Protein aggregation in the pathogenesis of familial and sporadic Parkinson's disease

MicroRNA-217-5p triggers dopaminergic neuronal degeneration via autophagy activation under Atrazine exposure

Atrazine (ATR) is a widely used agricultural herbicide, and its accumulation in soil and water can cause various environmental health problems. ATR has neurotoxic effects on dopaminergic neurons, which can lead to a Parkinson's disease (PD)-like syndrome. Epigenetics regulates gene expression dynamically through DNA methylation, histone post-translational modification, microRNA (miRNA) interaction, and RNA methylation. MicroRNA (miRNA), representing one of the primary epigenetic mechanisms responsible for regulating gene expression, plays a crucial role in maintaining normal cellular function, while dysregulation of miRNA expression has been observed in PD. This study aims to investigate the regulatory mechanisms of miRNA in ATR exposure. The results show that ATR-exposure significantly upregulates the expression level of miR-217-5p. Both miR-217-5p overexpression and ATR exposure is able to trigger the autophagy process and apoptosis. Conversely, inhibiting the expression of miR-217-5p can reverse the levels of ATR-induced autophagy and apoptosis. Moreover, ATR causes damage to dopaminergic neurons, as indicated by the altered expression of tyrosine hydroxylase and α-synuclein. Taken together, these results suggest that ATR-induced autophagy can accelerate the progression of neurodegenerative diseases and that miR-217-5p is probably an important target involved in ATR-induced dopaminergic damage, shedding important light on the development of a novel strategy for treating neurodegenerative diseases.

Prevalence of different types of wound infection in subjects with Parkinson's disease and total joint arthroplasty: A meta-Analysis

A meta-analysis study to assess the influence of Parkinson's disease (PD) on different types of wound infection (WI) in total joint arthroplasty (TJA) patients. A comprehensive literature examination till January 2023 was implemented and 1976 linked studies were appraised. The picked studies contained 76 661 subjects with TJA in the picked studies' baseline, 19 188 of them were PD, and 57 473 were non-PD. Odds ratio (OR) in addition to 95% confidence intervals (CIs) were used to calculate the consequence of PD on different types of WI in TJA patients by the dichotomous and continuous styles and a fixed or random model. PD had a significantly higher postoperative surgical site WI (OR, 1.76; 95% CI, 1.15-2.67, P = .009), superficial WI (OR, 3.36; 95% CI, 1.41-7.99, P = .006), and periprosthetic WI (OR, 4.89; 95% CI, 2.13-11.22, P < .001) compared to the non-PD in TJA patients' post-surgery wounds. PD had a significantly higher postoperative surgical site WI, superficial WI, and periprosthetic WI compared to the non-PD in TJA patients' post-surgery wounds. Though precautions should be taken when commerce with the consequences since some of the picked studies for this meta-analysis was with low sample sizes.

Translational molecular imaging and drug development in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder that primarily affects elderly people and constitutes a major source of disability worldwide. Notably, the neuropathological hallmarks of PD include nigrostriatal loss and the formation of intracellular inclusion bodies containing misfolded α-synuclein protein aggregates. Cardinal motor symptoms, which include tremor, rigidity and bradykinesia, can effectively be managed with dopaminergic therapy for years following symptom onset. Nonetheless, patients ultimately develop symptoms that no longer fully respond to dopaminergic treatment. Attempts to discover disease-modifying agents have increasingly been supported by translational molecular imaging concepts, targeting the most prominent pathological hallmark of PD, α-synuclein accumulation, as well as other molecular pathways that contribute to the pathophysiology of PD. Indeed, molecular imaging modalities such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) can be leveraged to study parkinsonism not only in animal models but also in living patients. For instance, mitochondrial dysfunction can be assessed with probes that target the mitochondrial complex I (MC-I), while nigrostriatal degeneration is typically evaluated with probes designed to non-invasively quantify dopaminergic nerve loss. In addition to dopaminergic imaging, serotonin transporter and N-methyl-D-aspartate (NMDA) receptor probes are increasingly used as research tools to better understand the complexity of neurotransmitter dysregulation in PD. Non-invasive quantification of neuroinflammatory processes is mainly conducted by targeting the translocator protein 18 kDa (TSPO) on activated microglia using established imaging agents. Despite the overwhelming involvement of the brain and brainstem, the pathophysiology of PD is not restricted to the central nervous system (CNS). In fact, PD also affects various peripheral organs such as the heart and gastrointestinal tract - primarily via autonomic dysfunction. As such, research into peripheral biomarkers has taken advantage of cardiac autonomic denervation in PD, allowing the differential diagnosis between PD and multiple system atrophy with probes that visualize sympathetic nerve terminals in the myocardium. Further, α-synuclein has recently gained attention as a potential peripheral biomarker in PD. This review discusses breakthrough discoveries that have led to the contemporary molecular concepts of PD pathophysiology and how they can be harnessed to develop effective imaging probes and therapeutic agents. Further, we will shed light on potential future trends, thereby focusing on potential novel diagnostic tracers and disease-modifying therapeutic interventions.

Alpha-synuclein oligomers alter the spontaneous firing discharge of cultured midbrain neurons

The aim of this work was to monitor the effects of extracellular α-synuclein on the firing activity of midbrain neurons dissociated from substantia nigra TH-GFP mice embryos and cultured on microelectrode arrays (MEA). We monitored the spontaneous firing discharge of the network for 21 days after plating and the role of glutamatergic and GABAergic inputs in regulating burst generation and network synchronism. Addition of GABA A , AMPA and NMDA antagonists did not suppress the spontaneous activity but allowed to identify three types of neurons that exhibited different modalities of firing and response to applied L-DOPA: high-rate (HR) neurons, low-rate pacemaking (LR-p), and low-rate non-pacemaking (LR-np) neurons. Most HR neurons were insensitive to L-DOPA, while the majority of LR-p neurons responded with a decrease of the firing discharge; less defined was the response of LR-np neurons. The effect of exogenous α-synuclein (α-syn) on the firing discharge of midbrain neurons was then studied by varying the exposure time (0-48 h) and the α-syn concentration (0.3-70 μM), while the formation of α-syn oligomers was monitored by means of AFM. Independently of the applied concentration, acute exposure to α-syn monomers did not exert any effect on the spontaneous firing rate of HR, LR-p, and LR-np neurons. On the contrary, after 48 h exposure, the firing activity was drastically altered at late developmental stages (14 days in vitro, DIV, neurons): α-syn oligomers progressively reduced the spontaneous firing discharge (IC50 = 1.03 μM), impaired burst generation and network synchronism, proportionally to the increased oligomer/monomer ratio. Different effects were found on early-stage developed neurons (9 DIV), whose firing discharge remained unaltered, regardless of the applied α-syn concentration and the exposure time. Our findings unravel, for the first time, the variable effects of exogenous α-syn at different stages of midbrain network development and provide new evidence for the early detection of neuronal function impairment associated to aggregated forms of α-syn.

