MicroRNAs in Parkinson's disease

Therapeutic Implications and Regulations of Protein Post-translational Modifications in Parkinsons Disease

Parkinsons disease (PD) is a neurodegenerative disorder characterized by dopaminergic neuron loss and alpha-synuclein aggregation. This comprehensive review examines the intricate role of post-translational modifications (PTMs) in PD pathogenesis, focusing on DNA methylation, histone modifications, phosphorylation, SUMOylation, and ubiquitination. Targeted PTM modulation, particularly in key proteins like Parkin, DJ1, and PINK1, emerges as a promising therapeutic strategy for mitigating dopaminergic degeneration in PD. Dysregulated PTMs significantly contribute to the accumulation of toxic protein aggregates and dopaminergic neuronal dysfunction observed in PD. Targeting PTMs, including epigenetic strategies, addressing aberrant phosphorylation events, and modulating SUMOylation processes, provides potential avenues for intervention. The ubiquitin-proteasome system, governed by enzymes like Parkin and Nedd4, offers potential targets for clearing misfolded proteins and developing disease-modifying interventions. Compounds like ginkgolic acid, SUMO E1 enzyme inhibitors, and natural compounds like Indole-3-carbinol illustrate the feasibility of modulating PTMs for therapeutic purposes in PD. This review underscores the therapeutic potential of PTM-targeted interventions in modulating PD-related pathways, emphasizing the need for further research in this promising area of Parkinsons disease therapeutics.

ncRNAs and their impact on dopaminergic neurons: Autophagy pathways in Parkinson's disease

Parkinson's Disease (PD) is a complex neurological illness that causes severe motor and non-motor symptoms due to a gradual loss of dopaminergic neurons in the substantia nigra. The aetiology of PD is influenced by a variety of genetic, environmental, and cellular variables. One important aspect of this pathophysiology is autophagy, a crucial cellular homeostasis process that breaks down and recycles cytoplasmic components. Recent advances in genomic technologies have unravelled a significant impact of ncRNAs on the regulation of autophagy pathways, thereby implicating their roles in PD onset and progression. They are members of a family of RNAs that include miRNAs, circRNA and lncRNAs that have been shown to play novel pleiotropic functions in the pathogenesis of PD by modulating the expression of genes linked to autophagic activities and dopaminergic neuron survival. This review aims to integrate the current genetic paradigms with the therapeutic prospect of autophagy-associated ncRNAs in PD. By synthesizing the findings of recent genetic studies, we underscore the importance of ncRNAs in the regulation of autophagy, how they are dysregulated in PD, and how they represent novel dimensions for therapeutic intervention. The therapeutic promise of targeting ncRNAs in PD is discussed, including the barriers that need to be overcome and future directions that must be embraced to funnel these ncRNA molecules for the treatment and management of PD.

Effects of MicroRNAs and Long Non-coding RNAs on Beneficial Action of Exercise on Cognition in Degenerative Diseases: A Review

Recent research has exposed a growing body of proof underscoring the importance of microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) in maintaining the physical composition of neurons and influencing cognitive functioning in both standard and atypical circumstances. Extensive research has been conducted on the possible application of miRNAs and lncRNAs as biomarkers for various diseases, with a particular focus on brain disorders, as they possess remarkable durability in cell-free surroundings and can endure repeated freezing and thawing processes. It is intriguing to note that miRNAs and lncRNAs have the ability to function through paracrine mechanisms, thereby playing a role in communication between different organs. Recent research has proposed that the improvement of cognitive abilities through physical exercise in mentally healthy individuals is a valuable method for uncovering potential connections between miRNAs, or microRNAs, and lncRNAs, and human cognitive function. The process of cross-correlating data from disease models and patients with existing data will be crucial in identifying essential miRNAs and lncRNAs, which can potentially act as biomarkers or drug targets in the treatment of cognitive disorders. By combining this method with additional research in animal models, we can determine the function of these molecules and their potential impact on therapy. This article discusses the latest research about the primary miRNAs, lncRNAs, and their exosomes that are affected by physical activity in terms of human cognitive function.

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.

Nuclear Factor Kappa B: A Nobel Therapeutic Target of FlavonoidsAgainst Parkinson's Disease

Parkinson's disease (PD), the most common brain-related neurodegenerative disorder, is comprised of several pathophysiological mechanisms, such as mitochondrial dysfunction, neuroinflammation, aggregation of misfolded alpha-synuclein, and synaptic loss in the substantia nigra pars compacta region of the midbrain. Misfolded alpha-synuclein, originating from damaged neurons, triggers a series of signaling pathways in both glial and neuronal cells. Activation of such events results in the production and expression of several proinflammatory cytokines via the activation of the nuclear factor κB (NF-κB) signaling pathway. Consequently, this cascade of events worsens the neurodegenerative processes, particularly in conditions, such as PD and synucleinopathies. Microglia, astrocytes, and neurons are just a few of the many cells and tissues that express the NF-κB family of inducible types of transcription factors. The dual role of NF-κB activation can be crucial for neuronal survival, although the classical NF-κB pathway is important for controlling the generation of inflammatory mediators during neuroinflammation. Modulating NF-κB-associated pathways through the selective action of several agents holds promise for mitigating dopaminergic neuronal degeneration and PD. Several naturally occurring compounds in medicinal plants can be an effective treatment option in attenuating PD-associated dopaminergic neuronal loss via selectively modifying the NF-κB-mediated signaling pathways. Recently, flavonoids have gained notable attention from researchers because of their remarkable anti-neuroinflammatory activity and significant antioxidant properties in numerous neurodegenerative disorders, including PD. Several subclasses of flavonoids, including flavones, flavonols, isoflavones, and anthocyanins, have been evaluated for neuroprotective effects against in vitro and in vivo models of PD. In this aspect, the present review highlights the pathological role of NF-κB in the progression of PD and investigates the therapeutic potential of natural flavonoids targeting the NF-κB signaling pathway for the prevention and management of PD-like manifestations with a comprehensive list for further reference. Available facts strongly support that bioactive flavonoids could be considered in food and/or as lead pharmacophores for the treatment of neuroinflammation-mediated PD. Furthermore, natural flavonoids having potent pharmacological properties could be helpful in enhancing the economy of countries that cultivate medicinal plants yielding bioactive flavonoids on a large scale.

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.

LINC00667 regulates MPP + ‐induced neuronal injury in Parkinson’s disease

Objective

Parkinson’s disease (PD), also known as paralysis tremor, is a chronic disease of the central nervous system. It has been reported that hepatocyte nuclear factor 4 alpha (HNF4A) is upregulated in PD, but its specific function has not been well explored.

Methods

We established an in vitro PD model in SH‐SY5Y cells stimulated with 1‐methyl‐4‐phenylpyridinium (MPP⁺). Meanwhile, the effect of HNF4A on MPP⁺‐treated SH‐SY5Y cell behavior was monitored by functional assays. Mechanism assays were conducted to verify the relationship among LINC00667/miR‐34c‐5p/HNF4A. Rescue experiments validated the regulatory mechanism in PD model.

Results

The results revealed that depletion of HNF4A suppressed cell cytotoxicity and apoptosis caused by MPP⁺. Knockdown of HNF4A recovered MPP⁺‐stimulated oxidative stress and neuroinflammation. Mechanically, HNF4A was targeted and inhibited by miR‐34c‐5p. Furthermore, we found that LINC00667 positively modulated HNF4A expression via sequestering miR‐34c‐5p in MPP⁺‐stimulated SH‐SY5Y cells. Interestingly, the data indicated that HNF4A could transcriptionally activate LINC00667 expression. Rescue experiments presented that miR‐34c‐5p interference or HNF4A overexpression could mitigate the effects of LINC00667 knockdown on cell viability, cytotoxicity, cell apoptosis, oxidative stress, and neuroinflammation in MPP⁺‐treated SH‐SY5Y cells.

Conclusion

Our study first proved LINC00667, miR‐34c‐5p, and HNF4A constructed a positive feedback loop in MPP⁺‐treated SH‐SY5Y cells, enriching our understanding of PD.

