MicroRNAs in neurodegenerative diseases and their therapeutic potential

Decoding paradoxical links of cytokine markers in cognition: Cross talk between physiology, inflammaging, and Alzheimer's disease- related cognitive decline

Recent research has revolutionized our understanding of memory consolidation by emphasizing the critical role of astrocytes, microglia, and immune cells in through cytokine signaling. Cytokines, compact proteins, play pivotal roles in neuronal development, synaptic transmission, and normal aging. This review explores the cellular mechanisms contributing to cognitive decline in inflammaging and Alzheimer's disease, highlighting the paradoxical effects of most studied cytokines (IL-1, IL-6, TNF-α) in brain function, which act as a double-edged sword in brain physiology, acting both as facilitators of healthy cognitive function and as a potential contributor to cognitive decline.

MicroRNA profiles in Zika virus infection: Insights from diverse sources

BACKGROUND

Zika virus (ZIKV) stands as one of the most significant reemerging viral pathogens, linked to neurological diseases such as meningoencephalitis and congenital microcephaly. Today there are no effective therapies for treating ZIKV-infected patients. MiRNAs play a critical role in regulating cellular signaling and physiological conditions, and alterations in their profiles can bear great significance in disease progression.

OBJECTIVES

Despite significant progress in understanding the interaction between the ZIKV and its host since the outbreak, a more comprehensive understanding on these interactions is imperative. This review aims to summarize the studies in the field and shed light on the intricate relationship between ZIKV and its host at the molecular level.

CONTENT

We found that in ZIKV-infected humans, over-expression of miR-431-5p and miR-30e-5p plays a crucial role in innate immune responses and contributes to neurological damage. Additionally, in ZIKA-infected mice, we observed upregulated expression of all the targets of miR-124-3p including CCL2, IL7, IRF1, and SBNO2. Notably, other targets of this miRNA include TLR6, TNF, STAT3, and NF-kB also exhibited upregulation in the central nervous system (CNS) of infected mice. Conversely, miR-654-3p levels were reduced, correlating with the upregulation of its predicted targets including FLT3LG, LITAF, CD69, and TLR2. In the case of insects, aae-miR-286a/b-3p was predicted to target all ZIKV genotypes. This specific miRNA is typically found in ovaries and can be transferred to embryos. In conclusion, our findings suggest that host microRNAs and ZIKV-encoded microRNAs hold promise as potential targets for the diagnosis of ZIKV infections and may even serve as a therapeutic approach for managing this infectious disease.

miR-449a mediated repression of the cell cycle machinery prevents neuronal apoptosis

Aberrant activation of the cell cycle of terminally differentiated neurons results in their apoptosis and is known to contribute to neuronal loss in various neurodegenerative disorders like Alzheimer's Disease. However, the mechanisms that regulate cell cycle-related neuronal apoptosis are poorly understood. We identified several miRNA that are dysregulated in neurons from a transgenic APP/PS1 mouse model for AD (TgAD). Several of these miRNA are known to and/or are predicted to target cell cycle-related genes. Detailed investigation on miR-449a revealed the following: a, it promotes neuronal differentiation by suppressing the neuronal cell cycle; b, its expression in cortical neurons was impaired in response to amyloid peptide Aβ42; c, loss of its expression resulted in aberrant activation of the cell cycle leading to apoptosis. miR-449a may prevent cell cycle-related neuronal apoptosis by targeting cyclin D1 and protein phosphatase CDC25A, which are important for G1-S transition. Importantly, the lentiviral-mediated delivery of miR-449a in TgAD mouse brain significantly reverted the defects in learning and memory, which are associated with AD.

Identification of molecular targets and small drug candidates for Huntington's disease via bioinformatics and a network-based screening approach

Huntington's disease (HD) is a gradually severe neurodegenerative ailment characterised by an increase of a specific trinucleotide repeat sequence (cytosine-adenine-guanine, CAG). It is passed down as a dominant characteristic that worsens over time, creating a significant risk. Despite being monogenetic, the underlying mechanisms as well as biomarkers remain poorly understood. Furthermore, early detection of HD is challenging, and the available diagnostic procedures have low precision and accuracy. The research was conducted to provide knowledge of the biomarkers, pathways and therapeutic targets involved in the molecular processes of HD using informatic based analysis and applying network-based systems biology approaches. The gene expression profile datasets GSE97100 and GSE74201 relevant to HD were studied. As a consequence, 46 differentially expressed genes (DEGs) were identified. 10 hub genes (TPM1, EIF2S3, CCN2, ACTN1, ACTG2, CCN1, CSRP1, EIF1AX, BEX2 and TCEAL5) were further differentiated in the protein-protein interaction (PPI) network. These hub genes were typically down-regulated. Additionally, DEGs-transcription factors (TFs) connections (e.g. GATA2, YY1 and FOXC1), DEG-microRNA (miRNA) interactions (e.g. hsa-miR-124-3p and has-miR-26b-5p) were also comprehensively forecast. Additionally, related gene ontology concepts (e.g. sequence-specific DNA binding and TF activity) connected to DEGs in HD were identified using gene set enrichment analysis (GSEA). Finally, in silico drug design was employed to find candidate drugs for the treatment HD, and while the possible modest therapeutic compounds (e.g. cortistatin A, 13,16-Epoxy-25-hydroxy-17-cheilanthen-19,25-olide, Hecogenin) against HD were expected. Consequently, the results from this study may give researchers useful resources for the experimental validation of Huntington's diagnosis and therapeutic approaches.

MicroRNA (miRNA) as a biomarker for diagnosis, prognosis, and therapeutics molecules in neurodegenerative disease

Neurodegenerative diseases that include Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), Huntington's disease (HD), and multiple sclerosis (MS) that arise due to numerous causes like protein accumulation and autoimmunity characterized by neurologic depletion which lead to incapacity in normal physiological function such as thinking and movement in these patients. Glial cells perform an important role in protective neuronal function; in the case of neuroinflammation, glial cell dysfunction can promote the development of neurodegenerative diseases. miRNA that participates in gene regulation and plays a vital role in many biological processes in the body; in the central nervous system (CNS), it can play an essential part in neural maturation and differentiation. In neurodegenerative diseases, miRNA dysregulation occurs, enhancing the development of these diseases. In this review, we discuss neurodegenerative disease (Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS)) and how miRNA is preserved as a diagnostic biomarker or therapeutic agent in these disorders. Finally, we highlight miRNA as therapy.

Dental pulp mesenchymal stem cell-derived exosomes inhibit neuroinflammation and microglial pyroptosis in subarachnoid hemorrhage via the miRNA-197-3p/FOXO3 axis

BACKGROUND

Subarachnoid hemorrhage (SAH) is a severe stroke subtype that lacks effective treatment. Exosomes derived from human dental pulp stem cells (DPSCs) are a promising acellular therapeutic strategy for neurological diseases. However, the therapeutic effects of DPSC-derived exosomes (DPSC-Exos) on SAH remain unknown. In this study, we investigated the therapeutic effects and mechanisms of action of DPSC-Exos in SAH.

MATERIALS AND METHODS

SAH was established using 120 male Sprague-Dawley rats. One hour after SAH induction, DPSC-Exos were administered via tail vein injection. To investigate the effect of DPSC-Exos, SAH grading, short-term and long-term neurobehavioral assessments, brain water content, western blot (WB), immunofluorescence staining, Nissl staining, and HE staining were performed. The role of miR-197-3p/FOXO3 in regulating pyroptosis was demonstrated through miRNA sequencing, bioinformatics analysis, and rescue experiments. The SAH model in vitro was established by stimulating BV2 cells with hemoglobin (Hb) and the underlying mechanism of DPSC-Exos was investigated through WB and Hoechst/PI staining.

RESULTS

The expressions of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) were increased after SAH. DPSC-Exos alleviated brain edema and neuroinflammation by inhibiting the expression of FOXO3 and reducing NLRP3 inflammasome activation, leading to improved neurobehavioral functions at 24 h after SAH. In vitro, the expression of the NLRP3 inflammasome components (NLRP3 and caspase1-p20), GSDMD-N, and IL-18 was inhibited in BV2 cells pretreated with DPSC-Exos. Importantly, DPSC-Exos overexpressing miR-197-3p had a more obvious protective effect than those from NC-transfected DPSCs, while those from DPSCs transfected with the miR-197-3p inhibitor had a weaker protective effect. Functional studies indicated that miR-197-3p bound to the 3'-untranslated region of FOXO3, inhibiting its transcription. Furthermore, the overexpression of FOXO3 reversed the protective effects of miR-197-3p.

CONCLUSIONS

DPSC-Exos inhibited activation of the NLRP3 inflammasome and related cytokine release via the miR-197-3p/FOXO3 pathway, alleviated neuroinflammation, and inhibited microglial pyroptosis. These findings suggest that using DPSC-Exos is a promising therapeutic strategy for SAH.

