Hong Qing

DNA methylation, a hand behind neurodegenerative diseases

Epigenetic alterations represent a sort of functional modifications related to the genome that are not responsible for changes in the nucleotide sequence. DNA methylation is one of such epigenetic modifications that have been studied intensively for the past several decades. The transfer of a methyl group to the 5 position of a cytosine is the key feature of DNA methylation. A simple change as such can be caused by a variety of factors, which can be the cause of many serious diseases including several neurodegenerative diseases. In this review, we have reviewed and summarized recent progress regarding DNA methylation in four major neurodegenerative diseases: Alzheimers disease (AD), Parkinsons disease (PD), Huntingtons disease (HD), and amyotrophic lateral sclerosis (ALS). The studies of these four major neurodegenerative diseases conclude the strong suggestion of the important role DNA methylation plays in these diseases. However, each of these diseases has not yet been understood completely as details in some areas remain unclear, and will be investigated in future studies. We hope this review can provide new insights into the understanding of neurodegenerative diseases from the epigenetic perspective.

Potential Therapeutic Strategies for Alzheimer’s Disease Targeting or Beyond β-Amyloid: Insights from Clinical Trials

Alzheimers disease (AD) is a progressive neurodegenerative disorder with two hallmarks: β-amyloid plagues and neurofibrillary tangles. It is one of the most alarming illnesses to elderly people. No effective drugs and therapies have been developed, while mechanism-based explorations of therapeutic approaches have been intensively investigated. Outcomes of clinical trials suggested several pitfalls in the choice of biomarkers, development of drug candidates, and interaction of drug-targeted molecules; however, they also aroused concerns on the potential deficiency in our understanding of pathogenesis of AD, and ultimately stimulated the advent of novel drug targets tests. The anticipated increase of AD patients in next few decades makes development of better therapy an urgent issue. Here we attempt to summarize and compare putative therapeutic strategies that have completed clinical trials or are currently being tested from various perspectives to provide insights for treatments of Alzheimers disease.

Biomarkers in Alzheimer’s Disease Analysis by Mass Spectrometry-Based Proteomics

Alzheimer’s disease (AD) is a common chronic and destructive disease. The early diagnosis of AD is difficult, thus the need for clinically applicable biomarkers development is growing rapidly. There are many methods to biomarker discovery and identification. In this review, we aim to summarize Mass spectrometry (MS)-based proteomics studies on AD and discuss thoroughly the methods to identify candidate biomarkers in cerebrospinal fluid (CSF) and blood. This review will also discuss the potential research areas on biomarkers.

The phosphorylation of α-synuclein: development and implication for the mechanism and therapy of the Parkinson's disease.

Parkinsons disease (PD) is cited to be the second most common neuronal degenerative disorders; however, the exact mechanism of PD is still unclear. α‐synuclein is one of the key proteins in PD pathogenesis as its the main component of the PD hallmark Lewy bodies (LBs). Nowadays, the study of α‐synuclein phosphorylation mechanism related to the PD pathology has become a research hotspot, given that 90% of α‐synuclein deposition in LBs is phosphorylated at Ser129, whereas in normal brains, only 4% or less of α‐synuclein is phosphorylated at the residue. Here, we review the related study of PD pathological mechanism involving the phosphorylation of α‐synuclein mainly at Ser129, Ser87, and Tyr125 residues in recent years, as well as some explorations relating to potential clinical application, in an attempt to describe the development and implication for the mechanism and therapy of PD. Given that some of the studies have yielded paradoxical results, there is need for more comprehensive research in the field. The phosphorylation of α‐synuclein might provide a breakthrough for PD mechanism study and even supply a new therapeutic strategy.

Iron contributes to the formation of catechol isoquinolines and oxidative toxicity induced by overdose dopamine in dopaminergic SH-SY5Y cells