Bioinformatics Approaches for Parkinson's Disease in Clinical Practice: Data-Driven Biomarkers and Pharmacological Treatment

Parkinson's disease is a gradually progressive neurodegenerative disorder characterized by a selective loss of dopaminergic neurons in the midbrain area called the substantia nigra pars compacta and cytoplasmic alpha-synuclein-rich inclusions termed Lewy bodies. The etiology and pathogenesis remain incompletely understood. The development of reliable biomarkers for the early and accurate diagnosis, including biochemical, genetic, clinical, and neuroimaging markers, is crucial for unraveling the pathogenic processes of the disease as well as patients' progress surveillance. High-throughput technologies and system biology methodologies can support the identification of potent molecular fingerprints together with the establishment of dynamic network biomarkers. Emphasis is given on multi-omics datasets and dysregulated pathways associated with differentially expressed transcripts, modified protein motifs, and altered metabolic profiles. Although there is no therapy that terminates the neurodegenerative process and dopamine replacement strategy with L-DOPA represents the most effective treatment, numerous therapeutic protocols such as dopamine receptor agonists, MAO-B inhibitors, and cholinesterase inhibitors represent candidate treatments providing at the same time valuable network-based approaches to drug repositioning. Computational methodologies and bioinformatics platforms for visualization, clustering, and validating of molecular and clinical datasets provide important insights into diagnostic processing and therapeutic pipeline.

Expression levels of specific microRNAs are increased after exercise and are associated with cognitive improvement in Parkinson's disease

There is a consensus regarding the efficacy of physical exercise in maintaining or improving human health; however, there are few studies examining the effect of physical exercise on the expression levels of microRNAs (miRNA/miRs) in Parkinson's disease (PD). The aim of the present study was to investigate the effects of an interval training program on a cycle ergometer on the expression levels of miR‑106a‑5p, miR‑103a‑3p and miR‑29a‑3p in serum samples from men with PD. This was a quasi‑experimental study with pre‑ and post‑testing and with a non‑equivalent group design. The participants were selected based on the eligibility criteria and subsequently classified into two groups: Experimental group and control group. The evaluations were performed at the beginning of the study (week 0) and after 8 weeks of the intervention program (week 9). The interval training program was performed on a cycle ergometer for 30 min, three times a week during an 8‑week period. The expression levels of miR‑106a‑5p, miR‑103a‑3p and miR‑29a‑3p in the experimental group were increased after physical exercise and were associated with cognitive improvement in men with PD. However, further studies are required to clarify the potential use of these circulating miRNAs as markers of adaptation to physical exercise. Collectively, the present results indicated that these three miRNAs may be associated with the exercise response and cognitive improvement in men with PD.

CaMKIIα-Positive Interneurons Identified via a microRNA-Based Viral Gene Targeting Strategy

Single-cell analysis is revealing increasing diversity in gene expression profiles among brain cells. Traditional promotor-based viral gene expression techniques, however, cannot capture the growing variety among single cells. We demonstrate a novel viral gene expression strategy to target cells with specific miRNA expression using miRNA-guided neuron tags (mAGNET). We designed mAGNET viral vectors containing a CaMKIIα promoter and microRNA-128 (miR-128) binding sites, and labeled CaMKIIα⁺ cells with naturally low expression of miR-128 (Lm128C cells) in male and female mice. Although CaMKIIα has traditionally been considered as an excitatory neuron marker, our single-cell sequencing results reveal that Lm128C cells are CaMKIIα⁺ inhibitory neurons of parvalbumin or somatostatin subtypes. Further evaluation of the physiological properties of Lm128C cell in brain slices showed that Lm128C cells exhibit elevated membrane excitability, with biophysical properties closely resembling those of fast-spiking interneurons, consistent with previous transcriptomic findings of miR-128 in regulating gene networks that govern membrane excitability. To further demonstrate the utility of this new viral expression strategy, we expressed GCaMP6f in Lm128C cells in the superficial layers of the motor cortex and performed in vivo calcium imaging in mice during locomotion. We found that Lm128C cells exhibit elevated calcium event rates and greater intrapopulation correlation than the overall CaMKIIα⁺ cells during movement. In summary, the miRNA-based viral gene targeting strategy described here allows us to label a sparse population of CaMKIIα⁺ interneurons for functional studies, providing new capabilities to investigate the relationship between gene expression and physiological properties in the brain.SIGNIFICANCE STATEMENT We report the discovery of a class of CaMKIIα⁺ cortical interneurons, labeled via a novel miRNA-based viral gene targeting strategy, combinatorial to traditional promoter-based strategies. The fact that we found a small, yet distinct, population of cortical inhibitory neurons that express CaMKIIα demonstrates that CaMKIIα is not as specific for excitatory neurons as commonly believed. As single-cell sequencing tools are providing increasing insights into the gene expression diversity of neurons, including miRNA profile data, we expect that the miRNA-based gene targeting strategy presented here can help delineate many neuron populations whose physiological properties can be readily related to the miRNA gene regulatory networks.

Circulating Cell-Free Nucleic Acids as Epigenetic Biomarkers in Precision Medicine

The circulating cell-free nucleic acids (ccfNAs) are a mixture of single- or double-stranded nucleic acids, released into the blood plasma/serum by different tissues via apoptosis, necrosis, and secretions. Under healthy conditions, ccfNAs originate from the hematopoietic system, whereas under various clinical scenarios, the concomitant tissues release ccfNAs into the bloodstream. These ccfNAs include DNA, RNA, microRNA (miRNA), long non-coding RNA (lncRNA), fetal DNA/RNA, and mitochondrial DNA/RNA, and act as potential biomarkers in various clinical conditions. These are associated with different epigenetic modifications, which show disease-related variations and so finding their role as epigenetic biomarkers in clinical settings. This field has recently emerged as the latest advance in precision medicine because of its clinical relevance in diagnostic, prognostic, and predictive values. DNA methylation detected in ccfDNA has been widely used in personalized clinical diagnosis; furthermore, there is also the emerging role of ccfRNAs like miRNA and lncRNA as epigenetic biomarkers. This review focuses on the novel approaches for exploring ccfNAs as epigenetic biomarkers in personalized clinical diagnosis and prognosis, their potential as therapeutic targets and disease progression monitors, and reveals the tremendous potential that epigenetic biomarkers present to improve precision medicine. We explore the latest techniques for both quantitative and qualitative detection of epigenetic modifications in ccfNAs. The data on epigenetic modifications on ccfNAs are complex and often milieu-specific posing challenges for its understanding. Artificial intelligence and deep networks are the novel approaches for decoding complex data and providing insight into the decision-making in precision medicine.

The Effect of Sialic Acid on the Expression of miR-218, NF-kB, MMP-9, and TIMP-1

Sialic acid (N-acetylneuraminic acid, NANA) is found at all cell surfaces of vertebrates. Although it is widely accepted that sialic acid is an essential substrate for brain development via a significant role in nerve transfers, structure of glycosides, and synaptogenesis phenomena, there are some reports on the elevated levels of sialic acid and prevalence of neurodegeneration. Matrix metalloproteases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) are involved in neuroinflammation disorders and produced by many cell types, including activated T cells, macrophages, neurons, astrocytes, and microglial cells. It can be hypothesized that sialic acid may have a potentially critical role in regulation of a wide range of uncovered neurodegeneration factors as its downstream targets. In this study, for the first time, we aimed to analyze the possible effect of the sialic acid solution exposure in the human C118 cell line, which was derived from a human brain astrocytoma (glial cells), on the expression patterns of miR-218, NF-kB, MMP-9, and TIMP-1. For MMP-9, protein levels were studied too. Half maximal inhibitory concentration (IC₅₀) value of NANA was obtained by MTT assay. Glial cell line was treated with sialic acid (300, 500, and 1000 µg/ml) for 24 h to investigate the effects of this ligand on the expression of miR-218, NF-kB, MMP-9, and TIMP-1 genes. Protein levels were checked by Western blotting, and by using zymography, the gelatinolytic activity of MMP-9 secreted into conditioned media was assayed. At 300 µM, 500 µM, and 1000 µM sialic acid treatments, the expression of miR-218 was downregulated; subsequently, the NF-kB, MMP-9, and TIMP-1 genes as well as their protein expressions were upregulated. More interestingly, the enzyme activity of secreted MMP-9 was upregulated too (p-values ≤ 0.05). This study could demonstrate the significant effect of sialic acid on miR-218, NF-kB, MMP-9 , and TIMP-1 expressions in gene and protein levels and also the levels of enzyme activity of secreted MMP-9. Therefore, provided information indicates the novel idea of a possible linkage between sialic acid species and regulation of these neuroinflammation genes in Glial cell line.