MicroRNA biomarkers as next-generation diagnostic tools for neurodegenerative diseases: a comprehensive review

Neurodegenerative diseases (NDs) are characterized by abnormalities within neurons of the brain or spinal cord that gradually lose function, eventually leading to cell death. Upon examination of affected tissue, pathological changes reveal a loss of synapses, misfolded proteins, and activation of immune cells-all indicative of disease progression-before severe clinical symptoms become apparent. Early detection of NDs is crucial for potentially administering targeted medications that may delay disease advancement. Given their complex pathophysiological features and diverse clinical symptoms, there is a pressing need for sensitive and effective diagnostic methods for NDs. Biomarkers such as microRNAs (miRNAs) have been identified as potential tools for detecting these diseases. We explore the pivotal role of miRNAs in the context of NDs, focusing on Alzheimer's disease, Parkinson's disease, Multiple sclerosis, Huntington's disease, and Amyotrophic Lateral Sclerosis. The review delves into the intricate relationship between aging and NDs, highlighting structural and functional alterations in the aging brain and their implications for disease development. It elucidates how miRNAs and RNA-binding proteins are implicated in the pathogenesis of NDs and underscores the importance of investigating their expression and function in aging. Significantly, miRNAs exert substantial influence on post-translational modifications (PTMs), impacting not just the nervous system but a wide array of tissues and cell types as well. Specific miRNAs have been found to target proteins involved in ubiquitination or de-ubiquitination processes, which play a significant role in regulating protein function and stability. We discuss the link between miRNA, PTM, and NDs. Additionally, the review discusses the significance of miRNAs as biomarkers for early disease detection, offering insights into diagnostic strategies.

The Phytochemical Agathisflavone Modulates miR146a and miR155 in Activated Microglia Involving STAT3 Signaling

MicroRNAs (miRs) act as important post-transcriptional regulators of gene expression in glial cells and have been shown to be involved in the pathogenesis of neurodegenerative diseases, including Alzheimer's disease (AD). Here, we investigated the effects of agathisflavone, a biflavonoid purified from the leaves of Cenostigma pyramidale (Tul.), on modulating the expression of miRs and inflammatory mediators in activated microglia. C20 human microglia were exposed to oligomers of the β-amyloid peptide (Aβ, 500 nM) for 4 h or to lipopolysaccharide (LPS, 1 µg/mL) for 24 h and then treated or not with agathisflavone (1 µM) for 24 h. We observed that β-amyloid and LPS activated microglia to an inflammatory state, with increased expression of miR-146a, miR-155, IL1-β, IL-6, and NOS2. Treatment with agathisflavone resulted in a significant reduction in miR146a and miR-155 induced by LPS or Aβ, as well as inflammatory cytokines IL1-β, IL-6, and NOS2. In cells stimulated with Aβ, there was an increase in p-STAT3 expression that was reduced by agathisflavone treatment. These data identify a role for miRs in the anti-inflammatory effect of agathisflavone on microglia in models of neuroinflammation and AD.

The Role of microRNAs Related to Apoptosis for N-Methyl-d-Aspartic Acid-Induced Neuronal Cell Death in the Murine Retina

Glaucoma is one of the leading causes of acquired blindness and characterized by retinal ganglion cell (RGC) death. MicroRNAs are small noncoding RNAs that degrade their target mRNAs. Apoptosis is one of the common mechanisms leading to neuronal death in many neurodegenerative diseases, including glaucoma. In the present study, we identified microRNAs that modulate RGC death caused by the intravitreal injection of N-methyl-d-aspartic acid (NMDA). We found an upregulation of miR-29b and downregulation of miR-124 in the retina of the NMDA-injected eyes. The intravitreal injection of an miR-29b inhibitor 18 h before NMDA injection reduced RGC death and the downregulation of myeloid cell leukemia 1 (MCL-1), an anti-apoptotic factor, induced by intravitreal NMDA. The intravitreal injection of an miR-124 mimic 18 h before NMDA injection also reduced RGC death and the upregulation of B-cell/chronic lymphocytic leukemia lymphoma 2 (bcl-2)-associated X protein (Bax) and bcl-2 interacting protein (Bim), pro-apoptotic factors, induced by intravitreal NMDA. These data suggest that expressional changes in microRNA are involved in the excitotoxicity of RGCs, and that complement and/or inhibition of microRNA may be a potential therapeutic approach for the diseases related to the excitotoxicity of RGCs, such as glaucoma and retinal central artery occlusion.

A Comprehensive Bioinformatics Approach to Identify Molecular Signatures and Key Pathways for the Huntington Disease

Huntington disease (HD) is a degenerative brain disease caused by the expansion of CAG (cytosine-adenine-guanine) repeats, which is inherited as a dominant trait and progressively worsens over time possessing threat. Although HD is monogenetic, the specific pathophysiology and biomarkers are yet unknown specifically, also, complex to diagnose at an early stage, and identification is restricted in accuracy and precision. This study combined bioinformatics analysis and network-based system biology approaches to discover the biomarker, pathways, and drug targets related to molecular mechanism of HD etiology. The gene expression profile data sets GSE64810 and GSE95343 were analyzed to predict the molecular markers in HD where 162 mutual differentially expressed genes (DEGs) were detected. Ten hub genes among them (DUSP1, NKX2-5, GLI1, KLF4, SCNN1B, NPHS1, SGK2, PITX2, S100A4, and MSX1) were identified from protein-protein interaction (PPI) network which were mostly expressed as down-regulated. Following that, transcription factors (TFs)-DEGs interactions (FOXC1, GATA2, etc), TF-microRNA (miRNA) interactions (hsa-miR-340, hsa-miR-34a, etc), protein-drug interactions, and disorders associated with DEGs were predicted. Furthermore, we used gene set enrichment analysis (GSEA) to emphasize relevant gene ontology terms (eg, TF activity, sequence-specific DNA binding) linked to DEGs in HD. Disease interactions revealed the diseases that are linked to HD, and the prospective small drug molecules like cytarabine and arsenite was predicted against HD. This study reveals molecular biomarkers at the RNA and protein levels that may be beneficial to improve the understanding of molecular mechanisms, early diagnosis, as well as prospective pharmacologic targets for designing beneficial HD treatment.

Multitask joint learning with graph autoencoders for predicting potential MiRNA-drug associations

The occurrence of many diseases is associated with miRNA abnormalities. Predicting potential drug-miRNA associations is of great importance for both disease treatment and new drug discovery. Most computation-based approaches learn one task at a time, ignoring the information contained in other tasks in the same domain. Multitask learning can effectively enhance the prediction performance of a single task by extending the valid information of related tasks. In this paper, we presented a multitask joint learning framework (MTJL) with a graph autoencoder for predicting the associations between drugs and miRNAs. First, we combined multiple pieces of information to construct a high-quality similarity network of both drugs and miRNAs and then used a graph autoencoder (GAE) to learn their embedding representations separately. Second, to further improve the embedding quality of drugs, we added an auxiliary task to classify drugs using the learned representations. Finally, the embedding representations of drugs and miRNAs were linearly transformed to obtain the predictive association scores between them. A comparison with other state-of-the-art models shows that MTJL has the best prediction performance, and ablation experiments show that the auxiliary task can enhance the embedding quality and improve the robustness of the model. In addition, we show that MTJL has high utility in predicting potential associations between drugs and miRNAs by conducting two case studies.

The Application of MicroRNAs in Glaucoma Research: A Bibliometric and Visualized Analysis

Glaucoma is similar to a neurodegenerative disorder and leads to global irreversible loss of vision. Despite extensive research, the pathophysiological mechanisms of glaucoma remain unclear, and no complete cure has yet been identified for glaucoma. Recent studies have shown that microRNAs can serve as diagnostic biomarkers or therapeutic targets for glaucoma; however, there are few bibliometric studies that focus on using microRNAs in glaucoma research. Here, we have adopted a bibliometric analysis in the field of microRNAs in glaucoma research to manifest the current tendencies and research hotspots and to present a visual map of the past and emerging tendencies in this field. In this study, we retrieved publications in the Web of Science database that centered on this field between 2007 and 2022. Next, we used VOSviewer, CiteSpace, Scimago Graphica, and Microsoft Excel to present visual representations of a co-occurrence analysis, co-citation analysis, tendencies, hotspots, and the contributions of authors, institutions, journals, and countries/regions. The United States was the main contributor. Investigative Ophthalmology and Visual Science has published the most articles in this field. Over the past 15 years, there has been exponential growth in the number of publications and citations in this field across various countries, organizations, and authors. Thus, this study illustrates the current trends, hotspots, and emerging frontiers and provides new insight and guidance for searching for new diagnostic biomarkers and clinical trials for glaucoma in the future. Furthermore, international collaborations can also be used to broaden and deepen the field of microRNAs in glaucoma research.