Cocoa Extract Provides Protection against 6-OHDA Toxicity in SH-SY5Y Dopaminergic Neurons by Targeting PERK

Parkinson’s disease (PD) represents one of the most common neurodegenerative disorders, characterized by a dopamine (DA) deficiency in striatal synapses and misfolded toxic α-synuclein aggregates with concomitant cytotoxicity. In this regard, the misfolded proteins accumulation in neurodegenerative disorders induces a remarkable perturbations of endoplasmic reticulum (ER) homeostasis leading to persistent ER stress, which in turn, effects protein synthesis, modification, and folding quality control. A large body of evidence suggests that natural products target the ER stress signaling pathway, exerting a potential action in cancers, diabetes, cardiovascular and neurodegenerative diseases. This study aims to assess the neuroprotective effect of cocoa extract and its purified fractions against a cellular model of Parkinson’s disease represented by 6-hydroxydopamine (6-OHDA)-induced SH-SY5Y human neuroblastoma. Our findings demonstrate, for the first time, the ability of cocoa to specifically targets PERK sensor, with significant antioxidant and antiapoptotic activities as both crude and fractioning extracts. In addition, cocoa also showed antiapoptotic properties in 3D cell model and a notable ability to inhibit the accumulation of α-synuclein in 6-OHDA-induced cells. Overall, these results indicate that cocoa exerts neuroprotective effects suggesting a novel possible strategy to prevent or, at least, mitigate neurodegenerative disorders, such as PD.

COVID-19 and Parkinson's Disease: Possible Links in Pathology and Therapeutics

The outbreak of SARs-CoV-2 with emerging new variants is leading to global health crisis and has brought a major concern for patients with comorbidities. Parkinson's disease (PD) is a motor neurodegenerative disease involving various metabolic and psychological ailments along with the common occurrence of hyposmia as observed in COVID-19 patients. In addition, the observed surplus inflammatory responses in both diseases are also alarming. Alongside, angiotensin-converting enzyme 2 (ACE2) receptor, essentially required by SARS-CoV-2 to enter the cell and dopamine decarboxylase (DDC), required for dopamine synthesis is known to co-regulate in the non-neuronal cells. Taken together, these conditions suggested the probable reciprocal pathological relation between COVID-19 and PD and also suggested that during comorbidities, the disease diagnosis and therapeutics are critical and may engender severe health complications. In this review, we discuss various events and mechanisms which may have implications for the exacerbation of PD conditions and must be taken into account during the treatment of patients.

Evaluating the neuroprotective activities of vinpocetine, punicalagin, niacin and vitamin E against behavioural and motor disabilities of manganese-induced Parkinson's disease in Sprague Dawley rats

The current study investigated the neuroprotective activity of some drugs and nutriceuticals with antioxidant and anti-inflammatory potential on the pathogenesis of Parkinson's disease (PD). Rats were categorized into seven groups: Rats received tween80 daily for 5 weeks as a control group, MnCl₂ (10 mg/kg, i.p) either alone (group II) or in combination with vinpocetine (VIN) (20 mg/kg) (group III), punicalagin (PUN) (30 mg/kg) (group IV), niacin (85 mg/kg) (group V), vitamin E (Vit E) (100 mg/kg) (group VI) or their combination (group VII). Motor activities was examined using open-field and catalepsy. Striatal monamines, acetylcholinesterase, excitatory/inhibitory neurotransmitters, redox status, pro-oxidant content, brain inflammatory, apoptotic and antioxidant biomarkers levels were assessed. Besides, histopathological investigations of different brain regions were determined. Groups (IV -GVII) showed improved motor functions of PD rats. Applied drugs significantly increased the brain levels of monoamines with the strongest effect to PUN. Meanwhile, they significantly decreased levels of acetylcholinesterase with a strongest effect to PUN. Moreover, they exhibited significant neuronal protection and anti-inflammatory abilities through significant reduction of the brain levels of COX2, TNF-α and Il-1β with a strongest effect to the PUN. Interestingly; groups (IV - GVII) showed restored glutamate/GABA balance and exhibited a pronounced decrease in caspase-3 content and GSK-3β protein expression levels. In addition, they significantly increased Bcl2 mRNA expression levels with a strongest effect for PUN. All these findings were further confirmed by the histopathological examinations. As a conclusion, we propose VIN and PUN to mitigate the progression of PD via their antioxidant, anti-inflammatory, anti-apoptotic, neurotrophic and neurogenic activities.

Exploration of Protein Aggregations in Parkinson's Disease Through Computational Approaches and Big Data Analytics

Protein aggregation has been implicated in numerous neurodegenerative disorders whose etiologies are poorly understood, and for which there are no effective treatments. Here we show that the computational approaches may help us to better understand the basics of Parkinson's disease (PD). The high-resolution structural, dynamical, and mechanistic insights delivered by computational studies of protein aggregation have a unique potential to enable the rational manipulation of oligomer formation. Additionally, big data and machine learning methods may provide valuable insights to better understand the nature of proteins involved in PD and their aggregative behavior for the betterment of PD treatment.

Review of Metabolomics-Based Biomarker Research for Parkinson's Disease

Parkinson's disease (PD), as the second most common neurodegenerative disease, is seriously affecting the life quality of the elderly. However, there is still a lack of efficient medical methods to diagnosis PD before apparent symptoms occur. In recent years, clinical biomarkers including genetic, imaging, and tissue markers have exhibited remarkable benefits in assisting PD diagnoses. Due to the advantages of high-throughput detection of metabolites and almost non-invasive sample collection, metabolomics research of PD is widely used for diagnostic biomarker discovery. However, there are also a few shortages for those identified biomarkers, such as the scarcity of verifications regarding the sensitivity and specificity. Thus, reviewing the research progress of PD biomarkers based on metabolomics techniques is of great significance for developing PD diagnosis. To comprehensively clarify the progress of current metabolic biomarker studies in PD, we reviewed 20 research articles regarding the discovery and validation of biomarkers for PD diagnosis from three mainstream academic databases (NIH PubMed, ISI Web of Science, and Elsevier ScienceDirect). By analyzing those materials, we summarized the metabolic biomarkers identified by those metabolomics studies and discussed the potential approaches used for biomarker verifications. In conclusion, this review provides a comprehensive and updated overview of PD metabolomics research in the past two decades and particularly discusses the validation of disease biomarkers. We hope those discussions might provide inspiration for PD biomarker discovery and verification in the future.