Down regulation of miR-218, miR-124, and miR-144 relates to Parkinson's disease via activating NF-κB signaling

Parkinson's disease (PD) is a neurological degenerative disorder that is partially induced by inflammation in the neural system. To explore the roles of disordered microRNAs in the development of PD, we screened 10 miRNAs in the brain samples of 15 postmortem PD patients and 10 postmortem healthy controls by qRT-PCR. The direct targets of miRNAs were predicted by informatics tools and further confirmed by dual luciferase assay and immunoblotting. The function of miRNAs in regulating NF-κB/p65 translocation was examined by immunoblotting, and the overactivation of NF-κB signaling was examined by ELISA. The relationship between dysregulated miRNAs and cytokines was analyzed by correlation analysis. Three miRNAs were found to be reduced in the brains of patients with PD. KPNB1, KPNA3, and KPNA4 were identified as direct targets of miR-218, miR-124, and miR-144. Additionally, KPNA3 was identified as a direct target of miR-124, and KPNA4 was a direct target of both miR-124 and miR-218. The p65 translocation from the cytoplasm to the nucleus was repressed by miR-124, miR-218, and miR-144 in the SH-SY5Y cells. The NF-κB signaling pathway was overactivated after miRNA inhibitor transfection. The upregulation of KPNB1, KPNA3, and KPNA4 in the brain samples of PD patients was confirmed by immunoblotting, and negative correlations were found between dysregulated miRNAs and cytokines. In conclusion, we identified that the downregulation of miR-218, miR-124, and miR-144 in the brain was related to PD via activation of NF-κB signaling, helping to unveil the role played by dysregulated miRNAs in the pathogenesis of PD and provide new potential targets for PD treatment.

Differentiation Induction and Proliferation Inhibition by A Cell-Free Approach for Delivery of Exogenous miRNAs to Neuroblastoma Cells Using Mesenchymal Stem Cells

Objective

Neuroblastoma (NB) is one of the frequently observed malignant solid tumors of childhood and infancy, accounting for 15% of pediatric cancer deaths. Recently, the approach of differentiation therapy has shown considerable promise in effective treatment of NB patients. MiR-124 belongs to the nervous system-specific miRNAs that is increased during neuronal differentiation and may be one of the potential therapeutic targets for the treatment of NB. However, despite its well-established therapeutic potential, its efficient delivery to the targeted tumor cells is a challenging task. Mesenchymal stem cells (MSCs) are multipotent adult progenitor cells that have antitumor properties, and they can migrate to cancer cells and tumors. This study aimed to assess whether human adipose tissue-derived MSCs (hAD- MSCs) have the potential to deliver exogenous miRNAs to NB cells to induce differentiation and decrease proliferation of cancer cells.

Materials and Methods

In this experimental study, hAD-MSCs were isolated, cultured, and differentiated. The M17 human NB cell line were also cultured. A specific type of miRNAs, i.e., miR-124 was successfully delivered to M17 NB cells with the aid of hAD-MSCs using the direct or indirect (exosome-based) contacts.

Results

It was shown that indirect delivery of miR-124 considerably decreased the proliferation of NB cells and induced their differentiation.

Conclusion

The results suggest the use of delivered exogenous miRNAs by the derived exosomes from hAD-MSCs as a novel cell-free stem cell-based therapy for NB cancer.

Effects of Physical Exercise on the Expression of MicroRNAs: A Systematic Review

Silva, FCd, Iop, RdR, Andrade, A, Costa, VP, Gutierres Filho, PJB, and Silva, Rd. Effects of physical exercise on the expression of microRNAs: A systematic review 34(1): 270-280, 2020-Studies have detected changes in the expression of miRNAs after physical exercise, which brings new insight into the molecular control of adaptation to exercise. Therefore, the objective of the current systematic review of experimental and quasiexperimental studies published in the past 10 years was to assess evidence related to acute effects, chronic effects, and both acute and chronic effects of physical exercise on miRNA expression in humans, as well as its functions, evaluated in serum, plasma, whole blood, saliva, or muscle biopsy. For this purpose, the following electronic databases were selected: MEDLINE by Pubmed, SCOPUS, Web of Science, and also a manual search in references of the selected articles to April 2017. Experimental and quasiexperimental studies were included. Results indicate that, of the 345 studies retrieved, 40 studies met the inclusion criteria and two articles were included as a result of the manual search. The 42 studies were analyzed, and it can be observed acute and chronic effects of physical exercises (aerobic and resistance) on the expression of several miRNAs in healthy subjects, athletes, young, elderly and in patients with congestive heart failure, chronic kidney disease, diabetes mellitus type 2 associated with morbid obesity, prediabetic, and patients with intermittent claudication. It is safe to assume that miRNA changes, both in muscle tissues and bodily fluids, are presumably associated with the benefits induced by acute and chronic physical exercise. Thus, a better understanding of changes in miRNAs as a response to physical exercise might contribute to the development of miRNAs as therapeutic targets for the improvement of exercise capacity in individuals with any given disease. However, additional studies are necessary to draw accurate conclusions.

HIF-1α/microRNA-128-3p axis protects hippocampal neurons from apoptosis via the Axin1-mediated Wnt/β-catenin signaling pathway in Parkinson's disease models

Parkinson's disease (PD) is a progressive neurodegenerative disorder. A common and disabling disease of the elderly, the standard dopamine replacement therapies do not arrest the ongoing neurodegeneration, thus calling for new treatment strategies. The present study aimed to clarify the functional relevance of the hypoxia inducible factor-1α (HIF-1α)/microRNA-128-3p (miR-128-3p) axis in hippocampal neurodegeneration in a PD mouse model obtained by intraperitoneal injection of MPTP. Targeting relationship between miR-128-3p and Axin1 was verified, so we probed the roles of Hif1a, miR-128-3p, and Axin1 in apoptosis of hippocampal neurons with gain- and loss-of function experiments using flow cytometry and TUNEL staining. We found that Axin1 was upregulated in hippocampal tissues and cells of the MPTP-lesioned mouse model of PD, while Hif1a and miR-128-3p were downregulated. Elevation of HIF-1α/miR-128-3p inhibited apoptosis of hippocampal neurons via Wnt/β-catenin signaling pathway activation due to the suppression of Axin1 in PD. In addition, forced overexpression of Hif1a could ameliorate motor dysfunction and pathological changes in the model. Collectively, activation of the HIF-1α/miR-128-3p axis could repress hippocampal neurodegeneration in MPTP-lesioned mice through an activated Wnt/β-catenin pathway due to Axin1 downregulation.

LncRNA BDNF-AS promotes autophagy and apoptosis in MPTP-induced Parkinson's disease via ablating microRNA-125b-5p

BACKGROUNDS

Recently, extensive evidence has indicated that the biological role of long non-coding RNAs (lncRNAs) in neurodegenerative diseases is becoming increasingly evident. The lncRNA brain-derived neurotrophic factor anti-sense (BDNF-AS) has been found to be dysregulated in Huntington's Disease. However, the function of BDNF-AS in Parkinson's disease (PD) remains unknown. The purpose of this present study was to explore the effect of BDNF-AS on PD and its underlying molecular mechanisms.

METHODS

The MPTP-induced mouse model of PD and MPP+-induced SH-SY5Y cell model were established. Immunofluorescence was performed to determine the number of TH + positive cells. Mice behavioral changes were detected by pole and rota-rod test. SH-SY5Y cells viability, apoptosis was detected by MTT assay and flow cytometry. The number of autophagosome was measured by transmission electron microscopy. Dopamine content was tested by high performance liquid chromatography. Dual-luciferase reporter gene assay was utilized to verify the correlation between BDNF-AS and miR-125b-5p. qRT-PCR and western blot were used to detect gene expression levels.

RESULTS

Our results showed that BDNF-AS was up-regulated in MPTP-induced PD model and dopamine neurons, and MPP + treated SH-SY5Y cells, while miR-125b-5p was down-regulated. The expression of BDNF-AS was positively related with the MPP + concentration. BDNF-AS knockdown could significantly promote cell proliferation, while inhibit apoptosis and autophagy in SH-SY5Y cells treated by MPP + . Silencing BDNF-AS could also increase TH positive neurons and significantly suppress the autophagy of PD mice. Additionally, miR-125b-5p, a putative target gene of BDNF-AS, was involved in the effects of BDNF-AS on SH-SY5Y cell apoptosis and autophagy.

