microRNAs in Parkinson's Disease: From Pathogenesis to Novel Diagnostic and Therapeutic Approaches

MicroRNA-Targeted Gene Regulation in Salivary Gland Tissue of De Novo Parkinson's Disease Patients

Although α-synucleinopathy has been confirmed in the submandibular gland (SMG) tissue of Parkinson's disease (PD) patients, in-depth disease-related molecular research, such as tissue-specific transcriptional signals, has not been performed. In the present study, disease-relevant tissue-specific transcriptional signals in SMG tissue from PD patients were investigated to identify potential diagnostic, prognostic, and pathophysiologic biomarkers. Here, seven de novo drug-naïve PD patients and six age- and sex-matched individuals without neurological or psychological diseases were enrolled. Total RNA sequencing (RNA-seq) and total small RNA-seq (smRNA-seq) were performed on SMG tissue and blood samples, with 26 RNA-seq and 26 smRNA-seq samples used for the final analysis. Differentially expressed genes (DEGs) and microRNAs in SMG tissue and blood from PD patients were obtained and their functional integration and interaction network were analyzed. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that the DEGs interacted with cytokine-, inflammation-, and immune-related pathways. Synphilin-1 expression was significantly downregulated in SMG tissue of PD patients, and α-synuclein expression did not significantly differ between PD patients and controls in either SMG tissue or blood. Fifteen tissue-specific miRNA signals in SMG tissue were identified that showed better diagnostic ability compared with those in blood samples. The correlation between DEGs and environmental factors appeared altered in PD patients. The results indicated the DEGs and microRNA signatures identified in SMG tissue may be promising diagnostic and prognostic biomarkers. These molecular insights offer potential avenues for the development of novel therapeutic strategies targeting the underlying disease mechanisms in PD patients.

Scoping review of epigenetics on neurodegenerative diseases: research frontiers and publication status

Aims

Epigenetics has significantly evolved and emerged as important players in the pathogenesis of neurodegenerative diseases. However, a scientometric synthesis of such changes over time is currently lacking.

Methods

We conducted a comprehensive search of the Web of Science Core Collection from inception until November 5, 2022, using appropriate keywords. Our primary objective was to employ scientometric analysis to depict changes in keywords over time and to assess the structure and credibility of clusters. Additionally, we examined the network of research (countries, institutions, and authors) using CiteSpace and VOSviewer.

Results

We identified 25 clusters with well-structured networks (Q = 0.82) and highly credible clustering (S = 0.91) from 16,181 articles published between 1999 and 2022. Our findings are as follows: (a) the literature and research interest concerning the epigenetics of neurodegenerative diseases are continuously growing; (b) the three most productive countries are the USA, China, and Germany; (c) international collaborative relationships exist, alongside small, isolated collaboration networks of individual institutions.

Conclusion

The number and impact of global publications on the epigenetics of neurodegenerative diseases have expanded rapidly over the past 20 years. This review provides valuable guidelines for researchers interested in neurodegenerative diseases research.

Roflumilast-loaded nanostructured lipid carriers attenuate oxidative stress and neuroinflammation in Parkinson's disease model

Parkinson's disease (PD) is a progressive neurodegenerative disorder with limited symptomatic treatment options. Targeting phosphodiesterase 4 (PDE4) has shown a promising result in several preclinical studies. In our study, we aim to repurpose US FDA-approved PDE4 inhibitor for PD. Through in-silico study, we identified roflumilast (ROF) as the potential candidate targeting PDE4B2. In Drosophila PD expressing the A30P mutant α-synuclein model, ROF exhibited anti-PD effects as indicated by negative geotaxis and antioxidant activities. Given the low brain distribution of ROF (<50%) at clinical doses, incorporation into nanostructured lipid carriers (NLCs) was carried out to enhanced blood-brain barrier permeability. In vitro release studies indicated sustained ROF release from NLCs (≈75%) over 24 h. Single-dose oral toxicity studies reported no mortality or toxicity signs. ROF-loaded NLCs significantly alleviated behavioural deficits, increased antioxidant parameters (p < 0.05), and reduced TNF-α and IL-6 levels (p < 0.5) in the striatum compared to pure ROF. ROF-loaded NLCs demonstrated potential anti-PD effects with high efficacy than pure ROF. Our study suggests that nanostructured lipid carriers (NLCs) can be a promising drug delivery system to overcome limitations associated with poor brain bioavailability of lipophilic drugs like ROF for PD treatment. Further investigation related to brain occupancy and underlying mechanisms of our formulation is warranted to confirm and strengthen our current findings.

Bibliometric analysis of microRNAs and Parkinson's disease from 2014 to 2023

Background

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the degeneration of dopaminergic neurons. Recent research has emphasized a significant correlation between microRNAs (miRNAs) and PD. To identify key research areas, provide a comprehensive overview of current research in various fields, and propose potential directions for future studies, a bibliometric analysis was conducted on the involvement of miRNAs in Parkinson's disease from 2014 to 2023.

Methods

Relevant literature records were collected from the Web of Science Core Collection on February 29, 2024. Subsequently, the data underwent analysis using the Bibliometrix R package and VOSviewer (version 1.6.19).

Results

The annual scientific publications on miRNAs and Parkinson's disease demonstrated an increasing trend, with an annual growth rate of 12.67%. China, the United States, and India emerged as the top three most productive countries/regions. The University of Barcelona had the highest annual publications, followed by Central South University and the Helmholtz Association. The INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES held the top position in terms of H-index and total citations, reflecting its extensive influence and prolific publication output. Kim, J., Junn, E., Hébert, S.S., and Doxakis, E. were the most frequently co-cited authors in the field. Based on the analysis of keywords, the most frequently occurring terms included "alpha-synuclein," "neurodegenerative disease," "exosome," "neuroinflammation," "oxidative stress," "autophagy," and "amyotrophic lateral sclerosis," which have emerged as prominent research topics. Concurrently, there has been notable interest in topics such as "ceRNA," "lncRNAs," "mitochondrial dysfunction," and "circular RNA."

Conclusion

This study focused on identifying emerging trends and critical research topics in the bibliometric analysis of microRNAs related to Parkinson's disease. These findings highlight the diverse research landscape and evolving trend of miRNA-related research in PD. The field of miRNA research in Parkinson's disease is actively exploring the underlying mechanisms of miRNA function, identifying potential diagnostic markers, and developing innovative therapeutic strategies. The results of our study offer significant contributions to researchers' ability to track contemporary developments and guide the trajectory of future research in this domain.

Regulatory miR-SNP rs4636297A > G in miR-126 is linked to increased risk of rigidity feature in patients with Parkinson's disease

INTRODUCTION

A growing body of strong evidence shows that the dysfunction of miRNAs plays key roles in the development and progression of Parkinson's disease (PD), however, little data has been reported on the association of their SNPs with PD susceptibility. In this study, we investigated the association of regulatory miR-SNP rs4636297A > G with a functional effect on the expression of miRNA-126, as a key dysregulated miRNA in the PD, with the susceptibility and clinical features of the PD.

METHODS AND MATERIALS

In current study, we included a population consisting of 120 patients with PD and 120 clinically healthy individuals, and their blood samples were taken. After extracting the DNAs, the genotyping of the miR-SNP rs4636297A > G was done through RFLP-PCR technique. Finally, the association of this SNP with the risk and clinical features of PD was determined.

RESULTS

Although the results showed that the two groups did not differ significantly in terms of allelic and genotype frequencies, it was clinically found that individuals with genotypes carrying the minor allele G (AG and GG genotypes) of the miR-SNP rs4636297A > G had an increased risk of developing rigidity feature in the PD compared to its homozygous major AA genotype (GG genotype; OR = 5.14, p = 0.038 & GA genotype; OR = 4.32, p = 0.032).

CONCLUSION

We report for the first time a significant association of functional regulatory SNP rs4636297A > G in the miR-126 with the Parkinson's clinicopathology. Therefore, this miR-SNP can have a potential predictive biomarker capacity for rigidity in PD, although this hypothesis needs further investigation in the future.