Sodium Butyrate Exacerbates Parkinson's Disease by Aggravating Neuroinflammation and Colonic Inflammation in MPTP-Induced Mice Model

The abnormal production of short chain fatty acid (SCFAs) caused by gut microbial dysbiosis plays an important role in the pathogenesis and progression of Parkinson's disease (PD). This study sought to evaluate how butyrate, one of SCFAs, affect the pathology in a subacute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP) treated mouse model of PD. Sodium butyrate (NaB; 165 mg/kg/day i.g., 7 days) was administrated from the day after the last MPTP injection. Interestingly, NaB significantly aggravated MPTP-induced motor dysfunction (P < 0.01), decreased dopamine (P < 0.05) and 5-HT (P < 0.05) levels, exacerbated declines of dopaminergic neurons (34%, P < 0.05) and downregulated expression of tyrosine hydroxylase (TH, 47%, P < 0.05), potentiated glia-mediated neuroinflammation by increasing the number of microglia (17%, P < 0.05) and activating astrocytes (28%, P < 0.01). In vitro study also confirmed that NaB could significantly exacerbate pro-inflammatory cytokines expression (IL-1β, 4.11-fold, P < 0.01; IL-18, 3.42-fold, P < 0.01 and iNOS, 2.52-fold, P < 0.05) and NO production (1.55-fold, P < 0.001) in LPS-stimulated BV2 cells. In addition, NaB upregulated the expression of pro-inflammatory cytokines (IL-6, 3.52-fold, P < 0.05; IL-18, 1.72-fold, P < 0.001) and NLRP3 (3.11-fold, P < 0.001) in the colon of PD mice. However, NaB had no effect on NFκB, MyD88 and TNF-α expression in PD mice. Our results indicate that NaB exacerbates MPTP-induced PD by aggravating neuroinflammation and colonic inflammation independently of the NFκB/MyD88/TNF-α signaling pathway.

Effect of Parkinson's disease on primary total joint arthroplasty outcomes: A meta-analysis of matched control studies

BACKGROUND

Currently, no meta-analysis exists elucidate the outcomes of total joint arthroplasty (TJA) in patients with Parkinson's disease (PD). The aim of this study was to investigate the outcomes of TJA in patients with PD with respect to complication and revision in comparison to a TJA cohort without PD.

METHODS

MEDLINE, Scopus, EMBASE, and Cochrane Library databases were searched with English language restrictions. The primary outcome measures were complications and revision, whereas the secondary outcomes included length of stay (LOS) and total charge.

RESULTS

Seven studies with a total of 124163 patients were included. The most important finding from our study was that PD patients had a 42% higher risk for any medical complication (P = 0.004) and a 65% higher risk for any surgical complication (P = 0.01) compared to the matched cohort. Specifically, PD was associated with increased superficial wound infection (P = 0.006), dislocation (P = 0.01), deep vein thrombosis (DVT) (P = 0.02), LOS (P = 0.0005), and total hospital charges (P < 0.00001). However, PD did not increase the risks for periprosthetic infection (P = 0.32) and revision (P = 0.17).

CONCLUSIONS

Patients with PD are at increased risk for medical complication and surgery complications, particularly superficial wound infection, dislocation, and DVT as compared to patients without PD. PD patients also exhibit increased LOS and total hospital charges. However, PD did not increase the risks for periprosthetic infection and revision.

PERK-Mediated Unfolded Protein Response Activation and Oxidative Stress in PARK20 Fibroblasts

PARK20, an early onset autosomal recessive parkinsonism is due to mutations in the phosphatidylinositol-phosphatase Synaptojanin 1 (Synj1). We have recently shown that the early endosomal compartments are profoundly altered in PARK20 fibroblasts as well as the endosomal trafficking. Here, we report that PARK20 fibroblasts also display a drastic alteration of the architecture and function of the early secretory compartments. Our results show that the exit machinery from the Endoplasmic Reticulum (ER) and the ER-to-Golgi trafficking are markedly compromised in patient cells. As a consequence, PARK20 fibroblasts accumulate large amounts of cargo proteins within the ER, leading to the induction of ER stress. Interestingly, this stressful state is coupled to the activation of the PERK/eIF2α/ATF4/CHOP pathway of the Unfolded Protein Response (UPR). In addition, PARK20 fibroblasts reveal upregulation of oxidative stress markers and total ROS production with concomitant alteration of the morphology of the mitochondrial network. Interestingly, treatment of PARK20 cells with GSK2606414 (GSK), a specific inhibitor of PERK activity, restores the level of ROS, signaling a direct correlation between ER stress and the induction of oxidative stress in the PARK20 cells. All together, these findings suggest that dysfunction of early secretory pathway might contribute to the pathogenesis of the disease.

The deglycase activity of DJ-1 mitigates α-synuclein glycation and aggregation in dopaminergic cells: Role of oxidative stress mediated downregulation of DJ-1 in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder associated with the degeneration of dopamine neurons of the substantia nigra pars compacta (SNpc) and the presence of intra-neuronal aggregates of α-synuclein and its post-translational products. Based on emerging reports on the association between glycated α-synuclein and PD; and the newly identified deglycase activity of DJ-1, we sought to find the relevance of deglycase activity of DJ-1 on glycation of α-synuclein and its plausible role in PD. Our results demonstrate that DJ-1 has a higher affinity towards the substrate methylglyoxal (MGO) (Km = 900 mM) as compared to its familial mutant, L166P (Km = 1900 mM). Also, CML α-synuclein (CML-syn) served as a substrate for the deglycase activity of DJ-1. Treatment of cells with Parkinsonian mimetic, 1-methyl-4-phenylpyridinium ion (MPP⁺); oxidants, such as H₂O₂ and methylglyoxal (MGO) lead to a dose-dependent decrease in the levels of DJ-1 with a concomitant increase in CML-syn. Also, MGO induced cytosolic α-synuclein aggregates in cells which stained positive with the anti-CML antibody. Further, unilateral stereotaxic administration of MGO into the SNpc of mice induced α-synuclein aggregates and CML-syn with a concomitant reduction in the number of TH positive neurons, protein levels of TH and DJ-1 at the site of injection. Interestingly, overexpression of DJ-1 enhanced the clearance of preformed CML-syn in cells, mitigated MGO induced CML-syn and intracellular α-synuclein aggregates. Overall, the findings of our present study demonstrate that DJ-1 plays a pivotal role in the glycation and aggregation of α-synuclein. Reduced DJ-1 activity due to mutations or oxidative stress may lead to the accumulation of glycated α-synuclein and its aggregates.