CONCLUSIONS

Our study demonstrated that knockdown of BDNF-AS could elevate SH-SY5Y cell viability, inhibit autophagy and apoptosis in MPTP-induced PD models through regulating miR-125b-5p, suggesting that BDNF-AS might act as a potential therapeutic target for PD.

Up-regulation of microRNA-375 ameliorates the damage of dopaminergic neurons, reduces oxidative stress and inflammation in Parkinson's disease by inhibiting SP1

Background: This study is conducted to investigate the protective role of elevated microRNA-375 (miR-375) in dopaminergic neurons in Parkinson’s disease through down-regulating transcription factor specificity protein 1 (SP1).

Results: The successfully modeled rats with Parkinson’s disease showed aggregated neurobehavioral change, increased neuroinflammatory response and oxidative stress, and lowered dopamine content. Parkinson’s disease rats treated with overexpressed miR-375 displayed improved neurobehavioral change, ameliorated neuroinflammatory response and oxidative stress, heightened dopamine content and abated neuronal apoptosis by down-regulating SP1. Up-regulation of SP1 reversed the protective effect of upregulated miR-375 on Parkinson’s disease.

Conclusion: Up-regulation of miR-375 ameliorated the damage of dopaminergic neurons, reduced oxidative stress and inflammation in Parkinson’s disease by inhibiting SP1.

Methods: Parkinson’s disease rat model was established by targeted injection of 6-hydroxydopamine to damage the substantia nigra striatum. The successfully modeled Parkinson’s disease rats were intracerebroventricularly injected with miR-375 mimics or pcDNA3.1-SP1. The functions of miR-375 and SP1 in neurobehavioral change, neuroinflammatory response, oxidative stress, dopamine content and expression of apoptosis-related proteins in the substantia nigra of Parkinson’s disease rats were evaluated. The target relation of miR-375 and SP1 was confirmed by bioinformatics analysis and dual luciferase reporter gene assay.

Role of Nuclear Factor Kappa B (NF-κB) Signalling in Neurodegenerative Diseases: An Mechanistic Approach

A transcriptional regulatory nuclear factor kappa B (NF-κB) protein is a modulator of cellular biological activity via binding to a promoter region in the nucleus and transcribing various protein genes. The recent research implicated the intensive role of nuclear factor kappa B (NF-κB) in diseases like autoimmune disorder, inflammatory, cardiovascular and neurodegenerative diseases. Therefore, targeting the nuclear factor kappa B (NF-κB) protein offers a new opportunity as a therapeutic approach. Activation of IκB kinase/NF-κB signaling pathway leads to the development of various pathological conditions in human beings, such as neurodegenerative, inflammatory disorders, autoimmune diseases, and cancer. Therefore, the transcriptional activity of IκB kinase/NF- κB is strongly regulated at various cascade pathways. The nuclear factor NF-kB pathway plays a major role in the expression of pro-inflammatory genes, including cytokines, chemokines, and adhesion molecules. In response to the diverse stimuli, the cytosolic sequestered NF-κB in an inactivated form by binding with an inhibitor molecule protein (IkB) gets phosphorylated and translocated into the nucleus further transcribing various genes necessary for modifying various cellular functions. The various researches confirmed the role of different family member proteins of NF-κB implicated in expressing various genes products and mediating various cellular cascades. MicroRNAs, as regulators of NF- κB microRNAs play important roles in the regulation of the inflammatory process. Therefore, the inhibitor of NF-κB and its family members plays a novel therapeutic target in preventing various diseases. Regulation of NF- κB signaling pathway may be a safe and effective treatment strategy for various disorders.

Identification of biomarkers associated with Parkinson's disease by gene expression profiling studies and bioinformatics analysis

Parkinson's disease (PD) is associated with a selective loss of the neurons in the midbrain area called the substantia nigra pars compacta and the loss of projecting nerve fibers in the striatum. Predominant pathological hallmarks of PD are the degeneration of discrete neuronal populations and progressive accumulation of α-synuclein-containing intracytoplasmic inclusions called Lewy bodies and dystrophic Lewy neuritis. There is currently no therapy to terminate or delay the neurodegenerative process as the exact mechanisms underlying the pathogenesis of PD require further investigation. The identification and validation of novel biomarkers for the diagnosis of PD is a great challenge using contemporary approaches and optimizing sampling handling as well as interpretation using bioinformatics analysis. In this review, recent evidences associated with multi-omic data-sets and molecular mechanisms underlying PD are examined. A combined mapping of several transcriptional evidences could establish a patient-specific signature for early diagnose of PD though eligible systems biology tools, which can also help develop effective drug-based therapeutic approaches.

Current and future clinical utilities of Parkinson's disease and dementia biomarkers: can they help us conquer the disease?

Introduction: Biomarkers for Parkinson's disease and Alzheimer's disease are essential, not only for disease detection, but also provide insight into potential disease relationships leading to better detection and therapy. As metabolic disease is known to increase neurodegeneration risk, such mechanisms may reveal such novel targets for PD and AD. Moreover, metabolic disease, including insulin resistance, offer novel biomarker and therapeutic targets for neurodegeneration, including glucagon-like-peptide-1, dipeptidyl peptidase-4 and adiponectin. Areas covered: The authors reviewed PubMed-listed research articles, including ours, on a number of putative PD, AD and neurodegenerative disease targets of interest, focusing on the relevance of metabolic syndrome and insulin resistance mechanisms, especially type II diabetes, to PD and AD. We highlighted various issues surrounding the current state of knowledge and propose avenues for future development. Expert opinion: Biomarkers for PD and AD are indispensable for disease diagnosis, prognostication and tracking disease severity, especially for clinical therapy trials. Although no validated PD biomarkers exist, their potential utility has generated tremendous interest. Combining insulin-resistance biomarkers with other core biomarkers or using them to predict non-motor symptoms of PD may be clinically useful. Collectively, although still unclear, potential biomarkers and therapies can aid in shedding new light on novel aspects of both PD and AD.

miR‑153 promotes neural differentiation in the mouse hippocampal HT‑22 cell line and increases the expression of neuron‑specific enolase

MicroRNAs (miRNAs) have been found to play important regulatory roles in certain neurodegenerative diseases. The aim of the present study was to investigate the effect of miRNA-153 (miR-153) on the neural differentiation of HT-22 cells. Overexpression of miR-153 induced the differentiation of HT-22 cells, increasing the number of protrusions and branches, reducing the S phase distribution of the cell cycle, and attenuating the cell proliferation rate as determined using the Cell Counting Kit-8 assay. Furthermore, miR-153 increased the expression of neuron-specific γ-enolase (NSE), neuronal nuclei (NeuN), and N-ethylmaleimide-sensitive fusion attachment protein 23 (SNAP23) and SNAP25 at the transcriptional and protein level by PCR and western blot analysis. Moreover, miR-153 caused obvious upregulation of peroxiredoxin 5 (PRX5), which has been found to protect neural cells from death and apoptosis. miR-153 promoted neural differentiation and protected neural cells by upregulating the neuron markers γ-enolase, neuronal nuclei, and the functional proteins SNAP23, SNAP25 and PRX5. Therefore, miR-153 may be a potential target for the treatment of certain neurodegenerative diseases.

Suppressed microRNA-96 inhibits iNOS expression and dopaminergic neuron apoptosis through inactivating the MAPK signaling pathway by targeting CACNG5 in mice with Parkinson's disease

Background

There have been a number of reports implicating the association of microRNAs (miRs) and the MAPK signaling pathway with the dopaminergic neuron, which is involved in the development of Parkinson’s disease (PD). The present study was conducted with aims of exploring the role of miR-96 in the activation of iNOS and apoptosis of dopaminergic neuron through the MAPK signaling pathway in mice with PD.

Methods

The miR and the differentially expressed gene in PD were screened out and the relationship between them was verified. A mouse model of PD induced by MPTP and was then constructed and treated with miR-96 mimic/inhibitor and CACNG5 overexpression plasmid to extract nigral dopaminergic neuron for the purpose of detecting the effect of miR-96 on PD. The TH and iNOS positive neuronal cells, the apoptotic neuronal cells by TUNEL staining, and expression of miR-96, CACNG5, iNOS, p38MAPK, p-p38MAPK, c-Fos, Bax, and Bcl-2 in substantia nigra dopaminergic neuronal tissues were evaluated.

