Altered microRNA regulation in Huntington's disease models

Beneficial effects of miR-132/212 deficiency in the zQ175 mouse model of Huntington's disease

Huntington's disease (HD) is a rare genetic neurodegenerative disorder caused by an expansion of CAG repeats in the Huntingtin (HTT) gene. One hypothesis suggests that the mutant HTT gene contributes to HD neuropathology through transcriptional dysregulation involving microRNAs (miRNAs). In particular, the miR-132/212 cluster is strongly diminished in the HD brain. This study explores the effects of miR-132/212 deficiency specifically in adult HD zQ175 mice. The absence of miR-132/212 did not impact body weight, body temperature, or survival rates. Surprisingly, miR-132/212 loss seemed to alleviate, in part, the effects on endogenous Htt expression, HTT inclusions, and neuronal integrity in HD zQ175 mice. Additionally, miR-132/212 depletion led to age-dependent improvements in certain motor functions. Transcriptomic analysis revealed alterations in HD-related networks in WT- and HD zQ175-miR-132/212-deficient mice, including significant overlap in BDNF and Creb1 signaling pathways. Interestingly, however, a higher number of miR-132/212 gene targets was observed in HD zQ175 mice lacking the miR-132/212 cluster, especially in the striatum. These findings suggest a nuanced interplay between miR-132/212 expression and HD pathogenesis, providing potential insights into therapeutic interventions. Further investigation is needed to fully understand the underlying mechanisms and therapeutic potential of modulating miR-132/212 expression during HD progression.

Differential microRNA expression in the SH-SY5Y human cell model as potential biomarkers for Huntington's disease

Huntington's disease (HD) is caused by an expansion of CAG trinucleotide repeat in the HTT gene; the exact pathogenesis of HD currently remains unclear. One of the promising directions in the study of HDs is to determine the molecular mechanism underlying the development and role of microRNAs (miRNAs). This study aimed to identify the profile of miRNAs in an HD human cell line model as diagnostic biomarkers for HD. To study HD, the human SH-SY5Y HD cell model is based on the expression of two different forms: pEGFP-Q23 and pEGFP-Q74 of HTT. The expression of Htt protein was confirmed using aggregation assays combined with immunofluorescence and Western blotting methods. miRNA levels were measured in SH-SY5Y neuronal cell model samples stably expressing Q23 and Q74 using the extraction-free HTG EdgeSeq protocol. A total of 2083 miRNAs were detected, and 354 (top 18 miRNAs) miRNAs were significantly differentially expressed (DE) (p < 0.05) in Q23 and Q74 cell lines. A majority of the miRNAs were downregulated in the HD cell model. Moreover, we revealed that six DE miRNAs target seven genes (ATN1, GEMIN4, EFNA5, CSMD2, CREBBP, ATXN1, and B3GNT) that play important roles in neurodegenerative disorders and showed significant expression differences in mutant Htt (Q74) when compared to wild-type Htt (Q23) using RT-qPCR (p < 0.05 and 0.01). We demonstrated the most important DE miRNA-mRNA profiles, interaction binding sites, and their related pathways in HD using experimental and bioinformatics methods. This will allow the development of novel diagnostic strategies and provide alternative therapeutic routes for treating HD.

Advancing personalized medicine in neurodegenerative diseases: The role of epigenetics and pharmacoepigenomics in pharmacotherapy

About 80 % of brain disorders have a genetic basis. The pathogenesis of most neurodegenerative diseases is associated with a myriad of genetic defects, epigenetic alterations (DNA methylation, histone/chromatin remodeling, miRNA dysregulation), and environmental factors. The emergence of new sequencing technologies and tools to study the epigenome has led to identifying predictive biomarkers for earlier diagnosis, opening up the possibility of prophylactical interventions. As a result, advances in pharmacogenetics and pharmacoepigenomics now allow for personalized treatments based on the profile of each patient and the specific genetic and epigenetic mechanisms involved. This Review highlights the complexity of neurodegenerative diseases and the variability in patient responses to pharmacotherapy, emphasizing the influence of genetic polymorphisms on the pharmacokinetics and pharmacodynamics of drugs used to treat those conditions. We specifically discuss the potential modulatory effect of several genetic polymorphisms associated with an increased risk of developing different neurodegenerative diseases. We explore genetic and genomic technologies and the potential of analyzing individual-specific drug metabolism to predict and influence drug response and associated clinical outcomes. We also provide insights into the mechanism of action of the drugs under investigation and their potential impact on disease-modifying pathways. Finally, the Review underscores the great potential of this field to enhance the effectiveness and safety of drug treatments through personalized medicine.

The Role of miR-137 in Neurodegenerative Disorders

Neurodegenerative diseases affect an increasing part of the population of modern societies, burdening healthcare systems and causing immense suffering at the personal level. The pathogenesis of several of these disorders involves dysregulation of gene expression, which depends on several molecular processes ranging from transcription to protein stability. microRNAs (miRNAs) are short non-coding RNA molecules that modulate gene expression by suppressing the translation of partially complementary mRNAs. miR-137 is a conserved, neuronally enriched miRNA that is implicated in neurodegeneration. Here, we review the current body of knowledge about the role that miR-137 plays in five prominent neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and multiple sclerosis. The presented data indicate that, rather than having a general neuroprotective role, miR-137 modulates the pathology of distinct disorders differently.

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.

Posttranscriptional regulation of FAN1 by miR-124-3p at rs3512 underlies onset-delaying genetic modification in Huntington's disease

Many Mendelian disorders, such as Huntington's disease (HD) and spinocerebellar ataxias, arise from expansions of CAG trinucleotide repeats. Despite the clear genetic causes, additional genetic factors may influence the rate of those monogenic disorders. Notably, genome-wide association studies discovered somewhat expected modifiers, particularly mismatch repair genes involved in the CAG repeat instability, impacting age at onset of HD. Strikingly, FAN1, previously unrelated to repeat instability, produced the strongest HD modification signals. Diverse FAN1 haplotypes independently modify HD, with rare genetic variants diminishing DNA binding or nuclease activity of the FAN1 protein, hastening HD onset. However, the mechanism behind the frequent and the most significant onset-delaying FAN1 haplotype lacking missense variations has remained elusive. Here, we illustrated that a microRNA acting on 3'-UTR (untranslated region) SNP rs3512, rather than transcriptional regulation, is responsible for the significant FAN1 expression quantitative trait loci signal and allelic imbalance in FAN1 messenger ribonucleic acid (mRNA), accounting for the most significant and frequent onset-delaying modifier haplotype in HD. Specifically, miR-124-3p selectively targets the reference allele at rs3512, diminishing the stability of FAN1 mRNA harboring that allele and consequently reducing its levels. Subsequent validation analyses, including the use of antagomir and 3'-UTR reporter vectors with swapped alleles, confirmed the specificity of miR-124-3p at rs3512. Together, these findings indicate that the alternative allele at rs3512 renders the FAN1 mRNA less susceptible to miR-124-3p-mediated posttranscriptional regulation, resulting in increased FAN1 levels and a subsequent delay in HD onset by mitigating CAG repeat instability.

Tumor Suppressor MicroRNAs in Clinical and Preclinical Trials for Neurological Disorders

Cancers and neurological disorders are two major types of diseases in humans. We developed the concept called the "Aberrant Cell Cycle Disease (ACCD)" due to the accumulating evidence that shows that two different diseases share the common mechanism of aberrant cell cycle re-entry. The aberrant cell cycle re-entry is manifested as kinase/oncoprotein activation and tumor suppressor (TS) inactivation, which are associated with both tumor growth in cancers and neuronal death in neurological disorders. Therefore, some cancer therapies (e.g., kinase/oncogene inhibition and TS elevation) can be leveraged for neurological treatments. MicroRNA (miR/miRNA) provides a new style of drug-target binding. For example, a single tumor suppressor miRNA (TS-miR/miRNA) can bind to and decrease tens of target kinases/oncogenes, producing much more robust efficacy to block cell cycle re-entry than inhibiting a single kinase/oncogene. In this review, we summarize the miRNAs that are altered in both cancers and neurological disorders, with an emphasis on miRNA drugs that have entered into clinical trials for neurological treatment.