Parkinson's Disease: Basic Pathomechanisms and a Clinical Overview

PD is a common and a debilitating degenerative movement disorder. The number of patients is increasing worldwide and as yet there is no cure for the disease. The majority of existing treatments target motor symptom control. Over the last two decades the impact of the genetic contribution to PD has been appreciated. Significant discoveries have been made, which have advanced our understanding of the pathophysiological and molecular basis of PD. In this chapter we outline current knowledge of the clinical aspects of PD and the basic mechanistic understanding.

Real-time determination of aggregated alpha-synuclein induced membrane disruption at neuroblastoma cells using scanning ion conductance microscopy

Parkinson's disease (PD) is recognized as the second most common neurodegenerative disorder and has affected approximately one million people in the United States alone. A large body of evidence has suggested that deposition of aggregated alpha-synuclein (α-Syn), a brain protein abundant near presynaptic termini, in intracellular protein inclusions (Lewy bodies) results in neuronal cell damage and ultimately contributes to the progression of PD. However, the exact mechanism is still unclear. One hypothesis is that α-Syn aggregates disrupt the cell membrane's integrity, eventually leading to cell death. We used scanning ion conductance microscopy (SICM) to monitor the morphological changes of SH-SY5Y neuroblastoma cells and observed dramatic disruption of the cell membrane after adding α-Syn aggregates to the culturing media. This work demonstrates that SICM can be applied as a new approach to studying the cytotoxicity of α-Syn aggregates.

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

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

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

MicroRNA-181a Regulates Apoptosis and Autophagy Process in Parkinson's Disease by Inhibiting p38 Mitogen-Activated Protein Kinase (MAPK)/c-Jun N-Terminal Kinases (JNK) Signaling Pathways

Background

microRNA (miR)-181a has been reported to be downregulated in Parkinson’s disease (PD), but the regulatory mechanism of miR-181a on neuron apoptosis and autophagy is still poorly understood. We aimed to investigate the neuroprotective effects of miR-181a on PD in vitro.

Material/Methods

Human SK-N-SH neuroblastoma cells were incubated with different concentrations of 1-methyl-4-phenylpyridinium ion (MPP⁺) to induce the PD model. The expression of miR-181a was then analyzed. After transfection with miR-181a mimic or scramble following MPP⁺ treatment, the expression of autophagy protein markers (LC3II, LC3I, and Beclin 1) and p38 mitogen-activated protein kinase (MAPK)/c-Jun N-terminal kinases (JNK) signaling proteins (p-p38, p38, p-JNK, and JNK) and cell apoptosis were detected. Furthermore, the cells were transfected with miR-181a inhibitor and cultured in the presence or absence of p38 inhibitor SB203582 or JNK inhibitor SP600125, and the cell apoptosis was tested again.

Results

The expression of miR-181a was gradually decreased with the increase of MPP⁺ concentration (P<0.05, P<0.01, or P<0.001). Overexpression of miR-181a significantly decreased the LC3II/LC3I ratio, Beclin 1 expression, cell apoptosis, and the expression of p-p38 and p-JNK compared to the MPP⁺ + miR-181a scramble group (all P<0.05). In addition, we observed that SB203582 or SP600125 showed no effects on cell apoptosis, but the effects of miR-181a inhibitor on cell apoptosis were reversed by administration of SB203582 or SP600125 compared to the scramble group (P<0.05).

Conclusions

Our results suggest that miR-181a regulates apoptosis and autophagy in PD by inhibiting the p38 MAPK/JNK pathway.

Plasma levels of miR-137 and miR-124 are associated with Parkinson's disease but not with Parkinson's disease with depression

MicroRNAs (miRNAs) are a class of small, non-coding RNAs that regulate gene expression at the post-transcriptional level. Recently, it was reported that miR-137, miR-124, and miR-184 were widely expressed in the central nervous system and were vital to neuronal regulation. In this study, we detected the circulating levels of miR-137, miR-124, and miR-184 in PD patients, and explored the potential role of miR-124, miR-137, and miR-184 in the diagnosis of PD. We further described the relationship between these miRNAs and PD with depression (PD-Dep). The study recruited 60 controls and 60 PD patients, which were further divided into two subgroups, PD with depression (PD-Dep, n = 24) and non-depressed group (PD-NDep, n = 36) according to Hamilton Rating Scale for Depression. Plasma levels of miR-137, miR-124, and miR-184 were detected by qRT-PCR. Receiver-operating characteristic (ROC) curve was used to evaluate miR-124 and miR-137 levels as potential diagnostic biomarkers for PD. The results demonstrated that there were no significant differences in levels of miR-184 between PD patients and controls (p > 0.05). However, miR-137 levels were increased significantly for PD patients compared to controls (p < 0.05), while miR-124 levels were down-regulated (p < 0.05). The areas under the ROC curve (AUC) of miR-137 and miR-124 were 0.707 (95% CI 0.615-0.789, p < 0.05) and 0.709 (95% CI 0.618-0.633, p < 0.05), respectively. Correlation analysis revealed that there was no relationship between these two miRNAs levels and UPDRS scores or H&Y stage. There were no significant differences in miR-137 and miR-124 levels between PD-Dep and PD-NDep (p > 0.05). Thus, plasma levels of miR-137 and miR-124 are associated with Parkinson's disease and might be potential biomarkers of the diagnosis of PD. There were no associations of plasma miR-137 and miR-124 with the severity of PD motor symptoms or PD-Dep.

α-Synuclein binds to cytoplasmic vesicles in U251 glioblastoma cells

α-Synuclein is the major component of Lewy bodies, Lewy neurites, and glial cytoplasmic inclusions. It plays an important role in neurodegenerative diseases such as Parkinson's disease, multiple system atrophy, and other synucleinopathies. However, the pathogenesis and neurodegenerative effects of α-synuclein remain unknown. In this study, we established an α-synuclein and an α-synuclein-EGFP overexpressing U251 cell line. α-Synuclein overexpression increases oxidative stress and alters the cell surface and mitochondrial morphologies. We provide fluorescent-protein tagging, immunofluorescence and ultrastructural evidence showing that α-synuclein accumulations are associated with clusters of cytoplasmic vesicles and the diameter of these vesicles increases by H₂O₂ in a time- and dose-dependent manner.

