The miRNome of Alzheimer's disease: consistent downregulation of the miR-132/212 cluster

miR-132 and miR-942 Expression Levels in Children with Attention Deficit and Hyperactivity Disorder: A Controlled Study

OBJECTIVE

Although attention deficit hyperactivity disorder (ADHD) is a disease with high genetic transition, our knowledge about the mechanism of the disease is limited. In this study, it was aimed to evaluate the levels of miR-132-3p and miR-942-5p that are associated with the dopamine carrier protein gene (DAT1) and dopamine receptor 5 (DRD5) genes, which have been shown to play a role in the development of ADHD.

METHODS

According to the Diagnostic and Statistical Manual of Mental Disorders 5th edition, 50 children diagnosed with ADHD and 48 healthy controls were included in the study. Affective Disorders and Schizophrenia Interview Schedule-Now and Lifetime Version-Turkish Adaptation was used to evaluate ADHD and the diagnoses accompanying ADHD. Quantitative Real-Time Polymerase Chain Reaction was used to evaluate miR-132-3p and miR-942-5p expression levels.

RESULTS

It was observed that miR-132-3p level (p = 0.001) was significantly higher with children with ADHD compared to the control group, and the level of miR-942-5p (p = 0.181) was higher in ADHD but did not reach statistically significant level.

CONCLUSION

In our study, we found that the increase in the miR-132-3p levels of children with ADHD may be a therapeutic target of the disease.

Loss of Rbfox1 Does Not Affect Survival of Retinal Ganglion Cells Injured by Optic Nerve Crush

Rbfox1 is a multifunctional RNA binding protein that regulates alternative splicing, transcription, mRNA stability and translation. Its roles in neurogenesis and neuronal functions are well established. Recent studies also implicate Rbfox1 in the regulation of gene networks that support cell survival during stress. We have earlier characterized the expression of Rbfox1 in amacrine and retinal ganglion cells (RGCs) and showed that deletion of Rbfox1 in adult animals results in depth perception deficiency. The current study investigates the effect of Rbfox1 downregulation on survival of RGCs injured by optic nerve crush (ONC). Seven days after ONC, animals sustained severe degeneration of RGC axons in the optic nerve and significant loss of RGC somas. Semi-quantitative grading of optic nerve damage in control + ONC, control + tamoxifen + ONC, and Rbfox1 ^-/- + ONC groups ranged from 4.6 to 4.8 on a scale of 1 (normal; no degenerated axons were noted) to 5 (total degeneration; all axons showed degenerated organelles, axonal content, and myelin sheath), indicating a severe degeneration. Among these three ONC groups, no statistical significance was observed when any two groups were compared. The number of RGC somas were quantitatively analyzed in superior, inferior, nasal and temporal retinal quadrants at 0.5, 1, and 1.5 mm from the center of the optic disc. The average RGC densities (cells/mm²) were: control 6,438 ± 1,203; control + ONC 2,779 ± 573; control + tamoxifen 6,163 ± 861; control + tamoxifen + ONC 2,573 ± 555; Rbfox1 ^-/- 6,437 ± 893; and Rbfox1 ^-/- + ONC 2,537 ± 526. The RGC loss in control + ONC, control + tamoxifen + ONC and Rbfox1 ^-/- + ONC was 57% (P = 1.44954E-42), 58% (P = 1.37543E-57) and 61% (P = 5.552E-59) compared to RGC numbers in the relevant uninjured groups, respectively. No statistically significant difference was observed between any two groups of uninjured animals or between any two ONC groups. Our data indicate that Rbfox1-mediated pathways have no effect on survival of RGCs injured by ONC.

Alzheimer's Disease and microRNA-132: A Widespread Pathological Factor and Potential Therapeutic Target

Alzheimer's disease (AD) is a common neurodegenerative disease in the elderly and is the most common type of dementia. AD is mostly gradual onset, and involves slow, progressive mental decline, accompanied by personality changes; the incidence of AD gradually increases with age. The etiology of AD is unknown, although it is currently believed to be related to abnormal deposition of amyloid β-protein (Aβ) in the brain, hyperphosphorylation of microtubule-associated protein tau, and the release of various cytokines, complements, activators and chemokines by cells. MicroRNAs (miRNAs) are a class of highly conserved non-coding RNAs that regulate gene expression at the post-transcriptional level, and manipulate the functions of intracellular proteins and physiological processes. Emerging studies have shown that miRNA plays an important role in regulating AD-related genes. MiR-132 is known as "NeurimmiR" due to its involvement in numerous neurophysiological and pathological processes. Accumulating pre-clinical results suggest that miR-132 may be involved in the progression of Aβ and tau pathology. Moreover, clinical studies have indicated that decreased circulating miR-132 levels could be used a potential diagnostic biomarker in AD. Here, we review the pathogenic role of miR-132 activity in AD, and the potential of targeting miR-132 for developing future therapeutic strategies.

Neuroprotective effect of miR-212-5p on isoflurane-induced cognitive dysfunction by inhibiting neuroinflammation

BACKGROUND

Isoflurane is a commonly used inhalation anesthetic in the clinic, which can induce cognitive dysfunction and neuroinflammation. miR-212-5p has been demonstrated to be involved in the neuronal system and play vital roles in memory formation. Its function in the learning and memory impairment and neuroinflammation induced by isoflurane was investigated in this study.

METHODS

Cognitive dysfunction rat models were established by 3% isoflurane inhalation. The neurological function was evaluated by the modified Neurological Severity Scale. The learning and memory ability of rats was assessed by the Morris water maze test. The expression level of miR-212-5p was analyzed by RT-qPCR, and the protein levels of proinflammatory cytokines were detected by ELISA.

RESULTS

Isoflurane induced cognitive dysfunction in rats with the neurological scores and the escape latency increased, and time spent in the target quadrant decreased. The protein levels of IL-1β, IL-6, and TNF-α were increased in isoflurane treated rats. miR-212-5p was downregulated in cognitive impairment rats. The upregulation of miR-212-5p by the agomir injection decreased the neurological scores of rats and increased the learning and memory ability of impaired rats. Moreover, the neuroinflammation was inhibited by the overexpression of miR-212-5p.

CONCLUSION

miR-212-5p showed a neuroprotective effect in isoflurane-induced cognitive dysfunction rats by inhibiting neuroinflammation.

Tau Exon 10 Inclusion by PrPC through Downregulating GSK3β Activity

Tau protein is largely responsible for tauopathies, including Alzheimer’s disease (AD), where it accumulates in the brain as insoluble aggregates. Tau mRNA is regulated by alternative splicing, and inclusion or exclusion of exon 10 gives rise to the 3R and 4R isoforms respectively, whose balance is physiologically regulated. In this sense, one of the several factors that regulate alternative splicing of tau is GSK3β, whose activity is inhibited by the cellular prion protein (PrP^C), which has different physiological functions in neuroprotection and neuronal differentiation. Moreover, a relationship between PrP^C and tau expression levels has been reported during AD evolution. For this reason, in this study we aimed to analyze the role of PrP^C and the implication of GSK3β in the regulation of tau exon 10 alternative splicing. We used AD human samples and mouse models of PrP^C ablation and tau overexpression. In addition, we used primary neuronal cultures to develop functional studies. Our results revealed a paralleled association between PrP^C expression and tau 4R isoforms in all models analyzed. In this sense, reduction or ablation of PrP^C levels induces an increase in tau 3R/4R balance. More relevantly, our data points to GSK3β activity downstream from PrP^C in this phenomenon. Our results indicate that PrP^C plays a role in tau exon 10 inclusion through the inhibitory capacity of GSK3β.