Discerning the Prospects of miRNAs as a Multi-Target Therapeutic and Diagnostic for Alzheimer's Disease

Although over the last few decades, numerous attempts have been made to halt Alzheimer's disease (AD) progression and mitigate its symptoms, only a few have been proven beneficial. Most medications available, still only cater to the symptoms of the disease rather than fixing the cause at the root level. A novel approach involving the use of miRNAs, which work on the principle of gene silencing, is being explored by scientists. Naturally present miRNAs in the biological system help to regulate various genes than may be implicated in AD-like BACE-1 and APP. One miRNA thus, holds the power to keep a check on several genes, conferring it the ability to be used as a multi-target therapeutic. With aging and the onset of diseased pathology, dysregulation of these miRNAs is observed. This flawed miRNA expression is responsible for the unusual buildup of amyloid proteins, fibrillation of tau proteins in the brain, neuronal death and other hallmarks leading to AD. The use of miRNA mimics and miRNA inhibitors provides an attractive perspective for fixing the upregulation and downregulation of miRNAs that led to abnormal cellular activities. Furthermore, the detection of miRNAs in the CSF and serum of diseased patients might be considered an earlier biomarker for the disease. While most of the therapies designed around AD have not succeeded completely, the targeting of dysregulated miRNAs in AD patients might give a new direction to scholars to develop an effective treatment for Alzheimer's disease.

Effectiveness of Treatments That Alter Metabolomics in Cancer Patients-A Systematic Review

INTRODUCTION

Cancer is the leading cause of death worldwide, with the most frequent being breast cancer in women, prostate cancer in men and colon cancer in both sexes. The use of metabolomics to find new biomarkers can provide knowledge about possible interventions based on the presence of oncometabolites in different cancer types.

OBJECTIVES

The primary purpose of this review is to analyze the characteristic metabolome of three of the most frequent cancer types. We further want to identify the existence and success rate of metabolomics-based intervention in patients suffering from those cancer types. Our conclusions are based on the analysis of the methodological quality of the studies.

METHODS

We searched for studies that investigated the metabolomic characteristics in patients suffering from breast cancer, prostate cancer or colon cancer in clinical trials. The data were analyzed, as well as the effects of specific interventions based on identified metabolomics and one or more oncometabolites. The used databases were PubMed, Virtual Health Library, Web of Science, EBSCO and Cochrane Library. Only nine studies met the selection criteria. Study bias was analyzed using the Cochrane risk of bias tool. This systematic review protocol was registered at the International Prospective Register of Systematic Reviews (PROSPERO: CRD42023401474).

RESULTS

Only nine studies about clinical trials were included in this review and show a moderate quality of evidence. Metabolomics-based interventions related with disease outcome were conflictive with no or small changes in the metabolic characteristics of the different cancer types.

CONCLUSIONS

This systematic review shows some interesting results related with metabolomics-based interventions and their effects on changes in certain cancer oncometabolites. The small number of studies we identified which fulfilled our inclusion criteria in this systematic review does not allow us to draw definitive conclusions. Nevertheless, some results can be considered as promising although further research is needed. That research must focus not only on the presence of possible oncometabolites but also on possible metabolomics-based interventions and their influence on the outcome in patients suffering from breast cancer, prostate cancer or colon cancer.

A Glance at Biogenesis and Functionality of MicroRNAs and Their Role in the Neuropathogenesis of Parkinson's Disease

MicroRNAs (miRNAs) are short, noncoding RNA transcripts. Mammalian miRNA coding sequences are located in introns and exons of genes encoding various proteins. As the central nervous system is the largest source of miRNA transcripts in living organisms, miRNA molecules are an integral part of the regulation of epigenetic activity in physiological and pathological processes. Their activity depends on many proteins that act as processors, transporters, and chaperones. Many variants of Parkinson's disease have been directly linked to specific gene mutations which in pathological conditions are cumulated resulting in the progression of neurogenerative changes. These mutations can often coexist with specific miRNA dysregulation. Dysregulation of different extracellular miRNAs has been confirmed in many studies on the PD patients. It seems reasonable to conduct further research on the role of miRNAs in the pathogenesis of Parkinson's disease and their potential use in future therapies and diagnosis of the disease. This review presents the current state of knowledge about the biogenesis and functionality of miRNAs in the human genome and their role in the neuropathogenesis of Parkinson's disease (PD)-one of the most common neurodegenerative disorders. The article also describes the process of miRNA formation which can occur in two ways-the canonical and noncanonical one. However, the main focus was on miRNA's use in in vitro and in vivo studies in the context of pathophysiology, diagnosis, and treatment of PD. Some issues, especially those regarding the usefulness of miRNAs in PD's diagnostics and especially its treatment, require further research. More standardization efforts and clinical trials on miRNAs are needed.

MicroRNA-593-5p contributes to cell death following exposure to 1-methyl-4-phenylpyridinium (MPP+) by targeting PTEN-induced putative kinase 1 (PINK1)

Neurodegenerative diseases are characterized by a decline in neuronal function and structure, leading to neuronal death. Understanding the molecular mechanisms of neuronal death is crucial for developing therapeutics. MicroRNAs (miRs) are small non-coding RNAs that regulate gene expression by degrading target mRNAs or inhibiting translation. MiR dysregulation has been linked to many neurodegenerative diseases, but the underlying mechanisms are not well understood. As mitochondrial dysfunction is one of the common molecular mechanisms leading to neuronal death in many neurodegenerative diseases, here we studied miRs that modulate neuronal death caused by 1-methyl-4-phenylpyridinium (MPP+), an inhibitor of complex I in mitochondria. We identified miR-593-5p, levels of which were increased in SH-SY5Y human neuronal cells, after exposure to MPP⁺. We found that intracellular Ca²⁺, but not of reactive oxygen species (ROS), mediated this miR-593-5p increase. Furthermore, we found the increase in miR-593-5p was due to enhanced stability, not increased transcription or miR processing. Importantly, we show the increase in miR-593-5p contributed to MPP⁺-induced cell death. Our data revealed that miR-593-5p inhibits a signaling pathway involving PTEN-induced putative kinase 1 (PINK1) and Parkin, two proteins responsible for the removal of damaged mitochondria from cells, by targeting the coding sequence of PINK1 mRNA. Our findings suggest that miR-593-5p contributes to neuronal death resulting from MPP⁺ toxicity, in part, by impeding the PINK1/Parkin-mediated pathway that facilitates the clearance of damaged mitochondria. Taken together, our observations highlight the potential significance of inhibiting miR-593-5p as a therapeutic approach for neurodegenerative diseases.

Small Extracellular Vesicles' miRNAs: Biomarkers and Therapeutics for Neurodegenerative Diseases

Neurodegenerative diseases are critical in the healthcare system as patients suffer from progressive diseases despite currently available drug management. Indeed, the growing ageing population will burden the country's healthcare system and the caretakers. Thus, there is a need for new management that could stop or reverse the progression of neurodegenerative diseases. Stem cells possess a remarkable regenerative potential that has long been investigated to resolve these issues. Some breakthroughs have been achieved thus far to replace the damaged brain cells; however, the procedure's invasiveness has prompted scientists to investigate using stem-cell small extracellular vesicles (sEVs) as a non-invasive cell-free therapy to address the limitations of cell therapy. With the advancement of technology to understand the molecular changes of neurodegenerative diseases, efforts have been made to enrich stem cells' sEVs with miRNAs to increase the therapeutic efficacy of the sEVs. In this article, the pathophysiology of various neurodegenerative diseases is highlighted. The role of miRNAs from sEVs as biomarkers and treatments is also discussed. Lastly, the applications and delivery of stem cells and their miRNA-enriched sEVs for treating neurodegenerative diseases are emphasised and reviewed.

State of the Art of microRNAs Signatures as Biomarkers and Therapeutic Targets in Parkinson's and Alzheimer's Diseases: A Systematic Review and Meta-Analysis

Identifying target microRNAs (miRNAs) might serve as a basis for developing advanced therapies for Parkinson's disease (PD) and Alzheimer's disease. This review aims to identify the main therapeutic targets of miRNAs that can potentially act in Parkinson's and Alzheimer's diseases. The publication research was conducted from May 2021 to March 2022, selected from Scopus, PubMed, Embase, OVID, Science Direct, LILACS, and EBSCO. A total of 25 studies were selected from 1549 studies evaluated. The total number of miRNAs as therapeutic targets evidenced was 90 for AD and 54 for PD. An average detection accuracy of above 84% for the miRNAs was observed in the selected studies of AD and PD. The major signatures were miR-26b-5p, miR-615-3p, miR-4722-5p, miR23a-3p, and miR-27b-3p for AD and miR-374a-5p for PD. Six miRNAs of intersection were found between AD and PD. This article identified the main microRNAs as selective biomarkers for diagnosing PD and AD and therapeutic targets through a systematic review and meta-analysis. This article can act as a microRNA guideline for laboratory research and pharmaceutical industries for treating Alzheimer's and Parkinson's diseases and offers the opportunity to evaluate therapeutic interventions earlier in the disease process.

Ageing at Molecular Level: Role of MicroRNAs

The progression of age triggers a vast number of diseases including cardiovascular, cancer, and neurodegenerative disorders. Regardless of our plentiful knowledge about age-related diseases, little is understood about molecular pathways that associate the ageing process with various diseases. Several cellular events like senescence, telomere dysfunction, alterations in protein processing, and regulation of gene expression are common between ageing and associated diseases. Accumulating information on the role of microRNAs (miRNAs) suggests targeting miRNAs can aid our understanding of the interplay between ageing and associated diseases. In the present chapter, we have attempted to explore the information available on the role of miRNAs in ageing of various tissues/organs and diseases and understand the molecular mechanism of ageing.

