis, but, at the same time, it is a promising approach for therapeutic intervention in these pathologies. A high-throughput screening initiative allowed us to discover ZPDm, the smallest active molecule in a library of more than 14.000 compounds. Although the ZPDm structure is highly related to that of the previously described ZPD-2 aggregation inhibitor, we show here that their mechanisms of action are entirely different. ZPDm inhibits the aggregation of wild-type, A30P, and H50Q α-Synuclein variants in vitro and interferes with α-Synuclein seeded aggregation in protein misfolding cyclic amplification assays. However, ZPDm distinctive feature is its strong potency to dismantle preformed α-Synuclein amyloid fibrils. Studies in a Caenorhabditis elegans model of Parkinson's Disease, prove that these in vitro properties are translated into a significant reduction in the accumulation of α-Synuclein inclusions in ZPDm treated animals. Together with previous data, the present work illustrates how different chemical groups on top of a common molecular scaffold can result in divergent but complementary anti-amyloid activities.

Effect of Caffeine Consumption on the Risk for Neurological and Psychiatric Disorders: Sex Differences in Human

Caffeine occurs naturally in various foods, such as coffee, tea, and cocoa, and it has been used safely as a mild stimulant for a long time. However, excessive caffeine consumption (1~1.5 g/day) can cause caffeine poisoning (caffeinism), which includes symptoms such as anxiety, agitation, insomnia, and gastrointestinal disorders. Recently, there has been increasing interest in the effect of caffeine consumption as a protective factor or risk factor for neurological and psychiatric disorders. Currently, the importance of personalized medicine is being emphasized, and research on sex/gender differences needs to be conducted. Our review focuses on the effect of caffeine consumption on several neurological and psychiatric disorders with respect to sex differences to provide a better understanding of caffeine use as a risk or protective factor for those disorders. The findings may help establish new strategies for developing sex-specific caffeine therapies.

Deciphering the roles of caveolin in neurodegenerative diseases: The good, the bad and the importance of context

Neurodegenerative diseases (NDDs), which contribute to progressive and irreversible impairments of both the structure and function of the nervous system, pose a substantial socioeconomic burden on society. Mitochondrial dysfunction, oxidative stress, membrane damage, DNA damage, and abnormal protein degradation pathways play pivotal roles in the etiology of NDDs. Recently, growing evidence has demonstrated that caveolins are important in the pathology of NDDs due to their cellular functions in signal transduction, endocytosis, transcytosis, cholesterol transport, and lipid homeostasis. Given the significance of caveolins, here we review the literature to clarify their molecular mechanisms and roles in NDDs. We first briefly introduce the general background on caveolins. Next, we focus on the various important functions of caveolins in the brain. Finally, we emphasize recent progress regarding caveolins, especially Cav-1, which exert both benefit and unfavorable effects in NDDs such as AD and PD. Collectively, the data presented here should advance the investigation of caveolins for the future development of innovative strategies for the treatment of NDDs.

Explorative Combined Lipid and Transcriptomic Profiling of Substantia Nigra and Putamen in Parkinson's Disease

Parkinson’s disease (PD) is characterized by the loss of dopaminergic neurons from the substantia nigra (SN) that project to the dorsal striatum (caudate-putamen). To better understand the molecular mechanisms underlying PD, we performed combined lipid profiling and RNA sequencing of SN and putamen samples from PD patients and age-matched controls. SN lipid analysis pointed to a neuroinflammatory component and included elevated levels of the endosomal lipid Bis (Monoacylglycero)Phosphate 42:8, while two of the three depleted putamen lipids were saturated sphingomyelin species. Remarkably, we observed gender-related differences in the SN and putamen lipid profiles. Transcriptome analysis revealed that the top-enriched pathways among the 354 differentially expressed genes (DEGs) in the SN were “protein folding” and “neurotransmitter transport”, and among the 261 DEGs from putamen “synapse organization”. Furthermore, we identified pathways, e.g., “glutamate signaling”, and genes, encoding, e.g., an angiotensin receptor subtype or a proprotein convertase, that have not been previously linked to PD. The identification of 33 genes that were common among the SN and putamen DEGs, which included the α-synuclein paralog β-synuclein, may contribute to the understanding of general PD mechanisms. Thus, our proof-of-concept data highlights new genes, pathways and lipids that have not been explored before in the context of PD.

Impact of Phenol-Enriched Virgin Olive Oils on the Postprandial Levels of Circulating microRNAs Related to Cardiovascular Disease

SCOPE

We investigate the postprandial modulation of cardiovascular-related microRNAs elicited by extra virgin olive oil (EVOOs) containing different levels of their own polyphenols.

METHODS AND RESULTS

It is randomized, postprandial, parallel, double-blind study. Twelve healthy participants consumed 30 mL of EVOO containing low (L-EVOO; 250 mg total phenols kg-1 of oil), medium (M-EVOO; 500 mg total phenols kg-1 of oil), and high (H-EVOO; 750 mg total phenols kg-1 of oil) enriched EVOOs. Postprandial plasma microRNAs levels are analyzed by real-time quantitative PCR. The results show that L-EVOO intake is associated with decreased let-7e-5p and miR-328a-3p levels and increased miR-17-5p and miR-20a-5p, concentrations. M-EVOO decreases plasma let-7e-5p and increases miR-17-5p, miR-20a-5p, and miR-192-5p levels. Finally, H-EVOO decreases let-7e-5p, miR-10a-5p, miR-21-5p, and miR-26b-5p levels.

CONCLUSION

During the postprandial state, the levels of let-7e-5p decrease with EVOO regardless of polyphenol content suggesting a general response to the fatty acid composition of EVOO or/and the presence of at least 250 mg polyphenol kg-1 olive oil. Moreover, the miR-17-92 cluster increases by low and medium polyphenol content suggesting a role in fatty acid metabolism and nutrient sensing. Thus, postprandial modulation of circulating microRNAs levels could be a potential mechanism for the cardiovascular benefits associated with EVOO intake.

Urinary kynurenine as a biomarker for Parkinson's disease

OBJECTIVE

To examine whether urine kynurenine (KYN) levels were associated with early-stage Parkinson's disease (PD), as well as the value of urine KYN as a potential biomarker in early-stage PD.

METHOD

Eighty-two participants including 41 PD patients and 41 healthy controls were enrolled into this study. Urine KYN levels were measured with a KYN enzyme-linked immunoassay kit. In order to explore the correlation between some clinical parameters and urine KYN, the clinical parameters for these participants were recorded. Diagnostic value and clinical relevance of urine KYN were assessed by using receiver operator characteristic (ROC) curve and correlation analysis.

RESULTS

Urine KYN levels were significantly higher in the PD group than in the healthy group (891.95 ± 276.65 pg/ml vs. 640.11 ± 122.37 pg/ml, p = 0.000). The correlations between urine KYN levels and clinical parameters are as follows: Hoehn-Yahr stage (r = 0.676, p = 0.000), disease duration (r = 0.772, p = 0.000), Mini-Mental State Examination scores (r = -0.434, p = 0.005). There was no statistically significant correlation between urine KYN with age, low-density cholesterol (LDL), triglycerides (TG), cholesterol (TC), homocysteine (HCY), uric acid (UA), and glomerular filtration rate (GFR). The ROC analysis showed that urine KYN optimal cutoff value of 751.88 pg/ml had a sensitivity of 65.9% and a specificity of 90.2% for distinguishing between PD and controls, with an area under the curve (AUC) of 0.776.

CONCLUSION

Urine KYN were significantly associated with PD severity and mild cognitive impairment. Urine KYN may be a new biomarker for early-stage PD.