Restoring miR-132 expression rescues adult hippocampal neurogenesis and memory deficits in Alzheimer's disease

Neural stem cells residing in the hippocampal neurogenic niche sustain lifelong neurogenesis in the adult brain. Adult hippocampal neurogenesis (AHN) is functionally linked to mnemonic and cognitive plasticity in humans and rodents. In Alzheimer's disease (AD), the process of generating new neurons at the hippocampal neurogenic niche is impeded, yet the mechanisms involved are unknown. Here we identify miR-132, one of the most consistently downregulated microRNAs in AD, as a potent regulator of AHN, exerting cell-autonomous proneurogenic effects in adult neural stem cells and their progeny. Using distinct AD mouse models, cultured human primary and established neural stem cells, and human patient material, we demonstrate that AHN is directly affected by AD pathology. miR-132 replacement in adult mouse AD hippocampus restores AHN and relevant memory deficits. Our findings corroborate the significance of AHN in mouse models of AD and reveal the possible therapeutic potential of targeting miR-132 in neurodegeneration.

Hyper-graph based sparse canonical correlation analysis for the diagnosis of Alzheimer's disease from multi-dimensional genomic data

The effective and accurate diagnosis of Alzheimer's disease (AD), especially in the early stage (i.e., mild cognitive impairment (MCI)) remains a big challenge in AD research. So far, multiple biomarkers have been associated with AD diagnosis and progression. However, most of the existing research only utilized single modality data for diagnostic biomarker identification, which did not take the advantages of multi-modal data that provide comprehensive and complementary information at multiple levels into consideration. In this paper, we integrate multi-modal genomic data from postmortem AD brains (i.e., mRNA, miRNA and epigenomic data) and propose a hyper-graph based sparse canonical correlation analysis (HGSCCA) method to extract the most correlated multi-modal biomarkers associated with AD and MCI. Specifically, our model utilizes the sparse canonical correlation analysis framework (SCCA), which aims at finding the best linear projections for each input modality so that the strongest correlation within the selected features of multi-dimensional genomic data can be captured. In addition, with the consideration of high-order relationships among different subjects, we also introduce a hyper-graph-based regularization term that will lead to the selection of more discriminative biomarkers. To evaluate the effectiveness of the proposed method, we conduct the experiments on the well-known AD cohort study, The Religious Orders Study and Memory and Aging Project (ROSMAP) dataset, and the results show that our method can not only identify meaningful biomarkers for the diagnosis AD disease, but also achieve superior classification performance than the comparing methods.

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.

LncRNA NEAT1 Regulates the Development of Parkinson's Disease by Targeting AXIN1 Via Sponging miR-212-3p

Long non-coding RNA (lncRNA) nuclear-enriched assembly transcript 1 (NEAT1) has been reported to be highly expressed in Parkinson's disease (PD). However, the mechanism of NEAT1 in PD progression has not been fully elucidated. 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine injection (MPTP) was used to construct PD mouse models in vivo, and 1-methyl-4-phenyl pyridine (MPP+) was used to build PD cell models in vitro. Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to test the expression of NEAT1, microRNA (miR)-212-3p and axis inhibition protein 1 (AXIN1). The viability, apoptosis and inflammation of cells were determined using cell counting kit 8 (CCK8) assay, flow cytometry and enzyme-linked immunosorbent assay (ELISA), respectively. Then, the protein levels of apoptosis-related markers and AXIN1 were measured by western blot (WB) analysis. Furthermore, dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were performed to verify the interaction between miR-212-3p and NEAT1 or AXIN1. NEAT1 was upregulated in PD mouse models and cell models. Function experiments confirmed that NEAT1 knockdown could promote the viability, suppress the apoptosis and inflammation of MPP+-stimulated SK-N-SH cells to restrain PD progression. MiR-212-3p was downregulated in PD, and its inhibitor could reverse the suppression effect of NEAT1 knockdown on PD progression. Additionally, AXIN1 was a target of miR-212-3p, and its overexpression could invert the inhibition effect of miR-212-3p mimic on PD progression. Furthermore, AXIN1 expression was inhibited by NEAT1 silencing and promoted by NEAT1 overexpression, while these effect could be recovered by miR-212-3p inhibitor and mimic, respectively. Our results demonstrated that NEAT1 knockdown suppressed PD progression through regulating the miR-212-3p/AXIN1 pathway, indicating that NEAT1 might be a therapeutic target for neuroprotection in PD.

Epigenetics of Alzheimer's Disease

There are currently no validated biomarkers which can be used to accurately diagnose Alzheimer's disease (AD) or to distinguish it from other dementia-causing neuropathologies. Moreover, to date, only symptomatic treatments exist for this progressive neurodegenerative disorder. In the search for new, more reliable biomarkers and potential therapeutic options, epigenetic modifications have emerged as important players in the pathogenesis of AD. The aim of the article was to provide a brief overview of the current knowledge regarding the role of epigenetics (including mitoepigenetics) in AD, and the possibility of applying these advances for future AD therapy. Extensive research has suggested an important role of DNA methylation and hydroxymethylation, histone posttranslational modifications, and non-coding RNA regulation (with the emphasis on microRNAs) in the course and development of AD. Recent studies also indicated mitochondrial DNA (mtDNA) as an interesting biomarker of AD, since dysfunctions in the mitochondria and lower mtDNA copy number have been associated with AD pathophysiology. The current evidence suggests that epigenetic changes can be successfully detected, not only in the central nervous system, but also in the cerebrospinal fluid and on the periphery, contributing further to their potential as both biomarkers and therapeutic targets in AD.

Validation of human microRNA target pathways enables evaluation of target prediction tools

MicroRNAs are regulators of gene expression. A wide-spread, yet not validated, assumption is that the targetome of miRNAs is non-randomly distributed across the transcriptome and that targets share functional pathways. We developed a computational and experimental strategy termed high-throughput miRNA interaction reporter assay (HiTmIR) to facilitate the validation of target pathways. First, targets and target pathways are predicted and prioritized by computational means to increase the specificity and positive predictive value. Second, the novel webtool miRTaH facilitates guided designs of reporter assay constructs at scale. Third, automated and standardized reporter assays are performed. We evaluated HiTmIR using miR-34a-5p, for which TNF- and TGFB-signaling, and Parkinson's Disease (PD)-related categories were identified and repeated the pipeline for miR-7-5p. HiTmIR validated 58.9% of the target genes for miR-34a-5p and 46.7% for miR-7-5p. We confirmed the targeting by measuring the endogenous protein levels of targets in a neuronal cell model. The standardized positive and negative targets are collected in the new miRATBase database, representing a resource for training, or benchmarking new target predictors. Applied to 88 target predictors with different confidence scores, TargetScan 7.2 and miRanda outperformed other tools. Our experiments demonstrate the efficiency of HiTmIR and provide evidence for an orchestrated miRNA-gene targeting.

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.

MicroRNAs in Alzheimer's Disease: Function and Potential Applications as Diagnostic Biomarkers

Alzheimer’s disease (AD) is the most common form of dementia. Although the incidence of AD is high, the rates of diagnosis and treatment are relatively low. Moreover, effective means for the diagnosis and treatment of AD are still lacking. MicroRNAs (miRNAs, miRs) are non-coding RNAs that play regulatory roles by targeting mRNAs. The expression of miRNAs is conserved, temporal, and tissue-specific. Impairment of microRNA function is closely related to AD pathogenesis, including the beta-amyloid and tau hallmarks of AD, and there is evidence that the expression of some microRNAs differs significantly between healthy people and AD patients. These properties of miRNAs endow them with potential diagnostic and therapeutic value in the treatment of this debilitating disease. This review provides comprehensive information about the regulatory function of miRNAs in AD, as well as potential applications as diagnostic biomarkers.

Plasma microRNAs biomarkers in mild cognitive impairment among patients with type 2 diabetes mellitus

OBJECTIVES

To assess the potential value of some miRNAs as diagnostic biomarkers for mild cognitive impairment (MCI) among patients with type2 diabetes mellitus (T2DM) and to identify other risk factors for MCI among them.

METHODS

This study enrolled 163 adults with T2DM using face to face interview. Cognitive function with its domains was assessed using Adenbrooke's Cognitive Examination III (ACE III). Lipid profile, glycated hemoglobin, and miR-128, miR-132, miR- 874, miR-134, miR-323, and miR-382 expressions, using quantitative real-time PCR, were assessed.

