MicroRNAs and Target Genes As Biomarkers for the Diagnosis of Early Onset of Parkinson Disease

Biomarkers of Parkinson's Disease: From Basic Research to Clinical Practice

Parkinson's disease (PD) is a common neurodegenerative disease characterized pathologically by dopaminergic neuron loss and the formation of Lewy bodies, which are enriched with aggregated α-synuclein (α-syn). PD currently has no cure, but therapeutic strategies are available to alleviate symptoms. Early diagnosis can greatly improve therapeutic interventions, but the clinical diagnosis of PD remains challenging and depends mainly on clinical features and imaging tests. Efficient and specific biomarkers are crucial for the diagnosis, monitoring, and evaluation of PD. Here, we reviewed the biomarkers of PD in different tissues and biofluids, along with the current clinical biochemical detection methods. We found that the sensitivity and specificity of single biomarkers are limited, and selecting appropriate indicators for combined detection can improve the diagnostic accuracy of PD.

Early-stage idiopathic Parkinson's disease is associated with reduced circular RNA expression

Neurodegeneration in Parkinson's disease (PD) precedes diagnosis by years. Early neurodegeneration may be reflected in RNA levels and measurable as a biomarker. Here, we present the largest quantification of whole blood linear and circular RNAs (circRNA) in early-stage idiopathic PD, using RNA sequencing data from two cohorts (PPMI = 259 PD, 161 Controls; ICICLE-PD = 48 PD, 48 Controls). We identified a replicable increase in TMEM252 and LMNB1 gene expression in PD. We identified novel differences in the expression of circRNAs from ESYT2, BMS1P1 and CCDC9, and replicated trends of previously reported circRNAs. Overall, using circRNA as a diagnostic biomarker in PD did not show any clear improvement over linear RNA, minimising its potential clinical utility. More interestingly, we observed a general reduction in circRNA expression in both PD cohorts, accompanied by an increase in RNASEL expression. This imbalance implicates the activation of an innate antiviral immune response and suggests a previously unknown aspect of circRNA regulation in PD.

Neuronal dysfunction and gene modulation by non-coding RNA in Parkinson's disease and synucleinopathies

Over the last few decades, emerging evidence suggests that non-coding RNAs (ncRNAs) including long-non-coding RNA (lncRNA), microRNA (miRNA) and circular-RNA (circRNA) contribute to the molecular events underlying progressive neuronal degeneration, and a plethora of ncRNAs have been identified significantly misregulated in many neurodegenerative diseases, including Parkinson's disease and synucleinopathy. Although a direct link between neuropathology and causative candidates has not been clearly established in many cases, the contribution of ncRNAs to the molecular processes leading to cellular dysfunction observed in neurodegenerative diseases has been addressed, suggesting that they may play a role in the pathophysiology of these diseases. Aim of the present Review is to overview and discuss recent literature focused on the role of RNA-based mechanisms involved in different aspects of neuronal pathology in Parkinson's disease and synucleinopathy models.

Current Updates on the Role of MicroRNA in the Diagnosis and Treatment of Neurodegenerative Diseases

BACKGROUND

MicroRNAs (miRNA) are small noncoding RNAs that play a significant role in the regulation of gene expression. The literature has explored the key involvement of miRNAs in the diagnosis, prognosis, and treatment of various neurodegenerative diseases (NDD), such as Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD). The miRNA regulates various signalling pathways; its dysregulation is involved in the pathogenesis of NDD.

OBJECTIVE

The present review is focused on the involvement of miRNAs in the pathogenesis of NDD and their role in the treatment or management of NDD. The literature provides comprehensive and cutting-edge knowledge for students studying neurology, researchers, clinical psychologists, practitioners, pathologists, and drug development agencies to comprehend the role of miRNAs in the NDD's pathogenesis, regulation of various genes/signalling pathways, such as α-synuclein, P53, amyloid-β, high mobility group protein (HMGB1), and IL-1β, NMDA receptor signalling, cholinergic signalling, etc. Methods: The issues associated with using anti-miRNA therapy are also summarized in this review. The data for this literature were extracted and summarized using various search engines, such as Google Scholar, Pubmed, Scopus, and NCBI using different terms, such as NDD, PD, AD, HD, nanoformulations of mRNA, and role of miRNA in diagnosis and treatment.

RESULTS

The miRNAs control various biological actions, such as neuronal differentiation, synaptic plasticity, cytoprotection, neuroinflammation, oxidative stress, apoptosis and chaperone-mediated autophagy, and neurite growth in the central nervous system and diagnosis. Various miRNAs are involved in the regulation of protein aggregation in PD and modulating β-secretase activity in AD. In HD, mutation in the huntingtin (Htt) protein interferes with Ago1 and Ago2, thus affecting the miRNA biogenesis. Currently, many anti-sense technologies are in the research phase for either inhibiting or promoting the activity of miRNA.

CONCLUSION

This review provides new therapeutic approaches and novel biomarkers for the diagnosis and prognosis of NDDs by using miRNA.

Multidimensional biomarkers for multiple system atrophy: an update and future directions

Multiple system atrophy (MSA) is a fatal progressive neurodegenerative disease. Biomarkers are urgently required for MSA to improve the diagnostic and prognostic accuracy in clinic and facilitate the development and monitoring of disease-modifying therapies. In recent years, significant research efforts have been made in exploring multidimensional biomarkers for MSA. However, currently few biomarkers are available in clinic. In this review, we systematically summarize the latest advances in multidimensional biomarkers for MSA, including biomarkers in fluids, tissues and gut microbiota as well as imaging biomarkers. Future directions for exploration of novel biomarkers and promotion of implementation in clinic are also discussed.