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.

Exploring the impact of miR-128 in inflammatory diseases: A comprehensive study on autoimmune diseases

microRNAs (miRNAs) play a crucial role in various biological processes, including immune system regulation, such as cell proliferation, tolerance (central and peripheral), and T helper cell development. Dysregulation of miRNA expression and activity can disrupt immune responses and increase susceptibility to neuroimmune disorders. Conversely, miRNAs have been shown to have a protective role in modulating immune responses and preventing autoimmunity. Specifically, reducing the expression of miRNA-128 (miR-128) in an Alzheimer's disease (AD) mouse model has been found to improve cognitive deficits and reduce neuropathology. This comprehensive review focuses on the significance of miR-128 in the pathogenesis of neuroautoimmune disorders, including multiple sclerosis (MS), AD, Parkinson's disease (PD), Huntington's disease (HD), epilepsy, as well as other immune-mediated diseases such as inflammatory bowel disease (IBD) and rheumatoid arthritis (RA). Additionally, we present compelling evidence supporting the potential use of miR-128 as a diagnostic or therapeutic biomarker for neuroimmune disorders. Collectively, the available literature suggests that targeting miR-128 could be a promising strategy to alleviate the behavioral symptoms associated with neuroimmune diseases. Furthermore, further research in this area may uncover new insights into the molecular mechanisms underlying these disorders and potentially lead to the development of novel therapeutic approaches.

Understanding the Roles and Regulation of Mitochondrial microRNAs (MitomiRs) in Neurodegenerative Diseases: Current Status and Advances

MicroRNAs (miRNA) are a class of small non-coding RNA, roughly 21 - 22 nucleotides in length, which are master gene regulators. These miRNAs bind to the mRNA's 3' - untranslated region and regulate post-transcriptional gene regulation, thereby influencing various physiological and cellular processes. Another class of miRNAs known as mitochondrial miRNA (MitomiRs) has been found to either originate from the mitochondrial genome or be translocated directly into the mitochondria. Although the role of nuclear DNA encoded miRNA in the progression of various neurological diseases such as Parkinson's disease, Alzheimer's disease, Huntington's disease, etc. is well known, accumulating evidence suggests the possible role of deregulated mitomiRs in the progression of various neurodegenerative diseases with unknown mechanism. We have attempted to outline the current state of mitomiRs role in controlling mitochondrial gene expression and function through this review, paying particular attention to their contribution to neurological processes, their etiology, and their potential therapeutic use.

Comparison of Oncogenes, Tumor Suppressors, and MicroRNAs Between Schizophrenia and Glioma: The Balance of Power

The risk of cancer in schizophrenia has been controversial. Confounders of the issue are cigarette smoking in schizophrenia, and antiproliferative effects of antipsychotic medications. The author has previously suggested comparison of a specific cancer like glioma to schizophrenia might help determine a more accurate relationship between cancer and schizophrenia. To accomplish this goal, the author performed three comparisons of data; the first a comparison of conventional tumor suppressors and oncogenes between schizophrenia and cancer including glioma. This comparison determined schizophrenia has both tumor-suppressive and tumor-promoting characteristics. A second, larger comparison between brain-expressed microRNAs in schizophrenia with their expression in glioma was then performed. This identified a core carcinogenic group of miRNAs in schizophrenia offset by a larger group of tumor-suppressive miRNAs. This proposed "balance of power" between oncogenes and tumor suppressors could cause neuroinflammation. This was assessed by a third comparison between schizophrenia, glioma and inflammation in asbestos-related lung cancer and mesothelioma (ALRCM). This revealed that schizophrenia shares more oncogenic similarity to ALRCM than glioma.

The Role of miR-128 in Neurodegenerative Diseases

Several neurodegenerative disorders are characterized by the accumulation of misfolded proteins and are collectively known as proteinopathies. Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD) represent some of the most common neurodegenerative disorders whose steady increase in prevalence is having a major socio-economic impact on our society. Multiple laboratories have reported hundreds of changes in gene expression in selective brain regions of AD, PD, and HD brains. While the mechanisms underlying these changes remain an active area of investigation, alterations in the expression of noncoding RNAs, which are common in AD, PD, and HD, may account for some of the changes in gene expression in proteinopathies. In this review, we discuss the role of miR-128, which is highly expressed in mammalian brains, in AD, PD, and HD. We highlight how alterations in miR-128 may account, at least in part, for the gene expression changes associated with proteinopathies. Indeed, miR-128 is involved, among other things, in the regulation of neuronal plasticity, cytoskeletal organization, and neuronal death, events linked to various proteinopathies. For example, reducing the expression of miR-128 in a mouse model of AD ameliorates cognitive deficits and reduces neuropathology. Overall, the data in the literature suggest that targeting miR-128 might be beneficial to mitigate the behavioral phenotype associated with these diseases.

Chronic nicotine exposure alters sperm small RNA content in C57BL/6J mouse model

Multigenerational inheritance is a nongenomic form of heritability characterized by altered phenotypes in the first generation born from the exposed parent. Multigenerational factors may account for inconsistencies and gaps in heritable nicotine addiction vulnerability. Our lab previously found that F1 offspring of male C57BL/6J mice chronically exposed to nicotine exhibited altered hippocampus functioning and related learning, nicotine-seeking, nicotine metabolism, and basal stress hormones. In an effort to identify germline mechanisms underlying these multigenerational phenotypes, the current study sequenced small RNA extracted from sperm of males chronically administered nicotine using our previously established exposure model. We identified 16 miRNAs whose expression in sperm was dysregulated by nicotine exposure. A literature review of previous research on these transcripts suggested an enrichment for regulation of psychological stress and learning. mRNAs predicted to be regulated by differentially expressed sperm small RNAs were further analyzed using exploratory enrichment analysis, which suggested potential modulation of pathways related to learning, estrogen signaling, and hepatic disease, among other findings. Overall, our findings point to links between nicotine-exposed F0 sperm miRNA and altered F1 phenotypes in this multigenerational inheritance model, particularly F1 memory, stress, and nicotine metabolism. These findings provide a valuable foundation for future functional validation of these hypotheses and characterization of mechanisms underlying male-line multigenerational inheritance.

The Impact of Dysregulated microRNA Biogenesis Machinery and microRNA Sorting on Neurodegenerative Diseases

MicroRNAs (miRNAs) are 22-nucleotide noncoding RNAs involved in the differentiation, development, and function of cells in the body by targeting the 3'- untranslated regions (UTR) of mRNAs for degradation or translational inhibition. miRNAs not only affect gene expression inside the cells but also, when sorted into exosomes, systemically mediate the communication between different types of cells. Neurodegenerative diseases (NDs) are age-associated, chronic neurological diseases characterized by the aggregation of misfolded proteins, which results in the progressive degeneration of selected neuronal population(s). The dysregulation of biogenesis and/or sorting of miRNAs into exosomes was reported in several NDs, including Huntington's disease (HD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Alzheimer's disease (AD). Many studies support the possible roles of dysregulated miRNAs in NDs as biomarkers and therapeutic treatments. Understanding the molecular mechanisms underlying the dysregulated miRNAs in NDs is therefore timely and important for the development of diagnostic and therapeutic interventions. In this review, we focus on the dysregulated miRNA machinery and the role of RNA-binding proteins (RBPs) in NDs. The tools that are available to identify the target miRNA-mRNA axes in NDs in an unbiased manner are also discussed.