RESULTS

MCI was detected among 59/163 (36.2%) patients with T2DM. Plasma expression of miR-132 was significantly higher in T2DM patients with MCI compared to those without MCI and to normal cognitive healthy individuals (median = 2, 1.1 and 1.2 respectively, P < 0.05. Logistic regression analysis showed that higher miR-132 expression with adjusted odds ratio (AOR): 1.2 (95% CI 1.0-1.3), female gender (AOR:2.1; 95%CI 1.0-4.3), education below postgraduate (secondary and university education with AOR: 9.5 & 19.4 respectively) were the significant predicting factors for MCI among T2DM patients. Using ROC curve, miR-132 was the only assayed miRNA that significantly differentiates T2DM patients with MCI from those with normal cognition with 72.3% sensitivity, 56.2% specificity, and 63.8% accuracy (P < 0.05). Other studied miRNAs showed lower sensitivity and specificity for detecting MCI among studied T2DM participants.

CONCLUSION

MCI affects nearly one-third of adult patients with T2DM. A significantly over expression of miR-132 was detected among T2DM with MCI compared to those with normal cognition.

Modulation of MicroRNAs as a Potential Molecular Mechanism Involved in the Beneficial Actions of Physical Exercise in Alzheimer Disease

Alzheimer disease (AD) is one of the most common neurodegenerative diseases, affecting middle-aged and elderly individuals worldwide. AD pathophysiology involves the accumulation of beta-amyloid plaques and neurofibrillary tangles in the brain, along with chronic neuroinflammation and neurodegeneration. Physical exercise (PE) is a beneficial non-pharmacological strategy and has been described as an ally to combat cognitive decline in individuals with AD. However, the molecular mechanisms that govern the beneficial adaptations induced by PE in AD are not fully elucidated. MicroRNAs are small non-coding RNAs involved in the post-transcriptional regulation of gene expression, inhibiting or degrading their target mRNAs. MicroRNAs are involved in physiological processes that govern normal brain function and deregulated microRNA profiles are associated with the development and progression of AD. It is also known that PE changes microRNA expression profile in the circulation and in target tissues and organs. Thus, this review aimed to identify the role of deregulated microRNAs in the pathophysiology of AD and explore the possible role of the modulation of microRNAs as a molecular mechanism involved in the beneficial actions of PE in AD.

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.

Circulating RNAs as Potential Biomarkers in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a complex multi-system neurodegenerative disorder with currently limited diagnostic and no therapeutic options. Despite the intense efforts no clinically applicable biomarkers for ALS are yet established. Most current research is thus focused, in particular, in identifying potential non-invasive circulating biomarkers for more rapid and accurate diagnosis and monitoring of the disease. In this review, we have focused on messenger RNA (mRNA), non-coding RNAs (lncRNAs), micro RNAs (miRNAs) and circular RNA (circRNAs) as potential biomarkers for ALS in peripheral blood serum, plasma and cells. The most promising miRNAs include miR-206, miR-133b, miR-27a, mi-338-3p, miR-183, miR-451, let-7 and miR-125b. To test clinical potential of this miRNA panel, a useful approach may be to perform such analysis on larger multi-center scale using similar experimental design. However, other types of RNAs (lncRNAs, circRNAs and mRNAs) that, together with miRNAs, represent RNA networks, have not been yet extensively studied in blood samples of patients with ALS. Additional research has to be done in order to find robust circulating biomarkers and therapeutic targets that will distinguish key RNA interactions in specific ALS-types to facilitate diagnosis, predict progression and design therapy.

Combining feature selection and shape analysis uncovers precise rules for miRNA regulation in Huntington's disease mice

Background

MicroRNA (miRNA) regulation is associated with several diseases, including neurodegenerative diseases. Several approaches can be used for modeling miRNA regulation. However, their precision may be limited for analyzing multidimensional data. Here, we addressed this question by integrating shape analysis and feature selection into miRAMINT, a methodology that we used for analyzing multidimensional RNA-seq and proteomic data from a knock-in mouse model (Hdh mice) of Huntington’s disease (HD), a disease caused by CAG repeat expansion in huntingtin (htt). This dataset covers 6 CAG repeat alleles and 3 age points in the striatum and cortex of Hdh mice.

Results

Remarkably, compared to previous analyzes of this multidimensional dataset, the miRAMINT approach retained only 31 explanatory striatal miRNA-mRNA pairs that are precisely associated with the shape of CAG repeat dependence over time, among which 5 pairs with a strong change of target expression levels. Several of these pairs were previously associated with neuronal homeostasis or HD pathogenesis, or both. Such miRNA-mRNA pairs were not detected in cortex.

Conclusions

These data suggest that miRNA regulation has a limited global role in HD while providing accurately-selected miRNA-target pairs to study how the brain may compute molecular responses to HD over time. These data also provide a methodological framework for researchers to explore how shape analysis can enhance multidimensional data analytics in biology and disease.

Brain microRNAs associated with late-life depressive symptoms are also associated with cognitive trajectory and dementia

Late-life depression is associated with an increased risk for dementia but we have limited knowledge of the molecular mechanisms underlying this association. Here we investigated whether brain microRNAs, important posttranscriptional regulators of gene expression, contribute to this association. Late-life depressive symptoms were assessed annually in 300 participants of the Religious Orders Study and Rush Memory and Aging Project for a mean of 7 years. Participants underwent annual cognitive testing, clinical assessment of cognitive status, and uniform neuropathologic examination after death. microRNAs were profiled from the prefrontal cortex using NanoString platform in the discovery cohort and small RNA sequencing in the replication cohort. A global microRNA association study of late-life depressive symptoms was performed using linear mixed model adjusting for the potential confounding factors. Four brain microRNAs were associated with late-life depressive symptoms at adjusted p < 0.05: miR-484, miR-26b-5p, miR-30d-5p, and miR-197-3p. Lower expression levels of these miRNAs were associated having greater depressive symptoms. Furthermore, lower levels of miR-484 and miR-197-3p were associated with faster decline of cognition over time. Moreover, lower miR-484 level was associated with higher probability of having Alzheimer's dementia. Importantly, the associations between miR-484 and depressive symptoms and Alzheimer's dementia, respectively, were replicated in an independent cohort. Lastly, the predicted targets of miR-484 were enriched in a brain protein co-expression module involving synaptic transmission and regulation of synaptic plasticity. This study identified four brain microRNAs associated with late-life depressive symptoms assessed longitudinally. In addition, we found a molecular connection between late-life depression and dementia through miR-484.

The Combined Therapy of Berberine Treatment with lncRNA BACE1-AS Depletion Attenuates Aβ25-35 Induced Neuronal Injury Through Regulating the Expression of miR-132-3p in Neuronal Cells

Accumulating articles reported that berberine (Ber) played a neuroprotective role in Alzheimer's disease (AD). Long noncoding RNAs (lncRNAs) have been identified as biomarkers and therapeutic targets of AD. However, the precise mechanism by which lncRNA β-amyloid cleaving enzyme 1 antisense RNA (BACE1-AS)regulates the progression of AD remains largely unknown. HPN and SK-N-SH cells treated with amyloid β 25-35 (Aβ_25-35) were regarded as AD model in vitro. Cell survival rate was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Lactate dehydrogenase (LDH) cytotoxicity assay was conducted to detect the cytotoxicity of neuronal cells. Flow cytometry was performed to determine the intracellular concentration of Ca²⁺, reactive oxygen species (ROS) and apoptosis of neuronal cells. Western blot assay was carried out to detect the apoptosis-related proteins of neuronal cells. The abundance of lncRNA BACE1-AS and miR-132-3p was measured by quantitative real time polymerase chain reaction (qRT-PCR). The binding sites between miR-132-3p and BACE1-AS were predicted by Starbase, and the combination was confirmed by dual-luciferase reporter assay. We found that Ber alleviated Aβ_25-35 induced neuronal injury in AD model, especially in high concentration Ber group. The enrichment of BACE1-AS was positively regulated by Aβ_25-35 and was inversely modulated by Ber in neuronal cells. The interference of BACE1-AS alleviated the neuronal damage of AD model. miR-132-3p was a direct target of lncRNA BACE1-AS in HEK293T cells, and it was negatively regulated by BACE1-AS in neuronal cells. BACE1-AS accumulation reversed the protective effect of miR-132-3p overexpression on AD model. Ber treatment and BACE1-AS intervention recovered the viability of AD model. Ber up-regulated the level of miR-132-3p via BACE1-AS in SK-N-SH and HPN neuronal cells. in conclucsion, Ber protected neuronal cells against Aβ_25-35 at least partly through BACE1-AS/miR-132-3p axis. The combined therapy of Ber treatment with BACE1-AS depletion might provide new insight into AD treatment.