MicroRNA schizophrenia: Etiology, biomarkers and therapeutic targets

The three sets of symptoms associated with schizophrenia-positive, negative, and cognitive-are burdensome and have serious effects on public health, which affects up to 1% of the population. It is now commonly believed that in addition to the traditional dopaminergic mesolimbic pathway, the etiology of schizophrenia also includes neuronal networks, such as glutamate, GABA, serotonin, BDNF, oxidative stress, inflammation and the immune system. Small noncoding RNA molecules called microRNAs (miRNAs) have come to light as possible participants in the pathophysiology of schizophrenia in recent years by having an impact on these systems. These small RNAs regulate the stability and translation of hundreds of target transcripts, which has an impact on the entire gene network. There may be improved approaches to treat and diagnose schizophrenia if it is understood how these changes in miRNAs alter the critical related signaling pathways that drive the development and progression of the illness.

Nutrigenomics in Parkinson's disease: diversity of modulatory actions of polyphenols on epigenetic effects induced by toxins

Although the pathogenesis of Parkinson's Disease (PD) is not completely understood, there is a consensus that it can be caused by multifactorial mechanisms involving genetic susceptibility, epigenetic modifications induced by toxins and mitochondrial dysfunction. In the past 20 years, great efforts have been made in order to clarify molecular mechanisms that are risk factors for this disease, as well as to identify bioactive agents for prevention and slowing down of its progression. Nutraceutical products have received substantial interest due to their nutritional, safe and therapeutic effects on several chronic diseases. The aim of this review was to gather the main evidence of the epigenetic mechanisms involved in the neuroprotective effects of phenolic compounds currently under investigation for the treatment of toxin-induced PD. These studies confirm that the neuroprotective actions of polyphenols involve complex epigenetic modulations, demonstrating that the intake of these natural compounds can be a promising, low-cost, pharmacogenomic strategy against the development of PD.

Plasma miR-153 and miR-223 Levels as Potential Biomarkers in Parkinson’s Disease

Background

Small molecule RNAs (miRNAs) could induce downregulation of α-synuclein (SNCA) expression by binding the 3’ untranslated region of SNCA, thus playing an important role in the pathogenesis of Parkinson’s disease (PD). Recent studies suggest that SNCA-related miRNAs in saliva are promising PD biomarkers. Research on those miRNAs in plasma is rare in patients with PD.

Objective

To detect the plasma expression levels of three SNCA related miRNAs (miR-7, miR-153, and miR-223) in PD, and to explore their diagnostic value and associations with clinical phenotype.

Methods

MiR-7, miR-153, and miR-223 levels were detected in the plasma of 75 PD patients and 73 normal controls (NCs) via real-time quantitative polymerase chain reaction. The receiver operating characteristic (ROC) curves were delineated to evaluate their diagnostic value in PD. In addition, their associations with demographic, key motor, and non-motor symptoms were explored by serial scales.

Results

The expression levels of plasma miR-153 and miR-223 were significantly decreased in patients with PD relative to NCs. The area under the ROC curve separating PD from NCs was 63.1% for miR-153 and 86.2% for miR-223, respectively. The plasma miR-153 level in de novo PD was lower than that in treated patients (p = 0.006), its level increased gradually with disease duration (r = 0.358, p = 0.002) and Unified Parkinson’s Disease Rating Scale Part III score (r = 0.264, p = 0.022). Plasma miR-223 level was decreased in patients with clinical possible rapid eye movement sleep behavior disorder (cpRBD) compared with those without cpRBD (p < 0.001), and its level was negatively associated with RBDSQ score (r = -0.334, p = 0.003). Multiple linear regression analysis revealed that disease duration (p = 0.049) was the independently associated factor of miR-153 level; whereas, RBDSQ (p = 0.009) was related to miR-223 level in PD.

Conclusion

Plasma miR-153 and miR-223 levels could be potential biomarkers of PD.

From the tyrosine hydroxylase hypothesis of Parkinson's disease to modern strategies: a short historical overview

A time span of 60 years covers the detection of catecholamines in the brain, their function in movement and correlation to Parkinson’s disease (PD). The clinical findings that orally given l-DOPA can alleviate or even prevent akinesia gave great hope for the treatment of PD. Attention focused on the role of tyrosine hydroxylase (TH) as the rate-limiting enzyme in the formation of catecholamines. It became evident that the enzyme driven formation is lowered in PD. Such results could only be obtained from studying human brain samples demonstrating the necessity for human brain banks. Originally, a TH enzyme deficiency was suspected in PD. Studies were conducted on the enzyme properties: its induction and turnover, the complex regulation starting with cofactor requirements as tetrahydrobiopterin and ferrous iron, and the necessity for phosphorylation for activity as well as inhibition by toxins or regulatory feedback inhibition by catecholamines. In the course of time, it became evident that neurodegeneration and cell death of dopaminergic neurons is the actual pathological process and the decrease of TH a cophenomenon. Nevertheless, TH immunochemistry has ever since been a valuable tool to study neuronal pathways, neurodegeneration in various animal models of neurotoxicity and cell cultures, which have been used as well to test potential neuroprotective strategies.

Cytokines, miRNAs, and Antioxidants as Combined Non-invasive Biomarkers for Parkinson's Disease

Parkinson's disease (PD) is one of the most common long-term degenerative disorders of the CNS that primarily affects the human locomotor system. Owing to the heterogeneity of PD etiology and the lack of appropriate diagnostic tests, blood-based biomarkers became the most promising method for diagnosing PD. Even though various biomarkers for PD have been found, their specificity and sensitivity are not optimum when used alone. Therefore, the aim of this study was directed to evaluate changes in a group of sensitive blood-based biomarkers in the same PD patients compared to healthy individuals. Serum samples were collected from 20 PD patients and 15 age-matched healthy controls. We analyzed serum levels of cytokines (IL10, IL12, and TNF-α), α-synuclein proteins, miRNAs (miR-214, miR-221, and miR-141), and antioxidants (UA, PON1, ARE). Our results showed an increase in sera levels of cytokines in PD patients as well as a positive correlation among them. Also, we found a significant increase in sera levels of α-synuclein protein associated with a decrease in miR-214 which regulates its gene expression. Lastly, we observed a decrease in sera levels of miR-221, miR-141, UA, PON1, and ARE, which have a prominent role against oxidative stress. Because of the many etiologies of PD, a single measure is unlikely to become a useful biomarker. Therefore, to correctly predict disease state and progression, a mix of noninvasive biomarkers is required. Although considerable work has to be done, this study sheds light on the role of certain biomarkers in the diagnosis of PD.

