Different microRNA profiles in chronic epilepsy versus acute seizure mouse models

miR-30a-5p mediates ferroptosis of hippocampal neurons in chronic cerebral hypoperfusion-induced cognitive dysfunction by modulating the SIRT1/NRF2 pathway

OBJECTIVE

Chronic cerebral hypoperfusion (CCH) is a common cause of brain dysfunction. As a microRNA (also known as miRNAs or miRs), miR-30a-5p participates in neuronal damage and relates to ferroptosis. We explored the in vivo and in vitro effects and functional mechanism of miR-30a-5p in CCH-triggered cognitive impairment through the silent information regulator 1 (SIRT1)/nuclear factor erythroid 2-related factor 2 (NRF2) pathway.

METHODS

After 1 month of CCH modeling through bilateral common carotid artery stenosis, mice were injected with 2 μL antagomir (also known as anti-miRNAs) miR-30a-5p, with cognitive function evaluated by Morris water maze and novel object recognition tests. In vitro HT-22 cell oxygen glucose deprivation (OGD) model was established, followed by miR-30a-5p inhibitor and/or si-SIRT1 transfections, with Fe2+ concentration, malonaldehyde (MDA) and glutathione (GSH) contents, reactive oxygen species (ROS), miR-30a-5p and SIRT1 and glutathione peroxidase 4 (GPX4) protein levels, NRF2 nuclear translocation, and miR-30a-5p-SIRT1 targeting relationship assessed.

RESULTS

CCH-induced mice showed obvious cognitive impairment, up-regulated miR-30a-5p, and down-regulated SIRT1. Ferroptosis occurred in hippocampal neurons, manifested by elevated Fe2+ concentration and ROS and MDA levels, mitochondrial atrophy, and diminished GSH content. Antagomir miR-30a-5p or miR-30a-5p inhibitor promoted SIRT1 expression and NRF2 nuclear translocation, increased GPX4, cell viability and GSH content, and reduced Fe2+ concentration and ROS and MDA levels. miR-30a-5p negatively regulated SIRT1. In vitro, miR-30a-5p knockout increased NRF2 nuclear translocation by up-regulating SIRT1, inhibiting OGD-induced ferroptosis in HT-22 cells.

CONCLUSION

miR-30a-5p induces hippocampal neuronal ferroptosis and exacerbates post-CCH cognitive dysfunction by targeting SIRT1 and reducing NRF2 nuclear translocation.

The dysregulation of miRNAs in epilepsy and their regulatory role in inflammation and apoptosis

Epilepsy is a neurological disorder that impacts millions of people worldwide, and it is characterized by the occurrence of recurrent seizures. The pathogenesis of epilepsy is complex, involving dysregulation of various genes and signaling pathways. MicroRNAs (miRNAs) are a group of small non-coding RNAs that play a vital role in the regulation of gene expression. They have been found to be involved in the pathogenesis of epilepsy, acting as key regulators of neuronal excitability and synaptic plasticity. In recent years, there has been a growing interest in exploring the miRNA regulatory network in epilepsy. This review summarizes the current knowledge of the regulatory miRNAs involved in inflammation and apoptosis in epilepsy and discusses its potential as a new avenue for developing targeted therapies for the treatment of epilepsy.

The ribose methylation enzyme FTSJ1 has a conserved role in neuron morphology and learning performance

FTSJ1 is a conserved human 2'-O-methyltransferase (Nm-MTase) that modifies several tRNAs at position 32 and the wobble position 34 in the anticodon loop. Its loss of function has been linked to X-linked intellectual disability (XLID), and more recently to cancers. However, the molecular mechanisms underlying these pathologies are currently unclear. Here, we report a novel FTSJ1 pathogenic variant from an X-linked intellectual disability patient. Using blood cells derived from this patient and other affected individuals carrying FTSJ1 mutations, we performed an unbiased and comprehensive RiboMethSeq analysis to map the ribose methylation on all human tRNAs and identify novel targets. In addition, we performed a transcriptome analysis in these cells and found that several genes previously associated with intellectual disability and cancers were deregulated. We also found changes in the miRNA population that suggest potential cross-regulation of some miRNAs with these key mRNA targets. Finally, we show that differentiation of FTSJ1-depleted human neural progenitor cells into neurons displays long and thin spine neurites compared with control cells. These defects are also observed in Drosophila and are associated with long-term memory deficits. Altogether, our study adds insight into FTSJ1 pathologies in humans and flies by the identification of novel FTSJ1 targets and the defect in neuron morphology.

Detection of Deregulated miRNAs in Childhood Epileptic Encephalopathies

The term "epileptic encephalopathy" is used to describe a possible relationship between epilepsy and developmental delay. The pathogenesis of developmental encephalopathies, independent of epilepsy, can be defined by genetic control mechanisms. The aim of this study was to investigate the use of miRNAs as serum biomarkers for the determination and discrimination of epileptic encephalopathies. Whole blood samples obtained from 54 individuals in 2 groups designated as epileptic encephalopathy patients' group (n = 24) and healthy controls (n = 30) were included in this study. The expression levels of 10 miRNAs were determined using qRT-PCR. After the determination of expression levels, the correlation of upregulated miRNA levels and Ki67 index was calculated using Pearson correlation test. The comparison of epileptic encephalopathy patients' group with healthy controls revealed the upregulation of one miRNAs (hsa-miR-324-5p) and downregulation of three miRNAs (hsa-miR-146a-5p, hsa-miR-138-5p, hsa-miR-187-3p). It has been determined that miRNAs with altered expression are an important factor in the formation of epileptic seizures and seizure-induced neuronal death. The fact that processes that play a key role in epiloptogenesis are under the control of miRNAs causes miRNAs to become meta-controllers of gene expression in the brain. We thought that further studies are needed to prove that especially hsa-miR-146a-5p, hsa-miR-138-5p, and hsa-miR-187-3p can be used as epileptic encephalopathy biomarkers. The detection of disease-specific miRNAs could contribute to the development of precision treatments.

Early Induction of Neurotrophin Receptor and miRNA Genes in Mouse Brain after Pentilenetetrazole-Induced Neuronal Activity

Neurotrophin receptors regulate neuronal survival and network formation, as well as synaptic plasticity in the brain via interaction with their ligands. Here, we examined early changes in the expression of neurotrophin receptor genes Ntk1 (TrkA), Ntrk2 (TrkB), Ntrk3 (TrkC), Ngfr (p75NTR) and miRNAs that target theses gens in the mouse brain after induction of seizure activity by pentylenetetrazol. We found that expression of Ntrk3 and Ngfr was upregulated in the cortex and the hippocampus 1-3 hours after the seizures, while Ntrk2 expression increased after 3-6 hours in the anterior cortex and after 1 and 6 hours in the hippocampus. At the same time, the ratio of Bcl-2/Bax signaling proteins increased in the anterior and posterior cortex, but not in the hippocampus, suggesting the activation of anti-apoptotic signaling. Expression of miRNA-9 and miRNA-29a, which were predicted to target Ntrk3, was upregulated in the hippocampus 3 hours after pentylenetetrazol injection. Therefore, early cellular response to seizures in the brain includes induction of the Ntrk2, Ntrk3, Ngfr, miRNA-9, and miRNA-29a expression, as well as activation of Bcl-2 and Bax signaling pathways, which may characterize them as important mediators of neuronal adaptation and survival upon induction of the generalized brain activity.