Neuroprotection Against Parkinson's Disease Through the Activation of Akt/GSK3β Signaling Pathway by Tovophyllin A

Parkinson’s disease (PD) is one of the most prevalent and life-threatening neurodegenerative disease and mainly characterized by lack of sufficient dopaminergic neurons in the substantia nigra pars compacta (SNc). Although current treatments help to alleviate clinical symptoms, effective therapies preventing neuronal loss remain scarce. Tovophyllin A (TA), one of the xanthones extracted from Garcinia mangostana L. (GM), has recently been reported to play a beneficial role in the therapy of neurodegenerative diseases. In our research, we explored whether TA has protective effects on dopaminergic neurons in PD models. We found that TA significantly reduced apoptotic cell death in primary cortical neurons treated with 1-methyl-4-phenyl pyridinium (MPP⁺) or paraquat (PQ) in the in vitro PD model. In an in vivo acute PD model induced by 1-methyl4-phenyl-1,2,3,5-tetrahydropyridine (MPTP) treatment, TA also attenuated the resulting behavioral dysfunctions and dopaminergic neuron loss. In the collected brain tissues, TA increased the phosphorylation of Akt and GSK-3β, which may be related to TA-mediated dopaminergic neuronal protective effects. In summary, our results illustrated that TA is a powerful cytoprotective agent for dopaminergic neurons in the MPTP-induced PD model, suggesting TA as a possible therapeutic candidate for PD.

Death-associated Protein Kinase 1 Phosphorylates α-Synuclein at Ser129 and Exacerbates Rotenone-induced Toxic Aggregation of α-Synuclein in Dopaminergic SH-SY5Y Cells

The formation of Lewy bodies (LBs), intracellular filamentous inclusions, is one of the hallmarks of Parkinson's disease (PD). α-Synuclein is the main component of LBs and its abnormal accumulation contributes to the pathogenesis of PD. Direct phosphorylation of α-synuclein at multiple Ser/Tyr residues is known to induce its aggregation, consequently promoting LB formation. Death-associated protein kinase 1 (DAPK1), originally identified as a positive mediator of γ-interferon-induced programmed cell death, possesses tumor-suppressive activity and mediates a wide range of cellular processes, including apoptosis and autophagy. Accumulating evidence suggests that DAPK1 is also associated with neuronal cell death and neurodegeneration. For example, DAPK1 phosphorylates tau and amyloid precursor protein, and induces tau aggregation and amyloid β production, respectively, in Alzheimer's disease. DAPK1 is also accumulated to a larger extent in a mouse model of PD, causing synucleinopathy and dopaminergic neuron degeneration. In this study, we attempted to determine whether DAPK1 phosphorylates α-synuclein and affects cell viability in human dopaminergic neuroblastoma SH-SY5Y cells. We demonstrated that DAPK1 directly phosphorylates α-synuclein at Ser129, and induces the formation of insoluble α-synuclein aggregates. We also showed that DAPK1 enhances rotenone-induced aggregation of α-synuclein, potentiating neuronal cell death. Taken together, these findings suggest that DAPK1 acts as a novel regulator of toxic α-synuclein aggregation, possibly affecting and playing a role in the development of PD.

Parkinson's Disease in Women and Men: What's the Difference?

Increasing evidence points to biological sex as an important factor in the development and phenotypical expression of Parkinson’s disease (PD). Risk of developing PD is twice as high in men than women, but women have a higher mortality rate and faster progression of the disease. Moreover, motor and nonmotor symptoms, response to treatments and disease risk factors differ between women and men. Altogether, sex-related differences in PD support the idea that disease development might involve distinct pathogenic mechanisms (or the same mechanism but in a different way) in male and female patients. This review summarizes the most recent knowledge concerning differences between women and men in PD clinical features, risk factors, response to treatments and mechanisms underlying the disease pathophysiology. Unraveling how the pathology differently affect the two sexes might allow the development of tailored interventions and the design of innovative programs that meet the distinct needs of men and women, improving patient care.

Dietary antioxidants associated with slower progression of parkinsonian signs in older adults

Background and Objective: Progressive loss of motor function including parkinsonian signs is common in older adults. As diet may contribute to the motor decline, we tested the hypothesis that dietary intake of antioxidant nutrients (carotenoids, vitamin E and vitamin C) is related to the progression of parkinsonian signs in older adults.Research Design and Methods: A total of 682 participants without a clinical diagnosis of Parkinson's Disease from the Rush Memory and Aging Project, were assessed annually over an average of 5.7 (±3.0) years using a 26-item modified version of the United Parkinson's Disease Rating Scale. The scale assesses the severity of four parkinsonian signs (bradykinesia, gait, tremors, and rigidity) that were averaged to construct a global parkinsonian sign score. Nutrient intakes were assessed at baseline using a validated food frequency questionnaire. The associations between quintiles of antioxidant nutrient intakes and progression of parkinsonian signs were assessed using mixed effects models adjusted for age, sex, education, smoking.Results: In separate adjusted models, a slower rate of progressive parkinsonian signs was observed among those in the highest intake quintiles of total carotenoids (β= -0.06, 95%CI: -0.10 to -0.02,), beta-carotene from foods (β= -0.04, 95% CI:-0.08 to -0.0021), lutein-zeaxanthin (β= -0.05, 95%CI:-0.09 to -0.02), vitamin E from foods (β= -0.04, 95%CI:-0.08 to -0.01,) and vitamin C from foods (β= -0.06, 95%CI:-0.10 to -0.02), when compared to those in the lowest quintiles of intake.Conclusion: A higher level of dietary antioxidant nutrients may slow the rate of parkinsonian sign progression in older adults.

A systematic review and meta-analysis of serum cholesterol and triglyceride levels in patients with Parkinson's disease

Objectives

Numerous studies have reported that lipid metabolic abnormalities may play an important role in the development of Parkinson’s disease (PD), with mixed results. This meta-analysis aims to systematically assess the relationship between serum cholesterol or triglyceride and the PD risk and to further determine the role of dyslipidemia in potential predictive value.

Methods

This research systematically consulted and screened observational studies to evaluate the association of serum lipids with the risk of PD as of April 01, 2020 based on the inclusion and exclusion criteria. Two researchers screened and extracted the data independently. Then this article summarized the characteristics of all clinical studies and collected the corresponding data to perform pooled and sensitivity analyses. The meta-analysis was performed by using the RevMan 5.3 software after data extraction, quality assessment and analysis of publication bias.

Results

Twenty-one related studies (13 case-control and 8 cohort studies) were selected with a total of 980,180 subjects, including 11,188 PD patients. Meta-analysis showed that higher levels of serum triglyceride (S-TG) [standard mean different (SMD) = − 0.26 (95% confidence interval (CI): − 0.39 to − 0.13, p<0.00001), relative risk (RR) = 0.67 (95% CI: 0.60 to 0.75, p<0.00001)] could be considered as protective factors for the pathogenesis of PD. However, there was no significant association between serum high density lipoprotein cholesterol (S-HDL) and the risk of PD. Meanwhile, serum low density lipoprotein cholesterol (S-LDL) [SMD = -0.26 (95% CI: − 0.43 to − 0.07, p = 0.006), RR = 0.76 (95% CI: 0.59 to 0.97, p = 0.03)] and serum total cholesterol (S-TC) levels [SMD = -0.21 (95% CI: − 0.33 to − 0.10, p = 0.0002), RR = 0.86 (95% CI: 0.77 to 0.97, p = 0.01)] were negatively associated with PD risk.