Analysis of MicroRNAs in Ferroptosis

MicroRNAs (miRNAs) are a class of small non-coding RNA molecules that are involved in a wide range of biological processes, including development, differentiation, and disease. They function by binding to the 3' untranslated region (UTR) of target mRNAs, leading to mRNA degradation or translational repression. miRNAs are involved in the regulation of many cellular processes, including cell proliferation, apoptosis, and metabolism. MiRNAs have been shown to modulate ferroptosis in several ways. Some miRNAs have been shown to promote ferroptosis by increasing the expression of genes involved in lipid peroxidation. Other miRNAs have been shown to inhibit ferroptosis by decreasing the expression of genes involved in iron uptake. The role of miRNAs in ferroptosis is still being studied, but they play a significant role in this cell death pathway. miRNAs may be potential targets for therapeutic intervention in diseases associated with ferroptosis, such as cancer and neurodegenerative diseases. This chapter outlines several methods used to study the connection between miRNAs and ferroptosis through target discovery and validation.

DNA walking system integrated with enzymatic cleavage reaction for sensitive surface plasmon resonance detection of miRNA

Abnormal expression levels of miRNA are associated with various tumor diseases, for example, glioma tumors are characterized by the up-regulation of miRNA-182. Surface plasmon resonance (SPR) assay for miRNA-182 from glioma patients was performed via DNA walking amplification strategy. The duplex between aminated swing arm DNA (swDNA) and block DNA (blDNA), and aminated track DNA (trDNA) with a biotin tag were tethered on the poly(ethylene glycol) (PEG)-modified chips. Upon formation of miRNA/blDNA duplex, the SPR signal decreased with the walking process of swDNA, as the biotinylated fragment of trDNA (biotin-TTGGAGT) was detached from the sensor surface caused by the nicking endonuclease Nb.BbvCI. Such a repeated hybridization and cleavage cycle occurred continuously and the detachment of more biotinylated fragments of trDNA from the chips led to the attachment of fewer streptavidin (SA) molecules and then smaller SPR signals. MiRNA-182 with concentrations ranging from 5.0 fM to 1.0 pM could be readily determined and a detection limit of 0.62 fM was achieved. The proposed method was highly selective and possessed remarkable capability for evaluating the expression levels of miRNA-182 in serum samples from healthy donors and glioma patients. The sensing protocol holds great promise for early diagnosis of cancer patients.

Identification of Potential miRNA-mRNA Regulatory Network Contributing to Parkinson's Disease

Parkinson's disease (PD) is a common neurodegenerative disease, and the mechanism underlying PD pathogenesis is not completely understood. Increasing evidence indicates that microRNAs (miRNAs) play a critical regulatory role in the pathogenesis of PD. This study aimed to explore the miRNA-mRNA regulatory network for PD. The differentially expressed miRNAs (DEmis) and genes (DEGs) between PD patients and healthy donors were screened from the miRNA dataset GSE16658 and mRNA dataset GSE100054 downloaded from the Gene Expression Omnibus (GEO) database. Target genes of the DEmis were selected when they were predicted by three or four online databases and overlapped with DEGs from GSE100054. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were then conducted by Database for Annotation, Visualization and Integrated Discovery (DAVID) and Metascape analytic tools. The correlation between the screened genes and PD was evaluated with the online tool Comparative Toxicogenomics Database (CTD), and protein-protein interaction (PPI) networks were built by the STRING platform. We further investigated the expression of genes in the miRNA-mRNA regulatory network in blood samples collected from PD patients and healthy donors via qRT-PCR. We identified 1505 upregulated and 1302 downregulated DEGs, and 77 upregulated and 112 downregulated DEmis were preliminarily screened from the GEO database. Further functional enrichment analysis identified 10 PD-related hub genes, including RAC1, IRS2, LEPR, PPARGC1A, CAMKK2, RAB10, RAB13, RAB27B, RAB11A, and JAK2, which were mainly involved in Rab protein signaling transduction, AMPK signaling pathway, and signaling by Leptin. A miRNA-mRNA regulatory network was then constructed with 10 hub genes, and their interacting miRNAs overlapped with DEmis, including miR-30e-5p, miR-142-3p, miR-101-3p, miR-32-3p, miR-508-5p, miR-642a-5p, miR-19a-3p, and miR-21-5p. Analysis of clinical samples verified significant upregulation of LEPR and downregulation of miR-101-3p and miR-30e-5p in PD patients as compared with healthy donors. Thus, the miRNA-mRNA regulatory network was initially constructed and has the potential to provide novel insights into the pathogenesis and treatment of PD.

Inhibition of miR-421 Preserves Mitochondrial Function and Protects against Parkinson's Disease Pathogenesis via Pink1/Parkin-Dependent Mitophagy

Mutations in PINK1 and Parkin are a major cause of Parkinson's disease (PD) pathogenesis. In addition, PINK1 and Parkin are two mitochondrial proteins that jointly contribute to mitochondrial homeostasis via mitophagy. Mitochondrial dysfunction is the most significant mechanism underlying PD pathogenesis. Thus, understanding the regulatory mechanism of PINK1 and Parkin expression is beneficial to the treatment of PD. In this study, we found that miR-421 expression was upregulated in mice treated with MPTP, as well as in SH-SY5Y cells treated with methyl-4-phenylpyridine (MPP+). Inhibition of miR-421 alleviated neurodegeneration in MPTP-treated mice and promoted mitophagy in MPP+-treated SH-SY5Y cells. Bioinformatics software predicted that Pink1 is a downstream target protein of miR-421. In addition, miR-421-induced Pink1 and Parkin inhibition negatively modulates mitophagy in MPP+-treated SH-SY5Y cells. In addition, our study confirmed that Pink1/Parkin is responsible for miR-421-regulated cell mitophagy. Overall, this study revealed that miR-421 regulates nerve cell mitophagy through the Pink1/Parkin pathway.

Differential expression of MicroRNAs in Alzheimer's disease: a systematic review and meta-analysis

Alzheimer's disease (AD) results in progressive cognitive decline owing to the accumulation of amyloid plaques and hyperphosphorylated tau. MicroRNAs (miRNAs) have attracted attention as a putative diagnostic and therapeutic target for neurodegenerative diseases. However, existing meta-analyses on AD and its association with miRNAs have produced inconsistent results. The primary objective of this study is to evaluate the magnitude and consistency of differences in miRNA levels between AD patients, mild cognitive impairment (MCI) patients and healthy controls (HC). Articles investigating miRNA levels in blood, brain tissue, or cerebrospinal fluid (CSF) of AD and MCI patients versus HC were systematically searched in PubMed/Medline from inception to February 16^th, 2021. Fixed- and random-effects meta-analyses were complemented with the I² statistic to measure the heterogeneity, assessment of publication bias, sensitivity subgroup analyses (AD severity, brain region, post-mortem versus ante-mortem specimen for CSF and type of analysis used to quantify miRNA) and functional enrichment pathway analysis. Of the 1512 miRNAs included in 61 articles, 425 meta-analyses were performed on 334 miRNAs. Fifty-six miRNAs were significantly upregulated (n = 40) or downregulated (n = 16) in AD versus HC and all five miRNAs were significantly upregulated in MCI versus HC. Functional enrichment analysis confirmed that pathways related to apoptosis, immune response and inflammation were statistically enriched with upregulated pathways in participants with AD relative to HC. This study confirms that miRNAs' expression is altered in AD and MCI compared to HC. These findings open new diagnostic and therapeutic perspectives for this disorder.

Emerging Evidence of Noncoding RNAs in Bleb Scarring after Glaucoma Filtration Surgery

PURPOSE

To conduct a narrative review of research articles on the potential anti- and pro-fibrotic mechanisms of noncoding RNAs following glaucoma filtration surgery.

METHODS

Keyword searches of PubMed, and Medline databases were conducted for articles discussing post-glaucoma filtration surgeries and noncoding RNA. Additional manual searches of reference lists of primary articles were performed.

RESULTS

Fifteen primary research articles were identified. Four of the included papers used microarrays and qRT-PCR to identify up- or down-regulated microRNA (miRNA, miR) profiles and direct further study, with the remainder focusing on miRNAs or long noncoding RNAs (lncRNAs) based on previous work in other organs or disease processes. The results of the reviewed papers identified miR-26a, -29b, -139, -155, and -200a as having anti-fibrotic effects. In contrast, miRs-200b and -216b may play pro-fibrotic roles in filtration surgery fibrosis. lncRNAs including H19, NR003923, and 00028 have demonstrated pro-fibrotic effects.

CONCLUSIONS

Noncoding RNAs including miRNAs and lncRNAs are emerging and promising therapeutic targets in the prevention of post-glaucoma filtration surgery fibrosis.

