Genetics of Parkinson disease

Impacts of gait freeze on quality of life in Parkinson's disease, from the perspectives of patients and their carers

BACKGROUND

The World Health Organisation (WHO) reports that morbidity and mortality due to Parkinson's disease (PD) are increasing faster than for other neurodegenerative conditions. People with Parkinson's (PwP) present with a variety of motor symptoms, such as tremor, bradykinesia, and rigidity. Freezing of gait (FoG) is a significant motor symptom that manifests as temporary episodes of inability to move one's feet, despite the intention to walk.

AIMS

This study examined the impact of FoG on quality of life (QoL) within an Irish cohort of PwP, from the perspectives of both PwP and their carers, using validated questionnaires that had been adapted for online use.

METHODS

PwP and their carers were recruited by outreach to the Irish Parkinson's Community. Anonymous online questionnaires were distributed, which combined a demographic survey with several clinically validated surveys, including Freezing of Gait Questionnaire (FoG-Q), Parkinson's Disease Questionnaire 8 (PDQ-8), and Parkinson's Disease Carer Questionnaire (PDQ-C).

RESULTS

There was a strong correlation (p < 0.001) between severity of FoG and lower QoL among PwP. Significant correlation was also found between FoG severity and several motor symptoms, such as postural instability and difficulty with balance, and non-motor symptoms, such as cognitive changes and pain/discomfort. FoG severity correlated with disease progression. Significant correlation was also found between FoG and symptoms, as assessed from the perspective of the patients' carers.

CONCLUSIONS

This study shows that FoG is a significant detriment to the QoL of PwP, from the perspectives of patients and carers. This method of assessing FoG and QoL using online questionnaires has potential to enhance the reach and flexibility of this type of research. These findings will inform future studies on larger cohorts and highlight unmet clinical needs in PwP.

Short-term lipopolysaccharide treatment leads to astrocyte activation in LRRK2 G2019S knock-in mice without loss of dopaminergic neurons

Background

The G2019S mutation of LRRK2, which enhances kinase activity of the protein, confers a substantial risk of developing Parkinson's disease (PD). However, the mutation demonstrates incomplete penetrance, suggesting the involvement of other genetic or environmental modulating factors. Here, we investigated whether LRRK2 G2019S knock-in (KI) mice treated with the inflammogen lipopolysaccharide (LPS) could model LRRK2 PD.

Results

We found that short-term (2 weeks) treatment with LPS did not result in the loss of dopaminergic neurons in either LRRK2 G2019S KI or wild-type (WT) mice. Compared with WT mice, LRRK2 G2019S-KI mice showed incomplete recovery from LPS-induced weight loss. In LRRK2 G2019S KI mice, LPS treatment led to upregulated phosphorylation of LRRK2 at the autophosphorylation site Serine 1292, which is known as a direct readout of LRRK2 kinase activity. LPS treatment caused a greater increase in the activated astrocyte marker glial fibrillary acidic protein (GFAP) in the striatum and substantia nigra of LRRK2 G2019S mice than in those of WT mice. The administration of caffeine, which was recently identified as a biomarker of resistance to developing PD in individuals with LRRK2 mutations, attenuated LPS-induced astrocyte activation specifically in LRRK2 G2019S KI mice.

Conclusions

Our findings suggest that 2 weeks of exposure to LPS is not sufficient to cause dopaminergic neuronal loss in LRRK2 G2019S KI mice but rather results in increased astrocyte activation, which can be ameliorated by caffeine.

Design, Synthesis and In Vitro Evaluation of Levodopa Stearic Acid Hydrazide Conjugate for the Management of Parkinson's DiseaseNovel Conjugate for Parkinson's Disease

Parkinson's disease is the highest prevalent neurodegenerative disease in elderly individuals after Alzheimer's disease. The pathological identification for Parkinson's disease is loss of dopaminergic neurons in substantia nigra region of the brain that in turn leads to dopamine deficiency that affects the body's normal physiological and neurological disorder. The important drawback in the modality of treatment is levodopa is only supplying depleted dopamine in the brain, it does not affect neurodegeneration. Even though levodopa manages the disease, an alternative treatment strategy is required to stop or prevent further degeneration of neuron. The compound with neuroprotector activity suits the requirement. Of them, stearic acid plays a vital role in protecting neurons against oxidative stress through a Phosphoinositide 3-kinase-dependent mechanism. Hence, our present study aimed to design, synthesize, and characterize the levodopa stearic acid hydrazide conjugate. Additionally, evaluate the cytotoxicity of synthesized compound in SHSY5Y: cell lines. In brief, levodopa was conjugated to the stearic acid successfully and was confirmed with Fourier-transform infrared spectroscopy, Nuclear magnetic resonance, and Mass Spectroscopy. In vitro cell viability study in SHSY5Y: cell lines showed elevated cell viability in 0.134 µm concentration of Conjugate, and 0.563 µm concentration of levodopa. Showing that the synthesized compound could offer an improved treatment strategy for Parkinson's disease.

Parkinson's Disease is Predominantly a Genetic Disease

The discovery of a pathogenic variant in the alpha-synuclein (SNCA) gene in the Contursi kindred in 1997 indisputably confirmed a genetic cause in a subset of Parkinson's disease (PD) patients. Currently, pathogenic variants in one of the seven established PD genes or the strongest known risk factor gene, GBA1, are identified in ∼15% of PD patients unselected for age at onset and family history. In this Debate article, we highlight multiple avenues of research that suggest an important - and in some cases even predominant - role for genetics in PD aetiology, including familial clustering, high rates of monogenic PD in selected populations, and complete penetrance with certain forms. At first sight, the steep increase in PD prevalence exceeding that of other neurodegenerative diseases may argue against a predominant genetic etiology. Notably, the principal genetic contribution in PD is conferred by pathogenic variants in LRRK2 and GBA1 and, in both cases, characterized by an overall late age of onset and age-related penetrance. In addition, polygenic risk plays a considerable role in PD. However, it is likely that, in the majority of PD patients, a complex interplay of aging, genetic, environmental, and epigenetic factors leads to disease development.

Parkinson's Disease: Advances in Treatment and the Syntheses of Various Classes of Pharmaceutical Drug Substances

An overview of Parkinson's disease (PD) prevalence, diagnosis, and currently available treatment options is provided. A comprehensive list of different classes of marketed pharmaceutical drug products and the syntheses of various drug substances are summarized based on published literature.