The SH-SY5Y cell line in Parkinson's disease research: a systematic review

Parkinson’s disease (PD) is a devastating and highly prevalent neurodegenerative disease for which only symptomatic treatment is available. In order to develop a truly effective disease-modifying therapy, improvement of our current understanding of the molecular and cellular mechanisms underlying PD pathogenesis and progression is crucial. For this purpose, standardization of research protocols and disease models is necessary. As human dopaminergic neurons, the cells mainly affected in PD, are difficult to obtain and maintain as primary cells, current PD research is mostly performed with permanently established neuronal cell models, in particular the neuroblastoma SH-SY5Y lineage. This cell line is frequently chosen because of its human origin, catecholaminergic (though not strictly dopaminergic) neuronal properties, and ease of maintenance. However, there is no consensus on many fundamental aspects that are associated with its use, such as the effects of culture media composition and of variations in differentiation protocols. Here we present the outcome of a systematic review of scientific articles that have used SH-SY5Y cells to explore PD. We describe the cell source, culture conditions, differentiation protocols, methods/approaches used to mimic PD and the preclinical validation of the SH-SY5Y findings by employing alternative cellular and animal models. Thus, this overview may help to standardize the use of the SH-SY5Y cell line in PD research and serve as a future user’s guide.

Down-regulation of p21-activated serine/threonine kinase 1 is involved in loss of mesencephalic dopamine neurons

BACKGROUND

Although the roles of p21-activated serine/threonine kinase 1 (PAK1) have been reported in some neurodegenerative diseases, details regarding neurodegeneration are still limited. Hence, we tried to determine the role of PAK1 and molecular mechanisms of neuronal death involved in neurodegeneration.

RESULTS

Expression of a dominant-negative form of PAK1 (PAK1(H83,86L, K229R), PAK1-DN) decreased the cell viability and increased cell death induced by oxidative stress. Indeed, oxidative stress decreased the phosphorylation of PAK1 in neuroblastoma cells, cultured dopamine (DA) neurons, or rat midbrains. PAK1-DN reduced the level of Bcl-2 protein, through an ubiquitin/proteasome-dependent mechanism. The level of Bcl-2 may be regulated by PAK1-ERK signaling and/or PAK1, directly. Conversely, expression of an active form of PAK1 (PAK1(T423E), PAK1-CA) could recover both loss of DA neurons in the substantia nigra (SN) and behavioral defects in a 6-OHDA-induced hemiparkinsonian rat model.

CONCLUSIONS

Our data suggest that the oxidative stress-induced down-regulation of PAK1 activity could be involved in the loss of mesencephalic DA neurons through modulation of neuronal death, suggesting a novel role of PAK1 as a molecular determinant and mechanisms in the pathogenesis of Parkinson's disease.

Mitochondrial Translocation of High Mobility Group Box 1 Facilitates LIM Kinase 2-Mediated Programmed Necrotic Neuronal Death

High mobility group box 1 (HMGB1) acts a signaling molecule regulating a wide range of inflammatory responses in extracellular space. HMGB1 also stabilizes nucleosomal structure and facilitates gene transcription. Under pathophysiological conditions, nuclear HMGB1 is immediately transported to the cytoplasm through chromosome region maintenance 1 (CRM1). Recently, we have reported that up-regulation of LIM kinase 2 (LIMK2) expression induces HMGB1 export from neuronal nuclei during status epilepticus (SE)-induced programmed neuronal necrosis in the rat hippocampus. Thus, we investigated whether HMGB1 involves LIMK2-mediated programmed neuronal necrosis, but such role is not reported. In the present study, SE was induced by pilocarpine in rats that were intracerebroventricularly infused with saline, control siRNA, LIMK2 siRNA or leptomycin B (LMB, a CRM1 inhibitor) prior to SE induction. Thereafter, we performed Fluoro-Jade B staining, western blots and immunohistochemical studies. LIMK2 knockdown effectively attenuated SE-induced neuronal death and HMGB1 import into mitochondria accompanied by inhibiting nuclear HMGB1 release and abnormal mitochondrial elongation. LMB alleviated SE-induced neuronal death and nuclear HMGB1 release. However, LMB did not prevent mitochondrial elongation induced by SE, but inhibited the HMGB1 import into mitochondria. The efficacy of LMB was less effective to attenuate SE-induced neuronal death than that of LIMK2 siRNA. These findings indicate that nuclear HMGB1 release and the subsequent mitochondrial import may facilitate and deteriorate programmed necrotic neuronal deaths. The present data suggest that the nuclear HMGB1 release via CRM1 may be a potential therapeutic target for the programmed necrotic neuronal death induced by SE.

Lipopolyplex for Therapeutic Gene Delivery and Its Application for the Treatment of Parkinson's Disease

Lipopolyplex is a core-shell structure composed of nucleic acid, polycation and lipid. As a non-viral gene delivery vector, lipopolyplex combining the advantages of polyplex and lipoplex has shown superior colloidal stability, reduced cytotoxicity, extremely high gene transfection efficiency. Following intravenous administration, there are many strategies based on lipopolyplex to overcome the complex biological barriers in systemic gene delivery including condensation of nucleic acids into nanoparticles, long circulation, cell targeting, endosomal escape, release to cytoplasm and entry into cell nucleus. Parkinson's disease (PD) is the second most common neurodegenerative disorder and severely influences the patients' life quality. Current gene therapy clinical trials for PD employing viral vectors didn't achieve satisfactory efficacy. However, lipopolyplex may become a promising alternative approach owing to its stability in blood, ability to cross the blood-brain barrier (BBB) and specific targeting to diseased brain cells.

Carnosic Acid Attenuates 6-Hydroxydopamine-Induced Neurotoxicity in SH-SY5Y Cells by Inducing Autophagy Through an Enhanced Interaction of Parkin and Beclin1

Enhanced removal of abnormal protein aggregates or injured organelles through autophagy is related to neuroprotection in Parkinson's disease. In this study, we explored whether the induction of autophagy is associated with the neuroprotection of rosemary carnosic acid (CA) against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in SH-SY5Y cells. The results indicated that cells treated with CA had increased protein levels of parkin and autophagy-related markers, including phosphatidylinositol 3-kinase p100, Beclin1, autophagy-related gene 7, and microtubule-associated protein 1 light chain 3-II, as well as enhanced formation of autophagic vacuoles. Treatment of cells with 6-OHDA decreased the levels of parkin and the autophagy markers, but CA pretreatment reversed these effects. However, wortmannin (an autophagosome formation blocker) pretreatment attenuated the effect of CA. After CA pretreatment, the induction of cleaved caspase 3, cleaved poly-ADP ribose polymerase, and nuclear condensation by 6-OHDA were alleviated. Both wortmannin and bafilomycin A1 (an autophagosome-lysosome fusion blocker) inhibited the anti-apoptosis effects of CA. Additionally, we performed immunoprecipitation with anti-parkin antibody and found that the interaction of parkin and Beclin1 protein was reduced by 6-OHDA but that this effect was reversed in cells pretreated with CA. Moreover, transfection of parkin siRNA in cells inhibited the ability of CA to alleviate 6-OHDA-decreased autophagy-related markers and nuclear condensation. In conclusion, CA protects against 6-OHDA-induced apoptosis by inducing autophagy through the interaction of parkin and Beclin1. These results provide a future strategy for use of CA in the prevention of Parkinson's disease.