Two-stage Bayesian GWAS of 9576 individuals identifies SNP regions that are targeted by miRNAs inversely expressed in Alzheimer's and cancer

INTRODUCTION

We compared genetic variants between Alzheimer's disease (AD) and two age-related cancers-breast and prostate -to identify single-nucleotide polymorphisms (SNPs) that are associated with inverse comorbidity of AD and cancer.

METHODS

Bayesian multinomial regression was used to compare sex-stratified cases (AD and cancer) against controls in a two-stage study. A ±500 KB region around each replicated hit was imputed and analyzed after merging individuals from the two stages. The microRNAs (miRNAs) that target the genes involving these SNPs were analyzed for miRNA family enrichment.

RESULTS

We identified 137 variants with inverse odds ratios for AD and cancer located on chromosomes 19, 4, and 5. The mapped miRNAs within the network were enriched for miR-17 and miR-515 families.

DISCUSSION

The identified SNPs were rs4298154 (intergenic), within TOMM40/APOE/APOC1, MARK4, CLPTM1, and near the VDAC1/FSTL4 locus. The miRNAs identified in our network have been previously reported to have inverse expression in AD and cancer.

Machine Learning to Detect Alzheimer's Disease from Circulating Non-coding RNAs

Blood-borne small non-coding (sncRNAs) are among the prominent candidates for blood-based diagnostic tests. Often, high-throughput approaches are applied to discover biomarker signatures. These have to be validated in larger cohorts and evaluated by adequate statistical learning approaches. Previously, we published high-throughput sequencing based microRNA (miRNA) signatures in Alzheimer’s disease (AD) patients in the United States (US) and Germany. Here, we determined abundance levels of 21 known circulating miRNAs in 465 individuals encompassing AD patients and controls by RT-qPCR. We computed models to assess the relation between miRNA expression and phenotypes, gender, age, or disease severity (Mini-Mental State Examination; MMSE). Of the 21 miRNAs, expression levels of 20 miRNAs were consistently de-regulated in the US and German cohorts. 18 miRNAs were significantly correlated with neurodegeneration (Benjamini-Hochberg adjusted P < 0.05) with highest significance for miR-532-5p (Benjamini-Hochberg adjusted P = 4.8 × 10⁻³⁰). Machine learning models reached an area under the curve (AUC) value of 87.6% in differentiating AD patients from controls. Further, ten miRNAs were significantly correlated with MMSE, in particular miR-26a/26b-5p (adjusted P = 0.0002). Interestingly, the miRNAs with lower abundance in AD were enriched in monocytes and T-helper cells, while those up-regulated in AD were enriched in serum, exosomes, cytotoxic t-cells, and B-cells. Our study represents the next important step in translational research for a miRNA-based AD test.

Hypoxia-Induced MicroRNA-212/132 Alter Blood-Brain Barrier Integrity Through Inhibition of Tight Junction-Associated Proteins in Human and Mouse Brain Microvascular Endothelial Cells

Blood-brain barrier (BBB) integrity is one of the important elements of central nervous system (CNS) homeostasis. MicroRNAs (miRs) have been demonstrated to play a role in many CNS disorders such as stroke and traumatic brain injury. MiR-212/132 are highly expressed in the CNS but their role at the BBB has not been characterized yet. Thus, we analyzed the expression of miR-212/132 in hypoxic mouse and human brain microvascular endothelial cells (BMEC) as well as in posttraumatic mouse and human brain tissue and serum exosomes. MiR-212/132 expression was detected in brain capillaries by in situ hybridization and was increased up to ten times in hypoxic BMEC. Over-expression of pre-miR-212/132 in BMEC decreased barrier properties and reduced migration of BMEC in the wound healing assay. We identified and validated tight junction proteins claudin-1 (Cldn1), junctional adhesion molecule 3 (Jam3), and tight junction-associated protein 1 (Tjap1) as potential miR-212/132 targets. Over-expression of miRs led to a decrease in mRNA and protein expression of Cldn1, Jam3, and Tjap1, which could be rescued by a respective anti-miR. In conclusion, our study identifies miR-212/132 as critical players at the hypoxic BBB. In addition, we propose three new direct miR-212/132 targets to be involved in miR-212/132-mediated effects on BBB properties.

miR-212 and miR-132 Are Downregulated in Neurally Derived Plasma Exosomes of Alzheimer's Patients

It was recently discovered that brain cells release extracellular vesicles (EV) which can pass from brain into blood. These findings raise the possibility that brain-derived EV’s present in blood can be used to monitor disease processes occurring in the cerebrum. Since the levels of certain micro-RNAs (miRNAs) have been reported to be altered in Alzheimer’s disease (AD) brain, we sought to assess miRNA dysregulation in AD brain tissue and to determine if these changes were reflected in neural EVs isolated from blood of subjects with AD. To this end, we employed high-content miRNA arrays to search for differences in miRNAs in RNA pools from brain tissue of AD (n = 5), high pathological control (HPC) (n = 5), or cognitively intact pathology-free controls (n = 5). Twelve miRNAs were altered by >1.5-fold in AD compared to controls, and six of these were also changed compared to HPCs. Analysis of hits in brain extracts from 11 AD, 7 HPCs and 9 controls revealed a similar fold difference in these six miRNAs, with three showing statistically significant group differences and one with a strong trend toward group differences. Thereafter, we focused on the four miRNAs that showed group differences and measured their content in neurally derived blood EVs isolated from 63 subjects: 16 patients with early stage dementia and a CSF Aβ42+ tau profile consistent with AD, 16 individuals with mild cognitive impairment (MCI) and an AD CSF profile, and 31 cognitively intact controls with normal CSF Aβ42+ tau levels. ROC analysis indicated that measurement of miR-132-3p in neurally-derived plasma EVs showed good sensitivity and specificity to diagnose AD, but did not effectively separate individuals with AD-MCI from controls. Moreover, when we measured the levels of a related miRNA, miR-212, we found that this miRNA was also decreased in neural EVs from AD patients compared to controls. Our results suggest that measurement of miR-132 and miR-212 in neural EVs should be further investigated as a diagnostic aid for AD and as a potential theragnostic.