Exploring the Therapeutic Effects of Multifunctional N-Salicylic Acid Tryptamine Derivative against Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide. Neuroinflammation and oxidative stress play an important role in the whole course of PD, which have been the focus of PD drug development. In our previous research, a series of N-salicylic acid tryptamine derivatives were synthesized, and the biological evaluation showed that the compound LZWL02003 has good anti-neuroinflammatory activity and displayed great therapeutic potency for neurodegenerative disease models. In this work, the neuroprotective efficiency of LZWL02003 against PD in vitro and in vivo has been explored. It was found that LZWL02003 could protect human neuron cells SH-SY5Y from MPP+-induced neuronal damage by inhibiting ROS generation, mitochondrial dysfunction, and cellular apoptosis. Moreover, LZWL02003 could improve cognition, memory, learning, and athletic ability in a rotenone-induced PD rat model. In general, our study has demonstrated that LZWL02003 has good activity against PD in in vitro and in vivo experiments, which can potentially be developed into a therapeutic candidate for PD.

Lewy bodies, iron, inflammation and neuromelanin: pathological aspects underlying Parkinson's disease

Since the description of some peculiar symptoms by James Parkinson in 1817, attempts have been made to define its cause or at least to enlighten the pathology of "Parkinson's disease (PD)." The vast majority of PD subtypes and most cases of sporadic PD share Lewy bodies (LBs) as a characteristic pathological hallmark. However, the processes underlying LBs generation and its causal triggers are still unknown. ɑ-Synuclein (ɑ-syn, encoded by the SNCA gene) is a major component of LBs, and SNCA missense mutations or duplications/triplications are causal for rare hereditary forms of PD. Thus, it is imperative to study ɑ-syn protein and its pathology, including oligomerization, fibril formation, aggregation, and spreading mechanisms. Furthermore, there are synergistic effects in the underlying pathogenic mechanisms of PD, and multiple factors-contributing with different ratios-appear to be causal pathological triggers and progression factors. For example, oxidative stress, reduced antioxidative capacity, mitochondrial dysfunction, and proteasomal disturbances have each been suggested to be causal for ɑ-syn fibril formation and aggregation and to contribute to neuroinflammation and neural cell death. Aging is also a major risk factor for PD. Iron, as well as neuromelanin (NM), show age-dependent increases, and iron is significantly increased in the Parkinsonian substantia nigra (SN). Iron-induced pathological mechanisms include changes of the molecular structure of ɑ-syn. However, more recent PD research demonstrates that (i) LBs are detected not only in dopaminergic neurons and glia but in various neurotransmitter systems, (ii) sympathetic nerve fibres degenerate first, and (iii) at least in "brain-first" cases dopaminergic deficiency is evident before pathology induced by iron and NM. These recent findings support that the ɑ-syn/LBs pathology as well as iron- and NM-induced pathology in "brain-first" cases are important facts of PD pathology and via their interaction potentiate the disease process in the SN. As such, multifactorial toxic processes posted on a personal genetic risk are assumed to be causal for the neurodegenerative processes underlying PD. Differences in ratios of multiple factors and their spatiotemporal development, and the fact that common triggers of PD are hard to identify, imply the existence of several phenotypical subtypes, which is supported by arguments from both the "bottom-up/dual-hit" and "brain-first" models. Therapeutic strategies are necessary to avoid single initiation triggers leading to PD.

Role of rodent models in advancing precision medicine for Parkinson's disease

With a current lack of disease-modifying treatments, an initiative toward implementing a precision medicine approach for treating Parkinson's disease (PD) has emerged. However, challenges remain in how to define and apply precision medicine in PD. To accomplish the goal of optimally targeted and timed treatment for each patient, preclinical research in a diverse population of rodent models will continue to be an essential part of the translational path to identify novel biomarkers for patient diagnosis and subgrouping, understand PD disease mechanisms, identify new therapeutic targets, and screen therapeutics prior to clinical testing. This review highlights the most common rodent models of PD and discusses how these models can contribute to defining and implementing precision medicine for the treatment of PD.

A homozygous PRKN-associated juvenile Parkinson's disease with pregnancy in China

Background

Although Parkinson's disease (PD) is the second most common neurodegenerative disorder, pregnancy in patients with PD is a relatively rare occurrence because the most common age of onset of PD is beyond the childbearing age, except in patients with Young-Onset PD (YOPD) caused by parkin RBR E3 ubiquitin protein ligase (PRKN) mutations.

Case

In this study, we report the case of a 30-year-old Chinese woman who was affected by PRKN-associated YOPD and was treated with levodopa/benserazide during pregnancy. She gave birth to a healthy baby boy with an Apgar score of 9 through an uncomplicated vaginal delivery.

Conclusion

This case further suggests that levodopa/benserazide during pregnancy is safe in the treatment of PRKN-associated YOPD.

Cell Biology of Parkin: Clues to the Development of New Therapeutics for Parkinson's Disease

Parkinson's disease is the second most prevalent neurodegenerative disease and contributes significantly to morbidity globally. Currently, no disease-modifying therapies exist to combat this disorder. Insights from the molecular and cellular pathobiology of the disease seems to indicate promising therapeutic targets. The parkin protein has been extensively studied for its role in autosomal recessive Parkinson's disease and, more recently, its role in sporadic Parkinson's disease. Parkin is an E3 ubiquitin ligase that plays a prominent role in mitochondrial quality control, mitochondrial-dependent cell death pathways, and other diverse functions. Understanding the numerous roles of parkin has introduced many new possibilities for therapeutic modalities in treating both autosomal recessive Parkinson's disease and sporadic Parkinson's disease. In this article, we review parkin biology with an emphasis on mitochondrial-related functions and propose novel, potentially disease-modifying therapeutic approaches for treating this debilitating condition.