Roles of clock genes in the pathogenesis of Parkinson's disease

Parkinson's disease (PD) is a common motor disorder that has become increasingly prevalent in the ageing population. Recent works have suggested that circadian rhythms disruption is a common event in PD patients. Clock genes regulate the circadian rhythm of biological processes in eukaryotic organisms, but their roles in PD remain unclear. Despite this, several lines of evidence point to the possibility that clock genes may have a significant impact on the development and progression of the disease. This review aims to consolidate recent understanding of the roles of clock genes in PD. We first summarized the findings of clock gene expression and epigenetic analyses in PD patients and animal models. We also discussed the potential contributory role of clock gene variants in the development of PD and/or its symptoms. We further reviewed the mechanisms by which clock genes affect mitochondrial dynamics as well as the rhythmic synthesis and secretion of endocrine hormones, the impairment of which may contribute to the development of PD. Finally, we discussed the limitations of the currently available studies, and suggested future potential studies to deepen our understanding of the roles of clock genes in PD pathogenesis.

MicroRNA-181a-2-3p shuttled by mesenchymal stem cell-secreted extracellular vesicles inhibits oxidative stress in Parkinson's disease by inhibiting EGR1 and NOX4

The current study investigated the physiological mechanisms by which extracellular vesicle (EV)-encapsulated miR-181a-2-3p derived from mesenchymal stem cells (MSCs) might mediate oxidative stress (OS) in Parkinson's disease (PD). First, 6-hydroxydopamine (6-OHDA)-induced PD cell and mouse models were established, after which miR-181a-2-3p, EGR1, and NOX4 expression patterns were determined in SH-SY5Y cells and substantia nigra (SN) of PD mice. Next, the binding affinity among miR-181a-2-3p, EGR1, and NOX4 was identified using multiple assays. Gain- or loss-of-function experiments were further adopted to detect SH-SY5Y cell proliferation and apoptosis and to measure the levels of SOD, MDA, and ROS. Finally, the effects of miR-181a-2-3p from MSC-derived EVs in PD mouse models were also explored. It was found that miR-181a-2-3p was poorly expressed in 6-OHDA-induced SH-SY5Y cells, whereas miR-181a-2-3p from MSCs could be transferred into SH-SY5Y cells via EVs. In addition, miR-181a-2-3p could target and inhibit EGR1, which promoted the expression of NOX4. The aforementioned miR-181a-2-3p shuttled by MSC-derived EVs facilitated SH-SY5Y proliferation and SOD levels, but suppressed apoptosis and MDA and ROS levels by regulating EGR1 via inhibition of NOX4/p38 MAPK, so as to repress OS of PD. Furthermore, in PD mice, miR-181a-2-3p was carried by EVs from MSCs to alleviate apoptosis of dopamine neurons and OS, accompanied by increased expressions of α-syn and decreased 4-HNE in SN tissues. Collectively, our findings revealed that MSC-derived EV-loaded miR-181a-2-3p downregulated EGR1 to inhibit OS via the NOX4/p38 MAPK axis in PD.

Evolutionary Changes in the Interaction of miRNA With mRNA of Candidate Genes for Parkinson's Disease

Parkinson’s disease (PD) exhibits the second-highest rate of mortality among neurodegenerative diseases. PD is difficult to diagnose and treat due to its polygenic nature. In recent years, numerous studies have established a correlation between this disease and miRNA expression; however, it remains necessary to determine the quantitative characteristics of the interactions between miRNAs and their target genes. In this study, using novel bioinformatics approaches, the quantitative characteristics of the interactions between miRNAs and the mRNAs of candidate PD genes were established. Of the 6,756 miRNAs studied, more than one hundred efficiently bound to mRNA of 61 candidate PD genes. The miRNA binding sites (BS) were located in the 5′-untranslated region (5′UTR), coding sequence (CDS) and 3′-untranslated region (3′UTR) of the mRNAs. In the mRNAs of many genes, the locations of miRNA BS with overlapping nucleotide sequences (clusters) were identified. Such clusters substantially reduced the proportion of nucleotide sequences of miRNA BS in the 5′UTRs, CDSs, and 3′UTRs. The organization of miRNA BS into clusters leads to competition among miRNAs to bind mRNAs. Differences in the binding characteristics of miRNAs to the mRNAs of genes expressed at different rates were identified. Single miRNA BS, polysites for the binding for one miRNA, and multiple BS for two or more miRNAs in one mRNA were identified. Evolutionary changes in the BS of miRNAs and their clusters in 5′UTRs, CDSs and 3′UTRs of mRNA of orthologous candidate PD genes were established. Based on the quantitative characteristics of the interactions between miRNAs and mRNAs candidate PD genes, several associations recommended as markers for the diagnosis of PD.

MicroRNAs, Parkinson's Disease, and Diabetes Mellitus

Parkinson’s disease (PD) is a neurodegenerative disorder that affects 1% of the population over the age of 60. Diabetes Mellitus (DM) is a metabolic disorder that affects approximately 25% of adults over the age of 60. Recent studies showed that DM increases the risk of developing PD. The link between DM and PD has been discussed in the literature in relation to different mechanisms including mitochondrial dysfunction, oxidative stress, and protein aggregation. In this paper, we review the common microRNA (miRNA) biomarkers of both diseases. miRNAs play an important role in cell differentiation, development, the regulation of the cell cycle, and apoptosis. They are also involved in the pathology of many diseases. miRNAs can mediate the insulin pathway and glucose absorption. miRNAs can also regulate PD-related genes. Therefore, exploring the common miRNA biomarkers of both PD and DM can shed a light on how these two diseases are correlated, and targeting miRNAs is a potential therapeutic opportunity for both diseases.