Engineering supramolecular dynamics of self-assembly and turnover of oncogenic microRNAs to drive their synergistic destruction in tumor models

Rationally-engineered functional biomaterials offer the opportunity to interface with complex biology in a predictive, precise, yet dynamic way to reprogram their behaviour and correct shortcomings. Success here may lead to a desired therapeutic effect against life-threatening diseases, such as cancer. Here, we engineered "Crab"-like artificial ribonucleases through coupling of peptide and nucleic acid building blocks, capable of operating alongside and synergistically with intracellular enzymes (RNase H and AGO2) for potent destruction of oncogenic microRNAs. "Crab"-like configuration of two catalytic peptides ("pincers") flanking the recognition oligonucleotide was instrumental here in providing increased catalytic turnover, leading to ≈30-fold decrease in miRNA half-life as compared with that for "single-pincer" conjugates. Dynamic modeling of miRNA cleavage illustrated how such design enabled "Crabs" to drive catalytic turnover through simultaneous attacks at different locations of the RNA-DNA heteroduplex, presumably by producing smaller cleavage products and by providing toeholds for competitive displacement by intact miRNA strands. miRNA cleavage at the 5'-site, spreading further into double-stranded region, likely provided a synergy for RNase H1 through demolition of its loading region, thus facilitating enzyme turnover. Such synergy was critical for sustaining persistent disposal of continually-emerging oncogenic miRNAs. A single exposure to the best structural variant (Crab-p-21) prior to transplantation into mice suppressed their malignant properties and reduced primary tumor volume (by 85 %) in MCF-7 murine xenograft models.

A marine-derived antioxidant astaxanthin as a potential neuroprotective and neurotherapeutic agent: A review of its efficacy on neurodegenerative conditions

Astaxanthin is a potent lipid-soluble carotenoid produced by several different freshwater and marine microorganisms, including microalgae, bacteria, fungi, and yeast. The proven therapeutic effects of astaxanthin against different diseases have made this carotenoid popular in the nutraceutical market and among consumers. Recently, astaxanthin is also receiving attention for its effects in the co-adjuvant treatment or prevention of neurological pathologies. In this systematic review, studies evaluating the efficacy of astaxanthin against different neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, cerebrovascular diseases, and spinal cord injury are analyzed. Based on the current literature, astaxanthin shows potential biological activity in both in vitro and in vivo models. In addition, its preventive and therapeutic activities against the above-mentioned diseases have been emphasized in studies with different experimental designs. In contrast, none of the 59 studies reviewed reported any safety concerns or adverse health effects as a result of astaxanthin supplementation. The preventive or therapeutic role of astaxanthin may vary depending on the dosage and route of administration. Although there is a consensus in the literature regarding its effectiveness against the specified diseases, it is important to determine the safe intake levels of synthetic and natural forms and to determine the most effective forms for oral intake.

Association of Serum Extracellular Vesicle miRNAs with Cognitive Functioning and Quality of Life in Parkinson's Disease

The identification of mechanisms associated with Parkinson disease (PD) development in cognitive functioning would be of great usefulness to clarify PD pathogenesis and to develop preventive and therapeutic strategies. In this study, blood serum extracellular vesicle (EV) levels of the candidate microRNAs (small noncoding RNAs that play a role in gene expression regulation):,miR-7, miR-21, miR-153, miR-155, miR-200a and miR-214, have been investigated for association with PD in a group of 93 patients with cognitive parameters, PD symptoms, affected quality of life and some clinical characteristics. MiRNA was extracted from patients' blood serum EVs, transcribed into cDNA and their expression was evaluated using RT-PCR. The miR-153 and miR-200a showed the most plausible correlations with cognitive functioning parameters such as general intellectual functioning, psychomotor speed, mental flexibility, and nonverbal executive functions. Moreover, lower levels of miR-153 were associated with attention span, working memory and psychomotor speed with learning. Increased levels of miR-200a, miR-7, miR-214, and miR-155 were also linked with neurological functioning, such as bradykinesia, tremor, balance and others. Despite the fact that due to small sample size, our results should be considered as preliminary, our study suggests that miRNA expression in EVs could be associated with symptom severity, cognitive impairment and quality of life in PD.

Exosomal microRNAs in Parkinson's disease: insights into biomarker potential and disease pathology

Parkinson's disease (PD) is a prevalent neurodegenerative condition primarily affecting the elderly population. Despite its high incidence in aged individuals, there are no reliable blood-based biomarkers for clinical diagnosis of PD and early screening of susceptible individuals. Recent studies have revealed the significance of exosomes in mediating cell-to-cell communications by transferring bioactive molecules, such as proteins, nucleic acids (including miRNAs), lipids, and metabolites, between cells. Due to their ability to carry diverse molecular cargo and their involvement in various physiological and pathological processes, exosomes have gained significant attention as potential disease biomarkers. Notably, exosomes have the ability to cross the blood-brain barrier, and as a result, they can be found in circulating body fluids, including cerebrospinal fluid (CSF), serum, and plasma. Therefore, the identification of PD-specific exosomes in blood samples could be a promising avenue with biomarker potential for advancing clinical diagnosis and planning therapeutic strategies. This review highlights the current understanding of exosomal miRNAs in PD pathology, emphasising their potential for clinical utility as biomarkers even though several challenges may have to be overcome to precisely utilize exosomal miRNAs as biomarkers specific to PD.

Epigenetic modifications in Parkinson's disease: A critical review

Parkinson's Disease (PD) is a progressive neurodegenerative disorder expected to increase by over 50% by 2030 due to increasing life expectancy. The disease's hallmarks include slow movement, tremors, and postural instability. Impaired protein processing is a major factor in the pathophysiology of PD, leading to the buildup of aberrant protein aggregates, particularly misfolded α-synuclein, also known as Lewy bodies. These Lewy bodies lead to inflammation and further death of dopaminergic neurons, leading to imbalances in excitatory and inhibitory neurotransmitters, causing excessive uncontrollable movements called dyskinesias. It was previously suggested that a complex interplay involving hereditary and environmental variables causes the specific death of neurons in PD; however, the exact mechanism of the association involving the two primary modifiers is yet unknown. An increasing amount of research points to the involvement of epigenetics in the onset and course of several neurological conditions, such as PD. DNA methylation, post-modifications of histones, and non-coding RNAs are the primary examples of epigenetic alterations, that is defined as alterations to the expression of genes and functioning without modifications in DNA sequence. Epigenetic modifications play a significant role in the development of PD, with genes such as Parkin, PTEN-induced kinase 1 (PINK1), DJ1, Leucine-Rich Repeat Kinase 2 (LRRK2), and alpha-synuclein associated with the disease. The aberrant epigenetic changes implicated in the pathophysiology of PD and their impact on the design of novel therapeutic approaches are the primary focus of this review.

An Overview of Epigenetic Changes in the Parkinson's Disease Brain

Parkinson's disease is a progressive neurodegenerative disorder, predominantly of the motor system. Although some genetic components and cellular mechanisms of Parkinson's have been identified, much is still unknown. In recent years, emerging evidence has indicated that non-DNA-sequence variation (in particular epigenetic mechanisms) is likely to play a crucial role in the development and progression of the disease. Here, we present an up-to-date overview of epigenetic processes including DNA methylation, DNA hydroxymethylation, histone modifications and non-coding RNAs implicated in the brain of those with Parkinson's disease. We will also discuss the limitations of current epigenetic research in Parkinson's disease, the advantages of simultaneously studying genetics and epigenetics, and putative novel epigenetic therapies.

Transferrin-conjugated magnetic nanoparticles for the isolation of brain-derived blood exosomal MicroRNAs: A novel approach for Parkinson's disease diagnosis

BACKGROUND

Brain-derived exosomes circulate in the bloodstream and other bodily fluids, serving as potential indicators of neurological disease progression. These exosomes present a promising avenue for the early and precise diagnosis of neurodegenerative conditions. Notably, miRNAs found in plasma extracellular vesicles (EVs) offer distinct diagnostic benefits due to their stability, abundance, and resistance to breakdown.

RESULTS

In this study, we introduce a method using transferrin conjugated magnetic nanoparticles (TMNs) to isolate these exosomes from the plasma of patients with neurological disorders. This TMNs technique is both quick (<35 min) and cost-effective, requiring no high-priced ingredients or elaborate equipment for EV extraction. Our method successfully isolated EVs from 33 human plasma samples, including those from patients with Parkinson's disease (PD), Multiple Sclerosis (MS), and Dementia. Using quantitative polymerase chain reaction (PCR) analysis, we evaluated the potential of 8 exosomal miRNA profiles as biomarker candidates. Six exosomal miRNA biomarkers (miR-195-5p, miR-495-3p, miR-23b-3P, miR-30c-2-3p, miR-323a-3p, and miR-27a-3p) were consistently linked with all stages of PD.