Human Induced Pluripotent Stem Cell Phenotyping and Preclinical Modeling of Familial Parkinson's Disease

Parkinson's disease (PD) is primarily idiopathic and a highly heterogenous neurodegenerative disease with patients experiencing a wide array of motor and non-motor symptoms. A major challenge for understanding susceptibility to PD is to determine the genetic and environmental factors that influence the mechanisms underlying the variations in disease-associated traits. The pathological hallmark of PD is the degeneration of dopaminergic neurons in the substantia nigra pars compacta region of the brain and post-mortem Lewy pathology, which leads to the loss of projecting axons innervating the striatum and to impaired motor and cognitive functions. While the cause of PD is still largely unknown, genome-wide association studies provide evidence that numerous polymorphic variants in various genes contribute to sporadic PD, and 10 to 15% of all cases are linked to some form of hereditary mutations, either autosomal dominant or recessive. Among the most common mutations observed in PD patients are in the genes LRRK2, SNCA, GBA1, PINK1, PRKN, and PARK7/DJ-1. In this review, we cover these PD-related mutations, the use of induced pluripotent stem cells as a disease in a dish model, and genetic animal models to better understand the diversity in the pathogenesis and long-term outcomes seen in PD patients.

Alternative Splicing and Hypoxia Puzzle in Alzheimer's and Parkinson's Diseases

Alternative pre-mRNA splicing plays a very important role in expanding protein diversity as it generates numerous transcripts from a single protein-coding gene. Therefore, alterations lead this process to neurological human disorders, including Alzheimer’s and Parkinson’s diseases. Moreover, accumulating evidence indicates that the splicing machinery highly contributes to the cells’ ability to adapt to different altered cellular microenvironments, such as hypoxia. Hypoxia is known to have an effect on the expression of proteins involved in a multiple of biological processes, such as erythropoiesis, angiogenesis, and neurogenesis, and is one of the important risk factors in neuropathogenesis. In this review, we discuss the current knowledge of alternatively spliced genes, which, as it is reported, are associated with Alzheimer’s and Parkinson’s diseases. Additionally, we highlight the possible influence of cellular hypoxic microenvironment for the formation of mRNA isoforms contributing to the development of these neurodegenerative diseases.

Parkinson's Disease: A Prionopathy?

The principal pathogenic event in Parkinson's disease is characterized by the conformational change of α-synuclein, which form pathological aggregates of misfolded proteins, and then accumulate in intraneuronal inclusions causing dopaminergic neuronal loss in specific brain regions. Over the last few years, a revolutionary theory has correlated Parkinson's disease and other neurological disorders with a shared mechanism, which determines α-synuclein aggregates and progresses in the host in a prion-like manner. In this review, the main characteristics shared between α-synuclein and prion protein are compared and the cofactors that influence the remodeling of native protein structures and pathogenetic mechanisms underlying neurodegeneration are discussed.

Alpha-Synuclein as a Biomarker of Parkinson's Disease: Good, but Not Good Enough

Parkinson's disease (PD) is the second most common neurodegenerative disorder of the elderly, presenting primarily with symptoms of motor impairment. The disease is diagnosed most commonly by clinical examination with a great degree of accuracy in specialized centers. However, in some cases, non-classical presentations occur when it may be difficult to distinguish the disease from other types of degenerative or non-degenerative movement disorders with overlapping symptoms. The diagnostic difficulty may also arise in patients at the early stage of PD. Thus, a biomarker could help clinicians circumvent such problems and help them monitor the improvement in disease pathology during anti-parkinsonian drug trials. This review first provides a brief overview of PD, emphasizing, in the process, the important role of α-synuclein in the pathogenesis of the disease. Various attempts made by the researchers to develop imaging, genetic, and various biochemical biomarkers for PD are then briefly reviewed to point out the absence of a definitive biomarker for this disorder. In view of the overwhelming importance of α-synuclein in the pathogenesis, a detailed analysis is then made of various studies to establish the biomarker potential of this protein in PD; these studies measured total α-synuclein, oligomeric, and post-translationally modified forms of α-synuclein in cerebrospinal fluid, blood (plasma, serum, erythrocytes, and circulating neuron-specific extracellular vesicles) and saliva in combination with certain other proteins. Multiple studies also examined the accumulation of α-synuclein in various forms in PD in the neural elements in the gut, submandibular glands, skin, and the retina. The measurements of the levels of certain forms of α-synuclein in some of these body fluids or their components or peripheral tissues hold a significant promise in establishing α-synuclein as a definitive biomarker for PD. However, many methodological issues related to detection and quantification of α-synuclein have to be resolved, and larger cross-sectional and follow-up studies with controls and patients of PD, parkinsonian disorders, and non-parkinsonian movement disorders are to be undertaken.

α-Synuclein Strains: Does Amyloid Conformation Explain the Heterogeneity of Synucleinopathies?

Synucleinopathies are a heterogeneous group of neurodegenerative diseases with amyloid deposits that contain the α-synuclein (SNCA/α-Syn) protein as a common hallmark. It is astonishing that aggregates of a single protein are able to give rise to a whole range of different disease manifestations. The prion strain hypothesis offers a possible explanation for this conundrum. According to this hypothesis, a single protein sequence is able to misfold into distinct amyloid structures that can cause different pathologies. In fact, a growing body of evidence suggests that conformationally distinct α-Syn assemblies might be the causative agents behind different synucleinopathies. In this review, we provide an overview of research on the strain hypothesis as it applies to synucleinopathies and discuss the potential implications for diagnostic and therapeutic purposes.

The dysregulated Pink1- Drosophila mitochondrial proteome is partially corrected with exercise

One of the genes which has been linked to the onset of juvenile/early onset Parkinson’s disease (PD) is PINK1. There is evidence that supports the therapeutic potential of exercise in the alleviation of PD symptoms. It is possible that exercise may enhance synaptic plasticity, protect against neuro-inflammation and modulate L-Dopa regulated signalling pathways. We explored the effects of exercise on Pink1 deficient Drosophila melanogaster which undergo neurodegeneration and muscle degeneration. We used a ‘power-tower’ type exercise platform to deliver exercise activity to Pink1^- and age matched wild-type Drosophila. Mitochondrial proteomic profiles responding to exercise were obtained. Of the 516 proteins identified, 105 proteins had different levels between Pink1^- and wild-type non-exercised Drosophila. Gene ontology enrichment analysis and STRING network analysis highlighted proteins and pathways with altered expression within the mitochondrial proteome. Comparison of the Pink1^- exercised proteome to wild-type proteomes showed that exercising the Pink1^- Drosophila caused their proteomic profile to return towards wild-type levels.