Therapeutics in the Pipeline Targeting α-Synuclein for Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder and the fastest growing neurologic disease in the world, yet no disease-modifying therapy is available for this disabling condition. Multiple lines of evidence implicate the protein α-synuclein (α-Syn) in the pathogenesis of PD, and as such, there is intense interest in targeting α-Syn for potential disease modification. α-Syn is also a key pathogenic protein in other synucleionpathies, most commonly dementia with Lewy bodies. Thus, therapeutics targeting this protein will have utility in these disorders as well. Here we discuss the various approaches that are being investigated to prevent and mitigate α-Syn toxicity in PD, including clearing its pathologic aggregates from the brain using immunization strategies, inhibiting its misfolding and aggregation, reducing its expression level, enhancing cellular clearance mechanisms, preventing its cell-to-cell transmission within the brain and perhaps from the periphery, and targeting other proteins associated with or implicated in PD that contribute to α-Syn toxicity. We also discuss the therapeutics in the pipeline that harness these strategies. Finally, we discuss the challenges and opportunities for the field in the discovery and development of therapeutics for disease modification in PD. SIGNIFICANCE STATEMENT: PD is the second most common neurodegenerative disorder, for which disease-modifying therapies remain a major unmet need. A large body of evidence points to α-synuclein as a key pathogenic protein in this disease as well as in dementia with Lewy bodies, making it of leading therapeutic interest. This review discusses the various approaches being investigated and progress made to date toward discovering and developing therapeutics that would slow and stop progression of these disabling diseases.

Identification of a Qualitative Signature for the Diagnosis of Dementia With Lewy Bodies

Background and purpose: Diagnosis of dementia with Lewy bodies (DLB) is highly challenging, primarily due to a lack of valid and reliable diagnostic tools. To date, there is no report of qualitative signature for the diagnosis of DLB. We aimed to develop a blood-based qualitative signature for differentiating DLB patients from healthy controls.

Methods: The GSE120584 dataset was downloaded from the public database Gene Expression Omnibus (GEO). We combined multiple methods to select features based on the within-sample relative expression orderings (REOs) of microRNA (miRNA) pairs. Specifically, we first quickly selected miRNA pairs related to DLB by identifying reversal stable miRNA pairs. Then, an optimal miRNA pair subset was extracted by random forest (RF) and support vector machine-recursive feature elimination (SVM-RFE) methods. Furthermore, we applied logistic regression (LR) and SVM to build several prediction models. The model performance was assessed using the receiver operating characteristic curve (ROC) analysis. Lastly, we conducted bioinformatics analyses to explore the molecular mechanisms of the discovered miRNAs.

Results: A qualitative signature consisted of 17 miRNA pairs and two clinical factors was identified for discriminating DLB patients from healthy controls. The signature is robust against experimental batch effects and applicable at the individual levels. The accuracies of the-signature-based models on the test set are 82.61 and 79.35%, respectively, indicating that the signature has acceptable discrimination performance. Moreover, bioinformatics analyses revealed that predicted target genes were enriched in 11 Go terms and 2 KEGG pathways. Moreover, five potential hub genes were found for DLB, including SRF, MAPK1, YWHAE, RPS6KA3, and KDM7A.

Conclusion: This study provided a blood-based qualitative signature with the potential to be used as an effective tool to improve the accuracy of DLB diagnosis.

Long Noncoding RNA NEAT1 Knockdown Ameliorates 1-Methyl-4-Phenylpyridine-Induced Cell Injury Through MicroRNA-519a-3p/SP1 Axis in Parkinson Disease

BACKGROUND

Parkinson disease is a neurodegenerative disease and is characterized by resting tremor, dementia, and gait disorder. Previous studies have indicated that long noncoding RNA participates in the regulation of the pathogenesis of Parkinson disease. The study aimed to reveal the effects of long noncoding RNA nuclear paraspeckle assembly transcript 1 (NEAT1) on 1-methyl-4-phenylpyridine (MPP+)-induced human neuroblastoma cell injury and the underlying mechanism.

METHODS

The expressions of NEAT1, microRNA (miR)-519a-3p, and transcription factor specific protein 1 (SP1) were detected by quantitative real-time polymerase chain reaction. The protein expressions of SP1 and inflammation-related factors were determined by Western blot. Cell viability was determined by 3-(4,5-dimethylthazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptosis was investigated by flow cytometry analysis. The targeting relationship between miR-519a-3p and NEAT1 or SP1 was predicted by starBase online database and verified by a dual-luciferase reporter assay.

RESULTS

NEAT1 and SP1 expressions were significantly upregulated, whereas miR-519a-3p was downregulated in MPP+-treated neuroblastoma cells in a dose- and time-dependent manner when compared with control groups. NEAT1 knockdown restrained MPP+-induced repression of cell viability and promotion of cell apoptosis and inflammation. Additionally, NEAT1 served as a sponge of miR-519a-3p and regulated MPP+-caused cell injury by interacting with miR-519a-3p. Also, SP1, a target gene of miR-519a-3p, rescued miR-519a-3p-mediated actions under MPP+ treatment. Importantly, NEAT1 stimulated SP1 expression through interaction with miR-519a-3p.

CONCLUSIONS

NEAT1 silencing protected against MPP+-induced neuroblastoma cell injury by regulating the miR-519a-3p/SP1 pathway. This finding provides a novel direction for the development of therapeutic strategies for Parkinson disease.

Serum miR-214 Serves as a Biomarker for Prodromal Parkinson's Disease

Circulating microRNAs (miRNAs) have been proposed to be accessible biomarkers for Parkinson’s disease (PD). However, there is a lack of known miRNAs that can serve as biomarkers for prodromal PD (pPD). We previously identified that miR-31 and miR-214 were dysregulated in PD. The aim of this study was to explore the roles of miR-31 and miR-214 in pPD. We recruited 25 pPD patients, 20 patients with de novo PD (dnPD), 24 advanced PD (aPD) patients and 21 controls. Next, we investigated the expression of miR-31 and miR-214. Compared to controls, miR-214 was found to be significantly upregulated in pPD patients while miR-31 was significantly upregulated in aPD patients. In addition, the expression of miR-214 was lower in aPD patients compared to both dnPD or pPD patients, while the expression of miR-31 was higher in aPD patients compared to dnPD patients. In order to predict pPD via miRNA expression, the receiver operating characteristic curve was constructed and the area under curve (AUC) was calculated. For pPD prediction by miR-214, the AUC was 0.756. The optimal cut-off value of miR-214 was 0.1962, and the sensitivity and specificity were 72.0% and 76.2%, respectively. On the other hand, the AUC for aPD detection by miR-31 was 0.744. The optimal cut-off value for miR-31 was 0.0148, with a sensitivity of 87.5% and a specificity of 71.4%. In conclusion, miR-214 can distinguish pPD patients from controls and may be used as a potential biomarker for pPD diagnosis.

Resilience in Long-Term Viral Infection: Genetic Determinants and Interactions

Virus-induced neurological sequelae resulting from infection by Theiler's murine encephalomyelitis virus (TMEV) are used for studying human conditions ranging from epileptic seizures to demyelinating disease. Mouse strains are typically considered susceptible or resistant to TMEV infection based on viral persistence and extreme phenotypes, such as demyelination. We have identified a broader spectrum of phenotypic outcomes by infecting strains of the genetically diverse Collaborative Cross (CC) mouse resource. We evaluated the chronic-infection gene expression profiles of hippocampi and thoracic spinal cords for 19 CC strains in relation to phenotypic severity and TMEV persistence. Strains were clustered based on similar phenotypic profiles and TMEV levels at 90 days post-infection, and we categorized distinct TMEV response profiles. The three most common profiles included "resistant" and "susceptible," as before, as well as a "resilient" TMEV response group which experienced both TMEV persistence and mild neurological phenotypes even at 90 days post-infection. Each profile had a distinct gene expression signature, allowing the identification of pathways and networks specific to each TMEV response group. CC founder haplotypes for genes involved in these pathways/networks revealed candidate response-specific alleles. These alleles demonstrated pleiotropy and epigenetic (miRNA) regulation in long-term TMEV infection, with particular relevance for resilient mouse strains.

Role of Mitochondria in Neurodegenerative Diseases: From an Epigenetic Perspective

Mitochondria, the centers of energy metabolism, have been shown to participate in epigenetic regulation of neurodegenerative diseases. Epigenetic modification of nuclear genes encoding mitochondrial proteins has an impact on mitochondria homeostasis, including mitochondrial biogenesis, and quality, which plays role in the pathogenesis of neurodegenerative diseases like Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis. On the other hand, intermediate metabolites regulated by mitochondria such as acetyl-CoA and NAD⁺, in turn, may regulate nuclear epigenome as the substrate for acetylation and a cofactor of deacetylation, respectively. Thus, mitochondria are involved in epigenetic regulation through bidirectional communication between mitochondria and nuclear, which may provide a new strategy for neurodegenerative diseases treatment. In addition, emerging evidence has suggested that the abnormal modification of mitochondria DNA contributes to disease development through mitochondria dysfunction. In this review, we provide an overview of how mitochondria are involved in epigenetic regulation and discuss the mechanisms of mitochondria in regulation of neurodegenerative diseases from epigenetic perspective.