MicroRNA binding site variation is enriched in psychiatric disorders

Psychiatric disorders have a polygenic architecture, often associated with dozens or hundreds of independent genomic loci. Most associated loci impact noncoding regions of the genome, suggesting that the majority of disease heritability originates from the disruption of regulatory sequences. While most research has focused on variants that modify regulatory DNA elements, those affecting cis-acting RNA sequences, such as miRNA binding sites, are also likely to have a significant impact. We intersected genome-wide association study (GWAS) summary statistics with the dbMTS database of predictions for miRNA binding site variants (MBSVs). We compared the distributions of MBSV association statistics to non-MBSVs within brain-expressed 3'UTR regions. We aggregated GWAS p values at the gene, pathway, and miRNA family levels to investigate cellular functions and miRNA families strongly associated with each trait. We performed these analyses in several psychiatric disorders as well as nonpsychiatric traits for comparison. We observed significant enrichment of MBSVs in schizophrenia, depression, bipolar disorder, and anorexia nervosa, particularly in genes targeted by several miRNA families, including miR-335-5p, miR-21-5p/590-5p, miR-361-5p, and miR-557, and a nominally significant association between miR-323b-3p MBSVs and schizophrenia risk. We identified evidence for the association between MBSVs in synaptic gene sets in schizophrenia and bipolar disorder. We also observed a significant association of MBSVs in other complex traits including type 2 diabetes. These observations support the role of miRNA in the pathophysiology of psychiatric disorders and suggest that MBSVs are an important class of regulatory variants that have functional implications for many disorders, as well as other complex human traits.

Widespread alterations in microRNA biogenesis in human Huntington’s disease putamen

Altered microRNA (miRNA) expression is a common feature of Huntington’s disease (HD) and could participate in disease onset and progression. However, little is known about the underlying causes of miRNA disruption in HD. We and others have previously shown that mutant Huntingtin binds to Ago2, a central component of miRNA biogenesis, and disrupts mature miRNA levels. In this study, we sought to determine if miRNA maturation per se was compromised in HD. Towards this end, we characterized major miRNA biogenesis pathway components and miRNA maturation products (pri-miRNA, pre-miRNA, and mature) in human HD (N = 41, Vonsattel grades HD2-4) and healthy control (N = 25) subjects. Notably, the striatum (putamen) and cortex (BA39) from the same individuals were analyzed in parallel. We show that Ago2, Drosha, and Dicer were strongly downregulated in human HD at the early stages of the disease. Using a panel of HD-related miRNAs (miR-10b, miR-196b, miR-132, miR-212, miR-127, miR-128), we uncovered various types of maturation defects in the HD brain, the most prominent occurring at the pre-miRNA to mature miRNA maturation step. Consistent with earlier findings, we provide evidence that alterations in autophagy could participate in miRNA maturation defects. Notably, most changes occurred in the striatum, which is more prone to HTT aggregation and neurodegeneration. Likewise, we observed no significant alterations in miRNA biogenesis in human HD cortex and blood, strengthening tissue-specific effects. Overall, these data provide important clues into the underlying mechanisms behind miRNA alterations in HD-susceptible tissues. Further investigations are now required to understand the biological, diagnostic, and therapeutic implications of miRNA/RNAi biogenesis defects in HD and related neurodegenerative disorders.

Altered m6A RNA methylation contributes to hippocampal memory deficits in Huntington's disease mice

N6-methyladenosine (m6A) regulates many aspects of RNA metabolism and is involved in learning and memory processes. Yet, the impact of a dysregulation of post-transcriptional m6A editing on synaptic impairments in neurodegenerative disorders remains unknown. Here we investigated the m6A methylation pattern in the hippocampus of Huntington’s disease (HD) mice and the potential role of the m6A RNA modification in HD cognitive symptomatology. m6A modifications were evaluated in HD mice subjected to a hippocampal cognitive training task through m6A immunoprecipitation sequencing (MeRIP-seq) and the relative levels of m6A-modifying proteins (FTO and METTL14) by subcellular fractionation and Western blot analysis. Stereotaxic CA1 hippocampal delivery of AAV-shFTO was performed to investigate the effect of RNA m6A dysregulation in HD memory deficits. Our results reveal a m6A hypermethylation in relevant HD and synaptic related genes in the hippocampal transcriptome of Hdh^+/Q111 mice. Conversely, m6A is aberrantly regulated in an experience-dependent manner in the HD hippocampus leading to demethylation of important components of synapse organization. Notably, the levels of RNA demethylase (FTO) and methyltransferase (METTL14) were modulated after training in the hippocampus of WT mice but not in Hdh^+/Q111 mice. Finally, inhibition of FTO expression in the hippocampal CA1 region restored memory disturbances in symptomatic Hdh^+/Q111 mice. Altogether, our results suggest that a differential RNA methylation landscape contributes to HD cognitive symptoms and uncover a role of m6A as a novel hallmark of HD.

The Role of miRNAs in Dexmedetomidine's Neuroprotective Effects against Brain Disorders

There are limited neuroprotective strategies for various central nervous system conditions in which fast and sustained management is essential. Neuroprotection-based therapeutics have become an intensively researched topic in the neuroscience field, with multiple novel promising agents, from natural products to mesenchymal stem cells, homing peptides, and nanoparticles-mediated agents, all aiming to significantly provide neuroprotection in experimental and clinical studies. Dexmedetomidine (DEX), an α2 agonist commonly used as an anesthetic adjuvant for sedation and as an opioid-sparing medication, stands out in this context due to its well-established neuroprotective effects. Emerging evidence from preclinical and clinical studies suggested that DEX could be used to protect against cerebral ischemia, traumatic brain injury (TBI), spinal cord injury, neurodegenerative diseases, and postoperative cognitive disorders. MicroRNAs (miRNAs) regulate gene expression at a post-transcriptional level, inhibiting the translation of mRNA into functional proteins. In vivo and in vitro studies deciphered brain-related miRNAs and dysregulated miRNA profiles after several brain disorders, including TBI, ischemic stroke, Alzheimer's disease, and multiple sclerosis, providing emerging new perspectives in neuroprotective therapy by modulating these miRNAs. Experimental studies revealed that some of the neuroprotective effects of DEX are mediated by various miRNAs, counteracting multiple mechanisms in several disease models, such as lipopolysaccharides induced neuroinflammation, β-amyloid induced dysfunction, brain ischemic-reperfusion injury, and anesthesia-induced neurotoxicity models. This review aims to outline the neuroprotective mechanisms of DEX in brain disorders by modulating miRNAs. We address the neuroprotective effects of DEX by targeting miRNAs in modulating ischemic brain injury, ameliorating the neurotoxicity of anesthetics, reducing postoperative cognitive dysfunction, and improving the effects of neurodegenerative diseases.

MicroRNA Alteration, Application as Biomarkers, and Therapeutic Approaches in Neurodegenerative Diseases

MicroRNAs (miRNAs) are essential post-transcriptional gene regulators involved in various neuronal and non-neuronal cell functions and play a key role in pathological conditions. Numerous studies have demonstrated that miRNAs are dysregulated in major neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, amyotrophic lateral sclerosis, or Huntington’s disease. Hence, in the present work, we constructed a comprehensive overview of individual microRNA alterations in various models of the above neurodegenerative diseases. We also provided evidence of miRNAs as promising biomarkers for prognostic and diagnostic approaches. In addition, we summarized data from the literature about miRNA-based therapeutic applications via inhibiting or promoting miRNA expression. We finally identified the overlapping miRNA signature across the diseases, including miR-128, miR-140-5p, miR-206, miR-326, and miR-155, associated with multiple etiological cellular mechanisms. However, it remains to be established whether and to what extent miRNA-based therapies could be safely exploited in the future as effective symptomatic or disease-modifying approaches in the different human neurodegenerative disorders.