MicroRNAs in central nervous system disorders: current advances in pathogenesis and treatment

MicroRNAs (miRNAs) are a class of short, non-coding, regulatory RNA molecules that function as post transcriptional regulators of gene expression. Altered expression of multiple miRNAs was found to be extensively involved in the pathogenesis of different neurological disorders including Alzheimer’s disease, Parkinson’s disease, stroke, epilepsy, multiple sclerosis, amyotrophic lateral sclerosis, and Huntington’s disease. miRNAs are implicated in the pathogenesis of excitotoxicity, apoptosis, oxidative stress, inflammation, neurogenesis, angiogenesis, and blood–brain barrier protection. Consequently, miRNAs can serve as biomarkers for different neurological disorders. In recent years, advances in the miRNA field led to identification of potentially novel prospects in the development of new therapies for incurable CNS disorders. MiRNA-based therapeutics include miRNA mimics and inhibitors that can decrease or increase the expression of target genes. Better understanding of the mechanisms by which miRNAs are implicated in the pathogenesis of neurological disorders may provide novel targets to researchers for innovative therapeutic strategies.

MiRNA Expression in Patients with Gaucher Disease Treated with Enzyme Replacement Therapy

Aims: The aim of the work was to establish potential biomarkers or drug targets by analysing changes in miRNA concentration among patients with Gaucher disease (GD) compared to in healthy subjects. Methods: This study was an observational, cross-sectional analysis of 30 adult participants: 10 controls and 20 adults with GD type 1. Patients with GD type 1 were treated with enzyme replacement therapy (ERT) for at least two years. The control group was composed of healthy volunteers, unrelated to the patients, adjusted with age, sex and body mass index (BMI). The miRNA alteration between these groups was examined. After obtaining preliminary results on a group of six GD patients by the high-output method (TaqMan low-density array (TLDA)), potential miRNAs were selected for confirming the results by using the qRT-PCR method. With Diane Tools, we analysed miRNAs of which differential expression is most significant and their potential role in GD pathophysiology. We also determined the essential pathways these miRNAs are involved in. Results: 266 dysregulated miRNAs were found among 753 tested. Seventy-eight miRNAs were downregulated, and 188 were upregulated. Thirty miRNAs were significantly altered; all of them were upregulated. The analysis of pathways regulated by the selected miRNAs showed an effect on bone development, inflammation or regulation of axonal transmission in association with Parkinson’s disease. Conclusions: We revealed few miRNAs, like miR-26-5p, which are highly altered and fit the GD pathophysiological model, might be considered as novel biomarkers of disease progression but need further evaluation.

Parkinson's disease and pesticides: Are microRNAs the missing link?

Parkinson's disease (PD) is a common neurodegenerative disorder that leads to significant morbidity and decline in the quality of life. It develops due to loss of dopaminergic neurons in the substantia nigra pars compacta, and among its pathogenic factors oxidative stress plays a critical role in disease progression. Pesticides are a broad class of chemicals widely used in agriculture and households for the protection of crops from insects and fungi. Several of them have been incriminated as risk factors for PD, but the underlying mechanisms have yet to be fully understood. MicroRNAs (miRNAs) are small, non-coding RNA molecules that play an important role in regulating mRNA translation and protein synthesis. miRNA levels have been shown to be affected in several diseases as well. Since the studies on the association between pesticides and PD have yet to reach definitive conclusions, here we review recent evidence on deregulated microRNAs upon pesticide exposure, and attempt to find an overlap between miRNAs deregulated in PD and pesticides, as a missing link between the two, and enhance future research in this direction.

Alpha-Synuclein in the Gastrointestinal Tract as a Potential Biomarker for Early Detection of Parkinson's Disease

The primary pathogenesis associated with Parkinson's disease (PD) occurs in peripheral tissues several years before the onset of typical motor symptoms. Early and reliable diagnosis of PD could provide new treatment options for PD patients and improve their quality of life. At present, however, diagnosis relies mainly on clinical symptoms, and definitive diagnosis is still based on postmortem pathological confirmation of dopaminergic neuronal degeneration. In addition, the similarity of the clinical, cognitive, and neuropathological features of PD with other neurodegenerative diseases calls for new biomarkers, suitable for differential diagnosis. Alpha-synuclein (α-Syn) is a potential PD biomarker, due to its close connection with the pathogenesis of the disease. Here we summarize the currently available information on the possible use of α-Syn as a biomarker of early stages of PD in gastrointestinal (GI) tissues, highlight its potential to distinguish PD and other neurodegenerative diseases, and suggest alternative methods (primarily developed for other tissue analysis) that could improve α-Syn detection procedures or diagnostic methods in general.

A compound downregulation of SRRM2 and miR-27a-3p with upregulation of miR-27b-3p in PBMCs of Parkinson's patients is associated with the early stage onset of disease

Parkinson’s disease (PD) is diagnosed when motor symptoms emerges, which almost 70% of dopamine neurons are lost. Therefore, early diagnosis of PD is crucial to prevent the progress of disease. Blood-based biomarkers, which are minimally invasive, potentially used for diagnosis of PD, including miRNAs. The aim of this study was to assess whether SRRM2 and miR-27a/b-3p could act as early diagnostic biomarkers for PD. Total RNAs from PBMCs of 30 PD’s patients and 14 healthy age and gender matched subjects was extracted. The expression levels of respective genes were assessed. Data were presented applying a two-tailed unpaired t-test and one-way ANOVA. We observed significant down-regulation of SRRM2 (p = 0.0002) and miR-27a-3p (p = 0.0001), and up-regulation of miR-27b-3p (p = 0.02) in PBMCs of Parkinson's patients. Down-regulation of miR-27a-3p is associated with increasing disease severity, whereas the up-regulation of miR-27b-3p was observed mostly at HY-1 and disease duration between 3–5 years. There was a negative correlation between SRRM2 and miR-27b-3p expressions, and miR-27a-3p positively was correlated with miR-27b-3p. Based on functional enrichment analysis, SRRM2 and miR-27a/b-3p acted on common functional pathways. miR-27a/b-3p could potentially predict the progression and severity of PD. Although both miRs had no similarity on expression, a positive correlation between both miRs was identified, supporting their potential role as biomarkers in clinical PD stages. Of note that SRRM2 and miR-27a-3p were able to distinguish PD patients from healthy individuals. Functional analysis of the similarity between genes associated with SRRM2 and miR-27a/b-3p indicates common functional pathways and their dysfunction correlates with molecular etiopathology mechanisms of PD onset.