MicroRNA-137-3p Protects PC12 Cells Against Oxidative Stress by Downregulation of Calpain-2 and nNOS

The imbalance between excess reactive oxygen species (ROS) generation and insufficient antioxidant defenses contribute to a range of neurodegenerative diseases. High ROS levels damage cellular macromolecules such as DNA, proteins and lipids, leading to neuron vulnerability and eventual death. However, the underlying molecular mechanism of the ROS regulation is not fully elucidated. Recently, an increasing number of studies suggest that microRNAs (miRNAs) emerge as the targets in regulating oxidative stress. We recently reported the neuroprotective effect of miR-137-3p for brachial plexus avulsion-induced motoneuron death. The present study is sought to investigate whether miR-137-3p also could protect PC12 cells against hydrogen peroxide (H2O2) induced neurotoxicity. By using cell viability assay, ROS assay, gene and protein expression assay, we found that PC-12 cells exposed to H2O2 exhibited decreased cell viability, increased expression levels of calpain-2 and neuronal nitric oxide synthase (nNOS), whereas a decreased miR-137-3p expression. Importantly, restoring the miR-137-3p levels in H2O2 exposure robustly inhibited the elevated nNOS, calpain-2 and ROS expression levels, which subsequently improved the cell viability. Furthermore, the suppressive effect of miR-137-3p on the elevated ROS level under oxidative stress was considerably blunted when we mutated the binding site of calpain-2 targted by miR-137-3p, suggesting the critical role of calpain-2 involving the neuroprotective effect of miR-137-3p. Collectively, these findings highlight the neuroprotective role of miR-137-3p through down-regulating calpain and NOS activity, suggesting its potential role for combating oxidative stress insults in the neurodegenerative diseases.

Bioinformatics analysis of differentially expressed genes and identification of an miRNA-mRNA network associated with entorhinal cortex and hippocampus in Alzheimer's disease

Background

Alzheimer’s disease (AD) is a fatal neurodegenerative disorder, and the lesions originate in the entorhinal cortex (EC) and hippocampus (HIP) at the early stage of AD progression. Gaining insight into the molecular mechanisms underlying AD is critical for the diagnosis and treatment of this disorder. Recent discoveries have uncovered the essential roles of microRNAs (miRNAs) in aging and have identified the potential of miRNAs serving as biomarkers in AD diagnosis.

Methods

We sought to apply bioinformatics tools to investigate microarray profiles and characterize differentially expressed genes (DEGs) in both EC and HIP and identify specific candidate genes and pathways that might be implicated in AD for further analysis. Furthermore, we considered that DEGs might be dysregulated by miRNAs. Therefore, we investigated patients with AD and healthy controls by studying the gene profiling of their brain and blood samples to identify AD-related DEGs, differentially expressed miRNAs (DEmiRNAs), along with gene ontology (GO) analysis, KEGG pathway analysis, and construction of an AD-specific miRNA–mRNA interaction network.

Results

Our analysis identified 10 key hub genes in the EC and HIP of patients with AD, and these hub genes were focused on energy metabolism, suggesting that metabolic dyshomeostasis contributed to the progression of the early AD pathology. Moreover, after the construction of an miRNA–mRNA network, we identified 9 blood-related DEmiRNAs, which regulated 10 target genes in the KEGG pathway.

Conclusions

Our findings indicated these DEmiRNAs having the potential to act as diagnostic biomarkers at an early stage of AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-021-00190-0.

The Role of Non-coding RNAs in Alzheimer's Disease: From Regulated Mechanism to Therapeutic Targets and Diagnostic Biomarkers

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder. AD is characterized by the production and aggregation of beta-amyloid (Aβ) peptides, hyperphosphorylated tau proteins that form neurofibrillary tangles (NFTs), and subsequent neuroinflammation, synaptic dysfunction, autophagy and oxidative stress. Non-coding RNAs (ncRNAs) can be used as potential therapeutic targets and biomarkers due to their vital regulatory roles in multiple biological processes involved in disease development. The involvement of ncRNAs in the pathogenesis of AD has been increasingly recognized. Here, we review the ncRNAs implicated in AD and elaborate on their main regulatory pathways, which might have contributions for discovering novel therapeutic targets and drugs for AD.

Alzheimer's Disorder: Epigenetic Connection and Associated Risk Factors

The gene based therapeutics and drug targets have shown incredible and appreciable advances in alleviating human sufferings and complexities. Epigenetics simply means above genetics or which controls the organism beyond genetics. At present it is very clear that all characteristics of an individual are not determined by DNA alone, rather the environment, stress, life style and nutrition play a vital part in determining the response of an organism. Thus, nature (genetic makeup) and nurture (exposure) play equally important roles in the responses observed, both at the cellular and organism levels. Epigenetics influence plethora of complications at cellular and molecular levels that includes cancer, metabolic and cardiovascular complications including neurological (psychosis) and neurodegenerative disorders (Alzheimer’s disease, Parkinson disease etc.). The epigenetic mechanisms include DNA methylation, histone modification and non coding RNA which have substantial impact on progression and pathways linked to Alzheimer’s disease. The epigenetic mechanism gets deregulated in Alzheimer’s disease and is characterized by DNA hyper methylation, deacetylation of histones and general repressed chromatin state which alter gene expression at the transcription level by upregulation, downregulation or silencing of genes. Thus, the processes or modulators of these epigenetic processes have shown vast potential as a therapeutic target in Alzheimer’s disease.

The pleiotropic neuroprotective effects of resveratrol in cognitive decline and Alzheimer's disease pathology: From antioxidant to epigenetic therapy

While the elderly segment of the population continues growing in importance, neurodegenerative diseases increase exponentially. Lifestyle factors such as nutrition, exercise, and education, among others, influence ageing progression, throughout life. Notably, the Central Nervous System (CNS) can benefit from nutritional strategies and dietary interventions that prevent signs of senescence, such as cognitive decline or neurodegenerative diseases such as Alzheimer's disease and Parkinson's Disease. The dietary polyphenol Resveratrol (RV) possesses antioxidant and cytoprotective effects, producing neuroprotection in several organisms. The oxidative stress (OS) occurs because of Reactive oxygen species (ROS) accumulation that has been proposed to explain the cause of the ageing. One of the most harmful effects of ROS in the cell is DNA damage. Nevertheless, there is also evidence demonstrating that OS can produce other molecular changes such as mitochondrial dysfunction, inflammation, apoptosis, and epigenetic modifications, among others. Interestingly, the dietary polyphenol RV is a potent antioxidant and possesses pleiotropic actions, exerting its activity through various molecular pathways. In addition, recent evidence has shown that RV mediates epigenetic changes involved in ageing and the function of the CNS that persists across generations. Furthermore, it has been demonstrated that RV interacts with gut microbiota, showing modifications in bacterial composition associated with beneficial effects. In this review, we give a comprehensive overview of the main mechanisms of action of RV in different experimental models, including clinical trials and discuss how the interconnection of these molecular events could explain the neuroprotective effects induced by RV.

High-Throughput Sequencing of BACHD Mice Reveals Upregulation of Neuroprotective miRNAs at the Pre-Symptomatic Stage of Huntington's Disease

Huntington’s disease (HD) is a genetic disorder marked by transcriptional alterations that result in neuronal impairment and death. MicroRNAs (miRNAs) are non-coding RNAs involved in post-transcriptional regulation and fine-tuning of gene expression. Several studies identified altered miRNA expression in HD and other neurodegenerative diseases, however their roles in early stages of HD remain elusive. Here, we deep-sequenced miRNAs from the striatum of the HD mouse model, BACHD, at the age of 2 and 8 months, representing the pre-symptomatic and symptomatic stages of the disease. Our results show that 44 and 26 miRNAs were differentially expressed in 2- and 8-month-old BACHD mice, respectively, as compared to wild-type controls. Over-representation analysis suggested that miRNAs up-regulated in 2-month-old mice control the expression of genes crucial for PI3K-Akt and mTOR cell signaling pathways. Conversely, miRNAs regulating genes involved in neuronal disorders were down-regulated in 2-month-old BACHD mice. Interestingly, primary striatal neurons treated with anti-miRs targeting two up-regulated miRNAs, miR-449c-5p and miR-146b-5p, showed higher levels of cell death. Therefore, our results suggest that the miRNAs altered in 2-month-old BACHD mice regulate genes involved in the promotion of cell survival. Notably, over-representation suggested that targets of differentially expressed miRNAs at the age of 8 months were not significantly enriched for the same pathways. Together, our data shed light on the role of miRNAs in the initial stages of HD, suggesting a neuroprotective role as an attempt to maintain or reestablish cellular homeostasis.