Results

The results obtained from the aforementioned procedure were then verified by cell culture of the SH-SY5Y cells, followed by treatment with miR-96 mimic/inhibitor, CACNG5 overexpression plasmid and the inhibitor of the MAPK signaling pathway. CACNG5 was confirmed as a target gene of miR-96. The inhibition of miR-96 resulted in a substantial increase in nigral cells, TH positive cells and expression of CACNG5 and Bcl-2 in nigral dopaminergic neuronal tissues, and a decrease in iNOS positive cells, apoptotic neuronal cells, and expression of iNOS, p38MAPK, p-p38MAPK, c-Fos, and Bax.

Conclusion

The above results implicated that the downregulation of miR-96 inhibits the activation of iNOS and apoptosis of dopaminergic neuron through the blockade of the MAPK signaling pathway by promoting CACNG5 in mice with PD.

miR-34a/BCL-2 signaling axis contributes to apoptosis in MPP+ -induced SH-SY5Y cells

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disorder which mainly affects the elderly population of various societies. The main hallmark of this disease is the loss of dopaminergic (DA) neurons. So far, numerous studies have implied the role of microRNAs in fine-tuning cellular processes including apoptosis. Studies have also shown that miR-34a is mainly involved in age-related disorders including Alzheimer's disease, and its expression is usually higher in the brain sample patients. Furthermore, the key role of miR-34a in the expression of BCL-2, and thus, in vitro and in vivo apoptosis has been revealed. miR-34a/BCL-2 axis is therefore of critical importance in inducing or inhibiting apoptosis.

METHODS

In this study, human SH-SY5Y cells were treated with MPP+ and the expression of miR-34a and BCL2 was assessed.

RESULTS

Our results also showed that treating human SH-SY5Y neuronal cells using MPP+ to induce oxidative stress and apoptosis led to the upregulation of miR-34a, as compared to the nontreated control group. Moreover, evaluating the expression level of BCL-2 in these cells indicated a contradictory pattern, as compared with miR-34a. It was also revealed that the expression of BCL-2 was significantly decreased in MPP+ -treated cells, thereby confirming previous studies regarding a new concept. In this study, we show that miR-34a/BCL-2 axis is directly correlated with oxidative stress and apoptosis in SH-SY5Y cells as a model of DA neurons.

CONCLUSION

miR-34a and its target gene, BCL-2, play a possible role in the induction of apoptosis in DA neurons, and therefore, they have a potential role in the pathogenesis of PD. Consequently, the therapeutic potential of miR-34a could be considered in order to inhibit the progression of PD.

Upregulated lncRNA small nucleolar RNA host gene 1 promotes 1-methyl-4-phenylpyridinium ion-induced cytotoxicity and reactive oxygen species production through miR-15b-5p/GSK3β axis in human dopaminergic SH-SY5Y cells

Long noncoding RNA (lncRNA) small nucleolar RNA host gene 1 (SNHG1) has been demonstrated to be upregulated and play a crucial role in the pathology of Parkinson's disease (PD). However, the exact role of SNHG1 and its underlying mechanisms in PD remains elusive. In this study, we found that SNHG1 and glycogen synthase kinase 3 beta (GSK3β) were upregulated, but miR-15b-5p was downregulated in 1-methyl-4-phenylpyridinium ion (MPP⁺ )-treated SH-SY5Y cells. The upregulation of SNHG1 enhanced MPP⁺ -induced cellular toxicity in SH-SY5Y cells, as shown by decreased cell viability, increased ROS production, and increased number of TdT-mediated dUTP Nick-End labeling-positive cells, accompanied with the upregulation of cleaved caspase 3 and elevation of cytochrome C release. Meanwhile, SNHG1 knockdown presented the converse effects. SNHG1 was demonstrated to interact with miR-15b-5p. Moreover, SNHG1 could attenuate the inhibitory effects of miR-15b-5p on MPP⁺ -induced cytotoxicity and production of ROS. Besides, GSK3β was identified as a direct target of miR-15b-5p. The inhibitory effects of SNHG1 knockdown or miR-15b-5p overexpression on MPP⁺ -induced cytotoxicity and reactive oxygen species (ROS) production were abrogated by upregulation of GSK3β. Taken together, these results demonstrate that upregulated lncRNA SNHG1 promotes MPP⁺ -induced cytotoxicity and ROS production through the miR-15b-5p/GSK3β axis in human dopaminergic SH-SY5Y cells, suggesting that SNHG1 may act as a potential therapeutic target for PD treatment in the future.

MicroRNAs to differentiate Parkinsonian disorders: Advances in biomarkers and therapeutics

Parkinsonian disorders are a set of progressive neurodegenerative movement disorders characterized by rigidity, tremor, bradykinesia, postural instability and their distinction has significant implications in terms of management and prognosis. Parkinson's disease (PD) is the most common among them. Its clinical diagnosis is challenging and, it can be misdiagnosed in the early stages. Multiple system atrophy and progressive supranuclear palsy are the close mimickers in early stages, due to overlapping clinical features. MicroRNAs are a class of stable non-coding small RNA molecules implicated in post-transcriptional gene regulation. Current studies propose that miRNAs play an essential role in the pathobiology of multiple neurodegenerative disorders including Parkinsonism, and they seem to be one of the reasonably available methods to aid in the differential diagnosis between PD and related disorders. MicroRNA-based diagnostic biomarkers and therapeutics are a powerful tool to understand and explore the function of the pathogenic gene/s, their mechanism in the disease pathobiology, and to validate drug targets. In this review, we emphasize on the recent developments in the usage of miRNAs as diagnostic biomarkers to identify PD and to differentiate it from atypical parkinsonian conditions, their role in disease pathogenesis, and their possible utility in the therapy of these disorders.

Modulation in miR-200a/SIRT1axis is associated with apoptosis in MPP+-induced SH-SY5Y cells

Previous studies have shown that miR-200a is markedly deregulated in various neurodegenerative disorders including Alzheimer's disease (AD), Multiple Sclerosis (MS) and PD. Furthermore, studies have shown the key role of miR-200a on expression of SIRT1 and apoptosis. Therefore, we hypothesized that miR-200a/SIRT1 axis should have a crucial role in apoptosis of dopaminergic (DA)neurons. In this study, human SH-SY5Y cells were treated with MPP+ and expression of miR-200a, SIRT1 and its target genes were assessed. Our results confirmed that expression of miR-200a significantly up-regulated during treating of human SH-SY5Y cells with MPP⁺ in order to induce oxidative stress and apoptosis. Additionally, transcript level of SIRT1 in these cells showed significant down-regulation confirming that SIRT1 is indeed decreased due to miR-200a up-regulation during apoptosis. Moreover, expression of P53, FOXO1 and BCL2 were modulated. In this study, we indicated that miR-200a/SIRT1 axis directly correlates with apoptosis and P53 signaling pathway. In conclusion, miR-200a and its target gene, SIRT1, may exert a possible role in induction of apoptosis in DA neurons through regulating P53, apoptosis and FOXO signaling pathways.

MiR-212 Attenuates MPP⁺-Induced Neuronal Damage by Targeting KLF4 in SH-SY5Y Cells

PURPOSE

Parkinson's disease (PD) is a common age-dependent neurodegenerative disease. MiR-212 has been demonstrated to exert protective effects in several neurological disorders. The present study aimed to investigate the role and underlying molecular mechanism of miR-212 in PD.

MATERIALS AND METHODS

1-methyl-4-phenylpyridinium (MPP+)-induced SH-SY5Y cells were applied as a PD model in vitro. RT-qPCR was used to measure the expression of miR-212 and Kruppel-like factor 4 (KLF4) mRNA. Western blot analysis was performed to detect the protein levels of KLF4, Notch1 and Jagged1. Cell viability and apoptosis were determined by the Cell Counting Kit-8 and flow cytometry, respectively. Quantitative analysis of caspase-3 activity, lactate dehydrogenase (LDH), reactive oxygen species (ROS), superoxide dismutase (SOD), tumor necrosis factor-α (TNF-α), and interleukin-1 beta (IL-1β) was conducted with corresponding ELISA kits. Dual-luciferase reporter assay was employed to evaluate the relationship between miR-212 and KLF4.

RESULTS

MiR-212 was downregulated in MPP⁺-induced SH-SY5Y cells. Also, miR-212 alleviated MPP⁺-induced SH-SY5Y cell damage, embodied by increased cell viability, decreased caspase-3 activity, LDH release, ROS production, TNF-α, and IL-1β expression, as well as elevated SOD levels. KLF4 was a direct target of miR-212, and miR-212 repressed KLF4 expression in a post-transcriptional manner. Moreover, miR-212-mediated protection effects were abated following KLF4 expression restoration in MPP⁺-induced SH-SY5Y cells, represented as lowered cell viability and enhanced apoptotic rate. Furthermore, Notch signaling was involved in the regulation of miR-212/KLF4 axis in MPP⁺-induced SH-SY5Y cells.