Modelling Parkinson's Disease: iPSCs towards Better Understanding of Human Pathology

Parkinson’s Disease (PD) is a chronic neurodegenerative disorder characterized by motor and non-motor symptoms, among which are bradykinesia, rigidity, tremor as well as mental symptoms such as dementia. The underlying cause of Parkinson disease is degeneration of dopaminergic neurons. It has been challenging to develop an efficient animal model to accurately represent the complex phenotypes found with PD. However, it has become possible to recapitulate the myriad of phenotypes underlying the PD pathology by using human induced pluripotent stem cell (iPSC) technology. Patient-specific iPSC-derived dopaminergic neurons are available and present an opportunity to study many aspects of the PD phenotypes in a dish. In this review, we report the available data on iPSC-derived neurons derived from PD patients with identified gene mutations. Specifically, we will report on the key phenotypes of the generated iPSC-derived neurons from PD patients with different genetic background. Furthermore, we discuss the relationship these cellular phenotypes have to PD pathology and future challenges and prospects for iPSC modelling and understanding of the pathogenesis of PD.

Membrane Interactions of α-Synuclein Probed by Neutrons and Photons

α-Synuclein (α-syn) is a key protein in the etiology of Parkinson's disease. In a disease state, α-syn accumulates as insoluble amyloid fibrils enriched in β-sheet structure. However, in its functional state, α-syn adopts an amphipathic helix upon membrane association and plays a role in synaptic vesicle docking, fusion, and clustering. In this Account, we describe our contributions made in the past decade toward developing a molecular understanding of α-syn membrane interactions, which are crucial for function and have pathological implications. Three topics are covered: α-syn membrane binding probed by neutron reflectometry (NR), the effects of membrane on α-syn amyloid formation, and interactions of α-syn with cellular membranes.NR offers a unique perspective by providing direct measurements of protein penetration depth. By the use of segmentally deuterated α-syn generated through native chemical ligation, the spatial resolution of specific membrane-bound polypeptide regions was determined by NR. Additionally, we used NR to characterize the membrane-bound complex of α-syn and glucocerebrosidase, a lysosomal hydrolase whose mutations are a common genetic risk factor for Parkinson's disease. Although phosphatidylcholine (PC) is the most abundant lipid species in mammalian cells, interactions of PC with α-syn have been largely ignored because they are substantially weaker compared with the electrostatically driven binding of negatively charged lipids. We discovered that α-syn tubulates zwitterionic PC membranes, which is likely related to its involvement in synaptic vesicle fusion by stabilization of membrane curvature. Interestingly, PC lipid tubules inhibit amyloid formation, in contrast to anionic phosphatidylglycerol lipid tubules, which stimulate protein aggregation. We also found that membrane fluidity influences the propensity of α-synuclein amyloid formation. Most recently, we obtained direct evidence of binding of α-syn to exocytic sites on intact cellular membranes using a method called cellular unroofing. This method provides direct access to the cytosolic plasma membrane. Importantly, measurements of fluorescence lifetime distributions revealed that α-syn is more conformationally dynamic at the membrane interface than previously appreciated. This exquisite responsiveness to specific lipid composition and membrane topology is important for both its physiological and pathological functions. Collectively, our work has provided insights into the effects of the chemical nature of phospholipid headgroups on the interplay among membrane remodeling, protein structure, and α-syn amyloid formation.

MMP13 Expression Is Increased Following Mutant α-Synuclein Exposure and Promotes Inflammatory Responses in Microglia

α-Synuclein is a 140-amino acid protein that readily misfolds and is associated with the Lewy body pathology found in sporadic and genetic forms of Parkinson's disease. We and others have shown that wild-type α-synuclein is a damage-associated molecular pattern that directly elicits a proinflammatory response in microglia through toll-like receptor activation. Here we investigated the direct effect of oligomeric mutant α-synuclein (A53T) on microglia morphology and activation. We found that misfolded A53T increased quantitative measures of amoeboid cell morphology, NFκB nuclear translocation and the expression of prototypical proinflammatory molecules. We also demonstrated that A53T increased expression of MMP13, a matrix metalloproteinase that remodels the extracellular matrix. To better understand the role of MMP13 in synucleinopathies, we further characterized the role of MMP13 in microglial signaling. We showed exposure of microglia to MMP13 induced a change in morphology and promoted the release of TNFα and MMP9. Notably, IL1β was not released indicating that the pathway involved in MMP13 activation of microglia may be different than the A53T pathway. Lastly, MMP13 increased the expression of CD68 suggesting that the lysosomal pathway might be altered by this MMP. Taken together this study shows that mutant α-synuclein directly induces a proinflammatory phenotype in microglia, which includes the expression of MMP13. In turn, MMP13 directly alters microglia supporting the need for multi-target therapies to treat Parkinson's disease patients.

Neuronal activity modulates alpha-synuclein aggregation and spreading in organotypic brain slice cultures and in vivo

Alpha-synuclein (αSyn) preformed fibrils (PFF) induce endogenous αSyn aggregation leading to reduced synaptic transmission. Neuronal activity modulates release of αSyn; however, whether neuronal activity regulates the spreading of αSyn pathology remains elusive. Here, we established a hippocampal slice culture system from wild-type (WT) mice and found that both Ca²⁺ influx and the uptake of αSyn PFF were higher in the CA3 than in the CA1 sub-region. Pharmacologically enhancing neuronal activity substantially increased αSyn pathology in αSyn PFF-treated hippocampal or midbrain slice cultures and accelerated dopaminergic neuron degeneration. Consistently, neuronal hyperactivity promoted PFF trafficking along axons/dendrites within microfluidic chambers. Unexpectedly, enhancing neuronal activity in LRRK2 G2019S mutant slice cultures further increased αSyn pathology, especially with more Lewy body (LB) forming than in WT slice cultures. Finally, following injection of αSyn PFF and chemogenetic modulators into the dorsal striatum of WT mice, both motor behavior and αSyn pathology were exacerbated likely by enhancing neuronal activity, since they were ameliorated by reducing neuronal activity. Thus, a greater understanding of the impact of neuronal activity on αSyn aggregation and spreading, as well as dopaminergic neuronal vulnerability, may provide new therapeutic strategies for patients with LB disease (LBD).