SIGNIFICANCE

The TMNs method provides a practical, cost-efficient way to isolate EVs from biological samples, paving the way for non-invasive neurological diagnoses. Furthermore, the identified miRNA biomarkers in these exosomes may emerge as innovative tools for precise diagnosis in neurological disorders including PD.

Sample-to-answer salivary miRNA testing: New frontiers in point-of-care diagnostic technologies

MicroRNA (miRNA), crucial non-coding RNAs, have emerged as key biomarkers in molecular diagnostics, prognosis, and personalized medicine due to their significant role in gene expression regulation. Salivary miRNA, in particular, stands out for its non-invasive collection method and ease of accessibility, offering promising avenues for the development of point-of-care diagnostics for a spectrum of diseases, including cancer, neurodegenerative disorders, and infectious diseases. Such development promises rapid and precise diagnosis, enabling timely treatment. Despite significant advancements in salivary miRNA-based testing, challenges persist in the quantification, multiplexing, sensitivity, and specificity, particularly for miRNA at low concentrations in complex biological mixtures. This work delves into these challenges, focusing on the development and application of salivary miRNA tests for point-of-care use. We explore the biogenesis of salivary miRNA and analyze their quantitative expression and their disease relevance in cancer, infection, and neurodegenerative disorders. We also examined recent progress in miRNA extraction, amplification, and multiplexed detection methods. This study offers a comprehensive view of the development of salivary miRNA-based point-of-care testing (POCT). Its successful advancement could revolutionize the early detection, monitoring, and management of various conditions, enhancing healthcare outcomes. This article is categorized under: Diagnostic Tools > Biosensing Diagnostic Tools > Diagnostic Nanodevices.

Exosomes: current knowledge and future perspectives

Exosomes are membrane-bound micro-vesicles that possess endless therapeutic potential for treatment of numerous pathologies including autoimmune, cardiovascular, ocular, and nervous disorders. Despite considerable knowledge about exosome biogenesis and secretion, still, there is a lack of information regarding exosome uptake by cell types and internal signaling pathways through which these exosomes process cellular response. Exosomes are key components of cell signaling and intercellular communication. In central nervous system (CNS), exosomes can penetrate BBB and maintain homeostasis by myelin sheath regulation and the waste products elimination. Therefore, the current review summarizes role of exosomes and their use as biomarkers in cardiovascular, nervous and ocular disorders. This aspect of exosomes provides positive hope to monitor disease development and enable early diagnosis and treatment optimization. In this review, we have summarized recent findings on physiological and therapeutic effects of exosomes and also attempt to provide insights about stress-preconditioned exosomes and stem cell-derived exosomes.

Experimental capture of miRNA targetomes: disease-specific 3'UTR library-based miRNA targetomics for Parkinson's disease

The identification of targetomes remains a challenge given the pleiotropic effect of miRNAs, the limited effects of miRNAs on individual targets, and the sheer number of estimated miRNA-target gene interactions (MTIs), which is around 44,571,700. Currently, targetome identification for single miRNAs relies on computational evidence and functional studies covering smaller numbers of targets. To ensure that the targetome analysis could be experimentally verified by functional assays, we employed a systematic approach and explored the targetomes of four miRNAs (miR-129-5p, miR-129-1-3p, miR-133b, and miR-873-5p) by analyzing 410 predicted target genes, both of which were previously associated with Parkinson's disease (PD). After performing 13,536 transfections, we validated 442 of the 705 putative MTIs (62,7%) through dual luciferase reporter assays. These analyses increased the number of validated MTIs by at least 2.1-fold for miR-133b and by a maximum of 24.3-fold for miR-873-5p. Our study contributes to the experimental capture of miRNA targetomes by addressing i) the ratio of experimentally verified MTIs to predicted MTIs, ii) the sizes of disease-related miRNA targetomes, and iii) the density of MTI networks. A web service to support the analyses on the MTI level is available online ( https://ccb-web.cs.uni-saarland.de/utr-seremato ), and all the data have been added to the miRATBase database ( https://ccb-web.cs.uni-saarland.de/miratbase ).

Insights into dietary phytochemicals targeting Parkinson's disease key genes and pathways: A network pharmacology approach

Parkinson's disease (PD) is a complex neurological disease associated with the degeneration of dopaminergic neurons. Oxidative stress is a key player in instigating apoptosis in dopaminergic neurons. To improve the survival of neurons many dietary phytochemicals have gathered significant attention recently. Thus, the present study implements a comprehensive network pharmacology approach to unravel the mechanisms of action of dietary phytochemicals that benefit disease management. A literature search was performed to identify ligands (i.e., comprising dietary phytochemicals and Food and Drug Administration pre-approved PD drugs) in the PubMed database. Targets associated with selected ligands were extracted from the search tool for interactions of chemicals (STITCH) database. Then, the construction of a gene-gene interaction (GGI) network, analysis of hub-gene, functional and pathway enrichment, associated transcription factors, miRNAs, ligand-target interaction network, docking were performed using various bioinformatics tools together with molecular dynamics (MD) simulations. The database search resulted in 69 ligands and 144 unique targets. GGI and subsequent topological measures indicate histone acetyltransferase p300 (EP300), mitogen-activated protein kinase 1 (MAPK1) or extracellular signal-regulated kinase (ERK)2, and CREB-binding protein (CREBBP) as hub genes. Neurodegeneration, MAPK signaling, apoptosis, and zinc binding are key pathways and gene ontology terms. hsa-miR-5692a and SCNA gene-associated transcription factors interact with all the 3 hub genes. Ligand-target interaction (LTI) network analysis suggest rasagiline and baicalein as candidate ligands targeting MAPK1. Rasagiline and baicalein form stable complexes with the Y205, K330, and V173 residues of MAPK1. Computational molecular insights suggest that baicalein and rasagiline are promising preclinical candidates for PD management.

Astrocytic transcription factors REST, YY1, and putative microRNAs in Parkinson's disease and advanced therapeutic strategies

Transcription factors (TF) and microRNAs are regulatory factors in astrocytes and are linked to several Parkinson's disease (PD) progression causes, such as disruption of glutamine transporters in astrocytes and concomitant disrupted glutamine uptake and inflammation. REST, a crucial TF, has been documented as an epigenetic repressor that limits the expression of neuronal genes in non-neural cells. REST activity is significantly linked to its corepressors in astrocytes, specifically histone deacetylases (HDACs), CoREST, and MECP2. Another REST-regulating TF, YY1, has been studied in astrocytes, and its interaction with REST has been investigated. In this review, the molecular processes that support the astrocytic control of REST and YY1 in terms of the regulation of glutamate transporter EAAT2 were addressed in a more detailed and comprehensive manner. Both TFs' function in astrocytes and how astrocyte abnormalities cause PD is still a mystery. Moreover, microRNAs (short non-coding RNAs) are key regulators that have been correlated to the expression and regulation of numerous genes linked to PD. The identification of numerous miRs that are engaged in astrocyte dysfunction that triggers PD has been shown. The term "Gut-brain axis" refers to the two systems' mutual communication. Gut microbial dysbiosis, which mediates an imbalance of the gut-brain axis, might contribute to neurodegenerative illnesses through altered astrocytic regulation. New treatment approaches to modify the gut-brain axis and prevent astrocytic repercussions have also been investigated in this review.