MiR-499a prevents astrocytes mediated inflammation in ischemic stroke by targeting PTEN

INTRODUCTION

Ischemic stroke (IS) is a common and severe neurological disorder and is associated with high rates of mortality and morbidity. Inflammatory reaction in astrocytes is one of the important pathological factors of stroke. Improved understanding of the underlying molecular mechanisms should aid better treatment of the disease. This study aimed to test our hypothesis that a miR-499a played an important role in the inflammatory response in astrocytes induced by IS targeting phosphatase and tensin homologue deleted on chromosome 10 (PTEN).

METHODS

This study was comprised of two models: oxygen-glucose deprivation (OGD) and reoxygenation model. Quantitative real-time PCR (qRT-PCR) and Western blot were used to examine gene expression levels, and MTT assay analysis were used to examine cell states. The relationships between miR-499a and PTEN were confirmed by luciferase reporter assay.

RESULTS

MiR-499a was robustly downregulated with OGD induced injury in astrocytes. Forced transient expression of miR-499a in OGD astrocytes nearly completely reversed the inflammatory response. Knockdown of miR-499a by its specific inhibitor in healthy astrocytes induced the inflammatory response resembling those produced by OGD. On the other hand, PTEN was markedly upregulated in OGD astrocytes, which was reciprocal to the expression of miR-499a. PTEN was experimentally validated as a direct target gene for miR-499a. Overexpression of PTEN was able to induce an inflammatory response of astrocytes. Moreover, PTEN siRNA counteracted the inflammatory response induced by OGD.

CONCLUSIONS

Taken together, our findings indicate miR-499a as an important factor to prevent inflammatory response and suggest miR-499a as a new molecule for the treatment of IS. The present study also demonstrated the relationship between miR-499a and PTEN, with PTEN as a downstream signaling mediator of miR-499a in the inflammatory response of astrocytes induced by IS.

miR-323a regulates ERBB4 and is involved in depression

Major depressive disorder (MDD) is a complex and debilitating illness whose etiology remains unclear. Small RNA molecules, such as micro RNAs (miRNAs) have been implicated in MDD, where they display differential expression in the brain and the periphery. In this study, we quantified miRNA expression by small RNA sequencing in the anterior cingulate cortex and habenula of individuals with MDD and psychiatrically-healthy controls. Thirty-two miRNAs showed significantly correlated expression between the two regions (False Discovery Rate < 0.05), of which four, miR-204-5p, miR-320b, miR-323a-3p, and miR-331-3p, displayed upregulated expression in MDD. We assessed the expression of predicted target genes of differentially expressed miRNAs in the brain, and found that the expression of erb-b2 receptor tyrosine kinase 4 (ERBB4), a gene encoding a neuregulin receptor, was downregulated in both regions, and was influenced by miR-323a-3p in vitro. Finally, we assessed the effects of manipulating miRNA expression in the mouse ACC on anxiety- and depressive-like behaviors. Mice in which miR-323-3p was overexpressed or knocked-down displayed increased and decreased emotionality, respectively. Additionally, these mice displayed significantly downregulated and upregulated expression of Erbb4, respectively. Overall, our findings indicate the importance of brain miRNAs in the pathology of MDD, and emphasize the involvement of miR-323a-3p and ERBB4 in this phenotype. Future studies further characterizing miR-323a-3p and neuregulin signaling in depression are warranted.

Decreased expression of the clock gene Bmal1 is involved in the pathogenesis of temporal lobe epilepsy

Clock genes not only regulate the circadian rhythm of physiological activities but also participate in the pathogenesis of many diseases. Previous studies have documented the abnormal expression of clock genes in epilepsy. However, the molecular mechanism of brain and muscle Arnt-like protein 1 (Bmal1), one of the core clock genes, in the epileptogenesis and seizures of temporal lobe epilepsy (TLE) remain unclear. We first investigated the levels of Bmal1 and other clock proteins in the hippocampus of subjects with epilepsy to define the function of Bmal1. The levels of Bmal1 were decreased during the latent and chronic phases in the experimental group compared with those in the control group. Knockout of Bmal1 in hippocampal dentate gyrus (DG) neurons of Bmal1flox/flox mice by Synapsin 1 (Syn1) promoter AAV (adeno-associated virus) lowered the threshold of seizures induced by pilocarpine administration. High-throughput sequencing analysis showed that PCDH19 (protocadherin 19), a gene associated with epilepsy, was regulated by Bmal1. PCDH19 expression was also decreased in the hippocampus of epileptic mice. Furthermore, the higher levels of Bmal1 and PCDH19 were detected in patients with no hippocampal sclerosis (no HS) than in patients with HS International League Against Epilepsy (ILAE) type I and III. Altogether, these data suggest that decreased expression of clock gene Bmal1 may participate in epileptogenesis and seizures via PCDH19 in TLE.

MicroRNA-210 Regulates Dendritic Morphology and Behavioural Flexibility in Mice

MicroRNAs are known to be critical regulators of neuronal plasticity. The highly conserved, hypoxia-regulated microRNA-210 (miR-210) has been shown to be associated with long-term memory in invertebrates and dysregulated in neurodevelopmental and neurodegenerative disease models. However, the role of miR-210 in mammalian neuronal function and cognitive behaviour remains unexplored. Here we generated Nestin-cre-driven miR-210 neuronal knockout mice to characterise miR-210 regulation and function using in vitro and in vivo methods. We identified miR-210 localisation throughout neuronal somas and dendritic processes and increased levels of mature miR-210 in response to neural activity in vitro. Loss of miR-210 in neurons resulted in higher oxidative phosphorylation and ROS production following hypoxia and increased dendritic arbour density in hippocampal cultures. Additionally, miR-210 knockout mice displayed altered behavioural flexibility in rodent touchscreen tests, particularly during early reversal learning suggesting processes underlying updating of information and feedback were impacted. Our findings support a conserved, activity-dependent role for miR-210 in neuroplasticity and cognitive function.