Urinary Biomarkers for Neurodegenerative Diseases

Global incidence of neurodegenerative diseases (NDDs) such as Alzheimer's disease (AD) and Parkinson's disease (PD) is rapidly increasing, but the diagnosis of these diseases at their early stage is challenging. Therefore, the availability of reproducible and reliable biomarkers to diagnose such diseases is more critical than ever. In addition, biomarkers could be used not only to diagnose diseases but also to monitor the development of disease therapeutics. Urine is an excellent biofluid that can be utilized as a source of biomarker to diagnose not only several renal diseases but also other diseases because of its abundance in invasive sampling. However, urine was conventionally regarded as inappropriate as a source of biomarker for neurodegenerative diseases because it is anatomically distant from the central nervous system (CNS), a major pathologic site of NDD, in comparison to other biofluids such as cerebrospinal fluid (CSF) and plasma. However, recent studies have suggested that urine could be utilized as a source of NDD biomarker if an appropriate marker is predetermined by metabolomic and proteomic approaches in urine and other samples. In this review, we summarize such studies related to NDD.

Circulating Exosome microRNAs as Diagnostic Biomarkers of Dementia

Dementia is a syndrome of acquired cognitive impairment that leads to a significant decline in a patient’s daily life, ability to learn, and the ability to communicate with others. Dementia occurs in many diseases, including Alzheimer’s disease (AD), dementia with Lewy bodies, frontotemporal dementia, and Parkinson’s disease dementia (PDD). Although the analysis of biomarkers in the cerebrospinal fluid (CSF) and peripheral blood physicochemical analysis can indicate neurological impairment, there are currently no sensitive biomarkers for early clinical diagnosis of dementia or for identifying the cause of dementia. Previous studies have suggested that circulating micro (mi)RNAs may be used as biomarkers for diagnosing neurological disorders. However, miRNAs are susceptible to interference by other components in the peripheral circulation, bringing into question the diagnostic value of circulating miRNAs. Exosomes secreted by most cell types contain proteins, mRNAs, and miRNAs that are closely associated with changes in cellular functions. Exosome miRNAs (ex-miRNAs) are highly stable and resistant to degradation. Therefore, these may serve as useful biomarkers for the early clinical diagnosis of dementia. Here, we review studies of ex-miRNAs that commonly cause clinical dementia and explore whether ex-miRNAs may be used as early diagnostic biomarkers of dementia.

Insights into the Effects of Mesenchymal Stem Cell-Derived Secretome in Parkinson's Disease

Mesenchymal stem cell (MSC)-derived secretome demonstrated therapeutic effects like those reported after MSCs transplantation. MSC-derived secretome may avoid various side effects of MSC-based therapy, comprising undesirable differentiation of engrafted MSCs and potential activation of the allogeneic immune response. MSC-derived secretome comprises soluble factors and encapsulated extravesicles (EVs). MSC-derived EVs comprise microvesicles, apoptotic bodies, and exosomes. In this review, we focus on the recent insights into the effects of MSC-derived secretome in Parkinson’s disease (PD). In particular, MSC-derived secretome and exosomal components counteracted neuroinflammation and enhanced antioxidant capacity and neurotrophic factors expression. In light of the insights reported in this review, MSC-derived secretome or their released exosomes may be used as a potential therapeutic approach or as adjuvant therapy to counteract the disease progression and improve PD symptoms. Also, MSC-derived secretome may be used as a vehicle in cell transplantation approaches to enhance the viability and survival of engrafted cells. Furthermore, since exosomes can cross the blood–brain barrier, they may be used as biomarkers of neural dysfunction. Further studies are necessary to fully characterize the bioactive molecules present in the secretome and to create a new, effective, cell-free therapeutic approach towards a robust clinical outcome for PD patients.

Development of early diagnosis of Parkinson's disease: Illusion or reality?

The fight against neurodegenerative diseases, Alzheimer disease and Parkinson's disease (PD), is a challenge of the 21st century. The low efficacy of treating patients is due to the late diagnosis and start of therapy, after the degeneration of most specific neurons and depletion of neuroplasticity. It is believed that the development of early diagnosis (ED) and preventive treatment will delay the onset of specific symptoms. This review evaluates methodologies for developing ED of PD. Since PD is a systemic disease, and the degeneration of certain neurons precedes that of nigrostriatal dopaminergic neurons that control motor function, the current methodology is based on searching biomarkers, such as premotor symptoms and changes in body fluids (BF) in patients. However, all attempts to develop ED were unsuccessful. Therefore, it is proposed to enhance the current methodology by (i) selecting among biomarkers found in BF in patients at the clinical stage those that are characteristics of animal models of the preclinical stage, (ii) searching biomarkers in BF in subjects at the prodromal stage, selected by detecting premotor symptoms and failure of the nigrostriatal dopaminergic system. Moreover, a new methodology was proposed for the development of ED of PD using a provocative test, which is successfully used in internal medicine.

Serum microRNA expression levels in Turkish patients with Parkinson's disease

Objectives: To determine the serum expression levels of seven candidate microRNAs (miRNA); miR-19a, miR-19b, miR-29a, miR-29c, miR-181, miR-195 and miR-221 in Turkish patients with Parkinson's disease (PD) and explored their potential role in the diagnosis of PD. We further described the relationship between these miRNAs with the clinical findings and treatment of PD.Materials and methods: The study included 51 PD patients and 20 healthy controls. The clinical severity of disease was assessed using the Hoehn Yahr staging scale and the Unified Parkinson's Disease Rating Scale (UPDRS). Venous blood samples were taken after fasting for 12 h, then centrifuged. Obtained serum samples were stored until analysis of miRNA. In the laboratory, expression levels of these miRNAs were analyzed using a real-time PCR instrument. Receiver-operating characteristic analysis and area-under the-curve (AUC) was used to evaluate these miRNA levels as potential diagnostic biomarkers for PD.Results: miR-29c expression levels were increased significantly for PD patients compared to healthy controls. There were no significant differences in levels of other miRNAs between PD patients and controls. The AUC of miR-29c was 0.689. The sensitivity and specificity of this diagnostic test was 54.9% and 80.0%, respectively. miR-195 level was found to have a significant positive correlation only with age. Significant negative correlation was found between miR-29a level and UPDRS total score. miR-19b was found higher in ropinirole drug used group than that of pramipexole group.Conclusion: This study suggests that serum miR-29c expression level might be potential biomarker in the diagnosis of Turkish Parkinson patients.