CONCLUSION

miR-212 might attenuate MPP⁺-induced neuronal damage by regulating KLF4/Notch signaling pathway in SH-SY5Y cells, a promising target for PD therapy.

LncRNA SNHG1 promotes α-synuclein aggregation and toxicity by targeting miR-15b-5p to activate SIAH1 in human neuroblastoma SH-SY5Y cells

Numerous long non-coding RNAs (lncRNAs) have been identified as aberrantly expressed in Parkinson's disease (PD). However, limited knowledge is available concerning the roles of dysregulated lncRNAs and the underlying molecular regulatory mechanism in the pathological process of PD. In this study, we found that lncRNA small nucleolar RNA host gene 1 (SNHG1) and seven in absentia homolog 1 (SIAH1) were upregulated, but microRNA-15b-5p (miR-15b-5p) was downregulated in SH-SY5Y cells pretreated with MPP+, as well as in MPTP-induced mouse model of PD. Overexpression of SIAH1 enhanced cellular toxicity of α-synuclein in SH-SY5Y cells, as indicated by the reduction of cell viability and elevation of LDH release. The percentage of α-synuclein aggregate-positive cells and the number of α-synuclein aggregates per cell were increased in SH-SY5Y cells transfected with pcDNA-SIAH1, while decreased after transfection with short interfering RNA specific for SIAH1 (si-SIAH1). Bioinformatics and luciferase reporter assay revealed that SIAH1 was a direct target of miR-15b-5p. We also found that SNHG1 could directly bind to miR-15-5p and repress miR-15-5p expression. Upregulation of miR-15b-5p alleviated α-synuclein aggregation and apoptosis by targeting SIAH1 in SH-SY5Y cells overexpressing α-synuclein. Overexpression of SNHG1 enhanced, whereas SNHG1 knockdown inhibited α-synuclein aggregation and α-synuclein-induced apoptosis. Moreover, the neuroprotective effect of si-SNHG1 was abrogated by downregulation of miR-15b-5p. In summary, our data suggest that SNHG1, as a pathogenic factor, promotes α-synuclein aggregation and toxicity by targeting the miR-15b-5p/SIAH1 axis, contributing to a better understanding of the mechanisms of Lewy body formation and loss of dopaminergic neurons in PD.

Use of Circulating and Cellular miRNAs Expression in Forensic Sciences

The current practice in the field of forensic medicine imposes the use of modern investigation techniques. The complexity of laboratory investigation methods needed for a final result of the investigation in forensic medicine needed new biomarkers of higher specificity and selectivity. Such biomarkers are the microRNAs (miRNAs), short, non-coding RNAs composed of 19–24 nucleotides. Their characteristics, such as high stability, selectivity, and specificity for biological fluids, differ from tissue to tissue and for certain pathologies, turning them into the ideal candidate for laboratory techniques used in forensic medicine. In this paper, we wish to highlight the biochemical properties and the usefulness of miRNAs in forensic medicine.

Loss of MicroRNA-7 Regulation Leads to α-Synuclein Accumulation and Dopaminergic Neuronal Loss In Vivo

Abnormal alpha-synuclein (α-synuclein) expression and aggregation is a key characteristic of Parkinson's disease (PD). However, the exact mechanism(s) linking α-synuclein to the other central feature of PD, dopaminergic neuron loss, remains unclear. Therefore, improved cell and in vivo models are needed to investigate the role of α-synuclein in dopaminergic neuron loss. MicroRNA-7 (miR-7) regulates α-synuclein expression by binding to the 3' UTR of the Synuclein Alpha Non A4 Component of Amyloid Precursor (SNCA) gene and inhibiting its translation. We show that miR-7 is decreased in the substantia nigra of patients with PD and, therefore, may play an essential role in the regulation of α-synuclein expression. Furthermore, we have found that lentiviral-mediated expression of miR-7 complementary binding sites to stably induce a loss of miR-7 function results in an increase in α-synuclein expression in vitro and in vivo. We have also shown that depletion of miR-7 using a miR-decoy produces a loss of nigral dopaminergic neurons accompanied by a reduction of striatal dopamine content. These data suggest that miR-7 has an important role in the regulation of α-synuclein and dopamine physiology and may provide a new paradigm to study the pathology of PD.

Reduced Circulating Levels of miR-433 and miR-133b Are Potential Biomarkers for Parkinson's Disease

Aberrant expression of microRNA (miRNA) in tissues may lead to altered level in circulation. Considerable evidence has suggested that miRNA deregulation is involved in the pathogenesis of Parkinson’s disease (PD). In this study, we screened a set of PD-associated miRNAs and aimed to identify differentially expressed miRNAs in plasma of PD patients and to evaluate their potentiality to serve as PD biomarkers. A total of 95 subjects consisting of 46 sporadic PD cases and 49 controls were recruited. Plasma levels of six miRNAs including miR-433, miR-133b, miR-34b, miR-34c, miR-153, and miR-7 were evaluated using reverse transcribed quantitative PCR, among which we found that miR-34c and miR-7 were below detection limit under our condition. The results showed that levels of circulating miR-433 (P = 0.003) and miR-133b (P = 0.006), but not miR-34b and miR-153, were reduced in PD patients. miR-433 and miR-133b were strongly correlated in both control and PD groups (r_s = 0.87 and 0.85, respectively). The correlation between miR-34b and miR-153 expressions was significantly reduced (P < 0.05) in the PD group. Although miR-433 and miR-133b were likely to be functionally complimentary as suggested by Pathway and Gene Ontology analyses, these two miRNAs per se might not be sufficient to predict PD. No correlation was observed between the four miRNAs and age or severity of disease. Collectively, our results demonstrate that circulating miR-433 and miR-133b are significantly altered in PD and may serve as PD biomarkers.

Polymorphism in MIR4697 but not VPS13C, GCH1, or SIPA1L2 is associated with risk of Parkinson's disease in a Han Chinese population

A large meta-analysis recently identified six new loci associated with risk of PD, but subsequent studies have given discrepant results. Here we conducted a case-control study in a Han Chinese population in an attempt to clarify risk associations in Chinese. Among the four single-nucleotide polymorphisms (SNPs) that we examined - VPS13C-rs2414739, MIR4697-rs329648, GCH1-rs11158026, and SIPA1L2- rs10797576 we detected a significant association between rs329648 and risk of developing PD in a recessive model. This association remained significant after adjusting for gender and age (OR 1.87, 95%CI 1.295-2.694, p=8.21×10^-4) or Bonferroni correction. The T allele of rs329648 occurred significantly more frequently among patients with PD than among healthy controls (OR 1.22, 95%CI 1.033-1.443, p=0.02), while there was no statistic significant after Bonferroni correction. Subgroup analysis showed a significant association specifically among males in a recessive model (OR 1.943, 95%CI 1.200-3.147, p=0.007). In contrast, genotye and allele frequencies at rs329648 did not differ significantly between female patients with PD and healthy female controls, or between patients with early-onset or late-onset PD. Our results suggest that rs329648 is associated with risk of developing PD in the Han Chinese population. Our findings should be verified in further studies, and they highlight the need for functional studies of MIR4697.

MicroRNA-181a Regulates Apoptosis and Autophagy Process in Parkinson's Disease by Inhibiting p38 Mitogen-Activated Protein Kinase (MAPK)/c-Jun N-Terminal Kinases (JNK) Signaling Pathways

Background

microRNA (miR)-181a has been reported to be downregulated in Parkinson’s disease (PD), but the regulatory mechanism of miR-181a on neuron apoptosis and autophagy is still poorly understood. We aimed to investigate the neuroprotective effects of miR-181a on PD in vitro.

Material/Methods

Human SK-N-SH neuroblastoma cells were incubated with different concentrations of 1-methyl-4-phenylpyridinium ion (MPP⁺) to induce the PD model. The expression of miR-181a was then analyzed. After transfection with miR-181a mimic or scramble following MPP⁺ treatment, the expression of autophagy protein markers (LC3II, LC3I, and Beclin 1) and p38 mitogen-activated protein kinase (MAPK)/c-Jun N-terminal kinases (JNK) signaling proteins (p-p38, p38, p-JNK, and JNK) and cell apoptosis were detected. Furthermore, the cells were transfected with miR-181a inhibitor and cultured in the presence or absence of p38 inhibitor SB203582 or JNK inhibitor SP600125, and the cell apoptosis was tested again.