Circulating microRNA: The Potential Novel Diagnostic Biomarkers to Predict Drug Resistance in Temporal Lobe Epilepsy, a Pilot Study

MicroRNAs (miRNAs) are small noncoding RNAs that have emerged as new potential epigenetic biomarkers. Here, we evaluate the efficacy of six circulating miRNA previously described in the literature as biomarkers for the diagnosis of temporal lobe epilepsy (TLE) and/or as predictive biomarkers to antiepileptic drug response. We measured the differences in serum miRNA levels by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) assays in a cohort of 27 patients (14 women and 13 men; mean ± SD age: 43.65 ± 17.07) with TLE compared to 20 healthy controls (HC) matched for sex, age and ethnicity (11 women and 9 men; mean ± SD age: 47.5 ± 9.1). Additionally, patients were classified according to whether they had drug-responsive (n = 17) or drug-resistant (n = 10) TLE. We have investigated any correlations between miRNAs and several electroclinical parameters. Three miRNAs (miR-142, miR-146a, miR-223) were significantly upregulated in patients (expressed as average expression ± SD). In detail, miR-142 expression was 0.40 ± 0.29 vs. 0.16 ± 0.10 in TLE patients compared to HC (t-test, p < 0.01), miR-146a expression was 0.15 ± 0.11 vs. 0.07 ± 0.04 (t-test, p < 0.05), and miR-223 expression was 6.21 ± 3.65 vs. 1.23 ± 0.84 (t-test, p < 0.001). Moreover, results obtained from a logistic regression model showed the good performance of miR-142 and miR-223 in distinguishing drug-sensitive vs. drug-resistant TLE. The results of this pilot study give evidence that miRNAs are suitable targets in TLE and offer the rationale for further confirmation studies in larger epilepsy cohorts.

Identification of hsa-miR-1275 as a Novel Biomarker Targeting MECP2 for Human Epilepsy of Unknown Etiology

Epilepsy affects around 70 million people worldwide, with a 65% rate of unknown etiology. This rate is known as epilepsy of unknown etiology (EUE). Dysregulation of microRNAs (miRNAs) is recognized to contribute to mental disorders, including epilepsy. However, miRNA dysregulation is poorly understood in EUE. Here, we conducted miRNA expression profiling of EUE by microarray technology and identified 57 pathogenic changed miRNAs with significance. The data and bioinformatic analysis results indicated that among these miRNAs, hsa-microRNA (miR)-1275 was highly associated with neurological disorders. Subsequently, new samples of serum and cerebrospinal fluid were collected for validation of hsa-miR-1275 expression by TaqMan assays. Results show that hsa-miR-1275 in serums of EUE were increased significantly, but in cerebrospinal fluid, the miRNA was decreased. Moreover, the MECP2 gene was selected as a hsa-miR-1275 target based on target prediction tools and gene ontology analysis. Validation of in vitro tests proved that MECP2 expression was specifically inhibited by hsa-miR-1275. Additionally, overexpression of hsa-miR-1275 can elevate expression of nuclear factor κB (NF-κB) and promote cell apoptosis. Taken together, hsa-miR-1275 might represent a novel biomarker targeting MECP2 for human EUE.

MicroRNAs as Immune Regulators of Inflammation in Children with Epilepsy

Epilepsy is a chronic clinical syndrome of brain function which is caused by abnormal discharge of neurons. MicroRNAs (miRNAs) are small non-coding RNAs which act post-transcriptionally to regulate negatively protein levels. They affect neuroinflammatory signaling, glial and neuronal structure and function, neurogenesis, cell death, and other processes linked to epileptogenesis. The aim of this study was to explore the possible role of miR-125a and miR-181a as regulators of inflammation in epilepsy through investigating their involvement in the pathogenesis of epilepsy, and their correlation with the levels of inflammatory cytokines. Thirthy pediatric patients with epilepsy and 20 healthy controls matched for age and sex were involved in the study. MiR-181a and miR-125a expression were evaluated in plasma of all subjects using qRT-PCR. In addition, plasma levels of inflammatory cytokines (IFN-γ and TNF-) were determined using ELISA. Our findings indicated significantly lower expression levels of miR-125a (P=0.001) and miR-181a (P=0.001) in epileptic patients in comparison with controls. In addition, the production of IFN-γ and TNF- was non-significantly higher in patients with epilepsy in comparison with the control group. Furthermore, there were no correlations between miR-125a and miR-181a with the inflammatory cytokines (IFN-γ and TNF-) in epileptic patients. MiR-125a and miR-181a could be involved in the pathogenesis of epilepsy and could serve as diagnostic biomarkers for pediatric patients with epilepsy.

Epilepsy miRNA Profile Depends on the Age of Onset in Humans and Rats

Temporal lobe epilepsy (TLE) is a severe neurological disorder accompanied by recurrent spontaneous seizures. Although the knowledge of TLE onset is still incomplete, TLE pathogenesis most likely involves the aberrant expression of microRNAs (miRNAs). miRNAs play an essential role in organism homeostasis and are widely studied in TLE as potential therapeutics and biomarkers. However, many discrepancies in discovered miRNAs occur among TLE studies due to model-specific miRNA expression, different onset ages of epilepsy among patients, or technology-related bias. We employed a massive parallel sequencing approach to analyze brain tissues from 16 adult mesial TLE (mTLE)/hippocampal sclerosis (HS) patients, 8 controls and 20 rats with TLE-like syndrome, and 20 controls using the same workflow and categorized these subjects based on the age of epilepsy onset. All categories were compared to discover overlapping miRNAs with an aberrant expression, which could be involved in TLE. Our cross-comparative analyses showed distinct miRNA profiles across the age of epilepsy onset and found that the miRNA profile in rats with adult-onset TLE shows the closest resemblance to the profile in mTLE/HS patients. Additionally, this analysis revealed overlapping miRNAs between patients and the rat model, which should participate in epileptogenesis and ictogenesis. Among the overlapping miRNAs stand out miR-142-5p and miR-142-3p, which regulate immunomodulatory agents with pro-convulsive effects and suppress neuronal growth. Our cross-comparison study enhanced the insight into the effect of the age of epilepsy onset on miRNA expression and deepened the knowledge of epileptogenesis. We employed the same methodological workflow in both patients and the rat model, thus improving the reliability and accuracy of our results.

[Differential expression of miR-30a-5p in post stroke depression and bioinformatics analysis of the possible mechanism]

OBJECTIVE

To investigate the differential expression of miR-30a-5p in patients with poststroke depression and explore the possible mechanism.

METHODS

We obtained the target microRNAs through searching PubMed using the online software VENNY2.1. We collected the baseline demographic, clinical and radiographic data from consecutive patients with first-ever acute ischemic stroke on admission in our department from October, 2018 to March, 2019. From each patient, 5 mL peripheral venous blood was collected upon admission. Hamilton Depression Scale (HAMD-17) was used to evaluate the degree of depression at the end of the 3-month follow-up. The patients with a HAMD-17 score≥7 were diagnosed to have depression according to the diagnostic criteria of the Fourth Edition of the Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association (DSM-IV). The patients were divided into post-stroke depression group (PSD group, n=11) and non-post-stroke depression group (non-PSD group, n=25), and their plasma levels of miR-30a-5p were detected using qPCR. The STARBASE Database ENCORI miRNA-mRNA module and Comparative Toxicogenomics Database were used to predict and screen the possible target genes related to miR-30a-5p, and the possible mechanism of the target genes was further analyzed through bioinformatics.