Dexmedetomidine Mitigates Microglial Activation Associated with Postoperative Cognitive Dysfunction by Modulating the MicroRNA-103a-3p/VAMP1 Axis

Surgery-induced microglial activation is critical in mediating postoperative cognitive dysfunction (POCD) in elderly patients, where the important protective effect of dexmedetomidine has been indicated. However, the mechanisms of action of dexmedetomidine during the neuroinflammatory response that underlies POCD remain largely unknown. We found that lipopolysaccharide (LPS) induced substantial inflammatory responses in primary and BV2 microglial cells. The screening of differentially expressed miRNAs revealed that miR-103a-3p was downregulated in these cell culture models. Overexpression of miR-103a-3p mimics and inhibitors suppressed and enhanced the release of inflammatory factors, respectively. VAMP1 expression was upregulated in LPS-treated primary and BV-2 microglial cells, and it was validated as a downstream target of miR-103-3p. VAMP1-knockdown significantly inhibited the LPS-induced inflammatory response. Dexmedetomidine treatment markedly inhibited LPS-induced inflammation and the expression of VAMP1, and miR-103a-3p expression reversed this inhibition. Moreover, dexmedetomidine mitigated microglial activation and the associated inflammatory response in a rat model of surgical trauma that mimicked POCD. In this model, dexmedetomidine reversed miR-103a-3p and VAMP1 expression; this effect was abolished by miR-103a-3p overexpression. Taken together, the data show that miR-103a-3p/VAMP1 is critical for surgery-induced microglial activation of POCD.

Role of miRNAs in Neurodegeneration: From Disease Cause to Tools of Biomarker Discovery and Therapeutics

Neurodegenerative diseases originate from neuronal loss in the central nervous system (CNS). These debilitating diseases progress with age and have become common due to an increase in longevity. The National Institute of Environmental Health Science’s 2021 annual report suggests around 6.2 million Americans are living with Alzheimer’s disease, and there is a possibility that there will be 1.2 million Parkinson’s disease patients in the USA by 2030. There is no clear-cut universal mechanism for identifying neurodegenerative diseases, and therefore, they pose a challenge for neurobiology scientists. Genetic and environmental factors modulate these diseases leading to familial or sporadic forms. Prior studies have shown that miRNA levels are altered during the course of the disease, thereby suggesting that these noncoding RNAs may be the contributing factor in neurodegeneration. In this review, we highlight the role of miRNAs in the pathogenesis of neurodegenerative diseases. Through this review, we aim to achieve four main objectives: First, we highlight how dysregulation of miRNA biogenesis led to these diseases. Second, we highlight the computational or bioinformatics tools required to identify the putative molecular targets of miRNAs, leading to biological molecular pathways or mechanisms involved in these diseases. Third, we focus on the dysregulation of miRNAs and their target genes leading to several neurodegenerative diseases. In the final section, we highlight the use of miRNAs as potential diagnostic biomarkers in the early asymptomatic preclinical diagnosis of these age-dependent debilitating diseases. Additionally, we discuss the challenges and advances in the development of miRNA therapeutics for brain targeting. We list some of the innovative strategies employed to deliver miRNA into target cells and the relevance of these viral and non-viral carrier systems in RNA therapy for neurodegenerative diseases. In summary, this review highlights the relevance of studying brain-enriched miRNAs, the mechanisms underlying their regulation of target gene expression, their dysregulation leading to progressive neurodegeneration, and their potential for biomarker marker and therapeutic intervention. This review thereby highlights ways for the effective diagnosis and prevention of these neurodegenerative disorders in the near future.

MicroRNA editing patterns in Huntington's disease

Huntington's disease (HD) is a neurodegenerative disease. MicroRNAs (miRNAs) are small non-coding RNAs that mediate post-transcriptional regulation of target genes. Although miRNAs are extensively edited in human brains, the editome of miRNAs in brains of HD patients is largely unknown. By analyzing the small RNA sequencing profiles of brain tissues of 28 HD patients and 83 normal controls, 1182 miRNA editing sites with significant editing levels were identified. In addition to 27 A-to-I editing sites, we identified 3 conserved C-to-U editing sites in miRNAs of HD patients. 30 SNPs in the miRNAs of HD patients were also identified. Furthermore, 129 miRNA editing events demonstrated significantly different editing levels in prefrontal cortex samples of HD patients (HD-PC) when compared to those of healthy controls. We found that hsa-mir-10b-5p was edited to have an additional cytosine at 5'-end in HD-PC, and the edited hsa-mir-10b repressed GTPBP10 that was often downregulated in HD. The down-regulation of GTPBP10 might contribute to the progression of HD by causing gradual loss of function of mitochondrial. These results provide the first endeavor to characterize the miRNA editing events in HD and their potential functions.

Deregulated mitochondrial microRNAs in Alzheimer's disease: Focus on synapse and mitochondria

Alzheimer's disease (AD) is the most common cause of dementia and is currently one of the biggest public health concerns in the world. Mitochondrial dysfunction in neurons is one of the major hallmarks of AD. Emerging evidence suggests that mitochondrial miRNAs potentially play important roles in the mitochondrial dysfunctions, focusing on synapse in AD progression. In this meta-analysis paper, a comprehensive literature review was conducted to identify and discuss the (1) role of mitochondrial miRNAs that regulate mitochondrial and synaptic functions; (2) the role of various factors such as mitochondrial dynamics, biogenesis, calcium signaling, biological sex, and aging on synapse and mitochondrial function; (3) how synapse damage and mitochondrial dysfunctions contribute to AD; (4) the structure and function of synapse and mitochondria in the disease process; (5) latest research developments in synapse and mitochondria in healthy and disease states; and (6) therapeutic strategies that improve synaptic and mitochondrial functions in AD. Specifically, we discussed how differences in the expression of mitochondrial miRNAs affect ATP production, oxidative stress, mitophagy, bioenergetics, mitochondrial dynamics, synaptic activity, synaptic plasticity, neurotransmission, and synaptotoxicity in neurons observed during AD. However, more research is needed to confirm the locations and roles of individual mitochondrial miRNAs in the development of AD.

Extracellular Vesicles, Stem Cells and the Role of miRNAs in Neurodegeneration

There are different modalities of intercellular communication governed by cellular homeostasis. In this review, we will explore one of these forms of communication called extracellular vesicles (EVs). These vesicles are released by all cells in the body and are heterogeneous in nature. The primary function of EVs is to share information through their cargo consisting of proteins, lipids and nucleic acids (mRNA, miRNA, dsDNA etc.) with other cells, which have a direct consequence on their microenvironment. We will focus on the role of EVs of mesenchymal stem cells (MSCs) in the nervous system and how these participate in intercellular communication to maintain physiological function and provide neuroprotection. However, deregulation of this same communication system could play a role in several neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, multiple sclerosis, prion disease and Huntington's disease. The release of EVs from a cell provides crucial information to what is happening inside the cell and thus could be used in diagnostics and therapy. We will discuss and explore new avenues for the clinical applications of using engineered MSC-EVs and their potential therapeutic benefit in treating neurodegenerative diseases.

Downregulation of lncRNA GAS5 prevents mitochondrial apoptosis and hypoxic-ischemic brain damage in neonatal rats through the microRNA-128-3p/Bax/Akt/GSK-3β axis

OBJECTIVE

Hypoxic/ischemic brain damage (HIBD) results in increased neonatal mortality and serious neurologic morbidity. Long noncoding RNAs (lncRNAs) are shown as essential modulators of various neurological diseases. Here, we determined the mechanisms of lncRNA GAS5 in mitochondrial apoptosis in HIBD rats.