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.

miR-221 and Parkinson's disease: A biomarker with therapeutic potential

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra, leading to various motor and non-motor symptoms. Several cellular and molecular mechanisms such as alpha-synuclein (α-syn) accumulation, mitochondrial dysfunction, oxidative stress and neuroinflammation are involved in the pathogenesis of this disease. MicroRNAs (miRNAs) play important roles in post-transcriptional gene regulation. They are typically about 21-25 nucleotides in length and are involved in the regulation of gene expression by binding to the messenger RNA (mRNA) molecules. miRNAs like miR-221 play important roles in various biological processes, including development, cell proliferation, differentiation and apoptosis. miR-221 promotes neuronal survival against oxidative stress and neurite outgrowth and neuronal differentiation. Additionally, the role of miR-221 in PD has been investigated in several studies. According to the results of these studies, (1) miR-221 protects PC12 cells against oxidative stress induced by 6-hydroxydopamine; (2) miR-221 prevents Bax/caspase-3 signalling activation by stopping Bim; (3) miR-221 has moderate predictive power for PD; (4) miR-221 directly targets PTEN, and PTEN over-expression eliminates the protective action of miR-221 on p-AKT expression in PC12 cells; and (5) miRNA-221 controls cell viability and apoptosis by manipulating the Akt signalling pathway in PD. This review study suggested that miR-221 has the potential to be used as a clinical biomarker for PD diagnosis and stage assignment.

Purple Carrot Extract Exhibits a Neuroprotective Profile in th e Nigrostriatal Pathway in the Reserpine-induced Model of Parkinson 's Disease

BACKGROUND

Parkinson's disease (PD) is a chronic neurodegenerative disorder characterized by the progressive loss of dopaminergic neurons in the nigrostriatal pathway. Even with scientific and technological advances, the therapeutic approaches used for the treatment of PD have shown to be largely ineffective in controlling the progression of symptoms in the long term. There is a growing demand for the development of novel therapeutic strategies for PD treatment. Different herbs and supplements have been considered as adjuvant to treat the symptoms of Parkinsonism. The carrot is one of the most consumed vegetable species worldwide, and its root is known for its content of anthocyanins, which possess antioxidant and antiinflammatory properties. This study evaluated the neuroprotective effect of purple carrot extract (CAR) in rats on the reserpine (RES)-induced progressive parkinsonism model.

METHODS

Male rats (6-month-old) received orally the CAR (400 mg/kg) or vehicle and subcutaneously RES (0.01 mg/kg) or vehicle for 28 days (Preventive Phase). From the 29th day, rats received CAR or vehicle daily and RES (0.1 mg/kg) or vehicle every other day (for 23 days, Protective phase). Behavioral tests were conducted throughout the treatment. Upon completion, the animals' brain were processed for tyrosine hydroxylase (TH) immunohistochemical assessment.

RESULTS

Our results showed that the chronic treatment of CAR protected against motor disabilities, reducing the time of catalepsy behavior and decreasing the frequency of oral movements, possibly by preserving TH levels in the Ventral Tegmental Area (VTA) and SNpc.

CONCLUSION

CAR extract is effective to attenuate motor symptoms in rats associated with increased TH+ levels in the Ventral Tegmental Area (VTA) and SNpc, indicating the potential nutraceutical benefits of CAR extract in a progressive parkinsonism model induced by RES.

The role of microRNAs in the pathophysiology of human central nervous system: A focus on neurodegenerative diseases

microRNAs (miRNAs) are suggested to play substantial roles in regulating the development and various physiologic functions of the central nervous system (CNS). These include neurogenesis, cell fate and differentiation, morphogenesis, formation of dendrites, and targeting non-neural mRNAs. Notably, deregulation of an increasing number of miRNAs is associated with several neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis and CNS tumors. They are particularly known to affect the amyloid β (Aβ) cleavage and accumulation, tau protein homeostasis, and expression of alpha-synuclein (α-syn), Parkin, PINK1, and brain-derived neurotrophic factor (BDNF) that play pivotal roles in the pathogenesis of neurodegenerative diseases. These include miR-16, miR-17-5p, miR-20a, miR-106a, miR-106b, miR-15a, miR-15b, miR-103, miR-107, miR-298, miR-328, miR-195, miR-485, and miR-29. In CNS tumors, several miRNAs, including miR-31, miR-16, and miR-21 have been identified to modulate tumorigenesis through impacting tumor invasion and apoptosis. In this review article, we have a look at the recent advances on our knowledge about the role of miRNAs in human brain development and functions, neurodegenerative diseases, and their clinical potentials.

Chiisanoside Mediates the Parkin/ZNF746/PGC-1α Axis by Downregulating MiR-181a to Improve Mitochondrial Biogenesis in 6-OHDA-Caused Neurotoxicity Models In Vitro and In Vivo: Suggestions for Prevention of Parkinson's Disease

The degeneration of dopamine (DA) neurons is known to be associated with defects in mitochondrial biogenesis caused by aging, environmental factors, or mutations in genes, leading to Parkinson's disease (PD). As PD has not yet been successfully cured, the strategy of using small molecule drugs to protect and restore mitochondrial biogenesis is a promising direction. This study evaluated the efficacy of synthetic chiisanoside (CSS) identified in the leaves of Acanthopanax sessiliflorus to prevent PD symptoms. The results show that in the 6-hydroxydopamine (6-OHDA) model, CSS pretreatment can effectively alleviate the reactive oxygen species generation and apoptosis of SH-SY5Y cells, thereby lessening the defects in the C. elegans model including DA neuron degeneration, dopamine-mediated food sensitivity behavioral disorders, and shortened lifespan. Mechanistically, we found that CSS could restore the expression of proliferator-activated receptor gamma coactivator-1-alpha (PGC-1α), a key molecule in mitochondrial biogenesis, and its downstream related genes inhibited by 6-OHDA. We further confirmed that this is due to the enhanced activity of parkin leading to the ubiquitination and degradation of PGC-1α inhibitor protein Zinc finger protein 746 (ZNF746). Parkin siRNA treatment abolished this effect of CSS. Furthermore, we found that CSS inhibited 6-OHDA-induced expression of miR-181a, which targets parkin. The CSS's ability to reverse the 6-OHDA-induced reduction in mitochondrial biogenesis and activation of apoptosis was abolished after the transfection of anti-miR-181a and miR-181a mimics. Therefore, the neuroprotective effect of CSS mainly promotes mitochondrial biogenesis by regulating the miR-181a/Parkin/ZNF746/PGC-1α axis. CSS potentially has the opportunity to be developed into PD prevention agents.

MicroRNA-based therapeutics for inflammatory disorders of the microbiota-gut-brain axis

An emerging but less explored shared pathophysiology across microbiota-gut-brain axis disorders is aberrant miRNA expression, which may represent novel therapeutic targets. miRNAs are small, endogenous non-coding RNAs that are important transcriptional repressors of gene expression. Most importantly, they regulate the integrity of the intestinal epithelial and blood-brain barriers and serve as an important communication channel between the gut microbiome and the host. A well-defined understanding of the mode of action, therapeutic strategies and delivery mechanisms of miRNAs is pivotal in translating the clinical applications of miRNA-based therapeutics. Accumulating evidence links disorders of the microbiota-gut-brain axis with a compromised gut-blood-brain-barrier, causing gut contents such as immune cells and microbiota to enter the bloodstream leading to low-grade systemic inflammation. This has the potential to affect all organs, including the brain, causing central inflammation and the development of neurodegenerative and neuropsychiatric diseases. In this review, we have examined in detail miRNA biogenesis, strategies for therapeutic application, delivery mechanisms, as well as their pathophysiology and clinical applications in inflammatory gut-brain disorders. The research data in this review was drawn from the following databases: PubMed, Google Scholar, and Clinicaltrials.gov. With increasing evidence of the pathophysiological importance for miRNAs in microbiota-gut-brain axis disorders, therapeutic targeting of cross-regulated miRNAs in these disorders displays potentially transformative and translational potential. Further preclinical research and human clinical trials are required to further advance this area of research.

Neuronally enriched microvesicle RNAs are differentially expressed in the serums of Parkinson's patients

Background

Circulating small RNAs (smRNAs) originate from diverse tissues and organs. Previous studies investigating smRNAs as potential biomarkers for Parkinson's disease (PD) have yielded inconsistent results. We investigated whether smRNA profiles from neuronally-enriched serum exosomes and microvesicles are altered in PD patients and discriminate PD subjects from controls.

Methods

Demographic, clinical, and serum samples were obtained from 60 PD subjects and 40 age- and sex-matched controls. Exosomes and microvesicles were extracted and isolated using a validated neuronal membrane marker (CD171). Sequencing and bioinformatics analyses were used to identify differentially expressed smRNAs in PD and control samples. SmRNAs also were tested for association with clinical metrics. Logistic regression and random forest classification models evaluated the discriminative value of the smRNAs.