MicroRNAs alteration as early biomarkers for cancer and neurodegenerative diseases: New challenges in pesticides exposure

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Current knowledge linking pesticide exposure, cancer and neuro-degenerative diseases to dysregulation of microRNA network was summarized.

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Literature indicates differential miRNA expression targeting biomolecules and pathways involved in cancer and neurodegenerative diseases.

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Evaluation of miRNA expression may be used to develop new non-invasive strategies for the prediction and prognosis of diseases including cancer.

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The application of miRNAs as diagnostic and therapeutic biomarkers in the clinical field is extremely challenging.

This review summarizes the current knowledge linking cancer and neuro-degenerative diseases to dysregulation of microRNA network following pesticide exposure. Most findings revealed differential miRNA expression targeting biomolecules and pathways involved in various neoplastic localizations and neurodegenerative diseases.

A growing body of evidence in recent literature indicates that alteration of specific miRNAs can represent an early biomarker of disease following exposure to chemical agents, including pesticides. Different miRNAs seem to regulate cell proliferation, apoptosis, migration, invasion, and metastasis via many biological pathways through modulation of the expression of target mRNAs.

The evaluation of miRNA expression levels may be used to develop new non-invasive strategies for the prediction and prognosis of many diseases, including cancer. However, the application of miRNAs as diagnostic and therapeutic biomarkers in the clinical field is extremely challenging.

α-synuclein accumulation in SH-SY5Y cell impairs autophagy in microglia by exosomes overloading miR-19a-3p

Aims: To reveal whether miRNAs in exosomes from α-synuclein transgenic SH-SY5Y cells are able to regulate autophagy in recipient microglia. Materials & methods: Microarray analysis and experimental verification were adopted to assess the significance of autophagy-associated miRNAs in exosomes from neuronal model of α-synucleinopathies. Results: We found that miR-19a-3p increased remarkably in the exosomes from α-synuclein gene transgenic SH-SY5Y cells. Further study inferred that α-synuclein gene transgenic SH-SY5Y cell-derived exosomes and miR-19a-3p mimic consistently inhibited the expression of phosphatase and tensin homolog and increased the phosphorylation of AKT and mTOR, both of which ultimately lead to the dysfunction of autophagy in recipient microglia. Conclusion: The data suggested that enhanced expression of miR-19a-3p in exosomes suppress autophagy in recipient microglia by targeting the phosphatase and tensin homolog/AKT/mTOR signaling pathway.

MicroRNAs Dysregulation and Metabolism in Multiple System Atrophy

Multiple system atrophy (MSA) is an adult onset, fatal disease, characterized by an accumulation of alpha-synuclein (α-syn) in oligodendroglial cells. MicroRNAs (miRNAs) are small non-coding RNAs involved in post-translational regulation and several biological processes. Disruption of miRNA-related pathways in the central nervous system (CNS) plays an important role in the pathogenesis of neurodegenerative diseases, including MSA. While the exact mechanisms underlying miRNAs in the pathogenesis of MSA remain unclear, it is known that miRNAs can repress the translation of messenger RNAs (mRNAs) that regulate the following pathogenesis associated with MSA: autophagy, neuroinflammation, α-syn accumulation, synaptic transmission, oxidative stress, and apoptosis. In this review, the metabolism of miRNAs and their functional roles in the pathogenesis of MSA are discussed, thereby highlighting miRNAs as potential new biomarkers for the diagnosis of MSA and in increasing our understanding of the disease process.

Upregulated Expression of MicroRNA-204-5p Leads to the Death of Dopaminergic Cells by Targeting DYRK1A-Mediated Apoptotic Signaling Cascade

MicroRNAs (miRs) downregulate or upregulate the mRNA level by binding to the 3′-untranslated region (3′UTR) of target gene. Dysregulated miR levels can be used as biomarkers of Parkinson’s disease (PD) and could participate in the etiology of PD. In the present study, 45 brain-enriched miRs were evaluated in serum samples from 50 normal subjects and 50 sporadic PD patients. The level of miR-204-5p was upregulated in serum samples from PD patients. An upregulated level of miR-204-5p was also observed in the serum and substantia nigra (SN) of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. Expression of miR-204-5p increased the level of α-synuclein (α-Syn), phosphorylated (phospho)-α-Syn, tau, or phospho-tau protein and resulted in the activation of endoplasmic reticulum (ER) stress in SH-SY5Y dopaminergic cells. Expression of miR-204-5p caused autophagy impairment and activation of c-Jun N-terminal kinase (JNK)-mediated apoptotic cascade in SH-SY5Y dopaminergic cells. Our study using the bioinformatic method and dual-luciferase reporter analysis suggests that miR-204-5p positively regulates mRNA expression of dual-specificity tyrosine phosphorylation regulated kinase 1A (DYRK1A) by directly interacting with 3′UTR of DYRK1A. The mRNA and protein levels of DYRK1A were increased in SH-SY5Y dopaminergic cells expressing miR-204-5p and SN of MPTP-induced PD mouse model. Knockdown of DYRK1A expression or treatment of the DYRK1A inhibitor harmine attenuated miR-204-5p-induced increase in protein expression of phospho-α-Syn or phospho-tau, ER stress, autophagy impairment, and activation of JNK-mediated apoptotic pathway in SH-SY5Y dopaminergic cells or primary cultured dopaminergic neurons. Our results suggest that upregulated expression of miR-204-5p leads to the death of dopaminergic cells by targeting DYRK1A-mediated ER stress and apoptotic signaling cascade.