Upregulation of miR‑132‑3p in cholangiocarcinoma tissues: A study based on RT‑qPCR, The Cancer Genome Atlas miRNA sequencing, Gene Expression Omnibus microarray data and bioinformatics analyses

MicroRNAs (miRNAs/miRs) have been reported to be closely associated with numerous human diseases, including cholangiocarcinoma (CCA). However, the number of miRNAs known to be involved in CCA is limited, and the association between miR-132-3p and CCA remains unknown. In the present study, the clinical role of miR-132-3p and its potential signaling pathways were investigated by multiple approaches. Reverse transcription-quantitative PCR (RT-qPCR), CCA-associated Gene Expression Omnibus (GEO), ArrayExpress and Sequence Read Archive (SRA) miRNA-microarray or miRNA-sequencing data were screened, and meta-analyses were conducted, in order to calculate the receiver operating characteristic (ROC) curve and standardized mean difference (SMD). The predicted target genes of miR-132-3p were obtained from 12 online databases and were combined with the downregulated differentially expressed genes identified in the RNA-sequencing data of CCA. Gene Ontology annotation and pathway analysis were performed in WebGestalt. Protein-protein interaction analyses were conducted in STRING. The Cancer Genome Atlas (TCGA) mRNA expression profiles were used to validate the expression levels of hub genes at the mRNA level. The Human Protein Atlas was used to identify the protein expression levels of hub genes in CCA tissues and non-tumor biliary epithelium. The meta-analyses comprised 10 groups of RT-qPCR data, eight GEO microarray datasets and one TCGA miRNA-sequencing dataset. The SMD of miR-132-3p in CCA was 0.75 (95% CI: 0.25, 1.24), which indicated that miR-132-3p was overexpressed in CCA tissues. This finding was supported by a summary ROC value of 0.80 (95% CI: 0.76, 0.83). The pooled sensitivity and specificity were 0.81 (95% CI: 0.59, 0.93) and 0.71 (95% CI: 0.58, 0.81), respectively. The relative expression level of miR-132-3p in the early stage of CCA (stages I–II) was 6.8754±0.5279, which was markedly lower than that in the advanced stage (stages III–IVB), 7.3034±0.3267 (P=0.003). Consistently, the miR-132-3p level in low-grade CCA (grades G1-G2) was 6.7581±0.5297, whereas it was 7.1191±0.4651 in patients with high-grade CCA (grades G3-G4) (P=0.037). Furthermore, 555 potential target genes of miR-132-3p in CCA were mainly enriched in the ‘Focal Adhesion-PI3K-Akt-mTOR-signaling pathway’. In conclusion, upregulation of miR-132-3p may serve a pivotal role in the tumorigenesis and progression of CCA by targeting different pathways. Further in vitro and in vivo studies are required to support the current findings.

miR-212-5p attenuates ferroptotic neuronal death after traumatic brain injury by targeting Ptgs2

Ferroptosis, a newly discovered form of iron-dependent regulated cell death, has been implicated in traumatic brain injury (TBI). MiR-212-5p has previously been reported to be downregulated in extracellular vesicles following TBI. To investigate whether miR-212-5p is involved in the ferroptotic neuronal death in TBI mice, we first examined the accumulation of malondialdehyde (MDA) and ferrous ion, and the expression of ferroptosis-related molecules at 6 h, 12 h, 24 h, 48 h and 72 h following controlled cortical impact (CCI) in mice. There was a significant upregulation in the expression of Gpx4 and Acsl4 at 6 h, Slc7a11 from 12 h to 72 h, and Nox2 and Sat1 from 6 h to 72 h post injury. Similarly, an upregulation in the expression of Gpx4 at 6 h, Nox2 from 6 h to 72 h, xCT from 12 h to 72 h, and Sat1 at 72 h after CCI was observed at the protein level. Interestingly, MDA and ferrous ion were increased whereas miR-212-5p was decreased in the CCI group compared to the sham group. Furthermore, we found that overexpression of miR-212-5p attenuated ferroptosis while downregulation of miR-212-5p promoted ferroptotic cell death partially by targeting prostaglandin-endoperoxide synthase-2 (Ptgs2) in HT-22 and Neuro-2a cell lines. In addition, administration of miR-212-5p in CCI mice significantly improved learning and spatial memory. Collectively, these findings indicate that miR-212-5p may protect against ferroptotic neuronal death in CCI mice partially by targeting Ptgs2.

The Missing Link: How Exosomes and miRNAs can Help in Bridging Psychiatry and Molecular Biology in the Context of Depression, Bipolar Disorder and Schizophrenia

MicroRNAs (miRNAs) only recently have been recognized as promising molecules for both fundamental and clinical neuroscience. We provide a literature review of miRNA biomarker studies in three most prominent psychiatric disorders (depression, bipolar disorder and schizophrenia) with the particular focus on depression due to its social and healthcare importance. Our search resulted in 191 unique miRNAs across 35 human studies measuring miRNA levels in blood, serum or plasma. 30 miRNAs replicated in more than one study. Most miRNAs targeted neuroplasticity and neurodevelopment pathways. Various limitations do not allow us to make firm conclusions on clinical potential of studied miRNAs. Based on our results we discuss the rationale for future research investigations of exosomal mechanisms to overcome methodological caveats both in studying etiology and pathogenesis, and providing an objective back-up for clinical decisions.

A Systematic Review of MicroRNA Expression as Biomarker of Late-Onset Alzheimer's Disease

Late-onset Alzheimer's disease (LOAD) is a high-occurrence neurological disorder but the difficulty in identifying precise and early biomarkers has complicated the understanding of the disease and the development of new treatments. In this sense, important knowledge is emerging regarding novel molecular and biological candidates with diagnostic potential, including microRNAs (miRNAs), which have a key role in gene repression. The aim of this systematic review was to define the role of miRNAs' expression as biomarkers for LOAD both in brain tissues, which could help understand the biology of the disease, and circulating tissues, which could serve as non-invasive markers of the pathology. A systematic search was performed in Web of Science and PubMed using the keywords ((Alzheimer or Alzheimer's) and (microRNA or microRNAs or miRNA or miRNAs or miR)) until August 2018 to retrieve all articles that presented independent original data evaluating the impact of miRNA expression on the development of LOAD in human population. A total of 90 studies investigating the role of miRNAs' expression in the development of LOAD were identified. While other widely studied miRNAs such as hsa-miR-146a presented contradictory results among studies, deregulation in brain tissue of seven miRNAs, hsa-miR-16-5p, hsa-miR-34a-5p, hsa-miR-107, hsa-miR-125-5p, hsa-miR-132-3p, hsa-miR-181-3p, and hsa-miR-212-3p, was consistently identified in LOAD patients. Their role in the disease could be mediated through the regulation of key pathways, such as axon guidance, longevity, insulin, and MAPK signaling pathway. However, regarding their role as non-invasive biomarkers of LOAD in fluids, although the limited results available are promising, further studies are required.

Circulating, Cell-Free Micro-RNA Profiles Reflect Discordant Development of Dementia in Monozygotic Twins

We aim to examine if circulating micro-RNA and cytokine levels associate with dementia diagnosis and cognitive scores. To test our hypothesis, we use plasma donated from 48 monozygotic twin pairs in 1997 and 46 micro-RNAs and 10 cytokines were quantified using microfluidic RT-qPCR and multiplex solid-phase immunoassays, respectively. Micro-RNA and cytokine profiling were examined for associations with dementia diagnoses in a longitudinal registry study or with cognitive scores at baseline. Thirty-six micro-RNAs and all cytokines were detected consistently. Micro-RNA profiles associate with diagnoses and cognitive scores at statistically significant levels while cytokine only showed trends pointing at chronic inflammation in twins having or developing dementia. The most notable findings were decreased miR-106a and miR-210, and increased miR-106b expression in twins with a dementia diagnosis. This pioneering evaluation of micro-RNA and cytokine and dementia diagnosis suggests micro-RNA targets in vasculogenesis, lipoprotein transport, and amyloid precursor protein genes.

MicroRNA-7 directly targets Reg1 in pancreatic cells

Regenerating islet-derived (Reg) proteins, which were first discovered in the pancreas, are associated with increased proliferation, prevention of apoptosis, and enhanced differentiation in normal and disease states, but very little is known about the regulation of their expression. We hypothesized that Reg expression is influenced by microRNAs. Bioinformatic analysis predicted Reg1 to be a target of microRNA-7 (miR-7), which influences pancreatic β-cell function. To this end, we investigated the effects of miR-7 on Reg1 expression in pancreatic acinar and islet β-cells. High levels of Reg1 were noted by immunostaining and Western blotting in acinar cells in contrast to islet cells. A reciprocal expression pattern was observed for miR-7. Overexpression of miR-7 resulted in Reg1 mRNA suppression and reduction of secreted Reg1 protein. Conversely, miR-7 knockdown led to increases in Reg1. Targeting of Reg1 by miR-7 was confirmed via luciferase activity assays. In contrast, miR-7 did not directly repress the human ortholog of Reg1 REG1A as well as REG1B indicating species differences in the regulation of Reg expression. This is the first account of microRNA modulation of any Reg member warranting studies to fill gaps in our knowledge of Reg protein biology, particularly in disease contexts.