Results

In serum CD171 enriched exosomes and microvesicles, a panel of 29 smRNAs was expressed differentially between PD and controls (false discovery rate (FDR) < 0.05). Among the smRNAs, 23 were upregulated and 6 were downregulated in PD patients. Pathway analysis revealed links to cellular proliferation regulation and signaling. Least absolute shrinkage and selection operator adjusted for the multicollinearity of these smRNAs and association tests to clinical parameters via linear regression did not yield significant results. Univariate logistic regression models showed that four smRNAs achieved an AUC ≥ 0.74 to discriminate PD subjects from controls. The random forest model had an AUC of 0.942 for the 29 smRNA panel.

Conclusion

CD171-enriched exosomes and microvesicles contain the differential expression of smRNAs between PD and controls. Future studies are warranted to follow up on the findings and understand the scientific and clinical relevance.

The Impact of microRNAs on Mitochondrial Function and Immunity: Relevance to Parkinson's Disease

Parkinson's Disease (PD), the second most common neurodegenerative disorder, is characterised by the severe loss of dopaminergic neurons in the Substantia Nigra pars compacta (SNpc) and by the presence of Lewy bodies. PD is diagnosed upon the onset of motor symptoms, such as bradykinesia, resting tremor, rigidity, and postural instability. It is currently accepted that motor symptoms are preceded by non-motor features, such as gastrointestinal dysfunction. In fact, it has been proposed that PD might start in the gut and spread to the central nervous system. Growing evidence reports that the gut microbiota, which has been found to be altered in PD patients, influences the function of the central and enteric nervous systems. Altered expression of microRNAs (miRNAs) in PD patients has also been reported, many of which regulate key pathological mechanisms involved in PD pathogenesis, such as mitochondrial dysfunction and immunity. It remains unknown how gut microbiota regulates brain function; however, miRNAs have been highlighted as important players. Remarkably, numerous studies have depicted the ability of miRNAs to modulate and be regulated by the host's gut microbiota. In this review, we summarize the experimental and clinical studies implicating mitochondrial dysfunction and immunity in PD. Moreover, we gather recent data on miRNA involvement in these two processes. Ultimately, we discuss the reciprocal crosstalk between gut microbiota and miRNAs. Studying the bidirectional interaction of gut microbiome-miRNA might elucidate the aetiology and pathogenesis of gut-first PD, which could lead to the application of miRNAs as potential biomarkers or therapeutical targets for PD.

Neuroprotective Effects of Lactobacillus plantarum PS128 in a Mouse Model of Parkinson’s Disease: The Role of Gut Microbiota and MicroRNAs

Parkinson’s disease (PD) is a neurodegenerative disease characterized by motor deficits and marked neuroinflammation in various brain regions. The pathophysiology of PD is complex and mounting evidence has suggested an association with the dysregulation of microRNAs (miRNAs) and gut dysbiosis. Using a rotenone-induced PD mouse model, we observed that administration of Lactobacillus plantarum PS128 (PS128) significantly improved motor deficits in PD-like mice, accompanied by an increased level of dopamine, reduced dopaminergic neuron loss, reduced microglial activation, reduced levels of inflammatory factors, and enhanced expression of neurotrophic factor in the brain. Notably, the inflammation-related expression of miR-155-5p was significantly upregulated in the proximal colon, midbrain, and striatum of PD-like mice. PS128 reduced the level of miR-155-5p, whereas it increased the expression of suppressor of cytokine signaling 1 (SOCS1), a direct target of miR-155-5p and a critical inhibitor of the inflammatory response in the brain. Alteration of the fecal microbiota in PD-like mice was partially restored by PS128 administration. Among them, Bifidobacterium, Ruminiclostridium_6, Bacteroides, and Alistipes were statistically correlated with the improvement of rotenone-induced motor deficits and the expression of miR-155-5p and SOCS1. Our findings suggested that PS128 ameliorates motor deficits and exerts neuroprotective effects by regulating the gut microbiota and miR-155-5p/SOCS1 pathway in rotenone-induced PD-like mice.

Promising biomarkers and therapeutic targets for the management of Parkinson's disease: recent advancements and contemporary research

Parkinson's disease (PD) is one of the progressive neurological diseases which affect around 10 million population worldwide. The clinical manifestation of motor symptoms in PD patients appears later when most dopaminergic neurons have degenerated. Thus, for better management of PD, the development of accurate biomarkers for the early prognosis of PD is imperative. The present work will discuss the potential biomarkers from various attributes covering biochemical, microRNA, and neuroimaging aspects (α-synuclein, DJ-1, UCH-L1, β-glucocerebrosidase, BDNF, etc.) for diagnosis, recent development in PD management, and major limitations with current and conventional anti-Parkinson therapy. This manuscript summarizes potential biomarkers and therapeutic targets, based on available preclinical and clinical evidence, for better management of PD.

Employing nanoparticle tracking analysis of salivary neuronal exosomes for early detection of neurodegenerative diseases

Neurodegenerative diseases are a set of progressive and currently incurable diseases that are primarily caused by neuron degeneration. Neurodegenerative diseases often lead to cognitive impairment and dyskinesias. It is now well recognized that molecular events precede the onset of clinical symptoms by years. Over the past decade, intensive research attempts have been aimed at the early diagnosis of these diseases. Recently, exosomes have been shown to play a pivotal role in the occurrence and progression of many diseases including cancer and neurodegenerative diseases. Additionally, because exosomes can cross the blood-brain barrier, they may serve as a diagnostic tool for neural dysfunction. In this review, we detail the mechanisms and current challenges of these diseases, briefly review the role of exosomes in the progression of neurodegenerative diseases, and propose a novel strategy based on salivary neuronal exosomes and nanoparticle tracking analysis that could be employed for screening the early onset of neurodegenerative diseases.

Characterizing microRNA editing and mutation sites in Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder whose pathogenesis is still unclear. MicroRNAs (miRNAs) are a kind of endogenous small non-coding RNAs that play important roles in the post-transcriptional regulation of genes. Recent researches show that miRNAs are edited in multiple ways especially in central nervous systems. A-to-I editing of RNA catalyzed by Adenosine deaminases acting on RNA (ADARs) happens intensively in brain and is also noticed in other organs and tissues. Although miRNAs are widely edited in human brain, miRNA editing in ASD is still largely unexplored. In order to reveal the editing events of miRNAs in ASD, we analyzed 131 miRNA-seq samples from 8 different brain regions of ASD patients and normal controls. We identified 834 editing sites with significant editing levels, of which 70 sites showed significantly different editing levels in the superior frontal gyrus samples of ASD patients (ASD-SFG) when compared with those of control samples. The editing level of an A-to-I editing site in hsa-mir-376a-1 (hsa-mir-376a-1_9_A_g) in ASD-SFG is higher than that of normal controls, and the difference is exaggerated in individuals under 10 years. The increased expression of ADAR1 is consistent with the increased editing level of hsa-mir-376a-1_9_A_g in ASD-SFG samples compared to normal SFG samples. Furthermore, we verify that A-to-I edited hsa-mir-376a-5p directly represses GPR85 and NAPB, which may contribute to the abnormal neuronal development of ASD patients. These results provide new insights into the mechanism of ASD.

Role and Dysregulation of miRNA in Patients with Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative synucleinopathy that has a not yet fully understood molecular pathomechanism behind it. The role of risk genes regulated by small non-coding RNAs, or microRNAs (miRNAs), has also been highlighted in PD, where they may influence disease progression and comorbidities. In this case-control study, we analyzed miRNAs on peripheral blood mononuclear cells by means of RNA-seq in 30 participants, with the aim of identifying miRNAs differentially expressed in PD compared to age-matched healthy controls. Additionally, we investigated the pathways influenced by differentially expressed miRNAs and assessed whether a specific pathway could potentially be associated with PD susceptibility (enrichment analyses performed using the Ingenuity Pathway Analysis tools). Overall, considering that the upregulation of miRNAs might be related with the downregulation of their messenger RNA targets, and vice versa, we found several putative targets of dysregulated miRNAs (i.e., upregulated: hsa-miR-1275, hsa-miR-23a-5p, hsa-miR-432-5p, hsa-miR-4433b-3p, and hsa-miR-4443; downregulated: hsa-miR-142-5p, hsa-miR-143-3p, hsa-miR-374a-3p, hsa-miR-542-3p, and hsa-miR-99a-5p). An inverse connection between cancer and neurodegeneration, called "inverse comorbidity", has also been noted, showing that some genes or miRNAs may be expressed oppositely in neurodegenerative disorders and in some cancers. Therefore, it may be reasonable to consider these miRNAs as potential diagnostic markers and outcome measures.