Multiplicity of α-Synuclein Aggregated Species and Their Possible Roles in Disease

α-Synuclein amyloid aggregation is a defining molecular feature of Parkinson's disease, Lewy body dementia, and multiple system atrophy, but can also be found in other neurodegenerative disorders such as Alzheimer's disease. The process of α-synuclein aggregation can be initiated through alternative nucleation mechanisms and dominated by different secondary processes giving rise to multiple amyloid polymorphs and intermediate species. Some aggregated species have more inherent abilities to induce cellular stress and toxicity, while others seem to be more potent in propagating neurodegeneration. The preference for particular types of polymorphs depends on the solution conditions and the cellular microenvironment that the protein encounters, which is likely related to the distinct cellular locations of α-synuclein inclusions in different synucleinopathies, and the existence of disease-specific amyloid polymorphs. In this review, we discuss our current understanding on the nature and structure of the various types of α-synuclein aggregated species and their possible roles in pathology. Precisely defining these distinct α-synuclein species will contribute to understanding the molecular origins of these disorders, developing accurate diagnoses, and designing effective therapeutic interventions for these highly debilitating neurodegenerative diseases.

Behavioral Tests in Neurotoxin-Induced Animal Models of Parkinson's Disease

Currently, neurodegenerative diseases are a major cause of disability around the world. Parkinson's disease (PD) is the second-leading cause of neurodegenerative disorder after Alzheimer's disease. In PD, continuous loss of dopaminergic neurons in the substantia nigra causes dopamine depletion in the striatum, promotes the primary motor symptoms of resting tremor, bradykinesia, muscle rigidity, and postural instability. The risk factors of PD comprise environmental toxins, drugs, pesticides, brain microtrauma, focal cerebrovascular injury, aging, and hereditary defects. The pathologic features of PD include impaired protein homeostasis, mitochondrial dysfunction, nitric oxide, and neuroinflammation, but the interaction of these factors contributing to PD is not fully understood. In neurotoxin-induced PD models, neurotoxins, for instance, 6-hydroxydopamine (6-OHDA), 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 1-Methyl-4-phenylpyridinium (MPP+), paraquat, rotenone, and permethrin mainly impair the mitochondrial respiratory chain, activate microglia, and generate reactive oxygen species to induce autooxidation and dopaminergic neuronal apoptosis. Since no current treatment can cure PD, using a suitable PD animal model to evaluate PD motor symptoms' treatment efficacy and identify therapeutic targets and drugs are still needed. Hence, the present review focuses on the latest scientific developments in different neurotoxin-induced PD animal models with their mechanisms of pathogenesis and evaluation methods of PD motor symptoms.

Classification algorithms applied to blood-based transcriptome meta-analysis to predict idiopathic Parkinson's disease

Diagnosis of Parkinson's disease (PD) remains a challenge in clinical practice, mostly due to lack of peripheral blood markers. Transcriptomic analysis of blood samples has emerged as a potential means to identify biomarkers and gene signatures of PD. In this context, classification algorithms can assist in detecting data patterns such as phenotypes and transcriptional signatures with potential diagnostic application. In this study, we performed gene expression meta-analysis of blood transcriptome from PD and control patients in order to identify a gene-set capable of predicting PD using classification algorithms. We examined microarray data from public repositories and, after systematic review, 4 independent cohorts (GSE6613, GSE57475, GSE72267 and GSE99039) comprising 711 samples (388 idiopathic PD and 323 healthy individuals) were selected. Initially, analysis of differentially expressed genes resulted in minimal overlap among datasets. To circumvent this, we carried out meta-analysis of 17,712 genes across datasets, and calculated weighted mean Hedges' g effect sizes. From the top-100- positive and negative gene effect sizes, algorithms of collinearity recognition and recursive feature elimination were used to generate a 59-gene signature of idiopathic PD. This signature was evaluated by 9 classification algorithms and 4 sample size-adjusted training groups to create 36 models. Of these, 33 showed accuracy higher than the non-information rate, and 2 models built on Support Vector Machine Regression bestowed best accuracy to predict PD and healthy control samples. In summary, the gene meta-analysis followed by machine learning methodology employed herein identified a gene-set capable of accurately predicting idiopathic PD in blood samples.

Redox Post-translational Modifications of Protein Thiols in Brain Aging and Neurodegenerative Conditions-Focus on S-Nitrosation

Reactive oxygen species and reactive nitrogen species (RONS) are by-products of aerobic metabolism. RONS trigger a signaling cascade that can be transduced through oxidation-reduction (redox)-based post-translational modifications (redox PTMs) of protein thiols. This redox signaling is essential for normal cellular physiology and coordinately regulates the function of redox-sensitive proteins. It plays a particularly important role in the brain, which is a major producer of RONS. Aberrant redox PTMs of protein thiols can impair protein function and are associated with several diseases. This mini review article aims to evaluate the role of redox PTMs of protein thiols, in particular S-nitrosation, in brain aging, and in neurodegenerative diseases. It also discusses the potential of using redox-based therapeutic approaches for neurodegenerative conditions.

The Maintenance of Mitochondrial DNA Integrity and Dynamics by Mitochondrial Membranes

Mitochondria are complex organelles that harbour their own genome. Mitochondrial DNA (mtDNA) exists in the form of a circular double-stranded DNA molecule that must be replicated, segregated and distributed around the mitochondrial network. Human cells typically possess between a few hundred and several thousand copies of the mitochondrial genome, located within the mitochondrial matrix in close association with the cristae ultrastructure. The organisation of mtDNA around the mitochondrial network requires mitochondria to be dynamic and undergo both fission and fusion events in coordination with the modulation of cristae architecture. The dysregulation of these processes has profound effects upon mtDNA replication, manifesting as a loss of mtDNA integrity and copy number, and upon the subsequent distribution of mtDNA around the mitochondrial network. Mutations within genes involved in mitochondrial dynamics or cristae modulation cause a wide range of neurological disorders frequently associated with defects in mtDNA maintenance. This review aims to provide an understanding of the biological mechanisms that link mitochondrial dynamics and mtDNA integrity, as well as examine the interplay that occurs between mtDNA, mitochondrial dynamics and cristae structure.