RESULTS

miR-30a-5p was identified by cross-screening as the target miRNA associated with stroke and depression and showed obvious differential expression between PSD and non-PSD patients (2.462±0.326 vs 1±0.126, P &lt; 0.0001). ROC curve analysis showed that the AUC of miR-30a-5p for predicting PSD was 0.869 (95%CI: 0.745-0.993, P=0.0005) at the cutoff value of 1.597, with a sensitivity and specificity of 0.727 and 0.840, respectively. The target proteins of miR-30a-5p involved a wide range of biological processes, including signal transduction, intercellular communication, regulation of nucleobase, nucleoside, nucleotide and nucleic acid metabolism. KEGG pathway enrichment analysis showed that the target proteins affected mainly the neural nutrient signaling pathway, axon guidance signaling pathway and insulin signaling system. We also identified the top 20 HUB genes that might be associated with post-stroke depression.

CONCLUSIONS

Plasma miR-30a-5p is differentially expressed in PSD and can serve as a new blood marker for diagnosis and also a therapeutic target of PSD.

A systems approach delivers a functional microRNA catalog and expanded targets for seizure suppression in temporal lobe epilepsy

Temporal lobe epilepsy is the most common drug-resistant form of epilepsy in adults. The reorganization of neural networks and the gene expression landscape underlying pathophysiologic network behavior in brain structures such as the hippocampus has been suggested to be controlled, in part, by microRNAs. To systematically assess their significance, we sequenced Argonaute-loaded microRNAs to define functionally engaged microRNAs in the hippocampus of three different animal models in two species and at six time points between the initial precipitating insult through to the establishment of chronic epilepsy. We then selected commonly up-regulated microRNAs for a functional in vivo therapeutic screen using oligonucleotide inhibitors. Argonaute sequencing generated 1.44 billion small RNA reads of which up to 82% were microRNAs, with over 400 unique microRNAs detected per model. Approximately half of the detected microRNAs were dysregulated in each epilepsy model. We prioritized commonly up-regulated microRNAs that were fully conserved in humans and designed custom antisense oligonucleotides for these candidate targets. Antiseizure phenotypes were observed upon knockdown of miR-10a-5p, miR-21a-5p, and miR-142a-5p and electrophysiological analyses indicated broad safety of this approach. Combined inhibition of these three microRNAs reduced spontaneous seizures in epileptic mice. Proteomic data, RNA sequencing, and pathway analysis on predicted and validated targets of these microRNAs implicated derepressed TGF-β signaling as a shared seizure-modifying mechanism. Correspondingly, inhibition of TGF-β signaling occluded the antiseizure effects of the antagomirs. Together, these results identify shared, dysregulated, and functionally active microRNAs during the pathogenesis of epilepsy which represent therapeutic antiseizure targets.

Antagomirs targeting miR-142-5p attenuate pilocarpine-induced status epilepticus in mice

MicroRNAs (miRNAs) are reported to involve in pathogenesis of temporal lobe epilepsy (TLE). miR-142-5p is found increased in TLE, but its role remains unknown. In the study, we established a mouse model of status epilepticus (SE) with pilocarpine and a cell model of TLE. Quantitative real-time PCR revealed an up-regulation of miR-142-5p and down-regulation of mitochondrial Rho 1 (Miro1) in the mouse mode of SE. Administration of miR-142-5p antagomirs via intracerebroventricular injection attenuated pilocarpine-induced SE and hippocampal damage, and alleviated mitochondrial dysfunction along with increased mitochondrial membrane potential and intracellular ATP and Ca (2+) levels. The expression of mitochondrial trafficking kinesin protein (Trak) 1 and Trak2 was up-regulated by inhibiting miR-142-5p. Antagomirs targeting miR-142-5p suppressed pilocarpine-induced oxidative stress as evidenced by decreased ROS generation and MPO activity, and increased SOD activity. Silencing miR-142-5p reduced neuronal death in pilocarpine-treated hippocampus and magnesium-free (MGF)-treated neurons. Inhibition of miR-142-5p decreased cytoplasmic Cytochrome C and increased mitochondrial Cytochrome C, reduced cleaved-caspase3 and Bax levels, and elevated Bcl2 in vivo and in vitro. Further, dual-luciferase assay verified Miro1 as a target of miR-142-5p, suggesting that miR-142-5p might function via targeting Mrio1. Depletion of Miro1 inhibited the protective effect of silencing miR-142-5p on hippocampal neurons in vitro. Taken together, down-regulation of miR-142-5p via targeting Miro1 inhibits neuronal death and mitochondrial dysfunction, and thus attenuates pilocarpine-induced SE, suggesting the potential involvement of miR-142-5p in the pathogenesis of TLE.

Altered Biogenesis and MicroRNA Content of Hippocampal Exosomes Following Experimental Status Epilepticus

Repetitive or prolonged seizures (status epilepticus) can damage neurons within the hippocampus, trigger gliosis, and generate an enduring state of hyperexcitability. Recent studies have suggested that microvesicles including exosomes are released from brain cells following stimulation and tissue injury, conveying contents between cells including microRNAs (miRNAs). Here, we characterized the effects of experimental status epilepticus on the expression of exosome biosynthesis components and analyzed miRNA content in exosome-enriched fractions. Status epilepticus induced by unilateral intra-amygdala kainic acid in mice resulted in acute subfield-specific, bi-directional changes in hippocampal transcripts associated with exosome biosynthesis including up-regulation of endosomal sorting complexes required for transport (ESCRT)-dependent and -independent pathways. Increased expression of exosome components including Alix were detectable in samples obtained 2 weeks after status epilepticus and changes occurred in both the ipsilateral and contralateral hippocampus. RNA sequencing of exosome-enriched fractions prepared using two different techniques detected a rich diversity of conserved miRNAs and showed that status epilepticus selectively alters miRNA contents. We also characterized editing sites of the exosome-enriched miRNAs and found six exosome-enriched miRNAs that were adenosine-to-inosine (ADAR) edited with the majority of the editing events predicted to occur within miRNA seed regions. However, the prevalence of these editing events was not altered by status epilepticus. These studies demonstrate that status epilepticus alters the exosome pathway and its miRNA content, but not editing patterns. Further functional studies will be needed to determine if these changes have pathophysiological significance for epileptogenesis.