Characterizing Relevant MicroRNA Editing Sites in Parkinson's Disease

MicroRNAs (miRNAs) are extensively edited in human brains. However, the functional relevance of the miRNA editome is largely unknown in Parkinson's disease (PD). By analyzing small RNA sequencing profiles of brain tissues of 43 PD patients and 88 normal controls, we found that the editing levels of five A-to-I and two C-to-U editing sites are significantly correlated with the ages of normal controls, which is disrupted in PD patients. We totally identified 362 miRNA editing sites with significantly different editing levels in prefrontal cortices of PD patients (PD-PC) compared to results of normal controls. We experimentally validated that A-to-I edited miR-497-5p, with significantly higher expression levels in PD-PC compared to normal controls, directly represses OPA1 and VAPB. Furthermore, overexpression of A-to-I edited miR-497-5p downregulates OPA1 and VAPB in two cell lines, and inhibits proliferation of glioma cells. These results suggest that the hyperediting of miR-497-5p in PD contributes to enhanced progressive neurodegeneration of PD patients. Our results provide new insights into the mechanistic understanding, novel diagnostics, and therapeutic clues of PD.

Exosomal noncoding RNAs in central nervous system diseases: biological functions and potential clinical applications

Central nervous system (CNS) disease is a general term for a series of complex and diverse diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), CNS tumors, stroke, epilepsy, and amyotrophic lateral sclerosis (ALS). Interneuron and neuron-glia cells communicate with each other through their homeostatic microenvironment. Exosomes in the microenvironment have crucial impacts on interneuron and neuron-glia cells by transferring their contents, such as proteins, lipids, and ncRNAs, constituting a novel form of cell-to-cell interaction and communication. Exosomal noncoding RNAs (ncRNAs), including microRNAs (miRNAs), long noncoding RNAs (lncRNAs), circular RNAs (circRNAs), and PIWI-interacting RNAs (piRNAs), regulate physiological functions and maintain CNS homeostasis. Exosomes are regarded as extracellular messengers that transfer ncRNAs between neurons and body fluids due to their ability to cross the blood-brain barrier. This review aims to summarize the current understanding of exosomal ncRNAs in CNS diseases, including prospective diagnostic biomarkers, pathological regulators, therapeutic strategies and clinical applications. We also provide an all-sided discussion of the comparison with some similar CNS diseases and the main limitations and challenges for exosomal ncRNAs in clinical applications.

MicroRNA Expression Profile Changes in the Leukocytes of Parkinson’s Disease Patients

Parkinson’s disease (PD) is one of the most common movement disorders. It is primarily diagnosed clinically. A correct diagnosis of PD in its early stages is important for the development of a pathogenic treatment, which necessitates a search for potential biomarkers of the disease. We evaluated the diagnostic value of several microRNAs and their relationship with the clinical characteristics of PD. The study included 70 PD patients and 40 healthy volunteers. We analyzed the expression of 15 microRNAs in blood leukocytes, which were selected based on literature data and modern concepts of molecular PD pathogenesis. All patients were evaluated using the Hoehn and Yahr scale, UPDRS, NMSQ, and PDQ-39. The data analysis revealed a statistically significant increase in the expression of miR-7-5p, miR-29c-3p, and miR-185-5p and a statistically significant decrease in the expression of miR-29a-3p and miR-30c-1-5p in leukocytes in PD. However, the altered microRNA profile was shown to have a moderate diagnostic value for PD diagnosis. MicroRNA expression changes were associated with the motor and non-motor phenotypic features of PD and administration of anti-Parkinson’s drugs. Also, a relationship between some of the microRNAs studied and the duration and severity of PD was found, which may potentially be used to monitor disease progression.

Recent developments in nucleic acid-based therapies for Parkinson's disease: Current status, clinical potential, and future strategies

Parkinson's disease is the second most common progressive neurodegenerative disease diagnosed mainly based on clinical symptoms caused by loss of nigrostriatal dopaminergic neurons. Although currently available pharmacological therapies provide symptomatic relief, however, the disease continues to progress eventually leading to severe motor and cognitive decline and reduced quality of life. The hallmark pathology of Parkinson's disease includes intraneuronal inclusions known as Lewy bodies and Lewy neurites, including fibrillar α-synuclein aggregates. These aggregates can progressively spread across synaptically connected brain regions leading to emergence of disease symptoms with time. The α-synuclein level is considered important in its fibrillization and aggregation. Nucleic acid therapeutics have recently been shown to be effective in treating various neurological diseases, raising the possibility of developing innovative molecular therapies for Parkinson's disease. In this review, we have described the advancements in genetic dysregulations in Parkinson's disease along with the disease-modifying strategies involved in genetic regulation with particular focus on downregulation of α-synuclein gene using various novel technologies, notably antisense oligonucleotides, microRNA, short interfering RNA, short hairpin RNAs, DNA aptamers, and gene therapy of vector-assisted delivery system-based therapeutics. In addition, the current status of preclinical and clinical development for nucleic acid-based therapies for Parkinson's disease have also been discussed along with their limitations and opportunities.

A Review of Molecular Interplay between Neurotrophins and miRNAs in Neuropsychological Disorders

Various neurotrophins (NTs), including nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin-4, promote cellular differentiation, survival, and maintenance, as well as synaptic plasticity, in the peripheral and central nervous system. The function of microRNAs (miRNAs) and other small non-coding RNAs, as regulators of gene expression, is pivotal for the appropriate control of cell growth and differentiation. There are positive and negative loops between NTs and miRNAs, which exert modulatory effects on different signaling pathways. The interplay between NTs and miRNAs plays a crucial role in the regulation of several physiological and pathological brain procedures. Emerging evidence suggests the diagnostic and therapeutic roles of the interactions between NTs and miRNAs in several neuropsychological disorders, including epilepsy, multiple sclerosis, Alzheimer's disease, Huntington's disease, amyotrophic lateral sclerosis, schizophrenia, anxiety disorders, depression, post-traumatic stress disorder, bipolar disorder, and drug abuse. Here, we review current data regarding the regulatory interactions between NTs and miRNAs in neuropsychological disorders, for which novel diagnostic and/or therapeutic strategies are emerging. Targeting NTs-miRNAs interactions for diagnostic or therapeutic approaches needs to be validated by future clinical studies.

Small Extracellular Vesicles Secreted by Nigrostriatal Astrocytes Rescue Cell Death and Preserve Mitochondrial Function in Parkinson's Disease

Extracellular vesicles (EVs) are emerging as powerful players in cell-to-cell communication both in healthy and diseased brain. In Parkinson's disease (PD)-characterized by selective dopaminergic neuron death in ventral midbrain (VMB) and degeneration of their terminals in striatum (STR)-astrocytes exert dual harmful/protective functions, with mechanisms not fully elucidated. Here, this study shows that astrocytes from the VMB-, STR-, and VMB/STR-depleted brains release a population of small EVs  in a region-specific manner. Interestingly, VMB-astrocytes secreted the highest rate of EVs, which is further exclusively increased in response to CCL3, a chemokine that promotes robust dopaminergic neuroprotection in different PD models. The neuroprotective potential of nigrostriatal astrocyte-EVs is investigated in differentiated versus undifferentiated SH-SY5Y cells exposed to oxidative stress and mitochondrial toxicity. EVs from both VMB- and STR-astrocytes counteract H2 O2 -induced caspase-3 activation specifically in differentiated cells, with EVs from CCL3-treated astrocytes showing a higher protective effect. High resolution respirometry further reveals that nigrostriatal astrocyte-EVs rescue neuronal mitochondrial complex I function impaired by the neurotoxin MPP+ . Notably, only EVs from VMB-astrocyte fully restore ATP production, again specifically in differentiated SH-SY5Y. These results highlight a regional diversity in the nigrostriatal system for the secretion and activities of astrocyte-EVs, with neuroprotective implications for PD.

