Proteomics in Parkinson’s disease: current trends,translational snags and future possibilities

Proteomic technologies are widely used to understand the molecular mechanism of Parkinson’s disease (PD) and to develop biomarkers for its early diagnosis. The differential expression patterns of brain, cerebrospinal fluid and blood proteins of patients or chemically induced animal models are used to identify protein fingerprints for developing diagnostic and therapeutic strategies for PD. A number of differentially expressed proteins associated with energy metabolism, oxidative stress, signal transduction, electron transport and detoxification pathways are identified using proteomic strategies. Proteomics immensely contributed to the detection of qualitative and quantitative changes of expressed proteins and their post-translational modifications. An update on proteomics-driven research for developing early biomarkers and understanding the molecular aspects of PD, along with their translational snags, challenges and future possibilities, are discussed in this review.     

Differential effects of human neuromelanin and synthetic dopamine melanin on neuronal and glial cells

We investigated the effects of neuromelanin (NM) isolated from the human substantia nigra and synthetic dopamine melanin (DAM) on neuronal and glial cell lines and on primary rat mesencephalic cultures. Lactate dehydrogenase (LDH) activity and lipid peroxidation were significantly increased in SK-N-SH cells by DAM but not by NM. In contrast, iron-saturated NM significantly increased LDH activity in SK-N-SH cells, compared with 100 mg/mL ETDA-treated NM containing a low concentration of bound iron. DAM, but not NM, stimulated hydroxyl radical production and increased SK-N-SH cell death via apoptotic-like mechanisms. Neither DAM nor NM induced any changes in the glial cell line U373. 3H-dopamine uptake in primary rat mesencephalic cultures was significantly reduced in DAM-compared with NM-treated cultures, accompanied by increased cell death via an apoptosis-like mechanism. Interestingly, Fenton-induced cell death was significantly decreased in cultures treated with both Fenton reagent and NM, an effect not seen in cultures treated with Fenton reagent plus DAM. These data are suggestive of a protective role for neuromelanin under conditions of high oxidative load. Our findings provide new evidence for a physiological role for neuromelanin in vivo and highlights the caution with which data based upon model systems should be interpreted.     

Mitochondrial proteomics as a selective tool for unraveling Parkinson’s disease pathogenesis

Parkinson’s disease (PD) is a neurodegenerative disease characterized by the large-scale loss of dopaminergic neurons in the substantia nigra and the formation of protein aggregates that accumulate in the cytoplasm of the remaining dopaminergic neurons. Most cases arise sporadically, while the precise cause remains obscure. This lack of understanding as to the etiology of PD continues to serve as a major barrier for delivering effective therapeutics. Mitochondria are potent integrators and coordinators of apoptosis, necrosis and cell survival. Neurotoxin-based and genetically modified animals, which mimic aspects of the core pathologies seen in human PD, support a role for oxidative stress, production of reactive oxygen species in excess and mitochondrial dysfunction in PD pathogenesis. This and other similar discoveries provide a convergence point for an explosion of morphological, biochemical, molecular, cell and animal model studies for investigating the contribution made by mitochondrial dysfunction to PD pathology. Proteomics screening technologies have proved to be a valuable aid in the investigator’s tool bag, by which to confirm a prominent role for mitochondrial proteins in PD pathology. Here, we discuss how an improved understanding of the mitochondrial proteome through the application of high-throughput proteomics, combined with genetic studies and pharmacological manipulations to influence mitochondrial dynamics and functions, promises to give insights into PD’s underlying disease mechanisms. Ultimately, such insights may pave the way towards designing novel strategies for providing symptomatic, neuroprotective and restorative therapeutic options to PD patients.     

Proteomics in cardiovascular disease: recent progress and clinical implication and implementation

Introduction: Although multiple efforts have been initiated to shed light into the molecular mechanisms underlying cardiovascular disease, it still remains one of the major causes of death worldwide. Proteomic approaches are unequivocally powerful tools that may provide deeper understanding into the molecular mechanisms associated with cardiovascular disease and improve its management.