Extracellular Vesicles in the Forebrain Display Reduced miR-346 and miR-331-3p in a Rat Model of Chronic Temporal Lobe Epilepsy

An initial precipitating injury in the brain, such as after status epilepticus (SE), evolves into chronic temporal lobe epilepsy (TLE). We investigated changes in the miRNA composition of extracellular vesicles (EVs) in the forebrain after the establishment of SE-induced chronic TLE. We induced SE in young Fischer 344 rats through graded intraperitoneal injections of kainic acid, which resulted in consistent spontaneous recurrent seizures at ~ 3 months post-SE. We isolated EVs from the entire forebrain of chronically epileptic rats and age-matched naïve control animals through an ultracentrifugation method and performed miRNA-sequencing studies to discern changes in the miRNA composition of forebrain-derived EVs in chronic epilepsy. EVs from both naïve and epileptic forebrains displayed spherical or cup-shaped morphology, a comparable size range, and CD63 expression but lacked the expression of a deep cellular marker GM130. However, miRNA-sequencing studies suggested downregulation of 3 miRNAs (miR-187-5p, miR-346, and miR-331-3p) and upregulation of 4 miRNAs (miR-490-5p, miR-376b-3p, miR-493-5p, and miR-124-5p) in EVs from epileptic forebrains with fold changes ranging from 1.5 to 2.4 (p < 0.0006; FDR < 0.05). By using geNorm and Normfinder software, we identified miR-487 and miR-221 as the best combination of reference genes for measurement of altered miRNAs found in the epileptic forebrain through qRT-PCR studies. The validation revealed that only miR-346 and miR-331-3p were significantly downregulated in EVs from the epileptic forebrain. The enrichment pathway analysis of these miRNAs showed an overrepresentation of signaling pathways that are linked to molecular mechanisms underlying chronic epilepsy, including GABA-ergic (miR-346 targets) and mTOR (miR-331-3p targets) systems. Thus, the packaging of two miRNAs into EVs in neural cells is considerably altered in chronic epilepsy. Functional studies on these two miRNAs may uncover their role in the pathophysiology and treatment of TLE.

Topologically inferring active miRNA-mediated subpathways toward precise cancer classification by directed random walk

Accurate predictions of classification biomarkers and disease status are indispensable for clinical cancer diagnosis and research. However, the robustness of conventional gene biomarkers is limited by issues with reproducibility across different measurement platforms and cohorts of patients. In this study, we collected 4775 samples from 12 different cancer datasets, which contained 4636 TCGA samples and 139 GEO samples. A new method was developed to detect miRNA‐mediated subpathway activities by using directed random walk (miDRW). To calculate the activity of each miRNA‐mediated subpathway, we constructed a global directed pathway network (GDPN) with genes as nodes. We then identified miRNAs with expression levels which were strongly inversely correlated with differentially expressed target genes in the GDPN. Finally, each miRNA‐mediated subpathway activity was integrated with the topological information, differential levels of miRNAs and genes, expression levels of genes, and target relationships between miRNAs and genes. The results showed that the proposed method yielded a more robust and accurate overall performance compared with other existing pathway‐based, miRNA‐based, and gene‐based classification methods. The high‐frequency miRNA‐mediated subpathways are more reliable in classifying samples and for selecting therapeutic strategies.

microRNA-132 is overexpressed in glia in temporal lobe epilepsy and reduces the expression of pro-epileptogenic factors in human cultured astrocytes

Temporal lobe epilepsy (TLE) is a chronic neurological disease in humans, which is refractory to pharmacological treatment in about 30% of the patients. Reactive glial cells are thought to play a major role during the development of epilepsy (epileptogenesis) via regulation of brain inflammation and remodeling of the extracellular matrix (ECM). These processes can be regulated by microRNAs (miRs), a class of small non‐coding RNAs, which can control entire gene networks at a post‐transcriptional level. The expression of miRs is known to change dynamically during epileptogenesis. miR‐132 is one of the most commonly upregulated miRs in animal TLE models with important roles shown in neurons. However, the possible role of miR‐132 in glia remains largely unknown. The aim of this study was to characterize the cell‐type specific expression of miR‐132 in the hippocampus of patients with TLE and during epileptogenesis in a rat TLE model. Furthermore, the potential role of miR‐132 was investigated by transfection of human primary cultured astrocytes that were stimulated with the cytokines IL‐1β or TGF‐β1. We showed an increased expression of miR‐132 in the human and rat epileptogenic hippocampus, particularly in glial cells. Transfection of miR‐132 in human primary astrocytes reduced the expression of pro‐epileptogenic COX‐2, IL‐1β, TGF‐β2, CCL2, and MMP3. This suggests that miR‐132, particularly in astrocytes, represents a potential therapeutic target that warrants further in vivo investigation.

MicroRNA inhibition upregulates hippocampal A-type potassium current and reduces seizure frequency in a mouse model of epilepsy

Epilepsy is often associated with altered expression or function of ion channels. One example of such a channelopathy is the reduction of A-type potassium currents in the hippocampal CA1 region. The underlying mechanisms of reduced A-type channel function in epilepsy are unclear. Here, we show that inhibiting a single microRNA, miR-324-5p, which targets the pore-forming A-type potassium channel subunit Kv4.2, selectively increased A-type potassium currents in hippocampal CA1 pyramidal neurons in mice. Resting membrane potential, input resistance and other potassium currents were not altered. In a mouse model of acquired chronic epilepsy, inhibition of miR-324-5p reduced the frequency of spontaneous seizures and interictal epileptiform spikes supporting the physiological relevance of miR-324-5p-mediated control of A-type currents in regulating neuronal excitability. Mechanistic analyses demonstrated that microRNA-induced silencing of Kv4.2 mRNA is increased in epileptic mice leading to reduced Kv4.2 protein levels, which is mitigated by miR-324-5p inhibition. By contrast, other targets of miR-324-5p were unchanged. These results suggest a selective miR-324-5p-dependent mechanism in epilepsy regulating potassium channel function, hyperexcitability and seizures.

Dual-center, dual-platform microRNA profiling identifies potential plasma biomarkers of adult temporal lobe epilepsy

Background

There are no blood-based molecular biomarkers of temporal lobe epilepsy (TLE) to support clinical diagnosis. MicroRNAs are short noncoding RNAs with strong biomarker potential due to their cell-specific expression, mechanistic links to brain excitability, and stable detection in biofluids. Altered levels of circulating microRNAs have been reported in human epilepsy, but most studies collected samples from one clinical site, used a single profiling platform or conducted minimal validation.

Method

Using a case-control design, we collected plasma samples from video-electroencephalogram-monitored adult TLE patients at epilepsy specialist centers in two countries, performed genome-wide PCR-based and RNA sequencing during the discovery phase and validated findings in a large (>250) cohort of samples that included patients with psychogenic non-epileptic seizures (PNES).

Findings

After profiling and validation, we identified miR-27a-3p, miR-328-3p and miR-654-3p with biomarker potential. Plasma levels of these microRNAs were also changed in a mouse model of TLE but were not different to healthy controls in PNES patients. We determined copy number of the three microRNAs in plasma and demonstrate their rapid detection using an electrochemical RNA microfluidic disk as a prototype point-of-care device. Analysis of the microRNAs within the exosome-enriched fraction provided high diagnostic accuracy while Argonaute-bound miR-328-3p selectively increased in patient samples after seizures. In situ hybridization localized miR-27a-3p and miR-328-3p within neurons in human brain and bioinformatics predicted targets linked to growth factor signaling and apoptosis.

Interpretation

This study demonstrates the biomarker potential of circulating microRNAs for epilepsy diagnosis and mechanistic links to underlying pathomechanisms.