Results

The expression of miR-181a was gradually decreased with the increase of MPP⁺ concentration (P<0.05, P<0.01, or P<0.001). Overexpression of miR-181a significantly decreased the LC3II/LC3I ratio, Beclin 1 expression, cell apoptosis, and the expression of p-p38 and p-JNK compared to the MPP⁺ + miR-181a scramble group (all P<0.05). In addition, we observed that SB203582 or SP600125 showed no effects on cell apoptosis, but the effects of miR-181a inhibitor on cell apoptosis were reversed by administration of SB203582 or SP600125 compared to the scramble group (P<0.05).

Conclusions

Our results suggest that miR-181a regulates apoptosis and autophagy in PD by inhibiting the p38 MAPK/JNK pathway.

Plasma levels of miR-137 and miR-124 are associated with Parkinson's disease but not with Parkinson's disease with depression

MicroRNAs (miRNAs) are a class of small, non-coding RNAs that regulate gene expression at the post-transcriptional level. Recently, it was reported that miR-137, miR-124, and miR-184 were widely expressed in the central nervous system and were vital to neuronal regulation. In this study, we detected the circulating levels of miR-137, miR-124, and miR-184 in PD patients, and explored the potential role of miR-124, miR-137, and miR-184 in the diagnosis of PD. We further described the relationship between these miRNAs and PD with depression (PD-Dep). The study recruited 60 controls and 60 PD patients, which were further divided into two subgroups, PD with depression (PD-Dep, n = 24) and non-depressed group (PD-NDep, n = 36) according to Hamilton Rating Scale for Depression. Plasma levels of miR-137, miR-124, and miR-184 were detected by qRT-PCR. Receiver-operating characteristic (ROC) curve was used to evaluate miR-124 and miR-137 levels as potential diagnostic biomarkers for PD. The results demonstrated that there were no significant differences in levels of miR-184 between PD patients and controls (p > 0.05). However, miR-137 levels were increased significantly for PD patients compared to controls (p < 0.05), while miR-124 levels were down-regulated (p < 0.05). The areas under the ROC curve (AUC) of miR-137 and miR-124 were 0.707 (95% CI 0.615-0.789, p < 0.05) and 0.709 (95% CI 0.618-0.633, p < 0.05), respectively. Correlation analysis revealed that there was no relationship between these two miRNAs levels and UPDRS scores or H&Y stage. There were no significant differences in miR-137 and miR-124 levels between PD-Dep and PD-NDep (p > 0.05). Thus, plasma levels of miR-137 and miR-124 are associated with Parkinson's disease and might be potential biomarkers of the diagnosis of PD. There were no associations of plasma miR-137 and miR-124 with the severity of PD motor symptoms or PD-Dep.

MicroRNA Biomarkers in Neurodegenerative Diseases and Emerging Nano-Sensors Technology

MicroRNAs (miRNAs) are essential small RNA molecules (20–24 nt) that negatively regulate the expression of target genes at the post-transcriptional level. Due to their roles in a variety of biological processes, the aberrant expression profiles of miRNAs have been identified as biomarkers for many diseases, such as cancer, diabetes, cardiovascular disease and neurodegenerative diseases. In order to precisely, rapidly and economically monitor the expression of miRNAs, many cutting-edge nanotechnologies have been developed. One of the nanotechnologies, based on DNA encapsulated silver nanoclusters (DNA/AgNCs), has increasingly been adopted to create nanoscale bio-sensing systems due to its attractive optical properties, such as brightness, tuneable emission wavelengths and photostability. Using the DNA/AgNCs sensor methods, the presence of miRNAs can be detected simply by monitoring the fluorescence alteration of DNA/AgNCs sensors. We introduce these DNA/ AgNCs sensor methods and discuss their possible applications for detecting miRNA biomarkers in neurodegenerative diseases.

MicroRNAs in bone development and their diagnostic and therapeutic potentials in osteoporosis

MicroRNAs (miRNAs) are small non-coding RNAs approximately 22 nucleotides in length. miRNAs play an important role in the posttranscriptional regulation of gene expression via translational repression and targeting messenger RNA for degradation. In vivo and in vitro evidence has established the importance of miRNAs in physiology and developmental processes such as cell proliferation, differentiation, survival and apoptosis. miRNA dysregulation is associated with the pathogenesis of cardiovascular diseases, metabolic syndromes, and degenerative diseases. An increasing number of miRNAs have been found to play an important role in bone homeostasis. In this review, the roles of miRNAs in the regulation of bone formation and resorption as well as miRNAs that regulate key transcription factors of osteogenesis are discussed. A special emphasis is given to miRNAs whose direct targets have been identified. The miRNAs that contribute to the pathogenesis of osteoporosis and their therapeutic potential are also considered.

A novel method for identifying potential disease-related miRNAs via a disease–miRNA–target heterogeneous network

MicroRNAs (miRNAs), as a kind of important small endogenous single-stranded non-coding RNA, play critical roles in a large number of human diseases.

microRNAs involved in Parkinson's disease: A systematic review

The aim of the present study was to determine the expression of blood microRNAs (miRNAs) involved in PD in humans. For this purpose the following electronic databases were selected: MEDLINE by Pubmed, Scopus and Web of Science. The search strategy included the proposed descriptors in the Medical Subject Headings. There were no restrictions with respect to the language of the publication. In the study selection two independent reviewers initially evaluated studies that were identified by the search strategy according to titles and abstracts. The reviewers evaluated (also unassisted) the complete articles and selected studies according to the eligibility criteria specified above. Studies that were not in accordance with the adopted criteria were excluded according to the boundaries imposed by the search strategy. The following data were extracted from the selected studies: Publication identification, location where the study was conducted, study design, the sample size, the participants' characteristics, the miRNAs involved in PD, the miRNA detection and analysis method, and the type of miRNA dysregulation in PD. Through this systematic review of the literature published over the last 10 years, the expression of 91 different miRNAs were analyzed in the context of PD, with the expression of 39 of these miRNAs differing significantly between individuals with PD and healthy controls and/or between treated and untreated patients with PD. The miRNAs were extracted from mononuclear cells, leukocytes, plasma, serum and peripheral blood, and the majority of the studies used reverse transcription‑quantitative polymerase chain reaction (RT-qPCR), which is considered to be the gold standard for miRNA analysis.

Neuroprotective Role of MicroRNA-22 in a 6-Hydroxydopamine-Induced Cell Model of Parkinson's Disease via Regulation of Its Target Gene TRPM7

Parkinson's disease (PD), the second most prevalent neurodegenerative disorder with only symptomatic treatment available, is characterized by a progressive loss of dopaminergic neurons in the midbrain. Ample evidence indicated that microRNAs (miRs) could regulate post-transcriptional gene expression and neuronal disease. In the present study, we have evaluated the effects and mechanism of miR-22 in PC12 pheochromocytoma cells treated with 6-hydroxydopamine (6-OHDA) to mimic PD. RT-PCR results showed that the expression of miR-22 is downregulated in 6-OHDA-treated PC12 cells, and the overexpression of miR-22 significantly promoted the survival and proliferation of 6-OHDA-induced PC12 cells, whereas miR-22 inhibitor reversed these effects. In addition, PC12 cells were treated with miR-22 mimics or inhibitor following 6-OHDA administration, which medicated ROS production and upregulation or downregulation of caspase-3 activity, respectively. A luciferase reporter assay revealed that transient receptor potential melastatin 7 (TRPM7) is a direct target gene of miR-22, and miR-22 overexpression markedly downregulated the level of TRPM7. Strikingly, further analysis showed that miR-22 mediated 6-OHDA-induced PC12 cell survival and proliferation by targeting TRPM7. Taken together, the present study showed that miR-22 overexpression exhibited neuroprotective and reversal effects on the 6-OHDA-induced PC12 cell growth and apoptosis by targeting TRPM7.