METHODS

The HIBD neonatal rat model was established and treated with shRNA-GAS5 or antagomir miR-128-3p. The morphological changes and apoptosis rate were observed by histological staining. Expressions of GAS5, miR-128-3p, and Bax mRNA in brain tissues of HIBD neonatal rats were determined. The binding relationships between GAS5 and miR-128-3p, and miR-128-3p and Bax were confirmed by dual-luciferase assay. Subsequently, the mitochondrial membrane potential and apoptosis-related factors in brain tissues of HIBD neonatal rats were detected. Western blot analysis was performed to detect the expression of Akt/GSK3β pathway-associated proteins.

RESULTS

The neurons in the brain tissue of HIBD neonatal rats decreased with disordered arrangement, and showed vacuolization and nuclear pyknosis, obvious brain damage, increased neuronal apoptosis, and enhanced mitochondrial apoptotic pathway. Downregulated miR-128-3p and upregulated GAS5 and Bax mRNA were found in HIBD neonatal rats. There were binding relationships between GAS5 and miR-128-3p, and miR-128-3p and Bax mRNA. Inhibition of lncRNA GAS5 in HIBD neonatal rats suppressed mitochondrial apoptosis. miR-128-3p knockdown annulled the inhibitory effect of inhibiting lncRNA GAS5 on mitochondrial apoptosis. Silencing GAS5 increased the phosphorylation levels of Akt and GSK3β.

CONCLUSION

Downregulation of lncRNA GAS5 prevents mitochondrial apoptosis in neonatal HIBD rats by regulating the miR-128-3p/Bax/Akt/GSK-3β axis.

Non-coding RNAs and their bioengineering applications for neurological diseases

Engineering of cellular biomolecules is an emerging landscape presenting creative therapeutic opportunities. Recently, several strategies such as biomimetic materials, drug-releasing scaffolds, stem cells, and dynamic culture systems have been developed to improve specific biological functions, however, have been confounded with fundamental and technical roadblocks. Rapidly emerging investigations on the bioengineering prospects of mammalian ribonucleic acid (RNA) is expected to result in significant biomedical advances. More specifically, the current trend focuses on devising non-coding (nc) RNAs as therapeutic candidates for complex neurological diseases. Given the pleiotropic and regulatory role, ncRNAs such as microRNAs and long non-coding RNAs are deemed as attractive therapeutic candidates. Currently, the list of non-coding RNAs in mammals is evolving, which presents the plethora of hidden possibilities including their scope in biomedicine. Herein, we critically review on the emerging repertoire of ncRNAs in neurological diseases such as Alzheimer’s disease, Parkinson’s disease, neuroinflammation and drug abuse disorders. Importantly, we present the advances in engineering of ncRNAs to improve their biocompatibility and therapeutic feasibility as well as provide key insights into the applications of bioengineered non-coding RNAs that are investigated for neurological diseases.

Altered microRNA expression in animal models of Huntington's disease and potential therapeutic strategies

A review of recent animal models of Huntington's disease showed many microRNAs had altered expression levels in the striatum and cerebral cortex, and which were mostly downregulated. Among the altered microRNAs were miR-9/9*, miR-29b, miR-124a, miR-132, miR-128, miR-139, miR-122, miR-138, miR-23b, miR-135b, miR-181 (all downregulated) and miR-448 (upregulated), and similar changes had been previously found in Huntington's disease patients. In the animal cell studies, the altered microRNAs included miR-9, miR-9*, miR-135b, miR-222 (all downregulated) and miR-214 (upregulated). In the animal models, overexpression of miR-155 and miR-196a caused a decrease in mutant huntingtin mRNA and protein level, lowered the mutant huntingtin aggregates in striatum and cortex, and improved performance in behavioral tests. Improved performance in behavioral tests also occurred with overexpression of miR-132 and miR-124. In the animal cell models, overexpression of miR-22 increased the viability of rat primary cortical and striatal neurons infected with mutant huntingtin and decreased huntingtin -enriched foci of ≥ 2 µm. Also, overexpression of miR-22 enhanced the survival of rat primary striatal neurons treated with 3-nitropropionic acid. Exogenous expression of miR-214, miR-146a, miR-150, and miR-125b decreased endogenous expression of huntingtin mRNA and protein in Hdh^Q111/Hdh^Q111 cells. Further studies with animal models of Huntington's disease are warranted to validate these findings and identify specific microRNAs whose overexpression inhibits the production of mutant huntingtin protein and other harmful processes and may provide a more effective means of treating Huntington's disease in patients and slowing its progression.

The emerging role of miRNA-132/212 cluster in neurologic and cardiovascular diseases: Neuroprotective role in cells with prolonged longevity

miRNA-132/212 are small regulators of gene expression with a function that fulfills a vital function in diverse biological processes including neuroprotection of cells with prolonged longevity in neurons and the cardiovascular system. In neurons, miRNA-132 appears to be essential for controlling differentiation, development, and neural functioning. Indeed, it also universally promotes axon evolution, nervous migration, plasticity as well, it is suggested to be neuroprotective against neurodegenerative diseases. Moreover, miRNA-132/212 disorder leads to neural developmental perturbation, and the development of degenerative disorders covering Alzheimer's, Parkinson's, and epilepsy's along with psychiatric perturbations including schizophrenia. Furthermore, the cellular mechanisms of the miRNA-132/212 have additionally been explored in cardiovascular diseases models. Also, the miRNA-132/212 family modulates cardiac hypertrophy and autophagy in cardiomyocytes. The protective and effective clinical promise of miRNA-132/212 in these systems is discussed in this review. To sum up, the current progress in innovative miRNA-based therapies for human pathologies seems of extreme concern and reveals promising novel therapeutic strategies.

Differential expression of microRNAs associated with neurodegenerative diseases and diabetic nephropathy in protein l-isoaspartyl methyltransferase-deficient mice

Protein l-isoaspartyl methyltransferase (PIMT/PCMT1), an enzyme repairing isoaspartate residues in peptides and proteins that result from the spontaneous decomposition of normal l-aspartyl and l-asparaginyl residues during aging, has been revealed to be involved in neurodegenerative diseases (NDDs) and diabetes. However, the molecular mechanisms for a putative association of PIMT dysfunction with these diseases have not been clarified. Our study aimed to identify differentially expressed microRNAs (miRNAs) in the brain and kidneys of PIMT-deficient mice and uncover the epigenetic mechanism of PIMT-involved NDDs and diabetic nephropathy (DN). Differentially expressed miRNAs by sequencing underwent target prediction and enrichment analysis in the brain and kidney of PIMT knockout (KO) mice and age-matched wild-type (WT) littermates. Sequence analysis revealed 40 differentially expressed miRNAs in the PIMT KO mouse brain including 25 upregulated miRNAs and 15 downregulated miRNAs. In the PIMT KO mouse kidney, there were 80 differentially expressed miRNAs including 40 upregulated miRNAs and 40 downregulated miRNAs. Enrichment analysis and a systematic literature review of differentially expressed miRNAs indicated the involvement of PIMT deficiency in the pathogenesis in NDDs and DN. Some overlapped differentially expressed miRNAs between the brain and kidney were quantitatively assessed in the brain, kidney, and serum-derived exosomes, respectively. Despite being preliminary, these results may aid in investigating the pathological hallmarks and identify the potential therapeutic targets and biomarkers for PIMT dysfunction-related NDDs and DN.