Oligonucleotides as therapeutic tools for brain disorders: Focus on major depressive disorder and Parkinson's disease

Remarkable advances in understanding the role of RNA in health and disease have expanded considerably in the last decade. RNA is becoming an increasingly important target for therapeutic intervention; therefore, it is critical to develop strategies for therapeutic modulation of RNA function. Oligonucleotides, including antisense oligonucleotide (ASO), small interfering RNA (siRNA), microRNA mimic (miRNA), and anti-microRNA (antagomir) are perhaps the most direct therapeutic strategies for addressing RNA. Among other mechanisms, most oligonucleotide designs involve the formation of a hybrid with RNA that promotes its degradation by activation of endogenous enzymes such as RNase-H (e.g., ASO) or the RISC complex (e.g. RNA interference - RNAi for siRNA and miRNA). However, the use of oligonucleotides for the treatment of brain disorders is seriously compromised by two main limitations: i) how to deliver oligonucleotides to the brain compartment, avoiding the action of peripheral RNAses? and once there, ii) how to target specific neuronal populations? We review the main molecular pathways in major depressive disorder (MDD) and Parkinson's disease (PD), and discuss the challenges associated with the development of novel oligonucleotide therapeutics. We pay special attention to the use of conjugated ligand-oligonucleotide approach in which the oligonucleotide sequence is covalently bound to monoamine transporter inhibitors (e.g. sertraline, reboxetine, indatraline). This strategy allows their selective accumulation in the monoamine neurons of mice and monkeys after their intranasal or intracerebroventricular administration, evoking preclinical changes predictive of a clinical therapeutic action after knocking-down disease-related genes. In addition, recent advances in oligonucleotide therapeutic clinical trials are also reviewed.

Dysregulation of MicroRNAs and PIWI-Interacting RNAs in a Caenorhabditis elegans Parkinson's Disease Model Overexpressing Human α-Synuclein and Influence of tdp-1

MicroRNAs (miRNAs) and PIWI-interacting RNAs (piRNAs) regulate gene expression and biological processes through specific genetic and epigenetic mechanisms. Recent studies have described a dysregulation of small non-coding RNAs in Parkinson’s disease (PD) tissues but have been limited in scope. Here, we extend these studies by comparing the dysregulation of both miRNAs and piRNAs from transgenic Caenorhabditis elegans (C. elegans) nematodes overexpressing pan-neuronally human α-synuclein wild-type (WT) (HASN^WT OX) or mutant (HASN^A53T OX). We observed 32 miRNAs and 112 piRNAs dysregulated in HASN^A53T OX compared with WT. Genetic crosses of HASN^A53T OX PD animal models with tdp-1 null mutants, the C. elegans ortholog of TDP-43, an RNA-binding protein aggregated in frontal temporal lobar degeneration, improved their behavioral deficits and changed the number of dysregulated miRNAs to 11 and piRNAs to none. Neuronal function-related genes T28F4.5, C34F6.1, C05C10.3, camt-1, and F54D10.3 were predicted to be targeted by cel-miR-1018, cel-miR-355-5p (C34F6.1 and C05C10.3), cel-miR-800-3p, and 21ur-1581 accordingly. This study provides a molecular landscape of small non-coding RNA dysregulation in an animal model that provides insight into the epigenetic changes, molecular processes, and interactions that occur during PD-associated neurodegenerative disorders.

Expression profiling of miRNA-196a biomarker in naïve hepatitis C virus-infected and Sofosbuvir plus Daclatasvir-treated patients

Micro-RNA (miRNA) is a short stretch of nucleotides that can regulate many genes associated with the various stages of the hepatitis C virus (HCV) life cycle and disease progression. This study evaluates the expression profiling of miRNA-196a in naïve HCV-infected, and Sofosbuvir plus Daclatasvir-treated patients. MiRNA-196a can inhibit HCV replication by silencing the HCV NS5A protein or downregulating the human BACH-I mRNA. The expression level of miRNA-196a was determined by quantitative reverse transcription PCR (RT-qPCR) using the whole RNA extracted from the recruited participant's serum. Results showed a 0.83-fold decrease in the miRNA-196a level in naïve HCV-infected than controls. On the contrary, an increase in the expression level by 0.06-fold was observed in Sofosbuvir plus Daclatasvir-treated patients. A negative but significant correlation was recorded between the HCV-RNA load and miRNA-196a expression level in the naïve-infected patients. Serum miRNA-196a ROC curve analysis revealed an area under the curve of 0.8278 (95% CI 0.7033-0.9524, p < 0.0001) with 82.05% sensitivity and 76.19% specificity in discriminating the healthy controls from the HCV-infected samples. In conclusion, our study explored the comparative expression levels of miRNA-196a in HCV-infected and Sofosbuvir plus Daclatasvir patients. Further studies are needed to examine the possible role of miR-196a as a therapeutic agent for treating HCV-infected patients.

Changes in neurodegeneration-related miRNAs in brains from CAPN1-/- mice

Calpain-1 knock-out (KO) mice exhibit enhanced susceptibility to neurodegeneration due to the lack of the neuroprotective function of calpain-1. Dicer has been shown to play a fundamental role in the biogenesis of most miRNAs. Here, we identified 45 differentially expressed miRNAs (DE miRNAs) in the brain of calpain-1 KO mice, as compared to wild-type mice. In particular, among all the DE miRNAs, 7 neurodegeneration-related miRNAs were found to be down-regulated in calpain-1 KO mice. We also found that Dicer is cleaved by calpain-1 in mouse brain, which generates an active fragment of Dicer with RNAse III activity and increases miRNA formation. Levels of active Dicer were reduced in brain homogenates from calpain-1 KO mice and incubation with calpain-1 and calcium restored Dicer activity and miRNA expression. Our results indicate that calpain-1 deletion results in decreased levels of active Dicer and changes in neurodegenerative-related miRNAs. These findings could account for some of the pathological changes found in brain of various mammals, including humans, with calpain-1 mutations or down-regulation.

Neuronal Development-Related miRNAs as Biomarkers for Alzheimer's Disease, Depression, Schizophrenia and Ionizing Radiation Exposure

Radiation exposure may induce Alzheimer's disease (AD), depression or schizophrenia. A number of experimental and clinical studies suggest the involvement of miRNA in the development of these diseases, and also in the neuropathological changes after brain radiation exposure. The current literature review indicated the involvement of 65 miRNAs in neuronal development in the brain. In the brain tissue, blood, or cerebral spinal fluid (CSF), 11, 55, or 28 miRNAs are involved in the development of AD respectively, 89, 50, 19 miRNAs in depression, and 102, 35, 8 miRNAs in schizophrenia. We compared miRNAs regulating neuronal development to those involved in the genesis of AD, depression and schizophrenia and also those driving radiation-induced brain neuropathological changes by reviewing the available data. We found that 3, 11, or 8 neuronal developmentrelated miRNAs from the brain tissue, 13, 16 or 14 miRNAs from the blood of patient with AD, depression and schizophrenia respectively were also involved in radiation-induced brain pathological changes, suggesting a possibly specific involvement of these miRNAs in radiation-induced development of AD, depression and schizophrenia respectively. On the other hand, we noted that radiationinduced changes of two miRNAs, i.e., miR-132, miR-29 in the brain tissue, three miRNAs, i.e., miR- 29c-5p, miR-106b-5p, miR-34a-5p in the blood were also involved in the development of AD, depression and schizophrenia, thereby suggesting that these miRNAs may be involved in the common brain neuropathological changes, such as impairment of neurogenesis and reduced learning memory ability observed in these three diseases and also after radiation exposure.

microRNA signatures in prodromal REM sleep behavior disorder and early Parkinson's disease as noninvasive biomarkers

The flow of gene expression or "The central dogma of molecular biology": DNA - RNA - protein, proposed by Watson & Crick sixty years ago, is a tightly controlled cell process. In the middle of this journey, the mRNA molecule is regulated by "RNA interference" (RNAi), a posttranscriptional gene silencing mechanism. A microRNA is an endogenous short double-stranded RNA that down-regulates hundreds of mRNAs by RNAi, maintaining healthy cell physiology. In contrast, aberrant expressions of microRNAs play a role in Parkinson's disease (PD) pathogenesis. The damage may start at an early period of brain degeneration, in the non-motor or "prodromal" stage, where autonomic, mood and sleep changes are often manifested. REM-sleep behavior disorder (RBD) is the prodromal manifestation with the highest odds for conversion into PD, thereby a valuable phenotype for disease prediction. The present review focuses on microRNAs' role in the pathogenesis of PD and RBD, summarizing the state-of-the-art of these RNA molecules as noninvasive biomarkers for non-motor prodromal (RBD) and early PD.

Diagnostic and therapeutic biomarkers for Alzheimer's disease in human-derived platelets

BACKGROUND

Diagnosis of current Alzheimer's disease (AD) is difficult even for medical specialists, and there is no clear biomarker. Also, aging is highly related to the onset of AD.

OBJECTIVES

The purpose of this study is to screen miRNA as an aging-considered biomarker for AD treatment and diagnosis.

METHODS

The patient group for this study was divided into a young normal, old normal, or AD group. We developed a method of discovering sequentially expressed miRNAs to distinguish miRNAs that were sequentially expressed in the three groups.

RESULTS

Sequentially expressed miRNAs correlated highly with the patient's age, and most showed expression patterns that distinguished young, old, and AD. Specifically, the miRNA expression we found showed similar patterns in the brains of patients with AD. Among the selected miRNAs, one set derived from the same precursor: The expression of miR-150 was a disease- and age-specific downregulation in both 3p and 5p forms, and the precursor also had the same pattern. We named that triple matching. Also, the found miR-150 precursor had AD-specific miRNA-imbalance characteristics.