Regulation of Parkinson's disease-associated genes by Pumilio proteins and microRNAs in SH-SY5Y neuronal cells

Parkinson's disease is the second most common age-related, neurodegenerative disease. A small collection of genes has been linked to Parkinson's disease including LRRK2, SAT1, and SNCA, the latter of which encodes the protein alpha-synuclein that aggregates in Lewy bodies as a hallmark of the disease. Overexpression of even wild-type versions of these genes can lead to pathogenesis, yet the regulatory mechanisms that control protein production of the genes are not fully understood. Pumilio proteins belong to the highly conserved PUF family of eukaryotic RNA-binding proteins that post-transcriptionally regulate gene expression through binding conserved motifs in the 3' untranslated region (UTR) of mRNA targets known as PUF Recognition Elements (PREs). The 3'UTRs of LRRK2, SNCA and SAT1 each contain multiple putative PREs. Knockdown (KD) of the two human Pumilio homologs (Pumilio 1 and Pumilio 2) in a neurodegenerative model cell line, SH-SY5Y, resulted in increased SNCA and LRRK2 mRNA, as well as alpha-synuclein levels, suggesting these genes are normally repressed by the Pumilio proteins. Some studies have indicated a relationship between Pumilio and microRNA activities on the same target, especially when their binding sites are close together. LRRK2, SNCA, and SAT1 each contain several putative microRNA-binding sites within the 3'UTR, some of which reside near PREs. Small RNA-seq and microRNA qPCR assays were performed in both wild type and Pumilio KD SH-SY5Y cells to analyze global and differential microRNA expression. One thousand four hundred and four microRNAs were detected across wild type and Pumilio KD cells. Twenty-one microRNAs were differentially expressed between treatments, six of which were previously established to be altered in Parkinson's disease patient samples or research models. Expression of ten miRs predicted to target LRRK2 and SNCA was verified by RT-qPCR. Collectively, our results demonstrate that Pumilios and microRNAs play a multi-faceted role in regulating Parkinson's disease-associated genes.

CircSV2b participates in oxidative stress regulation through miR-5107-5p-Foxk1-Akt1 axis in Parkinson's disease

As a novel type of non-coding RNAs, covalently closed circular RNAs (circRNAs) are ubiquitously expressed in eukaryotes. Emerging studies have indicated that dysregulation of circRNAs was related to neurological diseases. However, the biogenesis, regulation, function, and mechanism of circRNAs in Parkinson's disease (PD) remain largely unclear. In this study, thirty-three differentially expressed circRNAs (DECs) were detected by RNA-sequencing between the MPTP-induced PD mice model and the wild-type mice. Quantitative real-time PCR was used to determine the RNA level of DECs in the striatum (STR), substantia nigra pars compacta (SNpc), and serum exosomes, and it was found that circSV2b was downregulated in PD mice. Then, functional experiments in vivo were employed to explore the effect of circSV2b in PD. For the mechanism study, dual-luciferase reporter, fluorescence in situ hybridization (FISH), RNA immunoprecipitation (RIP), RNA pull-down, gene editing, and CUT & Tag were performed in vitro to confirm that circSV2b directly sponged miR-5107-5p and alleviated the suppression of the expression of the target gene Foxk1, and then positively regulated Akt1 transcription. In vivo, the mechanistic analysis demonstrated that circSV2b overexpression resisted oxidative stress damage through the ceRNA-Akt1 axis in PD models. Taken together, these findings suggested that the miR-5107-5p-Foxk1-Akt1 axis might serve as a key target of circSV2b overexpression in PD treatment, and highlighted the significant change of circSV2b in serum exosomes. Therefore, circSV2b might be a novel biomarker for the diagnosis and treatment of PD.

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CircSV2b in serum exosomes can be used as a biomarker for the diagnosis of PD.

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CircSV2b participates in the progress of PD through the ceRNA-Akt1 axis.

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CircSV2b overexpression is neuroprotective by resisting oxidative stress injury.

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Foxk1 can regulate Akt1 transcription.

Parkinson's Disease Derived Exosomes Aggravate Neuropathology in SNCA*A53T Mice

OBJECTIVE

Accumulation of α-synuclein (α-syn) in neurons is a prominent feature of Parkinson's disease (PD). Recently, researchers have considered that extracellular vesicles (EVs) may play an important role in protein exportation and propagation, and α-syn-containing EVs derived from the central nervous system (CNS) have been detected in peripheral blood. However, mechanistic insights into CNS-derived EVs have not been well-described.

METHODS

Likely neurogenic EVs were purified from the plasma of PD patients and healthy controls using a well-established immunoprecipitation assay with anti-L1CAM-coated beads. A Prnp-SNCAA53T transgenic PD mouse model was used to evaluate the neuronal pathology induced by PD-derived L1CAM-purified EVs. EV-associated microRNA (miRNA) profiling was used to screen for altered miRNAs in PD-derived L1CAM-purified EVs.

RESULTS

PD patient-derived L1CAM-purified (likely neurogenic) EVs facilitated α-syn pathology and neuron loss in Prnp-SNCAA53T transgenic PD mice. The miRNA, novel_miR_44438, was significantly increased in the PD group, which promoted α-syn accumulation and neuronal degeneration in a dose-dependent manner. Novel _miR_44438 directly targets NDST1 mRNA and inhibits the function of heparan sulfate, thus preventing exosome biogenesis and α-syn release from exosomes.

INTERPRETATION

Novel_miR_44438 in PD-derived L1CAM-purified EVs inhibits the α-syn efflux from neurons thereby promoting the pathological accumulation and aggregation of α-syn. ANN NEUROL 2022;92:230-245.

Microfluidic Invasion Chemotaxis Platform for 3D Neurovascular Co-Culture

Advances in microfabrication and biomaterials have enabled the development of microfluidic chips for studying tissue and organ models. While these platforms have been developed primarily for modeling human diseases, they are also used to uncover cellular and molecular mechanisms through in vitro studies, especially in the neurovascular system, where physiological mechanisms and three-dimensional (3D) architecture are difficult to reconstruct via conventional assays. An extracellular matrix (ECM) model with a stable structure possessing the ability to mimic the natural extracellular environment of the cell efficiently is useful for tissue engineering applications. Conventionally used techniques for this purpose, for example, Matrigels, have drawbacks of owning complex fabrication procedures, in some cases not efficient enough in terms of functionality and expenses. Here, we proposed a fabrication protocol for a GelMA hydrogel, which has shown structural stability and the ability to imitate the natural environment of the cell accurately, inside a microfluidic chip utilizing co-culturing of two human cell lines. The chemical composition of the synthesized GelMA was identified by Fourier transform infrared spectrophotometry (FTIR), its surface morphology was observed by field emission electron microscopy (FESEM), and the structural properties were analyzed by atomic force microscopy (AFM). The swelling behavior of the hydrogel in the microfluidic chip was imaged, and its porosity was examined for 72 h by tracking cell localization using immunofluorescence. GelMA exhibited the desired biomechanical properties, and the viability of cells in both platforms was more than 80% for seven days. Furthermore, GelMA was a viable platform for 3D cell culture studies and was structurally stable over long periods, even when prepared by photopolymerization in a microfluidic platform. This work demonstrated a viable strategy to conduct co-culturing experiments as well as modeling invasion and migration events. This microfluidic assay may have application in drug delivery and dosage optimization studies.

Exosomes in Alpha-Synucleinopathies: Propagators of Pathology or Potential Candidates for Nanotherapeutics?

The pathological accumulation of alpha-synuclein governs the pathogenesis of neurodegenerative disorders, such as Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy, collectively termed alpha-synucleinopathies. Alpha-synuclein can be released in the extracellular space, partly via exosomes, and this extracellular protein pool may contribute to disease progression by facilitating the spread of pathological alpha-synuclein or activating immune cells. The content of exosomes depends on their origin and includes specific proteins, lipids, functional mRNAs and various non-coding RNAs. Given their ability to mediate intercellular communication via the transport of multilevel information, exosomes are considered to be transporters of toxic agents. Beyond neurons, glial cells also release exosomes, which may contain inflammatory molecules and this glia-to-neuron or neuron-to-glia transmission of exosomal alpha-synuclein may contribute to the propagation of pathology and neuroinflammation throughout the brain. In addition, as their content varies as per their originating and recipient cells, these vesicles can be utilized as a diagnostic biomarker for early disease detection, whereas targeted exosomes may be used as scaffolds to deliver therapeutic agents into the brain. This review summarizes the current knowledge regarding the role of exosomes in the progression of alpha-synuclein-related pathology and their potential use as biomarkers and nanotherapeutics in alpha-synucleinopathies.