Mutated ATP10B increases Parkinson's disease risk by compromising lysosomal glucosylceramide export

Parkinson’s disease (PD) is a progressive neurodegenerative brain disease presenting with a variety of motor and non-motor symptoms, loss of midbrain dopaminergic neurons in the substantia nigra pars compacta and the occurrence of α-synuclein-positive Lewy bodies in surviving neurons. Here, we performed whole exome sequencing in 52 early-onset PD patients and identified 3 carriers of compound heterozygous mutations in the ATP10B P4-type ATPase gene. Genetic screening of a Belgian PD and dementia with Lewy bodies (DLB) cohort identified 4 additional compound heterozygous mutation carriers (6/617 PD patients, 0.97%; 1/226 DLB patients, 0.44%). We established that ATP10B encodes a late endo-lysosomal lipid flippase that translocates the lipids glucosylceramide (GluCer) and phosphatidylcholine (PC) towards the cytosolic membrane leaflet. The PD associated ATP10B mutants are catalytically inactive and fail to provide cellular protection against the environmental PD risk factors rotenone and manganese. In isolated cortical neurons, loss of ATP10B leads to general lysosomal dysfunction and cell death. Impaired lysosomal functionality and integrity is well known to be implicated in PD pathology and linked to multiple causal PD genes and genetic risk factors. Our results indicate that recessive loss of function mutations in ATP10B increase risk for PD by disturbed lysosomal export of GluCer and PC. Both ATP10B and glucocerebrosidase 1, encoded by the PD risk gene GBA1, reduce lysosomal GluCer levels, emerging lysosomal GluCer accumulation as a potential PD driver.

Juvenile Parkinsonism with PARK2 Gene Mutation Misdiagnosed as Dopa-responsive Dystonia: a Case Report

Parkinson's disease is prevalent in elderly patients, usually aged over 50 years. If clinical symptoms of parkinsonism appear before 21 years of age, it is called juvenile parkinsonism (JP). JP may present atypical features such as dystonia, and is often misdiagnosed as other diseases, including dopa-responsive dystonia (DRD). Here, we report a case of JP with PARK2 mutation misdiagnosed as DRD. A 32-year old female, who presented dystonia of both legs, was initially diagnosed with hereditary spastic paraplegia and showed a dramatic response to low-dose L-dopa, which led to the diagnosis of DRD. However, Parkinson's disease caused by a mutation in the PARK2 gene was later diagnosed via next-generation sequencing. Accurate understanding of JP is necessary for early diagnosis and comprehensive management of movement disorders at a young age.

Long-Term Exposure to PFE-360 in the AAV-α-Synuclein Rat Model: Findings and Implications

Parkinson's disease (PD) is a progressive neurodegenerative disorder associated with impaired motor function and several non-motor symptoms, with no available disease modifying treatment. Intracellular accumulation of pathological α-synuclein inclusions is a hallmark of idiopathic PD, whereas, dominant mutations in leucine-rich repeat kinase 2 (LRRK2) are associated with familial PD that is clinically indistinguishable from idiopathic PD. Recent evidence supports the hypothesis that an increase in LRRK2 kinase activity is associated with the development of not only familial LRRK2 PD, but also idiopathic PD. Previous reports have shown preclinical effects of LRRK2 modulation on α-synuclein-induced neuropathology. Increased subthalamic nucleus (STN) burst firing in preclinical neurotoxin models and PD patients is hypothesized to be causally involved in the development of the motor deficit in PD. To study a potential pathophysiological relationship between α-synuclein pathology and LRRK2 kinase activity in PD, we investigated the effect of chronic LRRK2 inhibition in an AAV-α-synuclein overexpression rat model. In this study, we report that chronic LRRK2 inhibition using PFE-360 only induced a marginal effect on motor function. In addition, the aberrant STN burst firing and associated neurodegenerative processes induced by α-synuclein overexpression model remained unaffected by chronic LRRK2 inhibition. Our findings do not strongly support LRRK2 inhibition for the treatment of PD. Therefore, the reported beneficial effects of LRRK2 inhibition in similar α-synuclein overexpression rodent models must be considered with prudence and additional studies are warranted in alternative α-synuclein-based models.

Gene-by-environment interactions in Alzheimer's disease and Parkinson's disease

Diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) arise from complex interactions of genetic and environmental factors, with genetic variants regulating individual responses to environmental exposures (i.e. gene-by-environment interactions). Identifying gene-by-environment interactions will be critical to fully understanding disease mechanisms and developing personalized therapeutics, though these interactions are still poorly understood and largely under-studied. Candidate gene approaches have shown that known disease risk variants often regulate response to environmental factors. However, recent improvements in exposome- and genome-wide association and interaction studies in humans and mice are enabling discovery of novel genetic variants and pathways that predict response to a variety of environmental factors. Here, we highlight recent approaches and ongoing developments in human and rodent studies to identify genetic modulators of environmental factors using AD and PD as exemplars. Identifying gene-by-environment interactions in disease will be critical to developing personalized intervention strategies and will pave the way for precision medicine.

Impact of gene mutation in the development of Parkinson's disease

Parkinson's disease (PD) is the second most common age related neurodegenerative disorder worldwide and presents as a progressive movement disorder. Globally seven million to 10 million people have Parkinson's disease. Parkinsonism is typically sporadic in nature. Loss of dopaminergic neurons from substantia nigra pars compacta (SNpc) and the neuronal intracellular Lewy body inclusions are the major cause of PD. Gene mutation and protein aggregation play a pivotal role in the degeneration of dopamine neurons. But the actual cause of dopamine degeneration remains unknown. However, several rare familial forms of PD are associated with genetic loci, and the recognition of causal mutations has provided insight into the disease process. Yet, the molecular pathways and gene transformation that trigger neuronal susceptibility are inadequately comprehended. The discovery of a mutation in new genes has provided a basis for much of the ongoing molecular work in the PD field and testing of targeted therapeutics. Single gene mutation in a dominantly or recessively inherited gene results a great impact in the development of Parkinson's disease. In this review, we summarize the molecular genetics of PD.