Potential Role of miRNAs as Theranostic Biomarkers of Epilepsy

Epilepsy includes a group of disorders of the brain characterized by an enduring predisposition to generate epileptic seizures. Although familial epilepsy has a genetic component and heritability, the etiology of the majority of non-familial epilepsies has no known associated genetic mutations. In epilepsy, recent epigenetic profiles have highlighted a possible role of microRNAs in its pathophysiology. In particular, molecular profiling identifies a significant number of microRNAs (miRNAs) altered in epileptic hippocampus of both animal models and human tissues. In this review, analyzing molecular profiles of different animal models of epilepsy, we identified a group of 20 miRNAs commonly altered in different epilepsy-animal models. As emerging evidences highlighted the poor overlap between signatures of animal model tissues and human samples, we focused our analysis on miRNAs, circulating in human biofluids, with a principal role in epilepsy hallmarks, and we identified a group of 8 diagnostic circulating miRNAs. We discussed the functional role of these 8 miRNAs in the epilepsy hallmarks. A few of them have also been proposed as therapeutic molecules for epilepsy treatment, revealing a great potential for miRNAs as theranostic molecules in epilepsy.

Hypoxia-Induced MicroRNA-210 Targets Neurodegenerative Pathways

Hypoxia-regulated microRNA-210 (miR-210) is a highly conserved microRNA, known to regulate various processes under hypoxic conditions. Previously we found that miR-210 is also involved in honeybee learning and memory, raising the questions of how neural activity may induce hypoxia-regulated genes and how miR-210 may regulate plasticity in more complex mammalian systems. Using a pull-down approach, we identified 620 unique target genes of miR-210 in humans, among which there was a significant enrichment of age-related neurodegenerative pathways, including Huntington's, Alzheimer's, and Parkinson's diseases. We have also validated that miR-210 directly regulates various identified target genes of interest involved with neuronal plasticity, neurodegenerative diseases, and miR-210-associated cancers. This data suggests a potentially novel mechanism for how metabolic changes may couple plasticity to neuronal activity through hypoxia-regulated genes such as miR-210.

MicroRNA-induced silencing in epilepsy: Opportunities and challenges for clinical application

MicroRNAs are master regulators of gene expression. Single microRNAs influence multiple proteins within diverse molecular pathways and networks. Therefore, changes in levels or activity of microRNAs can have profound effects on cellular function. This makes dysregulated microRNA-induced silencing an attractive potential disease mechanism in complex disorders like epilepsy, where numerous cellular pathways and processes are affected simultaneously. Indeed, several years of research in rodent models have provided strong evidence that acute or recurrent seizures change microRNA expression and function. Moreover, altered microRNA expression has been observed in brain and blood from patients with various epilepsy disorders, such as tuberous sclerosis. MicroRNAs can be easily manipulated using sense or antisense oligonucleotides, opening up opportunities for therapeutic intervention. Here, we summarize studies using these techniques to identify microRNAs that modulate seizure susceptibility, describe protein targets mediating some of these effects, and discuss cellular pathways, for example neuroinflammation, that are controlled by epilepsy-associated microRNAs. We critically assess current gaps in knowledge regarding target- and cell-specificity of microRNAs that have to be addressed before clinical application as therapeutic targets or biomarkers. The recent progress in understanding microRNA function in epilepsy has generated strong momentum to encourage in-depth mechanistic studies to develop microRNA-targeted therapies. Developmental Dynamics 247:94-110, 2018. © 2017 Wiley Periodicals, Inc.

MicroRNA-Mediated Downregulation of the Potassium Channel Kv4.2 Contributes to Seizure Onset

Seizures are bursts of excessive synchronized neuronal activity, suggesting that mechanisms controlling brain excitability are compromised. The voltage-gated potassium channel Kv4.2, a major mediator of hyperpolarizing A-type currents in the brain, is a crucial regulator of neuronal excitability. Kv4.2 expression levels are reduced following seizures and in epilepsy, but the underlying mechanisms remain unclear. Here, we report that Kv4.2 mRNA is recruited to the RNA-induced silencing complex shortly after status epilepticus in mice and after kainic acid treatment of hippocampal neurons, coincident with reduction of Kv4.2 protein. We show that the microRNA miR-324-5p inhibits Kv4.2 protein expression and that antagonizing miR-324-5p is neuroprotective and seizure suppressive. MiR-324-5p inhibition also blocks kainic-acid-induced reduction of Kv4.2 protein in vitro and in vivo and delays kainic-acid-induced seizure onset in wild-type but not in Kcnd2 knockout mice. These results reveal an important role for miR-324-5p-mediated silencing of Kv4.2 in seizure onset.

sPAGM: inferring subpathway activity by integrating gene and miRNA expression-robust functional signature identification for melanoma prognoses

MicroRNAs (miRNAs) regulate biological pathways by inhibiting gene expression. However, most current analytical methods fail to consider miRNAs, when inferring functional or pathway activities. In this study, we developed a model called sPAGM to infer subpathway activities by integrating gene and miRNA expressions. In this model, we reconstructed subpathway graphs by embedding miRNA components, and characterized subpathway activity (sPA) scores by simultaneously considering the expression levels of miRNAs and genes. The results showed that the sPA scores could distinguish different samples across tumor types, as well as samples between tumor and normal conditions. Moreover, the sPAGM model displayed more specificities than the entire pathway-based analyses. This model was applied to melanoma tumors to perform a prognosis analysis, which identified a robust 55-subpathway signature. By using The Cancer Genome Atlas and independently verified data sets, the subpathway-based signature significantly predicted the patients’ prognoses, which were independent of clinical variables. In the prognostic performance comparison, the sPAGM model was superior to the gene-only and miRNA-only methods. Finally, we dissected the functional roles and interactions of components within the subpathway signature. Taken together, the sPAGM model provided a framework for inferring subpathway activities and identifying functional signatures for clinical applications.

miRNA-Mediated Regulation of Adult Hippocampal Neurogenesis; Implications for Epilepsy

Hippocampal neural stem/progenitor cells (NSPCs) proliferate and differentiate to generate new neurons across the life span of most mammals, including humans. This process takes place within a characteristic local microenvironment where NSPCs interact with a variety of other cell types and encounter systemic regulatory factors. Within this microenvironment, cell intrinsic gene expression programs are modulated by cell extrinsic signals through complex interactions, in many cases involving short non-coding RNA molecules, such as miRNAs. Here we review the regulation of gene expression in NSPCs by miRNAs and its possible implications for epilepsy, which has been linked to alterations in adult hippocampal neurogenesis.

Intracerebroventricular injection of miR-146a relieves seizures in an immature rat model of lithium-pilocarpine induced status epilepticus

OBJECTIVE

Status epilepticus (SE) is a common, life-threatening neurological emergency that confers a high degree of morbidity and mortality. Increasing evidence indicates that neuroinflammation plays a critical role in the pathogenesis of SE. MicroRNA-146a (miR-146a) has been reported to be an important posttranscriptional inflammation-associated microRNA. The aim of this study was to investigate the effect of miR-146a in SE and the mechanism by which it operates.