Huntington's disease mice and human brain tissue exhibit increased G3BP1 granules and TDP43 mislocalization

Chronic cellular stress associated with neurodegenerative disease can result in the persistence of stress granule (SG) structures, membraneless organelles that form in response to cellular stress. In Huntington's disease (HD), chronic expression of mutant huntingtin generates various forms of cellular stress, including activation of the unfolded protein response and oxidative stress. However, it has yet to be determined whether SGs are a feature of HD neuropathology. We examined the miRNA composition of extracellular vesicles (EVs) present in the cerebrospinal fluid (CSF) of patients with HD and show that a subset of their target mRNAs were differentially expressed in the prefrontal cortex. Of these targets, SG components were enriched, including the SG-nucleating Ras GTPase-activating protein-binding protein 1 (G3BP1). We investigated localization and levels of G3BP1 and found a significant increase in the density of G3BP1-positive granules in the cortex and hippocampus of R6/2 transgenic mice and in the superior frontal cortex of the brains of patients with HD. Intriguingly, we also observed that the SG-associated TAR DNA-binding protein 43 (TDP43), a nuclear RNA/DNA binding protein, was mislocalized to the cytoplasm of G3BP1 granule-positive HD cortical neurons. These findings suggest that G3BP1 SG dynamics may play a role in the pathophysiology of HD.

MicroRNA Dysregulation in Parkinson's Disease: A Narrative Review

Parkinson’s disease (PD) is a severely debilitating neurodegenerative disease, affecting the motor system, leading to resting tremor, cogwheel rigidity, bradykinesia, walking and gait difficulties, and postural instability. The severe loss of dopaminergic neurons in the substantia nigra pars compacta causes striatal dopamine deficiency and the presence of Lewy bodies indicates a pathological hallmark of PD. Although the current treatment of PD aims to preserve dopaminergic neurons or to replace dopamine depletion in the brain, it is notable that complete recovery from the disease is yet to be achieved. Given the complexity and multisystem effects of PD, the underlying mechanisms of PD pathogenesis are yet to be elucidated. The advancement of medical technologies has given some insights in understanding the mechanism and potential treatment of PD with a special interest in the role of microRNAs (miRNAs) to unravel the pathophysiology of PD. In PD patients, it was found that striatal brain tissue and dopaminergic neurons from the substantia nigra demonstrated dysregulated miRNAs expression profiles. Hence, dysregulation of miRNAs may contribute to the pathogenesis of PD through modulation of PD-associated gene and protein expression. This review will discuss recent findings on PD-associated miRNAs dysregulation, from the regulation of PD-associated genes, dopaminergic neuron survival, α-synuclein-induced inflammation and circulating miRNAs. The next section of this review also provides an update on the potential uses of miRNAs as diagnostic biomarkers and therapeutic tools for PD.

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.

Small Non-coding RNAs Are Dysregulated in Huntington's Disease Transgenic Mice Independently of the Therapeutic Effects of an Environmental Intervention

Huntington's disease (HD) is a neurodegenerative disorder caused by a trinucleotide repeat expansion in the huntingtin gene. Transcriptomic dysregulations are well-documented in HD and alterations in small non-coding RNAs (sncRNAs), particularly microRNAs (miRNAs), could underpin that phenomenon. Additionally, environmental enrichment (EE), which is used to model a stimulating lifestyle in pre-clinical research, has been shown to ameliorate HD-related symptoms. However, the mechanisms mediating the therapeutic effects of EE remain largely unknown. This study assessed the effect of EE on sncRNA expression in the striatum of female R6/1 transgenic HD mice at 12 weeks (prior to over motor deficits) and 20 weeks (fully symptomatic) of age. When comparing wild-type and R6/1 mice in the standard housing condition, we found 6 and 64 miRNAs that were differentially expressed at 12 and 20 weeks of age, respectively. The 6 miRNAs (miR-132, miR-212, miR-222, miR-1a, miR-467a, and miR-669c) were commonly dysregulated at both time points. Additionally, genotype had minor effects on the levels of other sncRNAs, in particular, 1 piRNA was dysregulated at 12 weeks of age, and at 20 weeks of age 11 piRNAs, 1 tRNA- and 2 snoRNA-derived fragments were altered in HD mice. No difference in the abundance of other sncRNA subtypes, including rRNA- and snRNA- derived fragments, were observed. While EE improved locomotor symptoms in HD, we found no effect of the housing condition on any of the sncRNA populations examined. Our findings show that HD mainly affects miRNAs and has a minor effect on other sncRNA populations. Furthermore, the therapeutic effects of EE are not associated with the rescue of these dysregulated sncRNAs and may therefore exert these experience-dependent effects via other molecular mechanisms.

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

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

D1R- and D2R-Medium-Sized Spiny Neurons Diversity: Insights Into Striatal Vulnerability to Huntington's Disease Mutation

Huntington's disease (HD) is a devastating neurodegenerative disorder caused by an aberrant expansion of the CAG tract within the exon 1 of the HD gene, HTT. HD progressively impairs motor and cognitive capabilities, leading to a total loss of autonomy and ultimate death. Currently, no cure or effective treatment is available to halt the disease. Although the HTT gene is ubiquitously expressed, the striatum appears to be the most susceptible district to the HD mutation with Medium-sized Spiny Neurons (MSNs) (D1R and D2R) representing 95% of the striatal neuronal population. Why are striatal MSNs so vulnerable to the HD mutation? Particularly, why do D1R- and D2R-MSNs display different susceptibility to HD? Here, we highlight significant differences between D1R- and D2R-MSNs subpopulations, such as morphology, electrophysiology, transcriptomic, functionality, and localization in the striatum. We discuss possible reasons for their selective degeneration in the context of HD. Our review suggests that a better understanding of cell type-specific gene expression dysregulation within the striatum might reveal new paths to therapeutic intervention or prevention to ameliorate HD patients' life expectancy.

MicroRNA-22 contributes to dexamethasone-induced osteoblast differentiation inhibition and dysfunction through targeting caveolin-3 expression in osteoblastic cells

Osteoporosis is a common complication of long-term use of glucocorticoids (GCs) characterized by the loss of bone mass and damage of the microarchitecture as well as osteoblast dysfunction. Previous studies have demonstrated that microRNA-22 (miR-22) is the negative modulator of osteogenesis that may target caveolin-3 (CAV3), which has been reported to enhance bone formation and inhibit the progression of osteoporosis as well as apoptosis. The present study aimed to investigate whether miR-22 may be involved in dexamethasone (DEX)-induced inhibition of osteoblast differentiation and dysfunction by regulating CAV3 expression. Reverse transcription-quantitative PCR (RT-qPCR) was performed to measure the expression of miR-22 and western blotting was performed to determine protein levels. The results demonstrated that miR-22 expression was upregulated in DEX-treated osteoblastic cells compared with the control group. In addition, miR-22 mimic aggravated, whereas miR-22 inhibitor mitigated DEX-induced damage in osteoblastic cells compared with the control groups. Additionally, CAV3 was identified as the target of miR-22 in osteoblasts using RT-qPCR, western blotting and dual-luciferase reporter gene assay analysis. The results also demonstrated that silencing of CAV3 blocked the beneficial effects of miR-22 inhibitor against DEX-induced cell damage and apoptosis in osteoblasts, as evidenced by the increased expression levels of cleaved caspase-3, Bax and alkaline phosphatase activity as well as decreased cell viability and Bcl-2 levels. Collectively, these results indicate a novel molecular mechanism by which miR-22 contributes to DEX-induced osteoblast dysfunction and apoptosis via the miR-22/CAV3 pathway.