Conclusions

This systematic review suggests that elevated serum levels of TG, LDL and TC may be protective factors for the pathogenesis of PD. Further longitudinal and well-designed prospective studies with a large sample size are needed to confirm the findings in this meta-analysis.

Inhibiting thrombin improves motor function and decreases oxidative stress in the LRRK2 transgenic Drosophila melanogaster model of Parkinson's disease

Parkinson's disease (PD) is a complex neurodegenerative disease characterized by the presence of tremors, loss of dopaminergic neurons and accumulation of α-synuclein. While there is no single direct cause of PD, genetic mutations, exposure to pesticides, diet and traumatic brain injury have been identified as risk factors. Increasing evidence suggests that oxidative stress and neuroinflammation contribute to the pathogenesis of neuronal injury in neurodegenerative diseases such as PD and Alzheimer's disease (AD). We have previously documented that the multifunctional inflammatory mediator thrombin contributes to oxidative stress and neuroinflammation in AD. Here, for the first time, we explore the role of thrombin in a transgenic PD model, the LRRK2 mutant Drosophila melanogaster. Transgenic flies were treated with the direct thrombin inhibitor dabigatran for 7 days and locomotor activity and indices of oxidative stress evaluated. Our data show that dabigatran treatment significantly (p < 0.05) improved climbing activity, a measurement of locomotor ability, in male but had no effect on locomotor performance in female flies. Dabigatran treatment had no effect on tyrosine hydroxylase levels. Analysis of oxidative stress in male flies showed that dabigatran was able to significantly (p < 0.01) lower reactive oxygen species levels. Furthermore, Western blot analysis showed that the pro-oxidant proteins iNOS and NOX4 are elevated in LRRK2 male flies compared to wildtype and that treatment with dabigatran reduced expression of these proteins. Our results indicate that dabigatran treatment could improve motor function in PD by reducing oxidative stress. These data suggest that targeting thrombin may improve oxidative stress related pathologies in PD.

Tissue Engineering and Biomaterial Strategies to Elicit Endogenous Neuronal Replacement in the Brain

Neurogenesis in the postnatal mammalian brain is known to occur in the dentate gyrus of the hippocampus and the subventricular zone. These neurogenic niches serve as endogenous sources of neural precursor cells that could potentially replace neurons that have been lost or damaged throughout the brain. As an example, manipulation of the subventricular zone to augment neurogenesis has become a popular strategy for attempting to replace neurons that have been lost due to acute brain injury or neurodegenerative disease. In this review article, we describe current experimental strategies to enhance the regenerative potential of endogenous neural precursor cell sources by enhancing cell proliferation in neurogenic regions and/or redirecting migration, including pharmacological, biomaterial, and tissue engineering strategies. In particular, we discuss a novel replacement strategy based on exogenously biofabricated "living scaffolds" that could enhance and redirect endogenous neuroblast migration from the subventricular zone to specified regions throughout the brain. This approach utilizes the first implantable, biomimetic tissue-engineered rostral migratory stream, thereby leveraging the brain's natural mechanism for sustained neuronal replacement by replicating the structure and function of the native rostral migratory stream. Across all these strategies, we discuss several challenges that need to be overcome to successfully harness endogenous neural precursor cells to promote nervous system repair and functional restoration. With further development, the diverse and innovative tissue engineering and biomaterial strategies explored in this review have the potential to facilitate functional neuronal replacement to mitigate neurological and psychiatric symptoms caused by injury, developmental disorders, or neurodegenerative disease.

Nitroxide Radical-Containing Redox Nanoparticles Protect Neuroblastoma SH-SY5Y Cells against 6-Hydroxydopamine Toxicity

Parkinson's disease (PD) patients can benefit from antioxidant supplementation, and new efficient antioxidants are needed. The aim of this study was to evaluate the protective effect of selected nitroxide-containing redox nanoparticles (NRNPs) in a cellular model of PD. Antioxidant properties of NRNPs were studied in cell-free systems by protection of dihydrorhodamine 123 against oxidation by 3-morpholino-sydnonimine and protection of fluorescein against bleaching by 2,2-azobis(2-amidinopropane) hydrochloride and sodium hypochlorite. Model blood-brain barrier penetration was studied using hCMEC/D3 cells. Human neuroblastoma SH-SY5Y cells, exposed to 6-hydroxydopamine (6-OHDA), were used as an in vitro model of PD. Cells were preexposed to NRNPs or free nitroxides (TEMPO or 4-amino-TEMPO) for 2 h and treated with 6-OHDA for 1 h and 24 h. The reactive oxygen species (ROS) level was estimated with dihydroethidine 123 and Fluorimetric Mitochondrial Superoxide Activity Assay Kit. Glutathione level (GSH) was measured with ortho-phtalaldehyde, ATP by luminometry, changes in mitochondrial membrane potential with JC-1, and mitochondrial mass with 10-Nonyl-Acridine Orange. NRNP1, TEMPO, and 4-amino-TEMPO (25-150 μM) protected SH-SY5Y cells from 6-OHDA-induced viability loss; the protection was much higher for NRNP1 than for free nitroxides. NRNP1 were better antioxidants in vitro and permeated better the model BBB than free nitroxides. Exposure to 6-OHDA decreased the GSH level after 1 h and increased it considerably after 24 h (apparently a compensatory overresponse); NRNPs and free nitroxides prevented this increase. NRNP1 and free nitroxides prevented the decrease in ATP level after 1 h and increased it after 24 h. 6-OHDA increased the intracellular ROS level and mitochondrial superoxide level. Studied antioxidants mostly decreased ROS and superoxide levels. 6-OHDA decreased the mitochondrial potential and mitochondrial mass; both effects were prevented by NRNP1 and nitroxides. These results suggest that the mitochondria are the main site of 6-OHDA-induced cellular damage and demonstrate a protective effect of NRNP1 in a cellular model of PD.

Physical exercise protects against mitochondria alterations in the 6-hidroxydopamine rat model of Parkinson's disease

Parkinson's disease (PD) is typicaly caractherized by loss of dopaminergic neurons, as well as the presence of mitochondrial impairments. Although physical exercise is known to promote many beneficial effects in healthy subjects, such as enhancing mitocondrial biogenesis and function, it is not clear if these effects are evident after exercise in individuals with PD. The aim of this study was to investigate the effects of two different protocol durations on motor behavior (aphomorphine and gait tests), mitochondrial biogenesis signaling (PGC-1α, NRF-1 and TFAM), structure (oxidative phosphorylation system protein levels) and respiratory chain activity (complex I) in a unilateral PD rat model. For this, male Wistar rats were injected with 6-hydroxydopamine unilaterally into the striatum and submitted to an intermitent moderate treadmill exercise for one or four weeks. In the gait test, only stride width data revealed an improvement after one week of exercise. On the other hand, after 4 weeks of the exercise protocol all gait parameters analyzed and the aphomorphine test demonstrated a recovery. Analysis of protein revealed that one week of exercise was able to prevent PGC-1α and NRF-1 expression decrease in PD animals. In addition, after four weeks of physical exercise, besides PGC-1α and NRF-1, reduction in TFAM and complex I protein levels and increased complex I activity were also prevented in PD animals. Thus, our results suggest a neuroprotective and progressive effect of intermittent treadmill exercise, which could be related to its benefits on mitochondrial biogenesis signaling and respiratory chain modulation of the dopaminergic system in PD.