The Natural Progression of Parkinson's Disease in a Small Cohort with 15 Drug-naïve Patients

BACKGROUND

The studies of the natural progression of Parkinson's disease (PD) in Chinese populations have been lacking. To address this issue and obtain a preliminary data, we conducted a PD progression assessment in 15 adults with de novo PD from a nutritional intervention trial (NIT) cohort in Lin County China.

METHODS

Using the Copiah County screening questionnaire and United Kingdom Parkinson's Disease Society Brain Bank diagnostic criteria, we surveyed the available NIT cohort members in 2000 and diagnosed 86 patients as PD. In 2010, we resurveyed all PD patients and confirmed definite PD diagnosis in 15 cases with the rest of them being dead (54); having probable (10) PD or vascular Parkinsonism (3); refusing to participate (2); or being away (2). In both surveys, we used Hoehn and Yahr (HY) scale and assessed the disease progression. Unified Parkinson's Disease Rating Scale (UPDRS) was added to the second survey.

RESULTS

In 2010, the average disease duration for 15 definite PD patients was 13.6 ± 7.3 years. Over a 10-year time span, 9 out of 15 patients remained at the same HY stage while the remaining 6 progressed. Rigidity (47% vs. 100%; P = 0.002) and postural instability (7% vs. 47%; P = 0.005) worsened significantly. The mean UPDRS motor scores in 2010 were 39.4 ± 23.7.

CONCLUSIONS

Overall worsening of motor function in PD seems to be the rule in this untreated cohort, and their rate of progression seemed to be slower than those reported in the western populations.

MiR-124 Regulates Apoptosis and Autophagy Process in MPTP Model of Parkinson's Disease by Targeting to Bim

Parkinson's disease (PD) is the most prevalent movement disorder characterized by selective loss of midbrain dopaminergic (DA) neurons. MicroRNA-124 (miR-124) is abundantly expressed in the DA neurons and its expression level decreases in the 1-methyl-4-pheny-1, 2, 3, 6-tetrahydropyridine (MPTP) model of PD. However, whether the upregulation of miR-124 could attenuate neurodegeneration remains unknown. Here, we employed miR-124 agomir and miR-124 mimics to upregulate miR-124 expression in MPTP-treated mice and MPP(+) -intoxicated SH-SY5Y cells, respectively. We found that loss of DA neurons and striatal dopamine in MPTP-treated mice was significantly reduced by upregulating miR-124. In addition, we identified a target of miR-124, Bim that mediated the neuroprotection of miR-124. Indeed, treatment of miR-124 agomir in MPTP-treated mice inhibited Bim expression, thus suppressing Bax translocation to mitochondria. Moreover, impaired autophagy process in MPTP-treated mice and MPP(+) -intoxicated SH-SY5Y cells characterized as autophagosomes (AP) accumulation and lysosomal depletion were alleviated by the upregulation of miR-124. Taken together, these results indicate that upregulation of miR-124 could regulate apoptosis and impaired autophagy process in the MPTP model of PD, thus reducing the loss of DA neurons.

Nigral proteasome inhibition in mice leads to motor and non-motor deficits and increased expression of Ser129 phosphorylated α-synuclein

Parkinson's disease is a neurodegenerative disorder characterized by motor and non-motor disturbances. Various pathogenic pathways drive disease progression including oxidative stress, mitochondrial dysfunction, α-synuclein aggregation and impairment of protein degradation systems. Dysfunction of the ubiquitin-proteasome system in the substantia nigra of Parkinson's disease patients is believed to be one of the causes of protein aggregation and cell death associated with this disorder. Lactacystin, a potent inhibitor of the proteasome, was previously delivered to the nigrostriatal pathway of rodents to model nigrostriatal degeneration. Although lactacystin-treated animals develop parkinsonian motor impairment, it is currently unknown whether they also develop non-motor symptoms characteristic of this disorder. In order to further describe the proteasome inhibition model of Parkinson's disease, we characterized the unilateral lactacystin model, performed by stereotaxic injection of the toxin in the substantia nigra of mice. We studied the degree of neurodegeneration and the behavioral phenotype 1 and 3 weeks after lactacystin lesion both in terms of motor impairment, as well as non-motor symptoms. We report that unilateral administration of 3 μg lactacystin to the substantia nigra of mice leads to partial (~40%) dopaminergic cell loss and concurrent striatal dopamine depletion, accompanied by increased expression of Ser129-phosphorylated α-synuclein. Behavioral characterization of the model revealed parkinsonian motor impairment, as well as signs of non-motor disturbances resembling early stage Parkinson's disease including sensitive and somatosensory deficits, anxiety-like behavior, and perseverative behavior. The consistent finding of good face validity, together with relevant construct validity, warrant a further evaluation of proteasome inhibition models of Parkinson's disease in pre-clinical research and validation of therapeutic targets.

Upregulation of alphaB-crystallin expression in the substantia nigra of patients with Parkinson's disease

Parkinson's disease (PD) is one of the most devastating neurodegenerative disorders. The underlying mechanisms of the characteristic neurodegeneration in the substantia nigra (SN) are still not fully understood. To better understand the molecular events occurring in the SN of PD brain, we used the culture-derived isotope tag-based quantitative proteomics to compare the protein expression profiles in the nigral tissue of PD patients and control subjects. We identified a total of 11 differentially expressed proteins, including alphaB-crystallin (Cryab). Both the levels and pattern of Cryab expression in the SN were validated. It was revealed that Cryab was markedly upregulated in the SN of PD brain. Cryab expression was also upregulated in reactive astrocytes and microglia in a neurotoxin-induced mouse PD model. Moreover, we showed increased expression of Cryab in cytoplasmic inclusions in a subset of glial cells in Parkinsonian brain. Thus, we identified Cryab that is highly expressed in the SN of PD brain and may be involved in the glial pathology during dopaminergic neuron degeneration in PD.

Neuroprotective effect of modified Chungsimyeolda-tang, a traditional Korean herbal formula, via autophagy induction in models of Parkinson's disease

AIM OF THE STUDY

Previous studies in our laboratory revealed the neuroprotective effect of modified Yeoldahanso-tang (MYH) in models of Parkinson׳s disease (PD). In this study, we investigated another traditional Korean herbal formula, modified Chungsimyeolda-tang (termed DG), as a potential treatment for PD. Chungsimyeolda-tang has been used in Korea to treat cerebrovascular diseases, such as stroke. Here, we verify the neuroprotective and autophagy-inducing effects of DG to evaluate any potential anti-parkinsonian properties.