Altered microRNAs related to synaptic function as potential plasma biomarkers for Alzheimer's disease

BACKGROUND

Several evidences suggest that failure of synaptic function occurs at preclinical stages of Alzheimer's disease (AD) preceding neuronal loss and the classical AD pathological hallmarks. Nowadays, there is an urgent need to identify reliable biomarkers that could be obtained with non-invasive methods to improve AD diagnosis at early stages. Here, we have examined plasma levels of a group of miRNAs related to synaptic proteins in a cohort composed of cognitive healthy controls (HC), mild cognitive impairment (MCI) and AD subjects.

METHODS

Plasma and brain levels of miRNAs were analysed in two different cohorts including 38 HC, 26 MCI, 56 AD dementia patients and 27 frontotemporal dementia (FTD) patients. D'Agostino and Pearson and Shapiro-Wilk tests were used to evaluate data normality. miRNA levels between groups were compared using a two-sided nonparametric Mann-Whitney test and sensitivity and specificity was determined by receiver operating characteristic curve analysis.

RESULTS

Significant upregulation of miR-92a-3p, miR-181c-5p and miR-210-3p was found in the plasma of both MCI and AD subjects. MCI patients that progress to AD showed higher plasma levels of these miRNAs. By contrast, no changes in miR-92a-3p, miR-181c-5p or miR-210-3p levels were observed in plasma obtained from a cohort of FTD.

CONCLUSION

Our study shows that plasma miR-92a-3p, miR-181c-5p and miR-210-3p constitute a specific molecular signature potentially useful as a potential biomarker for AD.

miR-132 regulates the expression of synaptic proteins in APP/PS1 transgenic mice through C1q

Cognitive impairment in Alzheimer’s disease (AD) is usually accompanied by synaptic loss in both the hippocampus and neocortex. In the early stage of AD, amyloid β-induced synapse changes is the main reason, while in the later stage, the accumulation of Tau protein promotes synapse degeneration as the key factor leading to dementia. MicroRNA (miRNA) is closely related to the expression changes of many AD-related genes. One of the most abundant brain-enriched miRNAs is miR-132, which has been shown to regulate both neuron morphogenesis and plasticity. It has been reported that miR-132 is significantly reduced in the brains of Alzheimer’s patients. Genetic deletion of miR-132 in mice promotes Aβ deposition, leading to impaired memory and enhanced Tau pathology, but how the miRNA-mediated gene expression dysregulation contributes to AD pathology remains unclear. Here we found the possible downstream target of miR-132 by in silico analysis, namely C1q. C1q is the primary protein of classical complement cascade, which is highly expressed in the synaptic regions of the central nervous system in Alzheimer’s patients. However, it is not clear whether miR-132 plays a role in AD through regulating C1q. To address this question, the APP/PS1 transgenic mice were transfected with miR-132 and given C1 inhibitors. Behavior tests were conducted to assess memory and cognitive abilities seven days after administration. In addition, we analyzed the expression of PSD95, Synapsin-1 and phosphorylated (p)- Synapsin. We found that the expression levels of the synaptic proteins treated with miR-132 or C1INH were significantly increased compared with the AD group. Further RT-qPCR result suggested that miR-132 might regulate C1q expression in AD.

MicroRNA in Brain pathology: Neurodegeneration the Other Side of the Brain Cancer

The mammalian brain is made up of billions of neurons and supporting cells (glial cells), intricately connected. Molecular perturbations often lead to neurodegeneration by progressive loss of structure and malfunction of neurons, including their death. On the other side, a combination of genetic and cellular factors in glial cells, and less frequently in neurons, drive oncogenic transformation. In both situations, microenvironmental niches influence the progression of diseases and therapeutic responses. Dynamic changes that occur in cellular transcriptomes during the progression of developmental lineages and pathogenesis are controlled through a variety of regulatory networks. These include epigenetic modifications, signaling pathways, and transcriptional and post-transcriptional mechanisms. One prominent component of the latter is small non-coding RNAs, including microRNAs, that control the vast majority of these networks including genes regulating neural stemness, differentiation, apoptosis, projection fates, migration and many others. These cellular processes are also profoundly dependent on the microenvironment, stemness niche, hypoxic microenvironment, and interactions with associated cells including endothelial and immune cells. Significantly, the brain of all other mammalian organs expresses the highest number of microRNAs, with an additional gain in expression in the early stage of neurodegeneration and loss in expression in oncogenesis. However, a mechanistic explanation of the concept of an apparent inverse correlation between the odds of cancer and neurodegenerative diseases is only weakly developed. In this review, we thus will discuss widespread de-regulation of microRNAome observed in these two major groups of brain pathologies. The deciphering of these intricacies is of importance, as therapeutic restoration of pre-pathological microRNA landscape in neurodegeneration must not lead to oncogenesis and vice versa. We thus focus on microRNAs engaged in cellular processes that are inversely regulated in these diseases. We also aim to define the difference in microRNA networks between pro-survival and pro-apoptotic signaling in the brain.

Melatonin protects against Aβ-induced neurotoxicity in primary neurons via miR-132/PTEN/AKT/FOXO3a pathway

Alzheimer's disease (AD) is a kind of neurodegenerative disorder associated with age. Investigations suggest that amyliod-β (Aβ) is implicated in the pathogenesis of AD. The accumulation of Aβ in the brain causes oxidative stress and synaptic toxicity, leads to synaptic dysfunction and neuronal death. Previous investigations suggest that melatonin an endogenous hormone can counteract Aβ-induced neurotoxicity. However, the molecular mechanisms of Aβ-induced toxicity and melatonin treatment remain elusive. Studies indicate that microRNA-132 is crucial for neuronal survival and plays a key role in the pathological process of AD. Moreover, PTEN and FOXO3a two key targets of miR-132 are upregulated in the AD brain. Here, we exposed the primary cultured cortical neurons with Aβ25-35 and treated with melatonin. Our investigations demonstrated that Aβ25-35 exposure significantly decreased the expression of miR-132 and elevated the expression of PTEN and FOXO3a. Whereas, melatonin treatment could rescue the expression of miR-132 and downregulate the level of PTEN and FOXO3a. Moreover, melatonin blocked the nuclear translocation of FOXO3a and thereby suppressed its pro-apoptotic pathways. In addition, our investigations suggested that the over-expression of miR-132 could block Aβ-induced neurotoxicity. We also found that VO-OHpic (PTEN inhibitor) could counteract Aβ-induced neuronal damage, and LY294002 (AKT inhibitor) suppressed the protective effect of melatonin. Together, these results indicate that melatonin exerts its neuroprotective effect in Aβ-induced neurotoxicity via miR-132/PTEN/AKT/FOXO3a pathway. © 2018 BioFactors, 44(6):609-618, 2018.

Clustered miRNAs and their role in biological functions and diseases

MicroRNAs (miRNAs) are endogenous, small non-coding RNAs known to regulate expression of protein-coding genes. A large proportion of miRNAs are highly conserved, localized as clusters in the genome, transcribed together from physically adjacent miRNAs and show similar expression profiles. Since a single miRNA can target multiple genes and miRNA clusters contain multiple miRNAs, it is important to understand their regulation, effects and various biological functions. Like protein-coding genes, miRNA clusters are also regulated by genetic and epigenetic events. These clusters can potentially regulate every aspect of cellular function including growth, proliferation, differentiation, development, metabolism, infection, immunity, cell death, organellar biogenesis, messenger signalling, DNA repair and self-renewal, among others. Dysregulation of miRNA clusters leading to altered biological functions is key to the pathogenesis of many diseases including carcinogenesis. Here, we review recent advances in miRNA cluster research and discuss their regulation and biological functions in pathological conditions.