Association Between Stroke and Parkinson's Disease: a Meta-analysis

Parkinson's disease (PD) and stroke are both associated with aging, but the relationship between these two disorders remains unclear. Recent evidence has shown that they frequently co-occur and are influenced by each another, although some studies have found inconsistent results. We performed this meta-analysis of patients with PD on stroke risk to clarify the relationship between these two disorders on the basis of the studies published from 1975 to July 2019 in the PubMed, EMBASE, and Cochrane Library databases. In total, 13 case-control studies met the inclusion criteria for meta-analysis. The pooled odds ratio (OR) for PD in relation to the stroke risk was 1.72 (95% confidence interval (CI) 1.19-2.49). The OR for the presence of cerebral infarct among PD in the four studies was 1.35 (95% CI 1.04-1.74). Moreover, the OR for the presence of stroke pathology among PD in the four postmortem studies was 1.86 (95% CI 1.17-2.98). In conclusion, our meta-analysis suggests that there is an association between stroke and PD. Sensitivity analysis was used to test the robustness of our results through the sequential removal of each one study at time, in order to investigate if a single study was driving the study results. These results indicate that PD and stroke may have a common pathogenesis and may share preventive treatment measures.

Striatal Dopamine D2-Muscarinic Acetylcholine M1 Receptor-Receptor Interaction in a Model of Movement Disorders

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by motor control deficits, which is associated with the loss of striatal dopaminergic neurons from the substantia nigra. In parallel to dopaminergic denervation, there is an increase of acetylcholine within the striatum, resulting in a striatal dopaminergic–cholinergic neurotransmission imbalance. Currently, available PD pharmacotherapy (e.g., prodopaminergic drugs) does not reinstate the altered dopaminergic–cholinergic balance. In addition, it can eventually elicit cholinergic-related adverse effects. Here, we investigated the interplay between dopaminergic and cholinergic systems by assessing the physical and functional interaction of dopamine D₂ and muscarinic acetylcholine M₁ receptors (D₂R and M₁R, respectively), both expressed at striatopallidal medium spiny neurons. First, we provided evidence for the existence of D₂R–M₁R complexes via biochemical (i.e., co-immunoprecipitation) and biophysical (i.e., BRET¹ and NanoBiT^®) assays, performed in transiently transfected HEK293T cells. Subsequently, a D₂R–M₁R co-distribution in the mouse striatum was observed through double-immunofluorescence staining and AlphaLISA^® immunoassay. Finally, we evaluated the functional interplay between both receptors via behavioral studies, by implementing the classical acute reserpine pharmacological animal model of experimental parkinsonism. Reserpinized mice were administered with a D₂R-selective agonist (sumanirole) and/or an M₁R-selective antagonist (VU0255035), and alterations in PD-related behavioral tasks (i.e., locomotor activity) were evaluated. Importantly, VU0255035 (10 mg/kg) potentiated the antiparkinsonian-like effects (i.e., increased locomotor activity and decreased catalepsy) of an ineffective sumanirole dose (3 mg/kg). Altogether, our data suggest the existence of putative striatal D₂R/M₁R heteromers, which might be a relevant target to manage PD motor impairments with fewer adverse effects.

Xenobiotics, Trace Metals and Genetics in the Pathogenesis of Tauopathies

Tauopathies are a disease group characterized by either pathological accumulation or release of fragments of hyperphosphorylated tau proteins originating from the central nervous system. The tau hypotheses of Parkinson’s and Alzheimer’s diseases contain a clinically diverse spectrum of tauopathies. Studies of case records of various tauopathies may reveal clinical phenotype characteristics of the disease. In addition, improved understanding of different tauopathies would disclose environmental factors, such as xenobiotics and trace metals, that can precipitate or modify the progression of the disorder. Important for diagnostics and monitoring of these disorders is a further development of adequate biomarkers, including refined neuroimaging, or proteomics. Our goal is to provide an in-depth review of the current literature regarding the pathophysiological roles of tau proteins and the pathogenic factors leading to various tauopathies, with the perspective of future advances in potential therapeutic strategies.

Postnatal zinc or paraquat administration increases paraquat or zinc-induced loss of dopaminergic neurons: insight into augmented neurodegeneration

Epidemiological evidences have shown an association of exposure to pesticides or heavy metals with increased incidences of Parkinson's disease (PD) in humans. Exposure to pesticides or metals during the decisive period of the brain development increases the susceptibility of dopaminergic neurons upon re-exposure in adult rodents. However, the effect of early life exposure to pesticide on the heavy metal-induced neurodegeneration or heavy metal on pesticide-induced neurodegeneration is not yet explored. The current study explored the effect of developmental exposure to zinc (Zn), a metal or paraquat (PQ), a pesticide on the nigrostriatal dopaminergic neurons of rats challenged to Zn or PQ during adulthood. Exposure of Zn or PQ during adulthood alone exhibited marked reduction in motor activities, striatal dopamine and metabolites, glutathione content and number of dopaminergic neurons. However, the levels of lipid peroxidation, protein carbonyls, superoxide dismutase activity, pro-inflammatory cytokines and 4-hydroxynonenal-protein adducts were increased. While the expression of vesicular monoamine transporter-2 and tyrosine hydroxylase were attenuated, dopamine transporter and microglial marker Iba-1 expression, activated microglia, nuclear factor-kappa B activation, mitochondrial cytochrome c release and caspase-3/9 activation were augmented following Zn or PQ exposure. Albeit postnatal alone exposure did not alter any of the studied parameters, the developmental administration of Zn/PQ in re-challenged adult rats produced more pronounced changes in the aforementioned variables as compared with adulthood Zn or PQ alone intoxicated animals. The results demonstrate that postnatal Zn/PQ intoxication dents the oxidative stress, inflammation, cell death and dopamine metabolism and storage regulating machineries, which speed up the toxicant-induced degeneration during adulthood.

Anti-neuroinflammatory effects of dimethylaminomylide (DMAMCL, i.e., ACT001) are associated with attenuating the NLRP3 inflammasome in MPTP-induced Parkinson disease in mice

Parthenolide (PTL) is a natural compound with anti-inflammatory and antioxidant properties and is an active ingredient extracted from the medicinal plant Tanacetum parthenium. ACT001 is derived from parthenolide and is a fumarate form of dimethylaminomylide (DMAMCL). Its effect is equivalent to that of PTL, but it is more stable in plasma and has lower acquisition costs. Related reports indicate that NLRP3-mediated neuroinflammation is involved in the progression of Parkinson's disease (PD). In our research, we explored whether ACT001 alleviates NLRP3-mediated neuroinflammation in PD mice induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Our results revealed that ACT001 reduces movement impairment and cognitive deficit in PD mice. In addition, it alleviates dopaminergic neurodegeneration in the nigrostriatal pathway and inhibits oxidative stress, the inflammatory response and activation of the NLRP3 inflammasome in the midbrain of MPTP-induced PD mice. Moreover, it attenuates microglial activation in the nigrostriatal pathway. Overall, our study showed that ACT001 alleviates NLRP3-mediated neuroinflammation in PD mice induced by MPTP.