MicroRNAs in Parkinson's disease

Parkinson's disease is the second most common neurodegenerative disease commonly affecting the older population. Loss of dopaminergic neurons in the substantia nigra of brain leads to impairment of motor activities as well as cognitive defects. There are many underlying causes to this disease, both genetic and epigenetic, which are yet to be fully explored. Non-coding RNAs are significant part of our genome and are involved in various cellular processes. MicroRNAs, which are small non-coding RNAs having 20-22 nucleotides, are involved in many underlying mechanisms of pathogenesis of several neurodegenerative diseases including Parkinson's. This review focuses on the role played by microRNAs in regulating various genes responsible for the onset and pathogenesis of Parkinson's disease and various literature evidences pointing at the usefulness of targeting specific microRNAs as a potential alternate therapeutic strategy for successful impairment of the disease progression. This review also discusses about various biofluid-based microRNA markers which may be potentially utilized for diagnostic purposes.

Bougainvillea spectabilis flowers extract protects against the rotenone-induced toxicity

OBJECTIVE

To investigate the effect of two extracts of Bougainvillea spectabilis (B. spectabilis) flowers with yellow and pink/purple on brain oxidative stress and neuronal damage caused in rats by systemic rotenone injection.

METHODS

Rotenone 1.5 mg/kg was given three times per week alone or in combination with B. spectabilis flowers extracts (25 mg or 50 mg) via the subcutaneous route for 2 weeks. Brain concentrations of the lipid peroxidation marker malondialdehyde (MDA), reduced glutathione, nitric oxide (nitrite), the pro-inflammatory cytokine interleukin-1beta (Il-1β) as well as butyrylcholinesterase, and paraoxonase-1 (PON-1) activities, were determined. Histopathology and caspase-3 immunohistochemistry were also performed.

RESULTS

Rotenone resulted in significant increases of brain MDA (the product of lipid peroxidation), and nitric oxide content along with decreased brain reduced glutathione. There were also marked and significant inhibition of brain PON-1 and BChE activities and increased Il-1β in brain of rotenone-treated rats. B. spectabilis flowers extract itself resulted in brain oxidative stress increasing both lipid peroxidation and nitrite content whilst inhibiting PON-1 activity. The yellow flowers extract inhibited BChE activity and increased brain Il-1β. When given to rotenone-treated rats, B. spectabilis extracts, however, decreased lipid peroxidation while their low administered doses increased brain GSH. Brain nitrite decreased by the pink extract but showed further increase by the yellow extract. Either extract, however, caused further inhibition of PON-1 activity while the yellow extract resulted in further inhibition of BChE activity. Histopathological studies indicated that both extracts protected against brain, liver and kidney damage caused by the toxicant.

CONCLUSIONS

These data indicate that B. spectabilis flowers extracts exert protective effect against the toxic effects of rotenone on brain, liver and kidney. B. spectabilis flowers extracts decreased brain lipid peroxidation and prevented neuronal death due to rotenone and might thus prove the value in treatment of Parkinson's disease.

Diacylglycerol Kinases as Emerging Potential Drug Targets for a Variety of Diseases: An Update

Ten mammalian diacylglycerol kinase (DGK) isozymes (α–κ) have been identified to date. Our previous review noted that several DGK isozymes can serve as potential drug targets for cancer, epilepsy, autoimmunity, cardiac hypertrophy, hypertension and type II diabetes (Sakane et al., 2008). Since then, recent genome-wide association studies have implied several new possible relationships between DGK isozymes and diseases. For example, DGKθ and DGKκ have been suggested to be associated with susceptibility to Parkinson's disease and hypospadias, respectively. In addition, the DGKη gene has been repeatedly identified as a bipolar disorder (BPD) susceptibility gene. Intriguingly, we found that DGKη-knockout mice showed lithium (BPD remedy)-sensitive mania-like behaviors, suggesting that DGKη is one of key enzymes of the etiology of BPD. Because DGKs are potential drug targets for a wide variety of diseases, the development of DGK isozyme-specific inhibitors/activators has been eagerly awaited. Recently, we have identified DGKα-selective inhibitors. Because DGKα has both pro-tumoral and anti-immunogenic properties, the DGKα-selective inhibitors would simultaneously have anti-tumoral and pro-immunogenic (anti-tumor immunogenic) effects. Although the ten DGK isozymes are highly similar to each other, our current results have encouraged us to identify and develop specific inhibitors/activators against every DGK isozyme that can be effective regulators and drugs against a wide variety of physiological events and diseases.

Potential Role of Caffeine in the Treatment of Parkinson's Disease

Parkinson’s disease [PD] is the second most common neurodegenerative disorder after Alzheimer’s disease, affecting 1% of the population over the age of 55. The underlying neuropathology seen in PD is characterised by progressive loss of dopaminergic neurons in the substantia nigra pars compacta with the presence of Lewy bodies. The Lewy bodies are composed of aggregates of α-synuclein. The motor manifestations of PD include a resting tremor, bradykinesia, and muscle rigidity. Currently there is no cure for PD and motor symptoms are treated with a number of drugs including levodopa [L-dopa]. These drugs do not delay progression of the disease and often provide only temporary relief. Their use is often accompanied by severe adverse effects. Emerging evidence from both in vivo and in vitro studies suggests that caffeine may reduce parkinsonian motor symptoms by antagonising the adenosine A_2A receptor, which is predominately expressed in the basal ganglia. It is hypothesised that caffeine may increase the excitatory activity in local areas by inhibiting the astrocytic inflammatory processes but evidence remains inconclusive. In addition, the co-administration of caffeine with currently available PD drugs helps to reduce drug tolerance, suggesting that caffeine may be used as an adjuvant in treating PD. In conclusion, caffeine may have a wide range of therapeutic effects which are yet to be explored, and therefore warrants further investigation in randomized clinical trials.

Role of 5-hydroxymethylcytosine in neurodegeneration

The recent discovery of 5-hydroxymethylcytosine (5hmC), an epigenetic modifier and oxidation product of 5-methylcytosine (5mC), has broadened the scope and understanding of neural development and neurodegenerative diseases. By virtue of their functional groups, 5mC and 5hmC exert opposite effects on gene expression; the former is generally associated with gene silencing whereas the latter is mainly involved in up-regulation of gene expression affecting the cellular processes such as differentiation, development, and aging. Although DNA methylation plays an important role in normal neural development and neuroprotection, an altered pathway due to complex interaction with environmental and genetic factors may cause severe neurodegeneration. The levels of 5hmC in brain increase progressively from birth until death, while in patients with neurodegenerative disorders, the levels are found to be highly compromised. This article discusses the recent developments in the area of hydroxymethylation, with particular emphasis on the role of 5hmC in neurodegenerative diseases including Alzheimer's disease, Parkinson's diseases and Huntington's disease. We have also included recent findings on the role of 5hmC in brain tumors (gliomas). Despite compelling evidence on the involvement of 5hmC in neurodegeneration, it is yet to be established whether this epigenetic molecule is the cause or the effect of the onset and progression of neurodegenerative diseases.