Areas covered: Cardiovascular proteomics is an emerging field and significant progress has been made during the past few years with the aim of defining novel candidate biomarkers and obtaining insight into molecular pathophysiology. To summarize the recent progress in the field, a literature search was conducted in PubMed and Web of Science. As a result, 704 studies from PubMed and 320 studies from Web of Science were retrieved. Findings from original research articles using proteomics technologies for the discovery of biomarkers for cardiovascular disease in human are summarized in this review.

Expert commentary: Proteins associated with cardiovascular disease represent pathways in inflammation, wound healing and coagulation, proteolysis and extracellular matrix organization, handling of cholesterol and LDL. Future research in the field should target to increase proteome coverage as well as integrate proteomics with other omics data to facilitate both drug development as well as clinical implementation of findings.     

Acacetin promotes healthy aging by altering stress response in Caenorhabditis elegans

The progression in lifespan has been associated with elevated intracellular reactive oxygen species (ROS) and oxidative stress level which contributes to development of age related disorders. The discovery of lifespan modulating phytomolecules may promote development of natural therapies against age related afflictions. Acacetin (5,7-dihydroxy-4-methoxyflavone), is a naturally occurring flavonoid known to possess therapeutic properties. To this end, the present study evaluates effect of acacetin (AC) on lifespan, stress and neurotoxicity for the first time by using well-established free living, multicellular Caenorhabditis elegans model system. The 25?μM dose of AC significantly prolonged the mean lifespan of worms by 27.31% in comparison to untreated control and other tested doses of AC. Additionally, AC enhanced stress resistance against oxidative and thermal stress in worms. Furthermore, AC attenuated age related intracellular ROS level, aggregation of age pigment lipofuscin and increased the mean survival in stress hypersensitive mev-1 mutant by 40.5%. AC supplementation also reduced the alpha synuclein aggregation in transgenic worm model of Parkinson’s disease. The enhanced stress resistance, lifespan and alleviation of age related pathology can be attributed to increment in stress modulatory enzymes like superoxide dismutase (SOD) and catalase (CAT) level. Altogether the results suggest AC exposure maintains stress level, health span and extends mean lifespan of C. elegans. The longevity promoting and neuromodulatory effects of AC are mediated by up regulation of the stress response genes sod-3 and gst-4. The present finding gives new insights of natural remedies and their future prospects in developing therapeutic interventions for managing age related diseases.     

Deep Multilayer Brain Proteomics Identifies Molecular Networks in Alzheimer’s Disease Progression

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Aberrant Tonic Inhibition of Dopaminergic Neuronal Activity Causes Motor Symptoms in Animal Models of Parkinson’s Disease

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Proteomics in Alzheimer's disease: insights into potential mechanisms of neurodegeneration

Proteomics involves the identification of unknown proteins following their separation, often using two-dimensional electrophoresis, digestion of particular proteins of interest by trypsin, determination of the molecular weight of the resulting peptides, and database searching to make the identification of the proteins. Application of proteomics to Alzheimer's disease (AD), the major dementing disorder of the elderly, has just begun. Differences in protein expression and post-translational modification (mostly oxidative modification) of proteins from AD brain and peripheral tissue, as well as in brain from rodent models of AD, have yielded insights into potential molecular mechanisms of neurodegeneration in this dementing disorder. This review surveys the proteomics studies relevant to AD, from which new understandings of the pathology, biochemistry, and physiology of AD are beginning to emerge.     