Synergism of Proneurogenic miRNAs Provides a More Effective Strategy to Target Glioma Stem Cells

Simple Summary

miRNAs function as critical regulators of gene expression and have been defined as contributors of cancer phenotypes by acting as oncogenes or tumor suppressors. Based on these findings, miRNA-based therapies have been explored in the treatment of many different malignancies. The use of single miRNAs has faced some challenges and showed limited success. miRNAs cooperate to regulate distinct biological processes and pathways and, therefore, combination of related miRNAs could amplify the repression of oncogenic factors and the effect on cancer relevant pathways. We established that the combination of tumor suppressor miRNAs miR-124, miR-128, and miR-137 is much more effective than single miRNAs in disrupting proliferation and survival of glioma stem cells and neuroblastoma lines and promoting differentiation and response to radiation. Subsequent genomic analyses showed that other combinations of tumor suppressor miRNAs could be equally effective, and its use could provide new routes to target in special cancer-initiating cell populations.

Abstract

Tumor suppressor microRNAs (miRNAs) have been explored as agents to target cancer stem cells. Most strategies use a single miRNA mimic and present many disadvantages, such as the amount of reagent required and the diluted effect on target genes. miRNAs work in a cooperative fashion to regulate distinct biological processes and pathways. Therefore, we propose that miRNA combinations could provide more efficient ways to target cancer stem cells. We have previously shown that miR-124, miR-128, and miR-137 function synergistically to regulate neurogenesis. We used a combination of these three miRNAs to treat glioma stem cells and showed that this treatment was much more effective than single miRNAs in disrupting cell proliferation and survival and promoting differentiation and response to radiation. Transcriptomic analyses indicated that transcription regulation, angiogenesis, metabolism, and neuronal differentiation are among the main biological processes affected by transfection of this miRNA combination. In conclusion, we demonstrated the value of using combinations of neurogenic miRNAs to disrupt cancer phenotypes and glioma stem cell growth. The synergistic effect of these three miRNA amplified the repression of oncogenic factors and the effect on cancer relevant pathways. Future therapeutic approaches would benefit from utilizing miRNA combinations, especially when targeting cancer-initiating cell populations.

Role of DNA Methyl-CpG-Binding Protein MeCP2 in Rett Syndrome Pathobiology and Mechanism of Disease

Rett Syndrome (RTT) is a severe, rare, and progressive developmental disorder with patients displaying neurological regression and autism spectrum features. The affected individuals are primarily young females, and more than 95% of patients carry de novo mutation(s) in the Methyl-CpG-Binding Protein 2 (MECP2) gene. While the majority of RTT patients have MECP2 mutations (classical RTT), a small fraction of the patients (atypical RTT) may carry genetic mutations in other genes such as the cyclin-dependent kinase-like 5 (CDKL5) and FOXG1. Due to the neurological basis of RTT symptoms, MeCP2 function was originally studied in nerve cells (neurons). However, later research highlighted its importance in other cell types of the brain including glia. In this regard, scientists benefitted from modeling the disease using many different cellular systems and transgenic mice with loss- or gain-of-function mutations. Additionally, limited research in human postmortem brain tissues provided invaluable findings in RTT pathobiology and disease mechanism. MeCP2 expression in the brain is tightly regulated, and its altered expression leads to abnormal brain function, implicating MeCP2 in some cases of autism spectrum disorders. In certain disease conditions, MeCP2 homeostasis control is impaired, the regulation of which in rodents involves a regulatory microRNA (miR132) and brain-derived neurotrophic factor (BDNF). Here, we will provide an overview of recent advances in understanding the underlying mechanism of disease in RTT and the associated genetic mutations in the MECP2 gene along with the pathobiology of the disease, the role of the two most studied protein variants (MeCP2E1 and MeCP2E2 isoforms), and the regulatory mechanisms that control MeCP2 homeostasis network in the brain, including BDNF and miR132.

The emerging role of miR-128 in musculoskeletal diseases

MicroRNA-128 (miR-128) is associated with cell proliferation, differentiation, migration, apoptosis, and survival. Genetic analysis studies have demonstrated that miR-128 participates in bone metabolism, which involves bone marrow-derived mesenchymal stem cells, osteoblasts, osteoclasts, and adipocytes. miR-128 also participates in regeneration of skeletal muscles by targeting myoblast-associated proteins. The deregulation of miR-128 could lead to a series of musculoskeletal diseases. In this review, we discuss recent findings of miR-128 in relation to bone metabolism and muscle regeneration to determine its potential therapeutic effects in musculoskeletal diseases, and to propose directions for future research in this significant field.

Non-Coding RNAs as Sensors of Oxidative Stress in Neurodegenerative Diseases

Oxidative stress (OS) results from an imbalance between the production of reactive oxygen species and the cellular antioxidant capacity. OS plays a central role in neurodegenerative diseases, where the progressive accumulation of reactive oxygen species induces mitochondrial dysfunction, protein aggregation and inflammation. Regulatory non-protein-coding RNAs (ncRNAs) are essential transcriptional and post-transcriptional gene expression controllers, showing a highly regulated expression in space (cell types), time (developmental and ageing processes) and response to specific stimuli. These dynamic changes shape signaling pathways that are critical for the developmental processes of the nervous system and brain cell homeostasis. Diverse classes of ncRNAs have been involved in the cell response to OS and have been targeted in therapeutic designs. The perturbed expression of ncRNAs has been shown in human neurodegenerative diseases, with these changes contributing to pathogenic mechanisms, including OS and associated toxicity. In the present review, we summarize existing literature linking OS, neurodegeneration and ncRNA function. We provide evidences for the central role of OS in age-related neurodegenerative conditions, recapitulating the main types of regulatory ncRNAs with roles in the normal function of the nervous system and summarizing up-to-date information on ncRNA deregulation with a direct impact on OS associated with major neurodegenerative conditions.

Bioinformatic gene analysis for potential therapeutic targets of Huntington's disease in pre-symptomatic and symptomatic stage

Background

Huntington’s disease (HD) is a neurodegenerative disorder characterized by psychiatric symptoms, serious motor and cognitive deficits. Certain pathological changes can already be observed in pre-symptomatic HD (pre-HD) patients; however, the underlying molecular pathogenesis is still uncertain and no effective treatments are available until now. Here, we reanalyzed HD-related differentially expressed genes from the GEO database between symptomatic HD patients, pre-HD individuals, and healthy controls using bioinformatics analysis, hoping to get more insight in the pathogenesis of both pre-HD and HD, and shed a light in the potential therapeutic targets of the disease.

Methods

Pre-HD and symptomatic HD differentially expressed genes (DEGs) were screened by bioinformatics analysis Gene Expression Omnibus (GEO) dataset GSE1751. A protein–protein interaction (PPI) network was used to select hub genes. Subsequently, Gene Ontology (GO) enrichment analysis of DEGs and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of hub genes were applied. Dataset GSE24250 was downloaded to verify our hub genes by the Kaplan–Meier method using Graphpad Prism 5.0. Finally, target miRNAs of intersected hub genes involved in pre-HD and symptomatic HD were predicted.

Results

A total of 37 and 985 DEGs were identified in pre-HD and symptomatic HD, respectively. The hub genes, SIRT1, SUZ12, and PSMC6, may be implicated in pre-HD, and the hub genes, FIS1, SIRT1, CCNH, SUZ12, and 10 others, may be implicated in symptomatic HD. The intersected hub genes, SIRT1 and SUZ12, and their predicted target miRNAs, in particular miR-22-3p and miR-19b, may be significantly associated with pre-HD.

Conclusion

The PSMC6, SIRT1, and SUZ12 genes and their related ubiquitin-mediated proteolysis, transcriptional dysregulation, and histone metabolism are significantly associated with pre-HD. FIS1, CCNH, and their related mitochondrial disruption and transcriptional dysregulation processes are related to symptomatic HD, which might shed a light on the elucidation of potential therapeutic targets in HD.