Deregulation of neuronal miRNAs induced by amyloid-β or TAU pathology

BACKGROUND

Despite diverging levels of amyloid-β (Aβ) and TAU pathology, different mouse models, as well as sporadic AD patients show predictable patterns of episodic memory loss. MicroRNA (miRNA) deregulation is well established in AD brain but it is unclear whether Aβ or TAU pathology drives those alterations and whether miRNA changes contribute to cognitive decline.

METHODS

miRNAseq was performed on cognitively intact (4 months) and impaired (10 months) male APPtg (APPswe/PS1L166P) and TAUtg (THY-Tau22) mice and their wild-type littermates (APPwt and TAUwt). We analyzed the hippocampi of 12 mice per experimental group (n = 96 in total), and employed a 2-way linear model to extract differentially expressed miRNAs. Results were confirmed by qPCR in a separate cohort of 4 M and 10 M APPtg and APPwt mice (n = 7-9 per group) and in human sporadic AD and non-demented control brain. Fluorescent in situ hybridization identified their cellular expression. Functional annotation of predicted targets was performed using GO enrichment. Behavior of wild-type mice was assessed after intracerebroventricular infusion of miRNA mimics.

RESULTS

Six miRNAs (miR-10a-5p, miR-142a-5p, miR-146a-5p, miR-155-5p, miR-211-5p, miR-455-5p) are commonly upregulated between APPtg and TAUtg mice, and four of these (miR-142a-5p, miR-146a-5p, miR-155-5p and miR-455-5p) are altered in AD patients. All 6 miRNAs are strongly enriched in neurons. Upregulating these miRNAs in wild-type mice is however not causing AD-related cognitive disturbances.

CONCLUSION

Diverging AD-related neuropathologies induce common disturbances in the expression of neuronal miRNAs. 4 of these miRNAs are also upregulated in AD patients. Therefore these 4 miRNAs (miR-142a-5p, miR-146a-5p, miR-155-5p and miR-455-5p) appear part of a core pathological process in AD patients and APPtg and TAUtg mice. They are however not causing cognitive disturbances in wild-type mice. As some of these miRNA target AD relevant proteins, they may be, in contrast, part of a protective response in AD.

MicroRNA-132 provides neuroprotection for tauopathies via multiple signaling pathways

MicroRNAs (miRNA) regulate fundamental biological processes, including neuronal plasticity, stress response, and survival. Here, we describe a neuroprotective function of miR-132, the miRNA most significantly downregulated in neurons in Alzheimer's disease. We demonstrate that miR-132 protects primary mouse and human wild-type neurons and more vulnerable Tau-mutant neurons against amyloid β-peptide (Aβ) and glutamate excitotoxicity. It lowers the levels of total, phosphorylated, acetylated, and cleaved forms of Tau implicated in tauopathies, promotes neurite elongation and branching, and reduces neuronal death. Similarly, miR-132 attenuates PHF-Tau pathology and neurodegeneration, and enhances long-term potentiation in the P301S Tau transgenic mice. The neuroprotective effects are mediated by direct regulation of the Tau modifiers acetyltransferase EP300, kinase GSK3β, RNA-binding protein Rbfox1, and proteases Calpain 2 and Caspases 3/7. These data suggest miR-132 as a master regulator of neuronal health and indicate that miR-132 supplementation could be of therapeutic benefit for the treatment of Tau-associated neurodegenerative disorders.

Presymptomatic change in microRNAs modulates Tau pathology

MicroRNAs (miRs) are 18~23 nucleotides long non-coding RNAs that regulate gene expression. To explore whether miR alterations in tauopathy contribute to pathological conditions, we first determined which hippocampal miRs are altered at the presymptomatic and symptomatic stages of tauopathy using rTg4510 mice (Tau mice), a well-characterized tauopathy model. miR-RNA pairing analysis using QIAGEN Ingenuity Pathway Analysis (IPA) revealed 401 genes that can be regulated by 71 miRs altered in Tau hippocampi at the presymptomatic stage. Among several miRs confirmed with real-time qPCR, miR142 (−3p and −5p) in Tau hippocampi were significantly upregulated by two-weeks of age and onward. Transcriptome studies by RNAseq and IPA revealed several overlapping biological and disease associated pathways affected by either Tau or miR142 overexpression, including Signal Transducer and Activator of Transcription 3 (Stat3) and Tumor Necrosis Factor Receptor 2 (Tnfr2) signaling pathways. Similar to what was observed in Tau brains, overexpressing miR142 in wildtype cortical neurons augments mRNA levels of Glial Fibrillary Acidic Protein (Gfap) and Colony Stimulating Factor 1 (Csf1), accompanied by a significant increase in microglia and reactive astrocyte numbers. Taken together, our study suggests that miR alterations by Tau overexpression may contribute to the neuroinflammation observed in Tau brains.

SIRT1, miR-132 and miR-212 link human longevity to Alzheimer's Disease

Alzheimer's Disease (AD) is the most common cause of dementia in the elderly. Centenarians - reaching the age of >100 years while maintaining good cognitive skills - seemingly have unique biological features allowing healthy aging and protection from dementia. Here, we studied the expression of SIRT1 along with miR-132 and miR-212, two microRNAs known to regulate SIRT1, in lymphoblastoid cell lines (LCLs) from 45 healthy donors aged 21 to 105 years and 24 AD patients, and in postmortem olfactory bulb and hippocampus tissues from 14 AD patients and 20 age-matched non-demented individuals. We observed 4.0-fold (P = 0.001) lower expression of SIRT1, and correspondingly higher expression of miR-132 (1.7-fold; P = 0.014) and miR-212 (2.1-fold; P = 0.036), in LCLs from AD patients compared with age-matched healthy controls. Additionally, SIRT1 expression was 2.2-fold (P = 0.001) higher in centenarian LCLs compared with LCLs from individuals aged 56-82 years; while centenarian LCLs miR-132 and miR-212 indicated 7.6-fold and 4.1-fold lower expression, respectively. Correlations of SIRT1, miR-132 and miR-212 expression with cognitive scores were observed for AD patient-derived LCLs and postmortem AD olfactory bulb and hippocampus tissues, suggesting that higher SIRT1 expression, possibly mediated by lower miR-132 and miR-212, may protect aged individuals from dementia and is reflected in their peripheral tissues.

Circulating microRNAs disclose biology of normal cognitive function in healthy elderly people - a discovery twin study

Neurobiology is regulated by miRNA. Here circulating plasma miRNAs were assayed on a 754 miRNA OpenArray platform using 90 monozygotic elderly twins (73-95 year of age) and associated with mini mental state examination (MMSE) and a five-component cognitive score (CCS) in an explorative study. Both ordinary individual and twin-pair analyses were performed with level of cognitive scores. Candidate miRNAs were further associated with cognitive decline over 10 years using up to six repeated assessments. A total of 278 miRNAs were expressed in plasma from at least ten participants and 23 miRNAs were nominally associated (i.e., at an uncorrected p < 0.05) with CCS or MMSE in the paired analyses. Generally, elderly individuals with poor cognitive function had increase miRNA expression compared with equivalent individuals who performed better on the cognitive scale. Three miRNAs, miR-151a-3p, miR-212-3p and miR-1274b were associated with CCS both in the paired and the individual analysis. Four miRNAs found to be associated with CCS in cross-sectional analysis were also found to show an association in longitudinal analysis such that increase miRNA expression was associated with steeper cognitive decline. We propose a shared biological path underlies dementia and normative cognitive aging.