帕金森病黑质多巴胺神经元易损伤性的内在因素

帕金森病（Parkinson’s disease,PD）主要症状是由中脑黑质致密部（substantia nigra compact,SNc）的多巴胺（dopamine,DA）神经元死亡引起。帕金森病发病过程中,路易小体病理（Lewy pathology,LP）和线粒体功能障碍最为突出,但SNc 多巴胺神经元为什么特别易遭受这两种病理损害尚不清楚。研究表明,与脑内其他神经元相比,SNc 多巴胺神经元具有特殊的解剖形态、生理和生化表型。SNc 多巴胺神经元具有高分支无髓鞘轴突和众多的突触终端,突触末梢物质和能量代谢的高要求需要大量的线粒体,巨大突触终端增加了突触蛋白质的表达、转运和降解的负担。SNc 多巴胺神经元具有独特的自主起搏电活动和缓慢钙振荡特性,Cav1-3钙通道活动及后续的级联反应增加了SNc 多巴胺神经元线粒体负担,增加了基础氧化应激、线粒体损伤和自噬,降低了处理错误折叠蛋白质的能力。SNc 多巴胺神经元特有的神经递质--多巴胺易被氧化成为反应性醌,具有潜在毒性,可破坏葡糖脑苷脂酶导致其活性降低,引起线粒体氧化应激和溶酶体功能障碍。总之,SNc 多巴胺神经元具有的这些内在因素综合起来,可能导致了其对线粒体功能障碍和路易小体病理损伤的易感性,并且SNc 多巴胺神经元所处的神经网络障碍也促使了帕金森病的进展。认识到这些特征会对研究帕金森病相关病理学机制和阻止疾病进展创造新的机会。     

溶酶体离子通道蛋白在神经退行性疾病发生发展中的作用及机制研究

溶酶体离子通道蛋白异常引起溶酶体功能障碍是导致阿尔茨海默病(Alzheimer’s disease,AD)和帕金森病(Parkinson’s disease,PD)等神经退行性疾病的重要因素.溶酶体离子通道蛋白调节溶酶体内离子稳态、溶酶体膜电压以及溶酶体的酸度.溶酶体离子通道蛋白的结构或功能缺陷会引起溶酶体降解功能障碍,导致神经退行性疾病的发生发展.在这篇综述中,我们总结了各种离子通道蛋白调节溶酶体功能的过程及机制,以及离子通道蛋白异常参与神经退行性疾病的过程和机制.调节离子通道蛋白改善溶酶体的功能、促进异常聚集蛋白的清除,是神经退行性疾病治疗的潜在途径.     

New insight into Parkinson’s disease pathogenesis from reactive oxygen species-mediated extracellular Zn2+ influx

BackgroundParkinson’s disease (PD) is the common neurodegenerative disorder in the elderly characterized by motor symptoms such as tremors, which is caused by selective loss of nigral dopaminergic neurons. Oxidative stress induced by the auto-oxidation of dopamine has been implicated as a key cause of the selective loss of dopaminergic neurons.MethodsTo understand the selective loss of nigral dopaminergic neurons, the PD pathogenesis is reviewed focused on paraquat (PQ) and 6-hydroxydopamine (6-OHDA)-induced PD in rats.ResultsReactive oxygen species (ROS), which are produced by PQ and 6-OHDA, are retrogradely transported to presynaptic glutamatergic neuron terminals. ROS activate presynaptic transient receptor potential melastatin 2 (TRPM2) cation channels and induce extracellular glutamate accumulation in the substantia nigra pars compacta (SNpc), followed by age-related intracellular Zn²⁺ dysregulation. Loss of nigral dopaminergic neurons is accelerated by age-related intracellular Zn²⁺ dysregulation in the SNpc of rat PD models. The intracellular Zn²⁺ dysregulation in nigral dopaminergic neurons is linked with the rapid influx of extracellular Zn²⁺ via postsynaptic AMPA receptor activation, suggesting that PQ- and 6-OHDA-induced pathogenesis is linked with age-related intracellular Zn²⁺ dysregulation in the SNpc. Postsynaptic TRPM2 channels may be also involved in intracellular Zn²⁺ dysregulation in the SNpc.ConclusionA novel mechanism of nigral dopaminergic degeneration, in which ROS induce rapid intracellular Zn²⁺ dysregulation, figures out the PD pathogenesis induced by PQ and 6-OHDA in rats. This review deals with new insight into PD pathogenesis from ROS-mediated extracellular Zn²⁺ influx and its proposed defense strategy.     