Plasma microRNA miR-26b as a potential diagnostic biomarker of degenerative myelopathy in Pembroke welsh corgis

BACKGROUND

Degenerative myelopathy (DM) is a progressive neurodegenerative disease frequently found in Pembroke Welsh Corgis (PWCs). Most DM-affected PWCs are homozygous for the mutant superoxide dismutase 1 (SOD1) allele; however, the genetic examination for the SOD1 mutation does not exclusively detect symptomatic dogs. In order to identify novel biomarkers, the plasma microRNA (miRNA) profiles of PWCs with DM were investigated.

RESULTS

Quantification of the plasma levels of 277 miRNAs by an RT-qPCR array identified 11 up-regulated miRNAs and 7 down-regulated miRNAs in DM-affected PWCs from those in wild-type SOD1 PWCs. A pathway analysis identified 3 miRNAs: miR-26b, miR-181a, and miR-196a, which potentially regulate several genes associated with SOD1. In order to validate the diagnostic accuracy of the candidate miRNAs in the aged PWC population, candidate miRNAs in plasma were measured by RT-qPCR and a receiver operating characteristic (ROC) curve analysis was performed. miR-26b had the largest area under the ROC curve for distinguishing DM PWCs from healthy PWCs (sensitivity, 66.7%; specificity, 87.0%). The plasma level of miR-26b was significantly higher in the DM group than in the healthy control group. A positive correlation was observed between increases in the plasma level of miR-26b and disease progression.

CONCLUSIONS

These results suggest that plasma miR-26b is a potential novel diagnostic biomarker of DM.

MicroRNA‑195 triggers neuroinflammation in Parkinson's disease in a Rho‑associated kinase 1‑dependent manner

Parkinson's disease (PD) is a common progressive neurodegenerative disorder occurring in older individuals. Mechanistically, neuroinflammation is a central pathological change in the progression of PD. Activation of microglia is widely considered to be a major trigger for neuroinflammation. Certain microRNAs (miRs) are key factors in inhibiting or stimulating inflammation during the occurrence and development of PD, among which miR‑195 may be a potential crucial biomarker. However, the underlying pathological mechanisms remain unclear. To investigate the pathogenesis of PD, lipopolysaccharide (LPS) was used to establish an in vitro model of microglia activation in the present study. It was revealed that miR‑195 expression was decreased in LPS‑stimulated BV2 cells, suggesting a potential mechanism of action of miR‑195 on microglia activation. Furthermore, gain‑ and loss‑of‑function experiments were performed by successful transfection of microglia with miR‑195 mimics or inhibitors. The results demonstrated that miR‑195 overexpression inhibited the release of pro‑inflammatory cytokines, including inducible nitric oxide synthase, interleukin‑6 (IL‑6) and tumor necrosis factor‑α, but induced the release of anti‑inflammatory cytokines in LPS‑treated BV2 cells, including IL‑4 and IL‑10. In addition, Rho‑associated kinase 1 (ROCK1), which is negatively regulated by miR‑195, was increased in LPS‑stimulated BV2 cells. ROCK1 knockdown with small interfering RNA exhibited the same effect as miR‑195 overexpression on regulating microglia status, suggesting that the miR‑195/ROCK1 interaction serves a central role in inducing microglia activation. Furthermore, inhibition of ROCK1 impaired cell viability and proliferation but induced cell apoptosis in LPS‑treated miR‑195‑deficient BV2 cells. The present results suggest that miR‑195 is a potential therapeutic target for PD.

Decreased miR-325-5p Contributes to Visceral Hypersensitivity Through Post-transcriptional Upregulation of CCL2 in Rat Dorsal Root Ganglia

Chronic visceral hypersensitivity is an important type of chronic pain with unknown etiology and pathophysiology. Recent studies have shown that epigenetic regulation plays an important role in the development of chronic pain conditions. However, the role of miRNA-325-5p in chronic visceral pain remains unknown. The present study was designed to determine the roles and mechanism of miRNA-325-5p in a rat model of chronic visceral pain. This model was induced by neonatal colonic inflammation (NCI). In adulthood, NCI led to a significant reduction in the expression of miRNA-325-5p in colon-related dorsal root ganglia (DRGs), starting to decrease at the age of 4 weeks and being maintained to 8 weeks. Intrathecal administration of miRNA-325-5p agomir significantly enhanced the colorectal distention (CRD) threshold in a time-dependent manner. NCI also markedly increased the expression of CCL2 (C-C motif chemokine ligand 2) in colon-related DRGs at the mRNA and protein levels relative to age-matched control rats. The expression of CXCL12, IL33, SFRS7, and LGI1 was not significantly altered in NCI rats. CCL2 was co-expressed in NeuN-positive DRG neurons but not in glutamine synthetase-positive glial cells. Furthermore, CCL2 was mainly expressed in isolectin B4-binding- and calcitonin gene-related peptide-positive DRG neurons but in few NF-200-positive cells. More importantly, CCL2 was expressed in miR-325-5p-positive DRG neurons. Intrathecal injection of miRNA-325-5p agomir remarkably reduced the upregulation of CCL2 in NCI rats. Administration of Bindarit, an inhibitor of CCL2, markedly raised the CRD threshold in NCI rats in a dose- and time-dependent manner. These data suggest that NCI suppresses miRNA-325-5p expression and enhances CCL2 expression, thus contributing to visceral hypersensitivity in adult rats.