Lipid Analysis of the 6-Hydroxydopamine-Treated SH-SY5Y Cell Model for Parkinson's Disease

Parkinson's disease (PD) is a highly prevalent neurodegenerative disease for which no disease-modifying treatments are available, mainly because knowledge about its pathogenic mechanism is still incomplete. Recently, a key role for lipids emerged, but lipid profiling of brain samples from human subjects is demanding. Here, we used an unbiased approach, lipidomics, to determine PD-linked changes in the lipid profile of a well-established cell model for PD, the catecholaminergic neuronal cell line SH-SY5Y treated with the neurotoxin 6-hydroxydopamine (6-OHDA). We observed changes in multiple lipid classes, including phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylinositol (PI), phosphatidylserine (PS), sphingomyelin (SM), and total cholesterol, in 6-OHDA-treated SH-SY5Y cells. Furthermore, we found differences in the length and degree of unsaturation of the fatty acyl chains, indicating changes in their metabolism. Except for the observed decreased PS levels, the alterations in PC, PG, PI, and cholesterol levels are in agreement with the results of previous studies on PD-patient material. Opposite to what has been previously described, the cholesterol-lowering drug statins did not have a protective effect, while low doses of cholesterol supplementation partially protected SH-SY5Y cells from 6-OHDA toxicity. However, cholesterol supplementation triggered neuronal differentiation, which could have confounded the results of cholesterol modulation. Taken together, our results show that 6-OHDA-treated SH-SY5Y cells display many lipid changes also found in PD patient and animal model brains, although the SH-SY5Y cell model seems less suitable to study the involvement of cholesterol in PD initiation and progression.

Microglial autophagy defect causes parkinson disease-like symptoms by accelerating inflammasome activation in mice

Microglial activation-induced neuroinflammation is closely associated with the development of Parkinson disease (PD). Macroautophagy/autophagy regulates many biological processes, but the role of autophagy in microglial activation during PD development remains largely unclear. In this study, we showed that deletion of microglial Atg5 caused PD-like symptoms in mice, characterized by impairment in motor coordination and cognitive learning, loss of tyrosine hydroxylase (TH) neurons, enhancement of neuroinflammation and reduction in dopamine levels in the striatum. Mechanistically, we found that inhibition of autophagy led to NLRP3 (NLR family pyrin domain containing 3) inflammasome activation via PDE10A (phosphodiesterase 10A)-cyclic adenosine monophosphate (cAMP) signaling in microglia, and the sequential upregulation of downstream IL1B/IL-1β in turn increased the expression of MIF (macrophage migration inhibitory factor [glycosylation-inhibiting factor]), a pro-inflammatory cytokine. Inhibition of NLRP3 inflammasome activation by administration of MCC950, a specific inhibitor for NLRP3, decreased MIF expression and neuroinflammatory levels, and rescued the loss of TH neurons in the substantial nigra (SN). Interestingly, we found that serum MIF levels in PD patients were significantly elevated. Taken together, our results reveal an important role of autophagy in microglial activation-driven PD-like symptoms, thus providing potential targets for the clinical treatment of PD. Abbreviations: ATG: autophagy related; cAMP: cyclic adenosine monophosphate; cKO: conditional knockout; NOS2/INOS: nitric oxide synthase 2, inducible; IL1B: interleukin 1 beta; ITGAM/CD-11b: integrin alpha M/cluster of differentiation molecule 11B; MAP1LC3: microtubule-associated protein 1 light chain 3; MIF: macrophage migration inhibitory factor (glycosylation-inhibiting factor); NLRP3: NLR family pyrin domain containing 3; PBS: phosphate-buffered saline; PD: parkinson disease; PDE10A: phosphodiesterase 10A; SN: substantial nigra; TH: tyrosine hydroxylase; TNF: tumor necrosis factor; WT: wild type.

Strategies for the Treatment of Parkinson's Disease: Beyond Dopamine

Parkinson’s disease (PD) is the second-leading cause of dementia and is characterized by a progressive loss of dopaminergic neurons in the substantia nigra alongside the presence of intraneuronal α-synuclein-positive inclusions. Therapies to date have been directed to the restoration of the dopaminergic system, and the prevention of dopaminergic neuronal cell death in the midbrain. This review discusses the physiological mechanisms involved in PD as well as new and prospective therapies for the disease. The current data suggest that prevention or early treatment of PD may be the most effective therapeutic strategy. New advances in the understanding of the underlying mechanisms of PD predict the development of more personalized and integral therapies in the years to come. Thus, the development of more reliable biomarkers at asymptomatic stages of the disease, and the use of genetic profiling of patients will surely permit a more effective treatment of PD.

Rasagiline and selegiline modulate mitochondrial homeostasis, intervene apoptosis system and mitigate α-synuclein cytotoxicity in disease-modifying therapy for Parkinson's disease

Parkinson's disease has been considered as a motor neuron disease with dopamine (DA) deficit caused by neuronal loss in the substantia nigra, but now proposed as a multi-system disorder associated with α-synuclein accumulation in neuronal and non-neuronal systems. Neuroprotection in Parkinson's disease has intended to halt or reverse cell death of nigro-striatal DA neurons and prevent the disease progression, but clinical studies have not presented enough beneficial results, except the trial of rasagiline by delayed start design at low dose of 1 mg/day only. Now strategy of disease-modifying therapy should be reconsidered taking consideration of accumulation and toxicity of α-synuclein preceding the manifest of motor symptoms. Hitherto neuroprotective therapy has been aimed to mitigate non-specific risk factors; oxidative stress, mitochondrial dysfunction, apoptosis, deficits of neurotrophic factors (NTFs), inflammation and accumulation of pathogenic protein. Future disease-modify therapy should target more specified pathogenic factors, including deregulated mitochondrial homeostasis, deficit of NTFs and α-synuclein toxicity. Selegiline and rasagiline, inhibitors of type B monoamine oxidase, have been proved to exhibit potent neuroprotective function: regulation of mitochondrial apoptosis system, maintenance of mitochondrial function, increased expression of genes coding antioxidant enzymes, anti-apoptotic Bcl-2 and pro-survival NTFs, and suppression of oligomerization and aggregation of α-synuclein and the toxicity in cellular and animal experiments. However, the present available pharmacological therapy starts too late to reverse disease progression, and future disease-modifying therapy should include also non-pharmacological complementary therapy during the prodromal stage.

Clinical Application of Circulating MicroRNAs in Parkinson's Disease: The Challenges and Opportunities as Diagnostic Biomarker

Discovery of evolutionarily conserved, nonprotein-coding, endogenous microRNAs has induced a paradigm shift in the overall understanding of gene regulation. Now, microRNAs are considered and classified as master regulators of gene expression as they regulate a wide range of processes – gene regulation, splicing, translation and posttranscriptional modifications. Besides, dysregulated microRNAs have been related to many diseases, including Parkinson's and related disorders. Several studies proposed that differentially expressed microRNAs as a potential biomarker. So far, there is no accepted clinical diagnostic test for Parkinson's disease based on biochemical analysis of biological fluids. However, circulating microRNAs possess many vital features typical of reliable biomarkers and discriminates Parkinson's patients from healthy control with much higher sensitivity and specificity. Though they show tremendous promise as a putative biomarker, translating these research findings to clinical application is often met with many obstacles. Most of the candidate microRNAs reported as a diagnostic biomarker is not organ-specific, and their overlap is low between studies. Therefore this review aimed to highlight the challenges in the application of microRNA in guiding disease discrimination decisions and its future prospects as a diagnostic biomarker in Parkinson's Disease.

Chronic Systemic Inflammation Exacerbates Neurotoxicity in a Parkinson's Disease Model

Systemic inflammation is a crucial factor for microglial activation and neuroinflammation in neurodegeneration. This work is aimed at assessing whether previous exposure to systemic inflammation potentiates neurotoxic damage by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and how chronic systemic inflammation participates in the physiopathological mechanisms of Parkinson's disease. Two different models of systemic inflammation were employed to explore this hypothesis: a single administration of lipopolysaccharide (sLPS; 5 mg/kg) and chronic exposure to low doses (mLPS; 100 μg/kg twice a week for three months). After three months, both groups were challenged with MPTP. With the sLPS administration, Iba1 staining increased in the striatum and substantia nigra, and the cell viability lowered in the striatum of these mice. mLPS alone had more impact on the proinflammatory profile of the brain, steadily increasing TNFα levels, activating microglia, reducing BDNF, cell viability, and dopamine levels, leading to a damage profile similar to the MPTP model per se. Interestingly, mLPS increased MAO-B activity possibly conferring susceptibility to MPTP damage. mLPS, along with MPTP administration, exacerbated the neurotoxic effect. This effect seemed to be coordinated by microglia since minocycline administration prevented brain TNFα increase. Coadministration of sLPS with MPTP only facilitated damage induced by MPTP without significant change in the inflammatory profile. These results indicate that chronic systemic inflammation increased susceptibility to MPTP toxic effect and is an adequate model for studying the impact of systemic inflammation in Parkinson's disease.