Iron, neuromelanin and ferritin content in the substantia nigra of normal subjects at different ages: consequences for iron storage and neurodegenerative processes

Information on the molecular distribution and ageing trend of brain iron in post‐mortem material from normal subjects is scarce. Because it is known that neuromelanin and ferritin form stable complexes with iron(III), in this study we measured the concentration of iron, ferritin and neuromelanin in substantia nigra from normal subjects, aged between 1 and 90 years, dissected post mortem. Iron levels in substantia nigra were 20 ng/mg in the first year of life, had increased to 200 ng/mg by the fourth decade and remained stable until 90 years of age. The H‐ferritin concentration was also very low (29 ng/mg) during the first year of life but increased rapidly to values of ≈ 200 ng/mg at 20 years of age, which then remained constant until the eighth decade of life. L ‐Ferritin also showed an increasing trend during life although the concentrations were ≈ 50% less than that of H‐ferritin at each age point. Neuromelanin was not detectable during the first year, increased to ≈ 1000 ng/mg in the second decade and then increased continuously to 3500 ng/mg in the 80th year. A Mössbauer study revealed that the high‐spin trivalent iron is probably arranged in a ferritin‐like iron?oxyhydroxide cluster form in the substantia nigra. Based on this data and on the low H‐ and L‐ferritin content in neurones it is concluded that neuromelanin is the major iron storage in substantia nigra neurones in normal individuals.     

Recent cerebrospinal fluid biomarker studies of Alzheimer’s disease

Alzheimer’s disease is a progressive neurodegenerative disorder and the most common form of dementia. The disease is confirmed by the presence of neuritic plaques and neurofibrillary tangles in the cerebral cortex at autopsy, but the accuracy of antemortem diagnosis, especially at the early stages of the disease, is not ideal. Thus, there is a substantial need for the discovery and validation of diagnostic biomarkers. Many Alzheimer’s disease biomarker discovery studies emphasize the analysis of cerebrospinal fluid (CSF) because of its close association with the brain. Here, we review recent mass spectrometry-based studies of Alzheimer’s disease CSF, and additionally discuss issues associated with CSF in proteomics studies.     

Comparison of transduction efficiency of recombinant AAV serotypes 1, 2, 5, and 8 in the rat nigrostriatal system

Enhanced delivery and expression of genes in specific neuronal systems is critical for the development of genetic models of neurodegenerative disease and potential gene therapy. Recent discovery of new recombinant adeno-associated viral (rAAV) capsid serotypes has resulted in improved transduction efficiency, but expression levels, spread of transgene, and potential toxicity can differ depending on brain region and among species. We compared the transduction efficiency of titer-matched rAAV 2/1, 2/5, and 2/8 to the commonly used rAAV2/2 in the rat nigrostriatal system via expression of the reporter transgene, enhanced green fluorescent protein. Newer rAAV serotypes 2/1, 2/5, and 2/8 demonstrated marked increase in transduction and spread of enhanced green fluorescent protein expression in dopaminergic nigrostriatal neurons and projections to the striatum and globus pallidus compared to rAAV2/2 at 2 weeks post-injection. The number of nigral cells transduced was greatest for rAAV2/1, but for serotypes 2/5 and 2/8 was still two- to threefold higher than that for 2/2. Enhanced transduction did not cause an increase in glial cell response or toxicity. New rAAV serotypes thus promise improved gene delivery to nigrostriatal system with the potential for better models and therapeutics for Parkinson disease and other neurodegenerative disorders.     

Clinical implications from proteomic studies in neurodegenerative diseases: lessons from mitochondrial proteins

Mitochondria play a key role in eukaryotic cells, being mediators of energy, biosynthetic and regulatory requirements of these cells. Emerging proteomics techniques have allowed scientists to obtain the differentially expressed proteome or the proteomic redox status in mitochondria. This has unmasked the diversity of proteins with respect to subcellular location, expression and interactions. Mitochondria have become a research ‘hot spot’ in subcellular proteomics, leading to identification of candidate clinical targets in neurodegenerative diseases in which mitochondria are known to play pathological roles. The extensive efforts to rapidly obtain differentially expressed proteomes and unravel the redox proteomic status in mitochondria have yielded clinical insights into the neuropathological mechanisms of disease, identification of disease early stage and evaluation of disease progression. Although current technical limitations hamper full exploitation of the mitochondrial proteome in neurosciences, future advances are predicted to provide identification of specific therapeutic targets for neurodegenerative disorders.