Therapeutic potentials of human adipose-derived stem cells on the mouse model of Parkinson's disease

The treatment of Parkinson's disease (PD) using stem cells has long been the focus of many researchers, but the ideal therapeutic strategy has not yet been developed. The consistency and high reliability of the experimental results confirmed by animal models are considered to be a critical factor in the stability of stem cell transplantation for PD. Therefore, the aim of this study was to investigate the preventive and therapeutic potential of human adipose-derived stem cells (hASC) for PD and was to identify the related factors to this therapeutic effect. The hASC were intravenously injected into the tail vein of a PD mouse model induced by 6-hydroxydopamine. Consequently, the behavioral performances were significantly improved at 3 weeks after the injection of hASC. Additionally, dopaminergic neurons were rescued, the number of structure-modified mitochondria was decreased, and mitochondrial complex I activity was restored in the brains of the hASC-injected PD mouse model. Overall, this study underscores that intravenously transplanted hASC may have therapeutic potential for PD by recovering mitochondrial functions.

Silencing of PINK1 inhibits insulin-like growth factor-1-mediated receptor activation and neuronal survival

The etiology of Parkinson's disease remains unknown. Mutations in PINK1 have provided an understanding of the molecular mechanisms of this pathology. PINK1 and Parkin are important in the dismissal of dysfunctional mitochondria. However, the role of PINK1 in the control of neuronal survival pathways is not clear. To determine the role of PINK1 in the control of the phosphatidyl inositol 3-kinase (PI3K)/Akt pathway mediated by insulin-like grow factor type 1 (IGF-1), we use a model of mesencephalic neurons (CAD cells), which were transfected with lentiviral PINK1 shRNA or control shRNA constructs. Silencing of PINK1 was determined by RT-PCR and immunoblotting; cell viability was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays; proteins of the PI3K/Akt signaling pathway were tested by immunoblotting and IGF-1 receptor, and mitochondria were examined using fluorescence microscopy. PINK1 shRNA-transfected cells showed a reduction in cell survival compared to control shRNA cells. Exposure to IGF-1 induced a rapid and high increase in the phosphorylation level of IGF-1 receptor in control shRNA-transfected cells; however, silencing of PINK1 decreases phosphorylation level of IGF-1 receptor and downstream target proteins such as Akt, GSK3-beta, IRS-1, and hexokinase. Our results further suggest that PINK1 may be regulating the PI3K/Akt neuronal survival pathway through tyrosine kinase receptors such as IGF-1 receptor.

Biological wires, communication systems, and implications for disease

Microtubules, actin, and collagen are macromolecular structures that compose a large percentage of the proteins in the human body, helping form and maintain both intracellular and extracellular structure. They are biological wires and are structurally connected through various other proteins. Microtubules (MTs) have been theorized to be involved in classical and quantum information processing, and evidence continues to suggest possible semiconduction through MTs. The previous Dendritic Cytoskeleton Information Processing Model has hypothesized how MTs and actin form a communication network in neurons. Here, we review information transfer possibilities involving MTs, actin, and collagen, and the evidence of an organism-wide high-speed communication network that may regulate morphogenesis and cellular proliferation. The direct and indirect evidence in support of this hypothesis, and implications for chronic diseases such as cancer and neurodegenerative diseases are discussed.

New insight into neurodegeneration: the role of proteomics

Recent advances within the field of proteomics, including both upstream and downstream protocols, have fuelled a transition from simple protein identification to functional analysis. A battery of proteomics approaches is now being employed for the analysis of protein expression levels, the monitoring of cellular activities and for gaining an increased understanding into biochemical pathways. Combined, these approaches are changing the way we study disease by allowing accurate and targeted, large scale protein analysis, which will provide invaluable insight into disease pathogenesis. Neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), prion disease, and other diseases that affect the neuromuscular system, are a leading cause of disability in the aging population. There are no effective intervention strategies for these disorders and diagnosis is challenging as it relies primarily on clinical symptomatic features, which often overlap at early stages of disease. There is, therefore, an urgent need to develop reliable biomarkers to improve early and specific diagnosis, to track disease progression, to measure molecular responses towards treatment regimes and ultimately devise new therapeutic strategies. To accomplish this, a better understanding of disease mechanisms is needed. In this review we summarize recent advances in the field of proteomics applicable to neurodegenerative disorders, and how these advances are fueling our understanding, diagnosis, and treatment of these complex disorders.

Genetic association study between STK39 and CCDC62/HIP1R and Parkinson's disease

Background

The first large-scale meta-analysis of published genome-wide association studies (GWAS) in Parkinson’s disease (PD) identified 5 new genetic loci (ACMSD, STK39, MCCC1/LAMP3, SYT11, and CCDC62/HIP1R). Very recently, a large-scale replication and heterogeneity study also reported that STK39 and CCDC62/HIP1R increased risk of PD in Asian and Caucasian populations. However, their roles still remain unclear in a Han Chinese population from mainland China.

Methods

We examined genetic associations of STK39 rs2102808 and CCDC62/HIP1R rs12817488 with PD susceptibility in a Han Chinese population of 783 PD patients and 725 controls. We also performed further stratified analyses by the age of onset and accomplished in-depth clinical characteristics analyses between the different genotypes for each locus.

Results

No significant differences were observed in the minor allele frequency (MAF) among cases and controls at the two loci (STK39 rs2102808: OR = 1.06, 95% CI = 0.91, 1.23, P = 0.467; CCDC62/HIP1R rs12817488: OR = 0.88, 95% CI = 0.76, 1.01, P = 0.072). Subgroup analyses by the age of onset also showed no significant differences among different subgroups of the two loci. In addition, minor allele carriers cannot be distinguished from non-carriers based on their clinical features at the two loci.

Conclusions

We are unable to demonstrate the association between STK39 and CCDC62/HIP1R and PD susceptibility in a Han Chinese population from mainland China. Additional replication studies in other populations and functional studies are warranted to better validate the role of the two new loci in PD risk.