CONCLUSIONS

We developed a novel AD diagnostic method using triple matching and miRNA-imbalance. The triple matching and miRNA imbalance-based relative ratio diagnosis method we developed will be very powerful in resolving the challenges of absolute diagnostic quantification based on biomarker expression. Also, our research results suggest the possibility of a treatment target for AD.

MicroRNAs Regulating Cytoskeleton Dynamics, Endocytosis, and Cell Motility-A Link Between Neurodegeneration and Cancer?

The cytoskeleton is one of the most mobile and complex cell structures. It is involved in cellular transport, cell division, cell shape formation and adaptation in response to extra- and intracellular stimuli, endo- and exocytosis, migration, and invasion. These processes are crucial for normal cellular physiology and are affected in several pathological processes, including neurodegenerative diseases, and cancer. Some proteins, participating in clathrin-mediated endocytosis (CME), play an important role in actin cytoskeleton reorganization, and formation of invadopodia in cancer cells and are also deregulated in neurodegenerative disorders. However, there is still limited information about the factors contributing to the regulation of their expression. MicroRNAs are potent negative regulators of gene expression mediating crosstalk between different cellular pathways in cellular homeostasis and stress responses. These molecules regulate numerous genes involved in neuronal differentiation, plasticity, and degeneration. Growing evidence suggests the role of microRNAs in the regulation of endocytosis, cell motility, and invasiveness. By modulating the levels of such microRNAs, it may be possible to interfere with CME or other processes to normalize their function. In malignancy, the role of microRNAs is undoubtful, and therefore changing their levels can attenuate the carcinogenic process. Here we review the current advances in our understanding of microRNAs regulating actin cytoskeleton dynamics, CME and cell motility with a special focus on neurodegenerative diseases, and cancer. We investigate whether current literature provides an evidence that microRNA-mediated regulation of essential cellular processes, such as CME and cell motility, is conserved in neurons, and cancer cells. We argue that more research effort should be addressed to study the neuron-specific functions on microRNAs. Disease-associated microRNAs affecting essential cellular processes deserve special attention both from the view of fundamental science and as future neurorestorative or anti-cancer therapies.

Antioxidant defense mechanisms and its dysfunctional regulation in the mitochondrial disease, Friedreich's ataxia

Redox stress is associated with the pathogenesis of a wide variety of disease states. This can be amplified potentially through redox active iron deposits in oxidatively active organelles such as the mitochondrion. There are a number of disease states, including Friedreich's ataxia (FA) and sideroblastic anemia, where iron metabolism is dysregulated and leads to mitochondrial iron accumulation. Considering FA, which is due to the decreased expression of the mitochondrial protein, frataxin, this iron accumulation does not occur within protective storage proteins such as mitochondrial ferritin. Instead, it forms unbound biomineral aggregates composed of high spin iron(III), phosphorous and sulfur, which probably contributes to the observed redox stress. There is also a dysregulated response to the ensuing redox assault, as the master regulator of oxidative stress, nuclear factor erythroid 2-related factor-2 (Nrf2), demonstrates marked down-regulation. The dysfunctional response of Nrf2 in FA is due to multiple mechanisms including: (1) up-regulation of Keap1 that is involved in Nrf2 degradation; (2) activation of the nuclear Nrf2 export/degradation machinery via glycogen synthase kinase-3β (Gsk3β) signaling; and (3) inhibited nuclear translocation of Nrf2. More recently, increased microRNA (miRNA) 144 expression has been demonstrated to down-regulate Nrf2 in several disease states, including an animal model of FA. Other miRNAs have also demonstrated to be dysregulated upon frataxin depletion in vivo in humans and animal models of FA. Collectively, frataxin depletion results in multiple, complex responses that lead to detrimental redox effects that could contribute to the mechanisms involved in the pathogenesis of FA.

Advances and Challenges in Understanding MicroRNA Function in Tauopathies: A Case Study of miR-132/212

In the past decade, several groups have reported that microRNAs (miRNAs) can participate in the regulation of tau protein at different levels, including its expression, alternative splicing, phosphorylation, and aggregation. These observations are significant, since the abnormal regulation and deposition of tau is associated with nearly 30 neurodegenerative disorders. Interestingly, miRNA profiles go awry in tauopathies such as Alzheimer's disease, progressive supranuclear palsy, and frontotemporal dementia. Understanding the role and impact of miRNAs on tau biology could therefore provide important insights into disease risk, diagnostics, and perhaps therapeutics. In this Perspective article, we discuss recent advances in miRNA research related to tau. While proof-of-principle studies hold promise, physiological validation remains limited. To help fill this gap, we describe herein a pure tauopathy mouse model deficient for the miR-132/212 cluster. This miRNA family is strongly downregulated in human tauopathies and shown to regulate tau in vitro and in vivo. No significant differences in survival, motor deficits or body weight were observed in PS19 mice lacking miR-132/212. Age-specific effects were seen on tau expression and phosphorylation but not aggregation. Moreover, various miR-132/212 targets previously implicated in tau modulation were unaffected (GSK-3β, Foxo3a, Mapk1, p300) or, unexpectedly, reduced (Mapk3, Foxo1, p300, Calpain 2) in miR-132/212-deficient PS19 mice. These observations highlight the challenges of miRNA research in living models, and current limitations of transgenic tau mouse models lacking functional miRNA binding sites. Based on these findings, we finally recommend different strategies to better understand the role of miRNAs in tau physiology and pathology.

Antisense oligonucleotide therapeutics in neurodegenerative diseases: the case of polyglutamine disorders

Polyglutamine (polyQ) disorders are a group of nine neurodegenerative diseases that share a common genetic cause, which is an expansion of CAG repeats in the coding region of the causative genes that are otherwise unrelated. The trinucleotide expansion encodes for an expanded polyQ tract in the respective proteins, resulting in toxic gain-of-function and eventually in neurodegeneration. Currently, no disease-modifying therapies are available for this group of disorders. Nevertheless, given their monogenic nature, polyQ disorders are ideal candidates for therapies that target specifically the gene transcripts. Antisense oligonucleotides (ASOs) have been under intense investigation over recent years as gene silencing tools. ASOs are small synthetic single-stranded chains of nucleic acids that target specific RNA transcripts through several mechanisms. ASOs can reduce the levels of mutant proteins by breaking down the targeted transcript, inhibit mRNA translation or alter the maturation of the pre-mRNA via splicing correction. Over the years, chemical optimization of ASO molecules has allowed significant improvement of their pharmacological properties, which has in turn made this class of therapeutics a very promising strategy to treat a variety of neurodegenerative diseases. Indeed, preclinical and clinical strategies have been developed in recent years for some polyQ disorders using ASO therapeutics. The success of ASOs in several animal models, as well as encouraging results in the clinic for Huntington's disease, points towards a promising future regarding the application of ASO-based therapies for polyQ disorders in humans, offering new opportunities to address unmet medical needs for this class of disorders. This review aims to present a brief overview of key chemical modifications, mechanisms of action and routes of administration that have been described for ASO-based therapies. Moreover, it presents a review of the most recent and relevant preclinical and clinical trials that have tested ASO therapeutics in polyQ disorders.

A Comprehensive Transcriptome Analysis Identifies FXN and BDNF as Novel Targets of miRNAs in Friedreich's Ataxia Patients

Friedreich's ataxia (FRDA) is a genetic neurodegenerative disease that is caused by guanine-adenine-adenine (GAA) nucleotide repeat expansions in the first intron of the frataxin (FXN) gene. Although present in the intron, this mutation leads to a substantial decrease in protein expression. Currently, no effective treatment is available for FRDA, and, in addition to FXN, other targets with therapeutic potential are continuously sought. As miRNAs can regulate the expression of a broad spectrum of genes, are used as biomarkers, and can serve as therapeutic tools, we decided to identify and characterize differentially expressed miRNAs and their targets in FRDA cells compared to unaffected control (CTRL) cells. In this study, we performed an integrated miRNAseq and RNAseq analysis using the same cohort of primary FRDA and CTRL cells. The results of the transcriptome studies were supported by bioinformatic analyses and validated by qRT-PCR. miRNA interactions with target genes were assessed by luciferase assays, qRT-PCR, and immunoblotting. In silico analysis identified the FXN transcript as a target of five miRNAs upregulated in FRDA cells. Further studies confirmed that miRNA-224-5p indeed targets FXN, resulting in decreases in mRNA and protein levels. We also validated the ability of miRNA-10a-5p to bind and regulate the levels of brain-derived neurotrophic factor (BDNF), an important modulator of neuronal growth. We observed a significant decrease in the levels of miRNA-10a-5p and increase in the levels of BDNF upon correction of FRDA cells via zinc-finger nuclease (ZFN)-mediated excision of expanded GAA repeats. Our comprehensive transcriptome analyses identified miRNA-224-5p and miRNA-10a-5p as negative regulators of the FXN and BDNF expression, respectively. These results emphasize not only the importance of miRNAs in the pathogenesis of FRDA but also their potential as therapeutic targets for this disease.