METHODS

To study the effect of miR-146a in SE, we chose intracerebroventricular injection for rat at 21-28days old, and made a lithium-pilocarpine-induced SE rat model. We assessed latency time and Lado grade by behavior observation. We performed qPCR, ELISA and western blot tests on rat hippocampus to measure the expression levels of miR-146a, IL-1β, TNF-α, TLR4 and NF-κB.

RESULTS

In the miR-146a antagomir injection group, the latency to generalized convulsions was shorter, the duration and degree of seizures were more severe, the expression level of miR-146a was clearly decreased, and IL-1β, TNF-α, TLR4 and NF-κB were all significantly up-regulated. The opposite was true for rats treated with miR-146a agomir.

CONCLUSION

Our findings elucidate the role of inflammation in the pathogenesis of SE in immature rats, and show that regulating the expression level of miR-146a may provide a novel insights into the pathogenesis of SE.

A distinct microRNA expression profile is associated with α[11C]-methyl-L-tryptophan (AMT) PET uptake in epileptogenic cortical tubers resected from patients with tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is characterized by hamartomatous lesions in various organs and arises due to mutations in the TSC1 or TSC2 genes. TSC mutations lead to a range of neurological manifestations including epilepsy, cognitive impairment, autism spectrum disorders (ASD), and brain lesions that include cortical tubers. There is evidence that seizures arise at or near cortical tubers, but it is unknown why some tubers are epileptogenic while others are not. We have previously reported increased tryptophan metabolism measured with α[¹¹C]-methyl-l-tryptophan (AMT) positron emission tomography (PET) in epileptogenic tubers in approximately two-thirds of patients with tuberous sclerosis and intractable epilepsy. However, the underlying mechanisms leading to seizure onset in TSC remain poorly characterized. MicroRNAs are enriched in the brain and play important roles in neurodevelopment and brain function. Recent reports have shown aberrant microRNA expression in epilepsy and TSC. In this study, we performed microRNA expression profiling in brain specimens obtained from TSC patients undergoing epilepsy surgery for intractable epilepsy. Typically, in these resections several non-seizure onset tubers are resected together with the seizure-onset tubers because of their proximity. We directly compared seizure onset tubers, with and without increased tryptophan metabolism measured with PET, and non-onset tubers to assess the role of microRNAs in epileptogenesis associated with these lesions. Whether a particular tuber was epileptogenic or non-epileptogenic was determined with intracranial electrocorticography, and tryptophan metabolism was measured with AMT PET. We identified a set of five microRNAs (miR-142-3p, 142-5p, 223-3p, 200b-3p and 32-5p) that collectively distinguish among the three primary groups of tubers: non-onset/AMT-cold (NC), onset/AMT-cold (OC), and onset/AMT-hot (OH). These microRNAs were significantly upregulated in OH tubers compared to the other two groups, and microRNA expression was most significantly associated with AMT-PET uptake. The microRNAs target a group of genes enriched for synaptic signaling and epilepsy risk, including SLC12A5, SYT1, GRIN2A, GRIN2B, KCNB1, SCN2A, TSC1, and MEF2C. We confirmed the interaction between miR-32-5p and SLC12A5 using a luciferase reporter assay. Our findings provide a new avenue for subsequent mechanistic studies of tuber epileptogenesis in TSC.

Systematic review and meta-analysis of differentially expressed miRNAs in experimental and human temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is a common chronic neurological disease in humans. A number of studies have demonstrated differential expression of miRNAs in the hippocampus of humans with TLE and in animal models of experimental epilepsy. However, the dissimilarities in experimental design have led to largely discordant results across these studies. Thus, a comprehensive comparison is required in order to better characterize miRNA profiles obtained in various post-status epilepticus (SE) models. We therefore created a database and performed a meta-analysis of differentially expressed miRNAs across 3 post-SE models of epileptogenesis (electrical stimulation, pilocarpine and kainic acid) and human TLE with hippocampal sclerosis (TLE-HS). The database includes data from 11 animal post-SE studies and 3 human TLE-HS studies. A total of 378 differentially expressed miRNAs were collected (274 up-regulated and 198 down-regulated) and analyzed with respect to the post-SE model, time point and animal species. We applied the novel robust rank aggregation method to identify consistently differentially expressed miRNAs across the profiles. It highlighted common and unique miRNAs at different stages of epileptogenesis. The pathway analysis revealed involvement of these miRNAs in key pathogenic pathways underlying epileptogenesis, including inflammation, gliosis and deregulation of the extracellular matrix.

Cerebrospinal fluid microRNAs are potential biomarkers of temporal lobe epilepsy and status epilepticus

There is a need for diagnostic biomarkers of epilepsy and status epilepticus to support clinical examination, electroencephalography and neuroimaging. Extracellular microRNAs may be potentially ideal biomarkers since some are expressed uniquely within specific brain regions and cell types. Cerebrospinal fluid offers a source of microRNA biomarkers with the advantage of being in close contact with the target tissue and sites of pathology. Here we profiled microRNA levels in cerebrospinal fluid from patients with temporal lobe epilepsy or status epilepticus, and compared findings to matched controls. Differential expression of 20 microRNAs was detected between patient groups and controls. A validation phase included an expanded cohort and samples from patients with other neurological diseases. This identified lower levels of miR-19b in temporal lobe epilepsy compared to controls, status epilepticus and other neurological diseases. Levels of miR-451a were higher in status epilepticus compared to other groups whereas miR-21-5p differed in status epilepticus compared to temporal lobe epilepsy but not to other neurological diseases. Targets of these microRNAs include proteins regulating neuronal death, tissue remodelling, gliosis and inflammation. The present study indicates cerebrospinal fluid contains microRNAs that can support differential diagnosis of temporal lobe epilepsy and status epilepticus from other neurological and non-neurological diseases.

Dynamic changes in murine forebrain miR-211 expression associate with cholinergic imbalances and epileptiform activity

Epilepsy is a common neurological disease, manifested in unprovoked recurrent seizures. Epileptogenesis may develop due to genetic or pharmacological origins or following injury, but it remains unclear how the unaffected brain escapes this susceptibility to seizures. Here, we report that dynamic changes in forebrain microRNA (miR)-211 in the mouse brain shift the threshold for spontaneous and pharmacologically induced seizures alongside changes in the cholinergic pathway genes, implicating this miR in the avoidance of seizures. We identified miR-211 as a putative attenuator of cholinergic-mediated seizures by intersecting forebrain miR profiles that were Argonaute precipitated, synaptic vesicle target enriched, or differentially expressed under pilocarpine-induced seizures, and validated TGFBR2 and the nicotinic antiinflammatory acetylcholine receptor nAChRa7 as murine and human miR-211 targets, respectively. To explore the link between miR-211 and epilepsy, we engineered dTg-211 mice with doxycycline-suppressible forebrain overexpression of miR-211. These mice reacted to doxycycline exposure by spontaneous electrocorticography-documented nonconvulsive seizures, accompanied by forebrain accumulation of the convulsive seizures mediating miR-134. RNA sequencing demonstrated in doxycycline-treated dTg-211 cortices overrepresentation of synaptic activity, Ca²⁺ transmembrane transport, TGFBR2 signaling, and cholinergic synapse pathways. Additionally, a cholinergic dysregulated mouse model overexpressing a miR refractory acetylcholinesterase-R splice variant showed a parallel propensity for convulsions, miR-211 decreases, and miR-134 elevation. Our findings demonstrate that in mice, dynamic miR-211 decreases induce hypersynchronization and nonconvulsive and convulsive seizures, accompanied by expression changes in cholinergic and TGFBR2 pathways as well as in miR-134. Realizing the importance of miR-211 dynamics opens new venues for translational diagnosis of and interference with epilepsy.