P2X7 Receptor Upregulation in Huntington's Disease Brains

Huntington’s disease (HD) is a fatal degenerative disorder affecting the nervous system. It is characterized by motor, cognitive, and psychiatric dysfunctions, with a late onset and an autosomal dominant pattern of inheritance. HD-causing mutation consists in an expansion of repeated CAG triplets in the huntingtin gene (HTT), encoding for an expanded polyglutamine (polyQ) stretch in the huntingtin protein (htt). The mutation causes neuronal dysfunction and loss through multiple mechanisms, affecting both the nucleus and cytoplasm. P2X7 receptor (P2X7R) emerged as a major player in neuroinflammation, since ATP – its endogenous ligand – is massively released under this condition. Indeed, P2X7R stimulation in the central nervous system (CNS) is known to enhance the release of pro-inflammatory cytokines from microglia and of neurotransmitters from neuronal presynaptic terminals, as well as to promote apoptosis. Previous experiments performed with neurons expressing the mutant huntingtin and exploiting HD mouse models demonstrated a role of P2X7R in HD. On the basis of those results, here, we explore for the first time the status of P2X7R in HD patients’ brain. We report that in HD postmortem striatum, as earlier observed in HD mice, the protein levels of the full-length form of P2X7R, also named P2X7R-A, are upregulated. In addition, the exclusively human naturally occurring variant lacking the C-terminus region, P2X7R-B, is upregulated as well. As we show here, this augmented protein levels can be explained by elevated mRNA levels. Furthermore, in HD patients’ striatum, P2X7R shows not only an augmented total transcript level but also an alteration of its splicing. Remarkably, P2X7R introns 10 and 11 are more retained in HD patients when compared with controls. Taken together, our data confirm that P2X7R is altered in brains of HD subjects and strengthen the notion that P2X7R may represent a potential therapeutic target for HD.

Circulating Exosome microRNAs as Diagnostic Biomarkers of Dementia

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

Analysis of the differential expression profile of miRNAs in myocardial tissues of rats with burn injury

Fifteen percent third-degree burn rat model was used to identify miRNAs that are markers of burn injury-induced myocardial damage. Cardiac tissues were evaluated to determine miRNA profile sequencing. Pearson's correlation analysis was used between miRNAs and injury markers. ROC curve analysis was used to estimate miRNA's sensitivity and specificity for the diagnosis of myocardial damage caused by burn injury. The sequencing analysis revealed 23 differentially expressed miRNAs. Pearson's correlation analysis revealed that rno-miR-190b-3p and C5b9, rno-miR-341, rno-miR-344b-3p and TnI, rno-miR-344b-3p and CK-MB were significantly positively correlated, respectively. ROC curve analysis demonstrated that rno-miR-341, rno-miR-344b-3p, and rno-miR-190b-3p exhibited high sensitivity and specificity for the diagnosis of myocardial damage caused by burn injury. In conclusion, our results suggest that rno-miR-341, rno-miR-344b-3p, and rno-miR-190b-3p have the potential to be used as sensitive and specific biomarkers to diagnose myocardial damage caused by burn injury.

MicroRNAs Dysregulation and Mitochondrial Dysfunction in Neurodegenerative Diseases

Neurodegenerative diseases are debilitating and currently incurable conditions causing severe cognitive and motor impairments, defined by the progressive deterioration of neuronal structure and function, eventually causing neuronal loss. Understand the molecular and cellular mechanisms underlying these disorders are essential to develop therapeutic approaches. MicroRNAs (miRNAs) are short non-coding RNAs implicated in gene expression regulation at the post-transcriptional level. Moreover, miRNAs are crucial for different processes, including cell growth, signal transmission, apoptosis, cancer and aging-related neurodegenerative diseases. Altered miRNAs levels have been associated with the formation of reactive oxygen species (ROS) and mitochondrial dysfunction. Mitochondrial dysfunction and ROS formation occur in many neurodegenerative diseases such as Alzheimer's, Parkinson's and Huntington's diseases. The crosstalk existing among oxidative stress, mitochondrial dysfunction and miRNAs dysregulation plays a pivotal role in the onset and progression of neurodegenerative diseases. Based on this evidence, in this review, with a focus on miRNAs and their role in mitochondrial dysfunction in aging-related neurodegenerative diseases, with a focus on their potential as diagnostic biomarkers and therapeutic targets.

Mitochondrial biology and the identification of biomarkers of Huntington's disease

Apart from finding novel compounds for treating Huntington's disease (HD) an important challenge at present consists in finding reliable read-outs or biomarkers that reflect key biological processes involved in HD pathogenesis. The core elements of HD biology, for example, HTT RNA levels or protein species can serve as biomarker, as could measures from biological systems or pathways in which Huntingtin plays an important role. Here we review the evidence for the involvement of mitochondrial biology in HD. The most consistent findings pertain to mitochondrial quality control, for example, fission/fusion. However, a convincing mitochondrial signature with biomarker potential is yet to emerge. This requires more research including in peripheral sources of human material, such as blood, or skeletal muscle.

Ageing, Drosophila melanogaster and Epigenetics

Ageing is a phenomenon where the accumulation of all the stresses that alter the functions of living organisms, halter them from maintaining their physiological balance and eventually lead to death. The emergence of epigenetic tremendously contributed to the knowledge of ageing. Epigenetic changes in cells or tissues like deoxyribonucleic acid (DNA) methylation, modification of histone proteins, transcriptional modification and also the involvement of non-coding DNA has been documented to be associated with ageing. In order to study ageing, scientists have taken advantage of several potential organisms to aid them in their study. Drosophila melanogaster has been an essential model in establishing current understanding of the mechanism of ageing as they possess several advantages over other competitors like having homologues to more than 75% of human disease genes, having 50% of Drosophila genes are homologues to human genes and most importantly they are genetically amenable. Here, we would like to summarise the extant knowledge about ageing and epigenetic process and the role of Drosophila as an ideal model to study epigenetics in association with ageing process.

Mitochondrial MicroRNAs in Aging and Neurodegenerative Diseases

MicroRNAs (miRNAs) are important regulators of several biological processes, such as cell growth, cell proliferation, embryonic development, tissue differentiation, and apoptosis. Currently, over 2000 mammalian miRNAs have been reported to regulate these biological processes. A subset of microRNAs was found to be localized to human mitochondria (mitomiRs). Through years of research, over 400 mitomiRs have been shown to modulate the translational activity of the mitochondrial genome. While miRNAs have been studied for years, the function of mitomiRs and their role in neurodegenerative pathologies is not known. The purpose of our article is to highlight recent findings that relate mitomiRs to neurodegenerative diseases, including Alzheimer’s, Parkinson’s, and Huntington’s. We also discuss the involvement of mitomiRs in regulating the mitochondrial genome in age-related neurodegenerative diseases.

How the enriched get richer? Experience-dependent modulation of microRNAs and the therapeutic effects of environmental enrichment

Environmental enrichment and physical exercise have many well-established health benefits. Although these environmental manipulations are known to delay symptom onset and progression in a variety of neurological and psychiatric conditions, the mechanisms underlying these effects remain poorly understood. A notable candidate molecular mechanism is that of microRNA, a family of small noncoding RNAs that are important regulators of gene expression. Research investigating the many diverse roles of microRNAs has greatly expanded over the past decade, with several promising preclinical and clinical studies highlighting the role of dysregulated microRNA expression (in the brain, blood and other peripheral systems) in understanding the aetiology of disease. Altered microRNA levels have also been described following environmental interventions such as exercise and environmental enrichment in non-clinical populations and wild-type animals, as well as in some brain disorders and associated preclinical models. Recent studies exploring the effects of stimulating environments on microRNA levels in the brain have revealed an array of changes that are likely to have important downstream effects on gene expression, and thus may regulate a variety of cellular processes. Here we review literature that explores the differential expression of microRNAs in rodents following environmental enrichment and exercise, in both healthy control animals and preclinical models of relevance to neurological and psychiatric disorders.