Emerging Role of Sirtuin 2 in Parkinson's Disease

Parkinson’s disease (PD), the main risk factor of which is age, is one of the most common neurodegenerative diseases, thus presenting a substantial burden on the health of affected individuals as well as an economic burden. Sirtuin 2 (SIRT2), a subtype in the family of sirtuins, belongs to class III histone deacetylases (HDACs). It is known that SIRT2 levels increase with aging, and a growing body of evidence has been accumulating, showing that the activity of SIRT2 mediates various processes involved in PD pathogenesis, including aggregation of α-synuclein (α-syn), microtubule function, oxidative stress, inflammation, and autophagy. There have been conflicting reports about the role of SIRT2 in PD, in that some studies indicate its potential to induce the death of dopaminergic (DA) neurons, and that inhibition of SIRT2 may, therefore, have protective effects in PD. Other studies suggest a protective role of SIRT2 in the context of neuronal damage. As current treatments for PD are directed at alleviating symptoms and are very limited, a comprehensive understanding of the enzymology of SIRT2 in PD may be essential for developing novel therapeutic agents for the treatment of this disease. This review article will provide an update on our knowledge of the structure, distribution, and biological characteristics of SIRT2, and highlight its role in the pathogenesis of PD.

The Immunomodulary Effects of Systematic Exercise in Older Adults and People with Parkinson's Disease

We sought to investigate whether regular balance training of moderate intensity (BT) has an effect on changes in selected cytokines, neurotrophic factors, CD200 and fractalkine in healthy older adults and participants with Parkinson’s disease (PD). Sixty-two subjects were divided into groups depending on experimental intervention: (1) group of people with PD participating in BT (PDBT), (2) group of healthy older people participating in BT (HBT), (3,4) control groups including healthy individuals (HNT) and people with PD (PDNT). Blood samples were collected twice: before and after 12 weeks of balance exercise (PDBT, HBT), or 12 weeks apart (PDNT, HNT). The study revealed significant increase of interleukin10 (PDBT, p = 0.026; HBT, p = 0.011), β-nerve growth factor (HBT, p = 0.002; PDBT, p = 0.016), transforming growth factor-β1 (PDBT, p = 0.018; HBT, p < 0.004), brain-derived neurotrophic factor (PDBT, p = 0.011; HBT, p < 0.001) and fractalkine (PDBT, p = 0.045; HBT, p < 0.003) concentration only in training groups. In PDBT, we have found a significant decrease of tumor necrosis factor alpha. No training effect on concentration of interleukin6, insulin-like growth factor 1 and CD200 was observed in both training and control groups. Regular training can modulate level of inflammatory markers and induce neuroprotective mechanism to reduce the inflammatory response.

Pharmacological intervention of histone deacetylase enzymes in the neurodegenerative disorders

Reversal of aging symptoms and related disorders are the challenging task where epigenetic is a crucial player that includes DNA methylation, histone modification; chromatin remodeling and regulation that are linked to the progression of various neurodegenerative disorders (NDDs). Overexpression of various histone deacetylase (HDACs) can activate Glycogen synthase kinase 3 which promotes the hyperphosphorylation of tau and inhibits its degradation. While HDAC is important for maintaining the neuronal morphology and brain homeostasis, at the same time, these enzymes are promoting neurodegeneration, if it is deregulated. Different experimental models have also confirmed the neuroprotective effects caused by HDAC enzymes through the regulation of neuronal apoptosis, inflammatory response, DNA damage, cell cycle regulation, and metabolic dysfunction. Apart from transcriptional regulation, protein-protein interaction, histone post-translational modifications, deacetylation mechanism of non-histone protein and direct association with disease proteins have been linked to neuronal imbalance. Histone deacetylases inhibitors (HDACi) can be able to alter gene expression and shown its efficacy on experimental models, and in clinical trials for NDD's and found to be a very promising therapeutic agent with certain limitation, for instance, non-specific target effect, isoform-selectivity, specificity, and limited number of predicted biomarkers. Herein, we discussed (i) the catalytic mechanism of the deacetylation process of various HDAC's in in vivo and in vitro experimental models, (ii) how HDACs are participating in neuroprotection as well as in neurodegeneration, (iii) a comprehensive role of HDACi in maintaining neuronal homeostasis and (iv) therapeutic role of biomolecules to modulate HDACs.

Inhibitory potential of plant secondary metabolites on anti-Parkinsonian drug targets: Relevance to pathophysiology, and motor and non-motor behavioural abnormalities

Parkinson's disease (PD), a progressive neurodegenerative motor disorder, is caused due to the loss of dopaminergic neurons in the substantia nigra pars compacta region of mid-brain and the resultant depletion of the levels of the neurotransmitter dopamine. Although the pathophysiology of the disease is least understood, studies in animal models revealed oxidative stress, mitochondrial dysfunction and inflammation to be the major contributors. Dopamine replenishment therapy by oral administration of L-DOPA, the precursor of dopamine remains to be the therapeutic gold-standard for symptomatic treatment of PD. In addition, use of inhibitors of dopamine metabolizing enzymes (viz. monoamine oxidase-B: MAO-B; and catechol-O-methyltransferase: COMT) are the other strategies for amelioration of the motor abnormalities. Further, PD is associated with non-motor behavioural abnormalities as well, including cognitive impairment and mood disorders, which are caused due to cholinergic neurodegeneration, and thus inhibition of Acetylcholinesterase (AChE) is suggested. However, the currently used drugs against the three crucial enzymes (MAO-B, COMT and AChE) elicit several side effects, and thus the search for novel compounds continues, and plant-based compounds have promising potential in this regard. In the present study, we have used computational modeling to determine the efficiency of 40 plant-based natural products in inhibiting the three anti-Parkinsonian drug targets. Further, statistical analysis was performed to identify the properties of the compounds which are crucial for inhibition of the enzymes. While all the phytochemicals showed potential in inhibiting the enzymes, Rutin, Demethoxycurcumin and Acteoside were found to be most effective inhibitors of MAO-B, COMT and AChE respectively. Since most of the compounds are established anti-oxidant and anti-inflammatory molecules, they are surmised to confer neuroprotection in PD, and prevent progression of the disease.

Iron chelator Deferoxamine protects human neuroblastoma cell line SH-SY5Y from 6-Hydroxydopamine-induced apoptosis and autophagy dysfunction

BACKGROUND

Intracellular iron involves in Fenton's reaction-mediated Hydroxyl radical (OH·) generation by reacting with the neurotoxic agent 6-Hydroxydopamine (6-OHDA) autoxidation derivative Hydrogen Peroxide (H₂O₂). Several studies have been conducted so far on the neuroprotective activities of the iron chelator Deferoxamine (DFO) but little or no clear evidence about the underlying cellular mechanism is available.