MATERIALS AND METHODS

1-Methyl-4-phenylpyridinium (MPP(+)) and rotenone were used to induce cytotoxicity in nerve growth factor (NGF)-differentiated rat pheochromocytoma (PC12) cells. Cell viability was measured using an MTT assay. Induction of autophagy by DG in NGF-differentiated PC12 cells was measured using an immunoblotting assay with an LC3 antibody. The proteasomal inhibitor lactacystin was used to induce ubiquitin-proteasome system (UPS) dysfunction in NGF-differentiated PC12 cells. DG-mediated clearance of aggregated proteins was measured using an immunoblotting assay with a ubiquitin antibody.

RESULTS AND CONCLUSIONS

Our findings indicate that DG robustly protects NGF-differentiated PC12 cells against the neurotoxic effects of MPP(+) and rotenone in an in vitro model. Furthermore, DG protects NGF-differentiated PC12 cells against lactacystin-induced cell death. This effect is partially mediated by an increased autophagy associated with the enhanced degradation of aggregated proteins. This study suggests that DG is an attractive candidate drug for inducing autophagy and, therefore, may represent a promising strategy to prevent diseases associated with misfolded/aggregated proteins in various neurodegenerative disorders, including Parkinson׳s disease.

Emerging therapies for Parkinson's disease: from bench to bedside

The prevalence of Parkinson's disease (PD) increases with age and is projected to increase in parallel to the rising average age of the population. The disease can have significant health-related, social, and financial implications not only for the patient and the caregiver, but for the health care system as well. While the neuropathology of this neurodegenerative disorder is fairly well understood, its etiology remains a mystery, making it difficult to target therapy. The currently available drugs for treatment provide only symptomatic relief and do not control or prevent disease progression, and as a result patient compliance and satisfaction are low. Several emerging pharmacotherapies for PD are in different stages of clinical development. These therapies include adenosine A2A receptor antagonists, glutamate receptor antagonists, monoamine oxidase inhibitors, anti-apoptotic agents, and antioxidants such as coenzyme Q10, N-acetyl cysteine, and edaravone. Other emerging non-pharmacotherapies include viral vector gene therapy, microRNAs, transglutaminases, RTP801, stem cells and glial derived neurotrophic factor (GDNF). In addition, surgical procedures including deep brain stimulation, pallidotomy, thalamotomy and gamma knife surgery have emerged as alternative interventions for advanced PD patients who have completely utilized standard treatments and still suffer from persistent motor fluctuations. While several of these therapies hold much promise in delaying the onset of the disease and slowing its progression, more pharmacotherapies and surgical interventions need to be investigated in different stages of PD. It is hoped that these emerging therapies and surgical procedures will strengthen our clinical armamentarium for improved treatment of PD.

Association of glycogen synthase kinase-3β with Parkinson's disease (review)

Glycogen synthase kinase-3 (GSK-3) is a pleiotropic serine/threonine protein kinase found in almost all eukaryotes. It is structurally highly conserved and has been identified as a multifaceted enzyme affecting a wide range of biological functions, including gene expression and cellular processes. There are two closely related isoforms of GSK-3; GSK-3α and GSK-3β. The latter appears to play crucial roles in regulating the pathogenesis of diverse diseases, including neurodegenerative disease. The present review focuses on the involvement of this protein in Parkinson’s disease (PD), a common neurodegenerative disorder characterized by the gradually progressive and selective loss of dopaminergic neurons, and by intracellular inclusions known as Lewy bodies (LBs) expressed in surviving neurons of the substantia nigra (SN). GSK-3β is involved in multiple signaling pathways and has several phosphorylation targets. Numerous apoptotic conditions can be facilitated by the GSK-3β signaling pathways. Studies have shown that GSK-3β inhibition protects the dopaminergic neurons from various stress-induced injuries, indicating the involvement of GSK-3β in PD pathogenesis. However, the underlying mechanisms of the protective effect of GSK-3β inhibition on dopaminergic neurons in PD is not completely understood. Multiple pathological events have been recognized to be responsible for the loss of dopaminergic neurons in PD, including mitochondrial dysfunction, oxidative stress, protein aggregation and neuroinflammation. The present review stresses the regulatory roles of GSK-3β in these events and in dopaminergic neuron degeneration, in an attempt to gain an improved understanding of the underlying mechanisms and to provide a potential effective therapeutic target for PD.

Proteomics analysis of human brain tissue infected by street rabies virus

In order to extend the knowledge of rabies pathogenesis, a two-dimensional electrophoresis/mass spectrometry based postmortem comparative proteomics analysis was carried out on human brain samples. Alteration in expression profile of several proteins was detected. Proteins related to cytoskeleton, metabolism, proteasome and immune regulatory systems showed the most changes in expression levels. Among these groups, the cytoskeleton related proteins (dynein light chain, β-centractin, tubulin alpha-1C chain and destrin) and metabolism associated proteins (fatty acid-binding protein, macrophage migration inhibitory factor, glutamine synthetase and alpha enolase) were the main altered proteins. These alterations may be considered as an evidence of disturbances in neuronal key processes including axonal transport, synaptic activity, signaling and metabolic pathways in rabies virus infected human brain.

Radiating amyloid fibril formation on the surface of lipid membranes through unit-assembly of oligomeric species of α-synuclein

Background

Lewy body in the substantia nigra is a cardinal pathological feature of Parkinson's disease. Despite enormous efforts, the cause-and-effect relationship between Lewy body formation and the disorder is yet to be explicitly unveiled.

Methodology/Principal Findings

Here, we showed that radiating amyloid fibrils (RAFs) were instantly developed on the surface of synthetic lipid membranes from the β-sheet free oligomeric species of α-synuclein through a unit-assembly process. The burgeoning RAFs were successfully matured by feeding them with additional oligomers, which led to concomitant dramatic shrinkage and disintegration of the membranes by pulling off lipid molecules to the extending fibrils. Mitochondria and lysosomes were demonstrated to be disrupted by the oligomeric α-synuclein via membrane-dependent fibril formation.

Conclusion

The physical structure formation of amyloid fibrils, therefore, could be considered as detrimental to the cells by affecting membrane integrity of the intracellular organelles, which might be a molecular cause for the neuronal degeneration observed in Parkinson's disease.