ObjectiveThe selective loss of dopaminergic neurons in Parkinson’s disease is suspected to correlate with the increase of cellular iron, which may be involved in the pathogenesis of PD by promotion of oxidative stress. This research investigated dopamine-induced oxidative stress toxicity contributed by iron and the production of dopamine-derived neurotoxins in dopaminergic SH-SY5Y cells.MethodsAfter the SH-SY5Y cells were pre-incubated with dopamine and Fe2+ for 24 h, the cell viability, hydroxyl radical, melondialdehyde, cell apoptosis, and catechol isoquinolines were measured by lactate dehydrogenase assay, salicylic acid trapping method, thiobarbuteric acid assay, Hoechst 33258 staining and HPLC-electrochemical detection (HPLC-ECD), respectively.Results(1) Optimal dopamine (150 μmol/L) and Fe2+ (40 or 80 μmol/L) significantly increased the concentrations of hydroxy radicals and melondialdehyde in SH-SY5Y cells. (2) Induction with dopamine alone or dopamine and Fe2+ (dopamine/Fe2+) caused cell apoptosis. (3) Compared with untreated cells, the catechol isoquinolines, salsolinol and N-methyl-salsolinol in dopamine/Fe2+-induced cells were detected in increasing amounts.ConclusionDue to dopamine/Fe2+-induced oxidative stress similar to the state in the parkinsonian substantia nigra neurons, dopamine and Fe2+ impaired SH-SY5Y cells could be used as the cell oxidative stress model of Parkinson’s disease. The catechol isoquinolines detected in cells may be involved in the pathogenesis of Parkinson’s disease as potential neurotoxins.摘要目的帕金森氏病(Pakinson’s disease, PD)中多巴胺能神经元选择性缺失与胞内铁水平升高有密切关系, 提示铁可能通过参与氧化应激在PD发病机制中起重要作用。本研究使用一定浓度的Fe2+和多巴胺诱导人多巴胺能成神经细胞瘤SH-SY5Y细胞产生氧化应激状态, 并且检测胞内是否有多巴胺衍生类的神经内毒素物质产生。方法多巴胺添加不同浓度的Fe2+诱导SH-SY5Y细胞, 24 h后用乳酸脱氢酶法、 水杨酸捕获法、 硫代巴比妥酸法、 Hoechst33258染色法和带有电化学检测器的高效液相色谱仪分别检测细胞存活率、 羟自由基生成量、 丙二醛含量、 细胞凋亡和儿茶酚异喹啉物质的生成情况。结果(1) 150 μmol/L 多巴胺添加40或80 μmol/L Fe2+后, 胞内羟自由基和丙二醛含量较对照组显著增加; (2) 单独多巴胺以及多巴胺加40或80 μmol/L Fe2+诱导后细胞发生凋亡; (3)在诱导后的胞内检测到Salsolinol和N-methylsalsolinol的含量高于对照组。结论一定浓度的Fe2+和多巴胺诱导SH-SY5Y细胞可模拟帕金森氏病人黑质区多巴胺能神经元所受到的氧化应激状态, 胞内检测到的儿茶酚异喹啉物质, 如去甲猪毛菜碱和N-methyl-salsolinol, 可能作为一类潜在的神经毒性物质与帕金森氏病的发病有关。

Epigenetics in Alzheimer’s Disease: Perspective of DNA Methylation

Research over the years has shown that causes of Alzheimer’s disease are not well understood, but over the past years, the involvement of epigenetic mechanisms in the developing memory formation either under pathological or physiological conditions has become clear. The term epigenetics represents the heredity of changes in phenotype that are independent of altered DNA sequences. Different studies validated that cytosine methylation of genomic DNA decreases with age in different tissues of mammals, and therefore, the role of epigenetic factors in developing neurological disorders in aging has been under focus. In this review, we summarized and reviewed the involvement of different epigenetic mechanisms especially the DNA methylation in Alzheimer’s disease (AD), late-onset Alzheimer’s disease (LOAD), familial Alzheimer’s disease (FAD), and autosomal dominant Alzheimer’s disease (ADAD). Down to the minutest of details, we tried to discuss the methylation patterns like mitochondrial DNA methylation and ribosomal DNA (rDNA) methylation. Additionally, we mentioned some therapeutic approaches related to epigenetics, which could provide a potential cure for AD. Moreover, we reviewed some recent studies that validate DNA methylation as a potential biomarker and its role in AD. We hope that this review will provide new insights into the understanding of AD pathogenesis from the epigenetic perspective especially from the perspective of DNA methylation.

The Critical Role of Proteolytic Relay through Cathepsins B and E in the Phenotypic Change of Microglia/Macrophage