METHODS

The present study was conducted on Human neuroblastoma cell line SH-SY5Y in the absence or presence of 6-OHDA or H₂O₂ and / or DFO. Following incubation, cell viability assay, intracellular reactive oxygen species (ROS) determination, flow cytometric quantification of apoptotic cells followed by nuclear staining, intracellular tracking of transfected fusion construct of microtubule-associated protein 1B-light chain with Green fluorescent protein - Red fluorescent protein (LC3B-GFP-RFP reporters) and immunocytochemistry of intracellular Cathepsin protein by confocal microscopy, were conducted. In addition, western blotting was carried out to detect expressions of apoptotic and autophagy related proteins.

RESULTS

This study confirmed the neuroprotective potential of DFO by inhibiting 6-OHDA-mediated cell death and ROS generation. Reduced percentage of apoptotic cells and appearance of altered nuclei architecture followed by a reduced expression of cleaved PARP (Poly-ADP-ribose Polymerase) and cleaved Caspase-3 were observed upon DFO treatment against 6-OHDA, and as well as against H₂O₂ in SH-SY5Y cell lines. Besides, DFO induced the intracellular autophagolysosome formation (red puncta) rather than autophagosome (yellow puncta) only. Thereafter it was observed that DFO restored the expression of intracellular lysosomal protease Cathepsin and reduced the expression of the LC3-II.

CONCLUSION

Taken together, this study clearly demonstrated that the anti-Fenton activity of DFO inhibited apoptosis and caused blockade in ALP or autophagy dysfunction in SH-SY5Y cell lines. These outcomes further suggest that DFO provides neuroprotection by inhibiting apoptosis and inducing the progression of Autophagy- lysosomal pathway (ALP).

A review of computational modeling and deep brain stimulation: applications to Parkinson's disease

Biophysical computational models are complementary to experiments and theories, providing powerful tools for the study of neurological diseases. The focus of this review is the dynamic modeling and control strategies of Parkinson's disease (PD). In previous studies, the development of parkinsonian network dynamics modeling has made great progress. Modeling mainly focuses on the cortex-thalamus-basal ganglia (CTBG) circuit and its sub-circuits, which helps to explore the dynamic behavior of the parkinsonian network, such as synchronization. Deep brain stimulation (DBS) is an effective strategy for the treatment of PD. At present, many studies are based on the side effects of the DBS. However, the translation from modeling results to clinical disease mitigation therapy still faces huge challenges. Here, we introduce the progress of DBS improvement. Its specific purpose is to develop novel DBS treatment methods, optimize the treatment effect of DBS for each patient, and focus on the study in closed-loop DBS. Our goal is to review the inspiration and insights gained by combining the system theory with these computational models to analyze neurodynamics and optimize DBS treatment.

Comprehensive Analysis of Neurotoxin-Induced Ablation of Dopaminergic Neurons in Zebrafish Larvae

Neurotoxin exposure of zebrafish larvae has been used to mimic a Parkinson’s disease (PD) phenotype and to facilitate high-throughput drug screening. However, the vulnerability of zebrafish to various neurotoxins was shown to be variable. Here, we provide a direct comparison of ablative effectiveness in order to identify the optimal neurotoxin-mediated dopaminergic (DAnergic) neuronal death in larval zebrafish. Transgenic zebrafish, Tg(dat:eGFP), were exposed to different concentrations of the neurotoxins MPTP, MPP⁺, paraquat, 6-OHDA, and rotenone for four days, starting at three days post-fertilization. The LC₅₀ of each respective neurotoxin concentration was determined. Confocal live imaging on Tg(dat:eGFP) showed that MPTP, MPP⁺, and rotenone caused comparable DAnergic cell loss in the ventral diencephalon (vDC) region while, paraquat and 6-OHDA caused fewer losses of DAnergic cells. These results were further supported by respective gene expression analyses of dat, th, and p53. Importantly, the loss of DAnergic cells from exposure to MPTP, MPP⁺, and rotenone impacted larval locomotor function. MPTP induced the largest motor deficit, but this was accompanied by the most severe morphological impairment. We conclude that, of the tested neurotoxins, MPP⁺ recapitulates a substantial degree of DAnergic ablation and slight locomotor perturbations without systemic defects indicative of a Parkinsonian phenotype.

Association between SNCA rs356220 polymorphism and Parkinson's disease: A meta-analysis

Several studies have investigated the correlation between single nucleotide polymorphism (SNP) rs356220 in the α-synuclein (SNCA) gene and Parkinson's disease (PD) with inconsistent results. Herein, a meta-analysis was conducted to ascertain the association of the SNCA rs356220 polymorphism with the risk of PD. Six eligible articles involving 5333 PD cases and 5477 controls were included in this meta-analysis. The pooled odds ratios (OR) and 95 % confidence interval (CI) were calculated to estimate the association. The fixed or random effect was selected based on the homogeneity among studies. Heterogeneity was detected by I². We performed sensitivity analysis to test the stablility of the results. Publication bias was evaluated by Funnel plot and Begg's test. The pooled results showed a significant association between SNCA rs356220 gene polymorphism and PD susceptibility in the codominant (FEM: OR = 1.31, 95 % CI = 1.24-1.39), dominant (FEM: OR = 1.38, 95 % CI = 1.27-1.49) and recessive (FEM: OR = 1.52, 95 % CI = 1.38-1.68) models. Furthermore, in the subgroup analysis stratified by ethnicity, increased risk of PD was identified in both Caucasian and Asian populations. Overall, the present meta-analysis provided evidence supporting that SNCA rs356220 polymorphism might act as a genetic susceptibility factor for PD.

ZPD-2, a Small Compound That Inhibits α-Synuclein Amyloid Aggregation and Its Seeded Polymerization

α-Synuclein (α-Syn) forms toxic intracellular protein inclusions and transmissible amyloid structures in Parkinson’s disease (PD). Preventing α-Syn self-assembly has become one of the most promising approaches in the search for disease-modifying treatments for this neurodegenerative disorder. Here, we describe the capacity of a small molecule (ZPD-2), identified after a high-throughput screening, to inhibit α-Syn aggregation. ZPD-2 inhibits the aggregation of wild-type α-Syn and the A30P and H50Q familial variants in vitro at substoichiometric compound:protein ratios. In addition, the molecule prevents the spreading of α-Syn seeds in protein misfolding cyclic amplification assays. ZPD-2 is active against different α-Syn strains and blocks their seeded polymerization. Treating with ZPD-2 two different PD Caenorhabditis elegans models that express α-Syn either in muscle or in dopaminergic (DA) neurons substantially reduces the number of α-Syn inclusions and decreases synuclein-induced DA neurons degeneration. Overall, ZPD-2 is a hit compound worth to be explored in order to develop lead molecules for therapeutic intervention in PD.