Advancing neurotrophic factors as treatments for age-related neurodegenerative diseases: developing and demonstrating "clinical proof-of-concept" for AAV-neurturin (CERE-120) in Parkinson's disease

Neurotrophic factors have long shown promise as potential therapies for age-related neurodegenerative diseases. However, 20 years of largely disappointing clinical results have underscored the difficulties involved with safely and effectively delivering these proteins to targeted sites within the central nervous system. Recent progress establishes that gene transfer can now likely overcome the delivery issues plaguing the translation of neurotrophic factors. This may be best exemplified by adeno-associated virus serotype-2-neurturin (CERE-120), a viral-vector construct designed to deliver the neurotrophic factor, neurturin to degenerating nigrostriatal neurons in Parkinson's disease. Eighty Parkinson's subjects have been dosed with CERE-120 (some 7+ years ago), with long-term, targeted neurturin expression confirmed and no serious safety issues identified. A double-blind, controlled Phase 2a trial established clinical "proof-of-concept" via 19 of the 24 prescribed efficacy end points favoring CERE-120 at the 12-month protocol-prescribed time point and all but one favoring CERE-120 at the 18-month secondary time point (p = 0.007 and 0.001, respectively). Moreover, clinically meaningful benefit was seen with CERE-120 on several specific protocol-prescribed, pairwise, blinded, motor, and quality-of-life end points at 12 months, and an even greater number of end points at 18 months. Because the trial failed to meet the primary end point (Unified Parkinson's Disease Rating Scale motor-off, measured at 12 months), a revised multicenter Phase 1/2b protocol was designed to enhance the neurotrophic effects of CERE-120, using insight gained from the Phase 2a trial. This review summarizes the development of CERE-120 from its inception through establishing "clinical proof-of-concept" and beyond. The translational obstacles and issues confronted, and the strategies applied, are reviewed. This information should be informative to investigators interested in translational research and development for age-related and other neurodegenerative diseases.

The Aggregation of Huntingtin and α-Synuclein

Huntington's and Parkinson's diseases are neurodegenerative disorders associated with unusual protein interactions. Although the origin and evolution of these diseases are completely different, characteristic deposits of protein aggregates (huntingtin and α-synuclein resp.), are a common feature in both diseases. After these observations, many studies are performed with both proteins. Some of them try to understand the nature and driving forces of the aggregation process; others try to find a correlation between the genetic and failure in protein function. Finally with the combination of both approaches, it was proposed that possible strategies deal with pathologic aggregation. Unfortunately, if protein aggregation is a cause or a consequence of the neurodegeneration observed in these pathologies, it is still debatable. This paper describes the process of aggregation of two proteins: huntingtin and α synuclein. The characteristics of the aggregation reaction of these proteins have been followed with novel methods both in vivo and in vitro; these studies include both the combination with other proteins and the presence of various chemical compounds. The ultimate goal of this study was to summarize recent findings on protein aggregation and its possible role as a therapeutic target in neurodegenerative diseases and their role in biomaterial science.

NRSF/REST neuronal deficient mice are more vulnerable to the neurotoxin MPTP

Parkinson's disease (PD) is characterized by progressing loss of dopaminergic neurons in the midbrain. Abnormal gene expression plays a critical role in its pathogenesis. Neuron-restrictive silencer factor (NRSF)/neuronal repressor element-1 silencing transcription factor (REST), a member of the zinc finger transcription factors, inhibits the expression of neuron-specific genes in nonneuronal cells, and regulates neurogenesis. Our previous work showed that 1-methyl-4-phenyl-pyridinium ion triggers dynamic changes of messenger RNA and protein expression of NRSF in human dopaminergic SH-SY5Y cells, and alteration of NRSF expression exacerbates 1-methyl-4-phenyl-pyridinium ion-induced cell death. The purpose of this study was to explore the in vivo role of NRSF in the progress of PD by using NRSF/REST neuron-specific conditional knockout mice (cKO). 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was adopted to generate PD models in the cKO mice and wild type littermates. At 1, 3, 7, 14, 21, and 28 days after MPTP injection, behavioral tests were performed, and cKO mice displayed some impairments in locomotor activities. Also, the reduction of tyrosine hydroxylase protein in the striatum and the loss of dopaminergic neurons in the substantia nigra were more severe in the cKO mice. Meanwhile, the cKO mice exhibited a more dramatic depletion of striatal dopamine, accompanied by an increase in glial fibrillary acidic protein (GFAP) expression and sustained interleukin-1β transcription. These results suggested that NRSF/REST neuronal cKO mice are more vulnerable to the dopaminergic neurotoxin MPTP. Disturbance of the homeostasis of NRSF and its target genes, gliogenesis, and inflammation may contribute to the higher MPTP sensitivity in NRSF/REST neuronal cKO mice.

Hormone replacement therapy and risk for neurodegenerative diseases

Over the past two decades, there has been a significant amount of research investigating the risks and benefits of hormone replacement therapy (HRT) with regards to neurodegenerative disease. Here, we review basic science studies, randomized clinical trials, and epidemiological studies, and discuss the putative neuroprotective effects of HRT in the context of Alzheimer's disease, Parkinson's disease, frontotemporal dementia, and HIV-associated neurocognitive disorder. Findings to date suggest a reduced risk of Alzheimer's disease and improved cognitive functioning of postmenopausal women who use 17β-estradiol. With regards to Parkinson's disease, there is consistent evidence from basic science studies for a neuroprotective effect of 17β-estradiol; however, results of clinical and epidemiological studies are inconclusive at this time, and there is a paucity of research examining the association between HRT and Parkinson's-related neurocognitive impairment. Even less understood are the effects of HRT on risk for frontotemporal dementia and HIV-associated neurocognitive disorder. Limits to the existing research are discussed, along with proposed future directions for the investigation of HRT and neurodegenerative diseases.

A mechanistic study of proteasome inhibition-induced iron misregulation in dopamine neuron degeneration

Ubiquitin proteasome system (UPS) impairment and iron misregulation have been implicated in dopamine (DA) neuron degeneration in Parkinson's disease. As previously shown, proteasome inhibition in a rodent model can cause nigral neuron degeneration accompanied by iron accumulation. To investigate the involvement of iron in DA neuron degeneration, we generated an in vitro model by applying proteasome inhibitor lactacystin in DAergic cell line MES23.5 culture. We found that lactacystin caused marked increase in labile iron, reactive oxygen species and ubiquitin-conjugated protein aggregation prior to cell injury. These effects were attenuated by iron chelators or antioxidants. Furthermore, we demonstrated that the iron regulatory protein (IRP)/iron response element system contributed to UPS impairment-mediated DA neuron injury. We documented that IRP2 disruption resulted in an increase in transferrin receptor 1 (TfR1), a decrease in ferritin heavy chain (H-Frt), and eventually cell death. These findings provide insight into the mechanistic interplay between UPS impairment and iron misregulation and suggest that the disturbances in IRP2, TfR1 and H-Frt may contribute to DA neuron degeneration.