Proteinase cascades are part of the basic machinery of neuronal death pathways. Neuronal cathepsin B (CatB), a typical cysteine lysosomal protease, plays a critical role in neuronal death through lysosomal leakage or excessive autophagy. On the other hand, much attention has been paid to microglial CatB in neuronal death. We herein show the critical role of proteolytic relay through microglial CatB and CatE in the polarization of microglia/macrophages in the neurotoxic phenotype, leading to hypoxia/ischemia (HI)-induced hippocampal neuronal damage in neonatal mice. HI caused extensive brain injury in neonatal wild-type mice, but not in CatB−/− mice. Furthermore, HI-induced polarization of microglia/macrophages in the neurotoxic phenotype followed by the neuroprotective phenotype in wild-type mice. On the other hand, microglia/macrophages exhibited only the early and transient polarization in the neuroprotective phenotype in CatB−/− mice. CA-074Me, a specific CatB inhibitor, significantly inhibited the neuronal death of primary cultured hippocampal neurons induced by the conditioned medium from cultured microglia polarized in the neurotoxic phenotype. Furthermore, CA-074Me prevented the activation of nuclear factor-κB (NF-κB) in cultured microglia by inhibiting autophagic inhibitor of κBα degradation following exposure to oxygen–glucose deprivation. Rather surprisingly, CatE increased the CatB expression after HI by the liberation of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) from microglia through the proteasomal pathway. A significant increase in CatB and CatE levels was found exclusively in microglia/macrophages after HI. Thus, a proteolytic relay through the early CatE/TRAIL-dependent proteosomal and late CatB-dependent autophagic pathways for NF-κB activation may play a critical role in the polarization of microglia/macrophages in the neurotoxic phenotype. SIGNIFICANCE STATEMENT Proteinase cascades are part of the basic machinery of neuronal death pathways. Cathepsin B, a typical cysteine lysosomal protease, plays a critical role in neuronal death through lysosomal leakage or excessive autophagy in neurons. On the other hand, much attention has been also paid to the role of microglial cathepsin B in neuronal death. In this study, using in vivo and in vitro models of relevance to brain ischemia, we found a critical role of proteolytic relay through cathepsin B and cathepsin E in the neurotoxic polarization of microglia/macrophages, which is responsible for aggravation of hypoxia/ischemia-induced neuronal injury. These findings suggest orally active selective inhibitors of cathepsin B or cathepsin E as promising pharmacological agents for the treatment of ischemic brain injury.

Study of rat hypothalamic proteome by HPLC/ESI ion trap and HPLC/ESI-Q-TOF MS.

The proteomic profile of hypothalamus, a key organ of CNS, is explored here by employing two widely used MS techniques, i.e. HPLC/ESI‐ion trap and HPLC/ESI‐quadrupole‐TOF MS. Strong cation exchange is used for the fractionation of peptides and protein search engine MASCOT is employed for data query. One hundred and thirty six proteins with 10 973 peptides were identified by HPLC/ESI‐ion trap MS, while 140 proteins with 32 183 peptides were characterized by HPLC/ESI‐quadrupole‐TOF MS. Among the total 198 proteins identified in both experiments, 78 proteins were common in both sets of conditions. The rest of the 120 proteins were identified distinctly in both MS strategies, i.e. 58 unique proteins were found using the quadrupole‐TOF while 62 were found with the HPLC/ESI‐ion trap. Moreover, these proteins were classified into groups based on their functions performed in the body. Results presented here identified some important signal and cellular defense proteins inevitable for survival in stressed conditions. Additionally, it is also shown that any single MS strategy is not reliable for good results due to loss of data depending on sensitivity of the instrument used.

Potential therapeutic applications of differentiated induced pluripotent stem cells (iPSCs) in the treatment of neurodegenerative diseases

Difficulties in realizing persistent neurogenesis, inabilities in modeling pathogenesis of most cases, and a shortage of disease material for screening therapeutic agents restrict our progress to overcome challenges presented by neurodegenerative diseases. We propose that reprogramming primary somatic cells of patients into induced pluripotent stem cells (iPSCs) provides a new avenue to overcome these impediments. Their abilities in self-renewal and differentiation into various cell types will enable disease investigation and drug development. In this review, we introduce efficient approaches to generate iPSCs and distinct iPSCs differentiation stages, and critically discuss paradigms of iPSCs technology application to investigate neurodegenerative diseases such as Alzheimers disease (AD), Parkinsons disease (PD), and Huntingtons disease (HD). Although iPSCs technology is in its infancy and faces many obstacles, it has great potential in helping to identify therapeutic targets for treating neurodegenerative diseases.

The formation of catechol isoquinolines in PC12 cells exposed to manganese

Chronic exposure to manganese causes parkinsonian symptoms and has been implicated as an environmental factor in the pathogenesis of Parkinsons disease (PD). Here we show that manganese inhibits the proliferation of PC12 cells and induces apoptosis through the formation of catechol isoquinolines. Manganese induces the production of 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (salsolinol, Sal) and N-methyl-salsolinol (NMSal) in PC12 cells, and increases the levels of malondialdehyde (MDA) in a dose-dependent manner. The data indicates that the formation of catechol isoquinolines due to oxidative stress induced by MnCl(2) may be a mechanism by which manganese causes degeneration of dopaminergic neurons.