Anthraquinone from Edible Fungi Pleurotus ostreatus Protects Human SH-SY5Y Neuroblastoma Cells Against 6-Hydroxydopamine-Induced Cell Death-Preclinical Validation of Gene Knockout Possibilities of PARK7, PINK1, and SNCA1 Using CRISPR SpCas9

Parkinson's disease (PD) results from the degeneration of the nervous tissue brought about by ecological and hereditary components which affects nerve cells in the brain. It is the world's second most normal neurodegenerative issue, which can essentially weaken the personal satisfaction, make reliance, and trigger untimely mortality of affected people. The commonness pace of PD is 0.5-1% among individuals in the age group of 65-69 years and 1-3% among those 80 or more. Clinical appearances incorporate bradykinesia, tremors, unbending nature, and postural unsteadiness; spectrums of non-motor symptoms include psychological hindrance and passionate and behavioral brokenness. In this study, 6-OHDA-induced neurotoxicity was analyzed for various cytotoxicity analyses. The genes identified were PINK1 (PTEN-induced kinase 1), PARK7 (Parkinsonism-associated deglycase) and SNCA 1 (alpha synuclein1) validated using CRISPR spcas9 genome editing tool. In this study, Anthraquinone isolated from Pleurotus ostreatus was treated against a dopaminergic neurotoxin, 6-hydroxydopamine (6-OHDA), which induced neurotoxicity in SH-SY5Y cells. Experimental groups in SH-SY5Y neuroblastoma cells were treated with anthraquinone (50 nM) and 6-OHDA (100 nM). MTT and ROS assays were performed to assess the cell viability and oxidative stress within the cells, followed by mixed-member proportional (Mitochondrial membrane potential), dual staining, and immunoblotting. 6-OHDA-induced cell death in SH-SY5Y cells was dose-dependently attenuated by treatment with anthraquinone. The genes responsible for mutation were studied and the mutated RNAs knockout possibilities was studied using CRISPR spcas9 genome editing tool. Treatment with anthraquinone attenuated the level of oxidative stress and reduced the mitochondrial dysfunction associated with 6-OHDA treatment. Immunoblot analysis carried out with apoptotic markers showed that cytochrome C and caspase-3 expression increased significantly in anthraquinone-treated cells, whereas 6-OHDA-treated group showed a significant decrease when compared with an experimental control group. The mutated genes PARK7, PINK1, and SNCA1 were analyzed and found to exhibit four gene knock possibilities to treat PD. Reports demonstrate that other than following up on the biosynthesis of dopamine and its metabolites, these mixes counteract D2 receptors' extreme touchiness. It is proposed that further examinations need be directed to better understand the activity of the bioactive mixes circulated in these edible fungi Pleurotus ostreatus. The gene knockout possibilities identified by CRISPR SpCas9 will pave a way for better research for PD treatment.

SIRT3 Regulation of Mitochondrial Quality Control in Neurodegenerative Diseases

Neurodegenerative diseases are disorders that are characterized by a progressive decline of motor and/or cognitive functions caused by the selective degeneration and loss of neurons within the central nervous system. The most common neurodegenerative diseases are Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD). Neurons have high energy demands, and dysregulation of mitochondrial quality and function is an important cause of neuronal degeneration. Mitochondrial quality control plays an important role in maintaining mitochondrial integrity and ensuring normal mitochondrial function; thus, defects in mitochondrial quality control are also significant causes of neurodegenerative diseases. The mitochondrial deacetylase SIRT3 has been found to have a large effect on mitochondrial function. Recent studies have also shown that SIRT3 has a role in mitochondrial quality control, including in the refolding or degradation of misfolded/unfolded proteins, mitochondrial dynamics, mitophagy, and mitochondrial biogenesis, all of which are affected in neurodegenerative diseases.

Critical Role of Oxidatively Damaged DNA in Selective Noradrenergic Vulnerability

An important pathology in Parkinson's disease (PD) is the earlier and more severe degeneration of noradrenergic neurons in the locus coeruleus (LC) than dopaminergic neurons in the substantia nigra. However, the basis of such selective vulnerability to insults remains obscure. Using noradrenergic and dopaminergic cell lines, as well as primary neuronal cultures from rat LC and ventral mesencephalon (VM), the present study compared oxidative DNA damage response markers after exposure of these cells to hydrogen peroxide (H₂O₂). The results showed that H₂O₂ treatment resulted in more severe cell death in noradrenergic cell lines SK-N-BE(2)-M17 and PC12 than dopaminergic MN9D cells. Furthermore, there were higher levels of oxidative DNA damage response markers in noradrenergic cells and primary neuronal cultures from the LC than dopaminergic cells and primary cultures from the VM. It included increased tail moments and tail lengths in Comet assay, and increased protein levels of phosphor-p53 and γ-H2AX after treatments with H₂O₂. Consistent with these measurements, exposure of SK-N-BE(2)-M17 cells to H₂O₂ resulted in higher levels of reactive oxygen species (ROS). Further experiments showed that exposure of SK-N-BE(2)-M17 cells to H₂O₂ caused an increased level of noradrenergic transporter, reduced protein levels of copper transporter (Ctr1) and 8-oxoGua DNA glycosylase, as well as amplified levels of Ca_v1.2 and Ca_v1.3 expression. Taken together, these experiments indicated that noradrenergic neuronal cells seem to be more vulnerable to oxidative damage than dopaminergic neurons, which may be related to the intrinsic characteristics of noradrenergic neuronal cells.

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.

Autophagic- and Lysosomal-Related Biomarkers for Parkinson's Disease: Lights and Shadows

Parkinson’s disease (PD) is a neurodegenerative disorder that currently affects 1% of the population over the age of 60 years, for which no disease-modifying treatments exist. This lack of effective treatments is related to the advanced stage of neurodegeneration existing at the time of diagnosis. Thus, the identification of early stage biomarkers is crucial. Biomarker discovery is often guided by the underlying molecular mechanisms leading to the pathology. One of the central pathways deregulated during PD, supported both by genetic and functional studies, is the autophagy-lysosomal pathway. Hence, this review presents different studies on the expression and activity of autophagic and lysosomal proteins, and their functional consequences, performed in peripheral human biospecimens. Although most biomarkers are inconsistent between studies, some of them, namely HSC70 levels in sporadic PD patients, and cathepsin D levels and glucocerebrosidase activity in PD patients carrying GBA mutations, seem to be consistent. Hence, evidence exists that the impairment of the autophagy-lysosomal pathway underlying PD pathophysiology can be detected in peripheral biosamples and further tested as potential biomarkers. However, longitudinal, stratified, and standardized analyses are needed to confirm their clinical validity and utility.

Neuroprotective Effect of Quercetin in Combination with Piperine Against Rotenone- and Iron Supplement-Induced Parkinson's Disease in Experimental Rats

Parkinson's disease (PD) is a neurodegenerative disorder caused by selective dopaminergic neuronal loss. Rotenone is a neurotoxin that selectively destroys dopaminergic neurons, leading to PD-like symptoms. Quercetin possesses antioxidant, anti-inflammatory, and neuroprotective properties but a major drawback is its low bioavailability. Therefore, the present study was designed to evaluate the neuroprotective effect of quercetin in combination with piperine against rotenone- and iron supplement-induced model of PD. Rotenone was administered at a dose of 1.5 mg/kg through an intraperitoneal route with iron supplement at a dose of 120 μg/g in diet from day 1 to day 28. Pre-treatment with quercetin (25 and 50 mg/kg, p.o.), piperine (2.5 mg/kg, p.o.) alone, quercetin (25 mg/kg, p.o.) in combination with piperine (2.5 mg/kg), and ropinirole (0.5 mg/kg, i.p.) was administered for 28 days 1 h prior to rotenone and iron supplement administration. All behavioral parameters were assessed on weekly basis. On the 29th day, all animals were sacrificed and striatum was isolated for biochemical (LPO, nitrite, GSH, mitochondrial complexes I and IV), neuroinflammatory (TNF-α, IL-1β, and IL-6), and neurotransmitter (dopamine, norepinephrine, serotonin, GABA, glutamate) estimation. Quercetin treatment attenuated rotenone- and iron supplement-induced motor deficits and biochemical and neurotransmitter alterations in experimental rats. However, combination of quercetin (25 mg/kg) with piperine (2.5 mg/kg) significantly enhanced its neuroprotective effect as compared with treatment with quercetin alone. The study concluded that combination of quercetin with piperine contributed to superior antioxidant, anti-inflammatory, and neuroprotective effect against rotenone- and iron supplement-induced PD in experimental rats.