Reliability of a Novel Video-Based Method for Assessing Age-Related Changes in Upper Limb Kinematics

Monitoring age-related changes in motor function can be used to identify deviations that represent underlying diseases for which early diagnosis is often paramount for efficacious, interventional therapies. Currently, the availability of cost-effective and reliable diagnostic tools capable of routine monitoring is limited. Adequate diagnostic systems are needed to identify, monitor and distinguish early subclinical symptoms of neurological diseases from normal aging-associated changes. Herein, we describe the development, initial validation and reliability of the Hand-Arm Movement Monitoring System (HAMMS), a video-based data acquisition system built using a programmable, versatile platform for acquiring temporal and spatial metrics of hand and arm movements. A healthy aging population of 111 adults were used to evaluate the HAMMS via a repetitive motion test of changing target size. The test required participants to move a fiducial on their hand between two targets presented on a video monitor. The test-retest reliability based on Intraclass Correlation Coefficient (ICCs) for the system ranged from 0.56 to 0.87 and the Linear Correlation Coefficients (LCCs) ranged from 0.58 to 0.87. Average speed, average acceleration, speed error and center offset all demonstrated a positive correlation with age. Using an intertarget path of hand motion, we observed an age-dependent increase in the average number of points outside the most direct motion path, indicating a reduction in hand-arm movement control with age. The reliability, flexibility and programmability of the HAMMS makes this low cost, video-based platform an effective tool for evaluating longitudinal changes in hand-arm related movements and a potential diagnostic device for neurological diseases where hand-arm movements are affected.

Parkinson's Disease: Biomarkers, Treatment, and Risk Factors

Parkinson's disease (PD) is a progressive neurodegenerative disorder caused mainly by lack of dopamine in the brain. Dopamine is a neurotransmitter involved in movement, motivation, memory, and other functions; its level is decreased in PD brain as a result of dopaminergic cell death. Dopamine loss in PD brain is a cause of motor deficiency and, possibly, a reason of the cognitive deficit observed in some PD patients. PD is mostly not recognized in its early stage because of a long latency between the first damage to dopaminergic cells and the onset of clinical symptoms. Therefore, it is very important to find reliable molecular biomarkers that can distinguish PD from other conditions, monitor its progression, or give an indication of a positive response to a therapeutic intervention. PD biomarkers can be subdivided into four main types: clinical, imaging, biochemical, and genetic. For a long time protein biomarkers, dopamine metabolites, amino acids, etc. in blood, serum, cerebrospinal liquid (CSF) were considered the most promising. Among the candidate biomarkers that have been tested, various forms of α-synuclein (α-syn), i.e., soluble, aggregated, post-translationally modified, etc. were considered potentially the most efficient. However, the encouraging recent results suggest that microRNA-based analysis may bring considerable progress, especially if it is combined with α-syn data. Another promising analysis is the advanced metabolite profiling of body fluids, called "metabolomics" which may uncover metabolic fingerprints specific for various stages of PD. Conventional pharmacological treatment of PD is based on the replacement of dopamine using dopamine precursors (levodopa, L-DOPA, L-3,4 dihydroxyphenylalanine), dopamine agonists (amantadine, apomorphine) and MAO-B inhibitors (selegiline, rasagiline), which can be used alone or in combination with each other. Potential risk factors include environmental toxins, drugs, pesticides, brain microtrauma, focal cerebrovascular damage, and genomic defects. This review covers molecules that might act as the biomarkers of PD. Then, PD risk factors (including genetics and non-genetic factors) and PD treatment options are discussed.

Identification of altered microRNAs in serum of a mouse model of Parkinson's disease

Parkinson's disease (PD) is the second most prevalent neurodegenerative disease, whose hallmark is the loss of dopamine terminals in the substantia nigra pars compacta (SNpc). PD is usually diagnosed after the appearance of motor symptoms, when about 70% of neurons in the SNpc have already been lost. Because of that, it is important to search for new methods that aid in the early diagnosis of PD. In recent years, microRNAs (miRs) have emerged as potential biomarkers for a variety of diseases and hold the potential to be used to aid in the diagnosis of PD. Therefore, the aim of this study was to characterize if specific miRs are differentially expressed in serum in a mouse model of PD. To induce PD-like damage, mice were subcutaneously injected with 25 mg/kg of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP) by administering 10 doses over a period of 5 weeks, with 3.5 days between doses. Expression of 71 different microRNAs was quantified in serum separated from blood collected at day 35, using next-generation sequencing. Histological analysis and quantification of neurotransmitters were performed to confirm dopaminergic neurodegeneration. Chronic MPTP treatment induced loss of dopaminergic terminals in the SNpc and caudate putamen, confirmed by a decrease in the number of tyrosine hydroxylase and dopamine transporter positive cells. In addition, MPTP decreased the concentration of dopamine and its metabolites in the SNpc, simulating the damage observed in PD. From the 71 miRs analyzed, only 4 were differentially expressed after MPTP treatment. Serum levels of miR19b, miR124, miR126a and miR133b were significantly decreased in MPTP-treated mice compared to control. These data suggest that specific miRs are downregulated in a pre-clinical model of PD and hold the potential to be used as biomarkers to aid in the diagnosis of this disease. Further experiments need to be conducted to validate the use of these miRs as biomarkers of PD in additional pre-clinical models as well as in samples from patients diagnosed with PD.

Sensing the Stress: A Role for the UPRmt and UPRam in the Quality Control of Mitochondria

Mitochondria exist as compartmentalized units, surrounded by a selectively permeable double membrane. Within is contained the mitochondrial genome and protein synthesis machinery, required for the synthesis of OXPHOS components and ultimately, ATP production. Despite their physical barrier, mitochondria are tightly integrated into the cellular environment. A constant flow of information must be maintained to and from the mitochondria and the nucleus, to ensure mitochondria are amenable to cell metabolic requirements and also to feedback on their functional state. This review highlights the pathways by which mitochondrial stress is signaled to the nucleus, with a particular focus on the mitochondrial unfolded protein response (UPR^mt) and the unfolded protein response activated by the mistargeting of proteins (UPR^am). Although these pathways were originally discovered to alleviate proteotoxic stress from the accumulation of mitochondrial-targeted proteins that are misfolded or unimported, we review recent findings indicating that the UPR^mt can also sense defects in mitochondrial translation. We further discuss the regulation of OXPHOS assembly and speculate on a possible role for mitochondrial stress pathways in sensing OXPHOS biogenesis.