Dysregulated miRNAs as Biomarkers and Therapeutical Targets in Neurodegenerative Diseases

Alzheimer’s disease (AD), Parkinson’s disease (PD), and Amyotrophic Lateral Sclerosis (ALS) are representative neurodegenerative diseases (NDs) characterized by degeneration of selective neurons, as well as the lack of effective biomarkers and therapeutic treatments. In the last decade, microRNAs (miRNAs) have gained considerable interest in diagnostics and therapy of NDs, owing to their aberrant expression and their ability to target multiple molecules and pathways. Here, we provide an overview of dysregulated miRNAs in fluids (blood or cerebrospinal fluid) and nervous tissue of AD, PD, and ALS patients. By emphasizing those that are commonly dysregulated in these NDs, we highlight their potential role as biomarkers or therapeutical targets and describe the use of antisense oligonucleotides as miRNA therapies.

LncRNA DLX6-AS1 promotes microglial inflammatory response in Parkinson's disease by regulating the miR-223-3p/NRP1 axis

Parkinson's disease (PD) is a prevailing neurodegenerative disorder. This study discussed the mechanism of lncRNA distal-less homeobox 6 antisense 1 (DLX6-AS1) on inflammatory responses in PD. With healthy male C57BL/6 mice (8-10 weeks) and BV2 microglia as study subjects, we established PD models in vivo/in vitro by injection of 1-methyl-4-phenyl-2, 3, 6-tetrahydropyridine (MPTP) for 4 weeks and treatment of lipopolysaccharide (LPS) for 24hours, respectively. DLX6-AS1 expression in PD mice and BV2 microglia was examined using reverse transcription quantitative-polymerase chain reaction and then down-regulated via stereotaxic catheter injection or cell transfection to evaluate its effect on neurological function. Meanwhile, the cell number of TH+/Caspase3+/IBA1+ in substantia nigra, cell viability, and apoptosis rate of BV2 microglia, inflammatory levels, and NLR family pyrin domain containing 3 (NLRP3) inflammasome were determined using immunohistochemistry, MTT assay, flow cytometry, ELISA assay, and Western blot. The binding relationship between miR-223-3p and DLX6-AS1/Neuropilin-1 (NRP1) was verified by dual-luciferase assay and RNA immunoprecipitation assay. After down-regulation of DLX6-AS1, we down-regulated/overexpressed miR-223-3p/NRP1 levels in BV2 microglia. DLX6-AS1 was overexpressed in PD mice. Silencing DLX6-AS1 improved neurological function and alleviated microglial inflammation in PD mice. Specifically, the latency of mice falling from the rotating rod was longer, and the latency of climbing rod test was shorter; TH+ cells increased, while Caspase3+/IBA1+ cells decreased; the levels of inflammatory were lowered. Silencing DLX6-AS1 inhibited LPS-induced inflammation of BV2 microglia. DLX6-AS1 acted as the ceRNA of miR-223-3p to promote NRP1. Down-regulation of miR-223-3p or overexpression of NRP1 partially annulled the effect of silencing DLX6-AS1 on BV2 microglial inflammation. Overall, DLX6-AS1 promotes the microglial inflammatory response in PD through the ceRNA mechanism of miR-223-3p/NRP1.

Alteration of miRNAs in Small Neuron-Derived Extracellular Vesicles of Alzheimer's Disease Patients and the Effect of Extracellular Vesicles on Microglial Immune Responses

Alzheimer's disease (AD) is one of the most severe neurodegenerative diseases observed in the elderly population. Although the hallmarks of AD have been identified, the methods for its definitive diagnosis and treatment are still lacking. Extracellular vesicles (EVs) have become a promising source for biomarkers since the identification of their content. EVs are released from multiple cell types and, when released from neurons, they pass from the brain to the blood with their cargo molecules. Hence, neuron-specific EV-resident microRNAs (miRNAs) are promising biomarkers for diagnosis of AD. This study aimed to identify altered miRNA content in small neuron-derived extracellular vesicles (sNDEVs) isolated from AD patients and healthy individuals. Furthermore, we examined the role of sNDEV-resident miRNAs in neuron-glia cellular interaction to understand their role in AD propagation. We identified 10 differentially expressed miRNAs in the sNDEVs of patients via next-generation sequencing and validated the most dysregulated miRNA, let-7e, with qRT-PCR. Let-7e was significantly increased in the sNDEVs of AD patients compared with those of healthy controls in a larger cohort. First, we evaluated the diagnostic utility of let-7e via ROC curve analysis, which revealed an AUC value of 0.9214. We found that IL-6 gene expression was increased in human microglia after treatment with sNDEVs of AD patients with a high amount of let-7e. Our study suggests that sNDEV-resident let-7e is a potential biomarker for AD diagnosis, and that AD patient-derived sNDEVs induce a neuroinflammatory response in microglia.

MiR-9-5p Inhibits the MMP+-Induced Neuron Apoptosis through Regulating SCRIB/β-Catenin Signaling in Parkinson's Disease

The pathogenesis of Parkinson's disease remains unclear that there is no cure for Parkinson's disease yet. The abnormal expressions of certain miRNA are closely related to the occurrence and progression of Parkinson's disease. Here, we demonstrate that miR-9-5p inhibits the dopaminergic neuron apoptosis via the regulation of β-catenin signaling which directly targets SCRIB, a tumor suppressor gene. Besides, miR-9-5p improved the motor function of mice with Parkinson's disease. The results of this study suggest that miR-9-5p might be a potential therapeutic target against Parkinson's disease.

Diagnostic Test to Identify Parkinson's Disease from the Blood Sera of Chinese Population: A Cross-Sectional Study

Background

Parkinson's disease (PD) is a neurodegenerative disease, a hallmark by the formation of misfolded and aggregated α-synuclein proteins. The expression of potential microRNA (miRNA) candidates isolated from serum and cerebrospinal fluid (CSF) exosomes of PD patients was assessed for their diagnostic value and their potential role as biomarkers for PD was explored. In this study, we characterize the expression level of miRNAs in the exosomes of blood sera and cerebrospinal fluid and explore their potential role as biomarkers for PD.

Materials and Methods

A total of 209 patients having an onset of PD, along with 60 neurodegenerative (ND) disorders and 50 healthy controls were enrolled. Blood samples and CSF samples were collected and exosomes were isolated. The isolated exosomes were characterized using CD63 detection and exosomal RNA was extracted. Serum miRNA profiling was carried out by synthesizing cDNA from the purified RNA and miRNA transcripts were determined by qRT-PCR using SYBR Green PremixScript. microRNA profiling strategy was employed for extracting the exosomal miRNAs from the exosomes.

Results

Five common miRNAs viz. miR-151a-5p, miR-24, mir-485-5p, mir-331-5p, and mir-214 were found to be upregulated with statistical significance in both the serum exosome and CSF exosomes. The investigation revealed that serum and CSF exosomal miRNA molecules are definitive biomarkers for PD with proper specificity and sensitivity.

Conclusions

The significant level of miR-151a-5p, miR-24, mir-485-5p, mir-331-5p, and mir-214 was observed in the serum and CSF which may be established as a biomarker for the diagnosis of PD.

MicroRNAs in Methamphetamine-Induced Neurotoxicity and Addiction

Methamphetamine (METH) abuse remains a significant public health concern globally owing to its strong addictive properties. Prolonged abuse of the drug causes irreversible damage to the central nervous system. To date, no efficient pharmacological interventions are available, primarily due to the unclear mechanisms underlying METH action in the brain. Recently, microRNAs (miRNAs) have been identified to play critical roles in various cellular processes. The expression levels of some miRNAs are altered after METH administration, which may influence the transcription of target genes to regulate METH toxicity or addiction. This review summarizes the miRNAs in the context of METH use, discussing their role in the reward effect and neurotoxic sequelae. Better understanding of the molecular mechanisms involved in METH would be helpful for the development of new therapeutic strategies in reducing the harm of the drug.