MicroRNA-146a down-regulation correlates with neuroprotection and targets pro-apoptotic genes in cerebral ischemic injury in vitro

MicroRNAs (miRNAs) are short, non-coding RNAs that negatively regulate target gene expression, and play an important role in cerebral ischemic injury. MiR-146a has been reported to be highly related to cell invasion, metastasis, immunity, inflammation and apoptosis. Previous studies have indicated that miR-146a can either inhibit or promote apoptosis through different pathophysiological processes. In our previous study, miR-146a in the blood was down-regulated during acute ischemic stroke. However, the connection between miR-146a and acute cerebral ischemic injury and the mechanism underlying the connection remain unclear. Here, we aimed to investigate the role of miR-146a and its possible target genes in human SK-N-SH cells subjected to 16h of oxygen-glucose deprivation and 12h of reperfusion (OGD/R) injury. Cells were transfected with miR-146a mimic or inhibitor to alter the expression of miR-146a. MiR-146a in the SK-N-SH cells was down-regulated after OGD/R injury. Moreover, bioinformatics analysis and dual luciferase assays demonstrated that miR-146a directly recognized the 3'-UTR of the pro-apoptotic genes, Caspase7 and Bcl-2-associated transcription factor 1 (Bclaf1). Furthermore, miR-146a over-expression effectively decreased the mRNA and protein expression of Caspase7 and Bclaf1, and aggravated OGD/R-induced cell apoptosis; in contrast, miR-146a down-regulation was neuroprotective. In conclusion, our study revealed that miR-146a contributes to OGD/R injury in vitro, while negatively regulating the pro-apoptotic genes, Caspase7 and Bclaf1. This special mechanism provides new insight into miRNA regulatory networks. In addition, miR-146a may offer a potential therapeutic approach to cerebral ischemic injury.

Role of Dicer and the miRNA system in neuronal plasticity and brain function

MicroRNAs (miRNAs) are small regulatory non-coding RNAs that contribute to fine-tuning regulation of gene expression by mRNA destabilization and/or translational repression. Their abundance in the nervous system, their temporally and spatially regulated expression and their ability to respond in an activity-dependent manner make miRNAs ideal candidates for the regulation of complex processes in the brain, including neuronal plasticity, memory formation and neural development. The conditional ablation of the RNase III Dicer, which is essential for the maturation of most miRNAs, is a useful model to investigate the effect of the loss of the miRNA system, as a whole, in different tissues and cellular types. In this review, we first provide an overview of Dicer function and structure, and discuss outstanding questions concerning the role of miRNAs in the regulation of gene expression and neuronal function, to later focus on the insight derived from studies in which the genetic ablation of Dicer was used to determine the role of the miRNA system in the nervous system. In particular, we highlight the collective role of miRNAs fine-tuning plasticity-related gene expression and providing robustness to neuronal gene expression networks.

Lipopolyplex for Therapeutic Gene Delivery and Its Application for the Treatment of Parkinson's Disease

Lipopolyplex is a core-shell structure composed of nucleic acid, polycation and lipid. As a non-viral gene delivery vector, lipopolyplex combining the advantages of polyplex and lipoplex has shown superior colloidal stability, reduced cytotoxicity, extremely high gene transfection efficiency. Following intravenous administration, there are many strategies based on lipopolyplex to overcome the complex biological barriers in systemic gene delivery including condensation of nucleic acids into nanoparticles, long circulation, cell targeting, endosomal escape, release to cytoplasm and entry into cell nucleus. Parkinson's disease (PD) is the second most common neurodegenerative disorder and severely influences the patients' life quality. Current gene therapy clinical trials for PD employing viral vectors didn't achieve satisfactory efficacy. However, lipopolyplex may become a promising alternative approach owing to its stability in blood, ability to cross the blood-brain barrier (BBB) and specific targeting to diseased brain cells.

Association of four new candidate genetic variants with Parkinson's disease in a Han Chinese population

Large-scale meta-analysis of genome-wide association data has identified six new risk loci (SIPA1L2, INPP5F, MIR4697, GCH1, VPS13C, and DDRGK1) for Parkinson's disease (PD). However, the characteristics of those loci in a Han Chinese population from mainland China are unknown. We examined genetic associations of VPS13C rs2414739, MIR4697 rs329648, GCH1 rs11158026, and SIPA1L2 rs10797576 with PD susceptibility in a Han Chinese population of 1028 sporadic PD patients and 1109 healthy controls. All subjects were genotyped for these loci using the Sequenom iPLEX Assay. We also conducted further stratified analysis according to age at onset and compared the clinical characteristics between minor allele carriers and non-carriers for each locus. However, we did not observe any significant difference in genotype distribution between PD patients and controls for the four loci, even after being stratified by age at onset. Besides, minor allele carriers cannot be distinguished from non-carriers based on their clinical features. Our findings first demonstrated that VPS13C rs2414739, MIR4697 rs329648, GCH1 rs11158026, and SIPA1L2 rs10797576 do not confer a significant risk for PD in Chinese population. Additional replication studies in other populations and functional studies are warranted to better validate the role of the four new loci in PD risk.

Nurr1-Based Therapies for Parkinson's Disease

Previous studies have documented that orphan nuclear receptor Nurr1 (also known as NR4A2) plays important roles in the midbrain dopamine (DA) neuron development, differentiation, and survival. Furthermore, it has been reported that the defects in Nurr1 are associated with Parkinson's disease (PD). Thus, Nurr1 might be a potential therapeutic target for PD. Emerging evidence from in vitro and in vivo studies has recently demonstrated that Nurr1-activating compounds and Nurr1 gene therapy are able not only to enhance DA neurotransmission but also to protect DA neurons from cell injury induced by environmental toxin or microglia-mediated neuroinflammation. Moreover, modulators that interact with Nurr1 or regulate its function, such as retinoid X receptor, cyclic AMP-responsive element-binding protein, glial cell line-derived neurotrophic factor, and Wnt/β-catenin pathway, have the potential to enhance the effects of Nurr1-based therapies in PD. This review highlights the recent progress in preclinical studies of Nurr1-based therapies and discusses the outlook of this emerging therapy as a promising new generation of PD medication.

microRNA-7 Protects Against 1-Methyl-4-Phenylpyridinium Iodide-Induced Cell Apoptosis in SH-SY5Y Cells by Directly Targeting Krüpple-Like Factor 4

This study intended to investigate the role and underling mechanism of microRNA-7 (miR-7) on neuronal death in Parkinson's disease (PD). Human neuroblastoma cell line SH-SY5Y was employed and 1-methyl-4-phenylpyridinium iodide [MPP(+)] was used to generate PD model in vitro. Furthermore, an upregulation of miR-7 was performed in SH-SY5Y by transfection with miR-7 mimics. Cell viability and cell apoptosis were determined. Moreover, the target and the mechanism of miR-7 in MPP(+)-induced cell death were also investigated. The upregulation of miR-7 promoted cell viability and suppressed cell apoptosis in MPP(+)-treated SH-SY5Y cells. Furthermore, miR-7 could directly bind to the 3'-untranslated region of Krüppel-like factor 4 (KLF4, positions 574-580). Moreover, knockdown of KLF4 by the specific siRNA inhibited SH-SY5Y apoptosis under MPP(+) treatment. In addition, KLF4 overexpression apparently attenuated the protective effect of miR-7 in MPP(+)-induced SH-SY5Y apoptosis. This study indicated that miR-7 protects from MPP(+)-induced cell apoptosis in SH-SY5Y by directly targeting KLF4.

MicroRNA-7 inhibits neuronal apoptosis in a cellular Parkinson's disease model by targeting Bax and Sirt2

Parkinson's disease (PD) is the second most common age-related neurodegenerative disease. MicroRNA-7 (miR-7) displays neuroprotective properties against PD. However, the biological roles of miR-7 and its underlying molecular mechanisms in PD remain unclear. We demonstrated herein that 1-methyl-4-phenylpyridinium ion (MPP(+)) confers toxic effects on dopaminergic neuron in a dose-dependent manner in a cellular PD model, although this phenomenon is attenuated by miR-7 treatment. Introduction of miR-7 inhibits MPP(+)-induced neuronal apoptosis as reflected by the reduced terminal transferase-mediated dUTP nick end labeling-positive rate, mitochondrial permeability potential, caspase 3 activity, and nucleosomal enrichment factor. Bax and sirtuin 2 (Sirt2) are the direct targets of miR-7. Moreover, the effects of miR-7 were counteracted by Bax and Sirt2 overexpression, respectively. The altered molecular expressions downstream of Bax and Sirt2 are also involved in miR-7 regulation of the MPP(+)-triggered neuronal apoptosis. These findings have implications on the potential application of miR-7 in PD treatment.