Whole transcriptome profiling of Late-Onset Alzheimer's Disease patients provides insights into the molecular changes involved in the disease

Alzheimer’s Disease (AD) is the most common cause of dementia affecting the elderly population worldwide. We have performed a comprehensive transcriptome profiling of Late-Onset AD (LOAD) patients using second generation sequencing technologies, identifying 2,064 genes, 47 lncRNAs and 4 miRNAs whose expression is specifically deregulated in the hippocampal region of LOAD patients. Moreover, analyzing the hippocampal, temporal and frontal regions from the same LOAD patients, we identify specific sets of deregulated miRNAs for each region, and we confirm that the miR-132/212 cluster is deregulated in each of these regions in LOAD patients, consistent with these miRNAs playing a role in AD pathogenesis. Notably, a luciferase assay indicates that miR-184 is able to target the 3’UTR NR4A2 - which is known to be involved in cognitive functions and long-term memory and whose expression levels are inversely correlated with those of miR-184 in the hippocampus. Finally, RNA editing analysis  reveals a general RNA editing decrease in LOAD hippocampus, with 14 recoding sites significantly and differentially edited in 11 genes. Our data underline specific transcriptional changes in LOAD brain and provide an important source of information for understanding the molecular changes characterizing LOAD progression.

microRNAs in Neurodegeneration: Current Findings and Potential Impacts

Significant advancements have been made in unraveling and understanding the non-coding elements of the human genome. New insights into the structure and function of noncoding RNAs have emerged. Their relevance in the context of both physiological cellular homeostasis and human diseases is getting appreciated. As a result, exploration of noncoding RNAs, in particular microRNAs (miRs), as therapeutic agents or targets of therapeutic strategies is under way. This review summarizes and discusses in depth the current literature on the role of miRs in neurodegenerative diseases.

miR-212 mediates counter-regulation on CRH expression and HPA axis activity in male mice

The mechanisms of hypothalamic-pituitary-adrenal (HPA) axis regulation have been studied persistently but still are not elucidated. Considering the emerging roles of microRNA in stress response, we conducted a microRNA microarray in mice hypothalamus to identify the potential role of microRNAs in regulating the HPA axis. In total, 41 microRNAs changed during heat stress in which we found that miR-212 contains a binding sequence with corticotropin-releasing hormone (Crh) 3'UTR according to a sequence analysis. We observed that miR-212 expression in the hypothalamus was escalated by repeated heat and restraint stress. By overexpression or inhibition of miR-212 and the dual-luciferase reporter assay, we proved that miR-212 could bind with Crh 3'UTR to regulate its expression in mice hypothalamus primary cells and in the hippocampus neuron cell line HT-22. In addition, we injected miR-212 agomir or antagomir in mice hypothalamus to overexpress or inhibit miR-212, which leads to alterations of CRH expression and HPA axis activity in vivo Furthermore, miR-212 and CRH were both transcribed by the cAMP response element-binding protein (CREB). Overexpression and inhibition of miR-212 affect CREB-dependent CRH expression. Taken together, our results suggest an inhibitory role of miR-212 on the HPA axis, which acts in a counter-regulatory manner.

NF-κB-regulated microRNA-574-5p underlies synaptic and cognitive impairment in response to atmospheric PM2.5 aspiration

Background

PM_2.5 (particulate matter ≤ 2.5 μm) is one of the leading environmental risk factors for the global burden of disease. Whereas increasing evidence has linked the adverse roles of PM_2.5 with cardiovascular and respiratory diseases, limited but growing emerging evidence suggests that PM_2.5 exposure can affect the nervous system, causing neuroinflammation, synaptic dysfunction and cognitive deterioration. However, the molecular mechanisms underlying the synaptic and cognitive deficits elicited by PM_2.5 exposure are largely unknown.

Methods

C57BL/6 mice received oropharyngeal aspiration of PM_2.5 (1 and 5 mg/kg bw) every other day for 4 weeks. The mice were also stereotaxically injected with β-site amyloid precursor protein cleaving enzyme 1 (β-secretase, BACE1) shRNA or LV-miR-574-5p lentiviral constructs in the absence or presence of PM_2.5 aspiration at 5 mg/kg bw every other day for 4 weeks. Spatial learning and memory were assessed with the Morris water maze test, and synaptic function integrity was evaluated with electrophysiological recordings of long-term potentiation (LTP) and immunoblot analyses of glutamate receptor subunit expression. The expression of α-secretase (ADAM10), BACE1, and γ-secretase (nicastrin) and the synthesis and accumulation of amyloid β (Aβ) were measured by immunoblot and enzyme-linked immunosorbent assay (ELISA). MicroRNA (miRNA) expression was screened with a microRNA microarray analysis and confirmed by real-time quantitative reverse transcription PCR (qRT-PCR) analysis. Dual-luciferase reporter gene and chromatin immunoprecipitation (ChIP) analyses were used to detect the binding of miR-574-5p in the 3’UTR of BACE1 and NF-κB p65 in the promoter of miR-574-5p, respectively.

Results

PM_2.5 aspiration caused neuroinflammation and deteriorated synaptic function integrity and spatial learning and memory, and the effects were associated with the induction of BACE1. The action was mediated by NF-κB p65-regulated downregulation of miR-574-5p, which targets BACE1. Overexpression of miR-574-5p in the hippocampal region decreased BACE1 expression, restored synaptic function, and improved spatial memory and learning following PM_2.5 exposure.

Conclusions

Taken together, our findings reveal a novel molecular mechanism underlying impaired synaptic and cognitive function following exposure to PM_2.5, suggesting that miR-574-5p is a potential intervention target for the prevention and treatment of PM_2.5-induced neurological disorders.

Electronic supplementary material

The online version of this article (10.1186/s12989-017-0215-3) contains supplementary material, which is available to authorized users.

Mir-132/212 is required for maturation of binocular matching of orientation preference and depth perception

MicroRNAs (miRNAs) are known to mediate post-transcriptional gene regulation, but their role in postnatal brain development is still poorly explored. We show that the expression of many miRNAs is dramatically regulated during functional maturation of the mouse visual cortex with miR-132/212 family being one of the top upregulated miRNAs. Age-downregulated transcripts are significantly enriched in miR-132/miR-212 putative targets and in genes upregulated in miR-132/212 null mice. At a functional level, miR-132/212 deletion affects development of receptive fields of cortical neurons determining a specific impairment of binocular matching of orientation preference, but leaving orientation and direction selectivity unaltered. This deficit is associated with reduced depth perception in the visual cliff test. Deletion of miR-132/212 from forebrain excitatory neurons replicates the binocular matching deficits. Thus, miR-132/212 family shapes the age-dependent transcriptome of the visual cortex during a specific developmental window resulting in maturation of binocular cortical cells and depth perception.

Linking deregulation of non-coding RNA to the core pathophysiology of Alzheimer's disease: An integrative review

The human genome encodes a vast repertoire of protein non-coding RNAs (ncRNA), some specific to the brain. MicroRNAs, which interfere with the translation of target mRNAs, are of particular interest since their deregulation has been implicated in neurodegenerative disorders like Alzheimer's disease (AD). However, it remains challenging to link the complex body of observations on miRNAs and AD into a coherent framework. Using extensive graphical support, this article discusses how a diverse panoply of miRNAs convergently and divergently impact (and are impacted by) core pathophysiological processes underlying AD: neuroinflammation and oxidative stress; aberrant generation of β-amyloid-42 (Aβ42); anomalies in the production, cleavage and post-translational marking of Tau; impaired clearance of Aβ42 and Tau; perturbation of axonal organisation; disruption of synaptic plasticity; endoplasmic reticulum stress and the unfolded protein response; mitochondrial dysfunction; aberrant induction of cell cycle re-entry; and apoptotic loss of neurons. Intriguingly, some classes of miRNA provoke these cellular anomalies, whereas others act in a counter-regulatory, protective mode. Moreover, changes in levels of certain species of miRNA are a consequence of the above-mentioned anomalies. In addition to miRNAs, circular RNAs, piRNAs, long non-coding RNAs and other types of ncRNA are being increasingly implicated in AD. Overall, a complex mesh of deregulated and multi-tasking ncRNAs reciprocally interacts with core pathophysiological mechanisms underlying AD. Alterations in ncRNAs can be detected in CSF and the circulation as well as the brain and are showing promise as biomarkers, with the ultimate goal clinical exploitation as targets for novel modes of symptomatic and course-altering therapy.