Identifying and Analyzing Novel Epilepsy-Related Genes Using Random Walk with Restart Algorithm

As a pathological condition, epilepsy is caused by abnormal neuronal discharge in brain which will temporarily disrupt the cerebral functions. Epilepsy is a chronic disease which occurs in all ages and would seriously affect patients' personal lives. Thus, it is highly required to develop effective medicines or instruments to treat the disease. Identifying epilepsy-related genes is essential in order to understand and treat the disease because the corresponding proteins encoded by the epilepsy-related genes are candidates of the potential drug targets. In this study, a pioneering computational workflow was proposed to predict novel epilepsy-related genes using the random walk with restart (RWR) algorithm. As reported in the literature RWR algorithm often produces a number of false positive genes, and in this study a permutation test and functional association tests were implemented to filter the genes identified by RWR algorithm, which greatly reduce the number of suspected genes and result in only thirty-three novel epilepsy genes. Finally, these novel genes were analyzed based upon some recently published literatures. Our findings implicate that all novel genes were closely related to epilepsy. It is believed that the proposed workflow can also be applied to identify genes related to other diseases and deepen our understanding of the mechanisms of these diseases.

Subpathway-GMir: identifying miRNA-mediated metabolic subpathways by integrating condition-specific genes, microRNAs, and pathway topologies

MicroRNAs (miRNAs) regulate disease-relevant metabolic pathways. However, most current pathway identification methods fail to consider miRNAs in addition to genes when analyzing pathways. We developed a powerful method called Subpathway-GMir to construct miRNA-regulated metabolic pathways and to identify miRNA-mediated subpathways by considering condition-specific genes, miRNAs, and pathway topologies. We used Subpathway-GMir to analyze two liver hepatocellular carcinomas (LIHC), one stomach adenocarcinoma (STAD), and one type 2 diabetes (T2D) data sets. Results indicate that Subpathway-GMir is more effective in identifying phenotype-associated metabolic pathways than other methods and our results are reproducible and robust. Subpathway-GMir provides a flexible platform for identifying abnormal metabolic subpathways mediated by miRNAs, and may help to clarify the roles that miRNAs play in a variety of diseases. The Subpathway-GMir method has been implemented as a freely available R package.

Potent Anti-seizure Effects of Locked Nucleic Acid Antagomirs Targeting miR-134 in Multiple Mouse and Rat Models of Epilepsy

Current anti-epileptic drugs (AEDs) act on a limited set of neuronal targets, are ineffective in a third of patients with epilepsy, and do not show disease-modifying properties. MicroRNAs are small noncoding RNAs that regulate levels of proteins by post-transcriptional control of mRNA stability and translation. MicroRNA-134 is involved in controlling neuronal microstructure and brain excitability and previous studies showed that intracerebroventricular injections of locked nucleic acid (LNA), cholesterol-tagged antagomirs targeting microRNA-134 (Ant-134) reduced evoked and spontaneous seizures in mouse models of status epilepticus. Translation of these findings would benefit from evidence of efficacy in non-status epilepticus models and validation in another species. Here, we report that electrographic seizures and convulsive behavior are strongly reduced in adult mice pre-treated with Ant-134 in the pentylenetetrazol model. Pre-treatment with Ant-134 did not affect the severity of status epilepticus induced by perforant pathway stimulation in adult rats, a toxin-free model of acquired epilepsy. Nevertheless, Ant-134 post-treatment reduced the number of rats developing spontaneous seizures by 86% in the perforant pathway stimulation model and Ant-134 delayed epileptiform activity in a rat ex vivo hippocampal slice model. The potent anticonvulsant effects of Ant-134 in multiple models may encourage pre-clinical development of this approach to epilepsy therapy.

Identification of microRNAs with Dysregulated Expression in Status Epilepticus Induced Epileptogenesis

The involvement of miRNA in mesial temporal lobe epilepsy (MTLE) pathogenesis has increasingly become a focus of epigenetic studies. Despite advances, the number of known miRNAs with a consistent expression response during epileptogenesis is still small. Addressing this situation requires additional miRNA profiling studies coupled to detailed individual expression analyses. Here, we perform a miRNA microarray analysis of the hippocampus of Wistar rats 24 hours after intra-hippocampal pilocarpine-induced Status Epilepticus (H-PILO SE). We identified 73 miRNAs that undergo significant changes, of which 36 were up-regulated and 37 were down-regulated. To validate, we selected 5 of these (10a-5p, 128a-3p, 196b-5p, 352 and 324-3p) for RT-qPCR analysis. Our results confirmed that miR-352 and 196b-5p levels were significantly higher and miR-128a-3p levels were significantly lower in the hippocampus of H-PILO SE rats. We also evaluated whether the 3 miRNAs show a dysregulated hippocampal expression at three time periods (0h, 24h and chronic phase) after systemic pilocarpine-induced status epilepticus (S-PILO SE). We demonstrate that miR-128a-3p transcripts are significantly reduced at all time points compared to the naïve group. Moreover, miR-196b-5p was significantly higher only at 24h post-SE, while miR-352 transcripts were significantly up-regulated after 24h and in chronic phase (epileptic) rats. Finally, when we compared hippocampi of epileptic and non-epileptic humans, we observed that transcript levels of miRNAs show similar trends to the animal models. In summary, we successfully identified two novel dysregulated miRNAs (196b-5p and 352) and confirmed miR-128a-3p downregulation in SE-induced epileptogenesis. Further functional assays are required to understand the role of these miRNAs in MTLE pathogenesis.

Involvement of microRNAs in epileptogenesis

Patients who have sustained brain injury or had developmental brain lesions present a non-negligible risk for developing delayed epilepsy. Finding therapeutic strategies to prevent development of epilepsy in at-risk patients represents a crucial medical challenge. Noncoding microRNA molecules (miRNAs) are promising candidates in this area. Indeed, deregulation of diverse brain-specific miRNAs has been observed in animal models of epilepsy as well as in patients with epilepsy, mostly in temporal lobe epilepsy (TLE). Herein we review deregulated miRNAs reported in epilepsy with potential roles in key molecular and cellular processes underlying epileptogenesis, namely neuroinflammation, cell proliferation and differentiation, migration, apoptosis, and synaptic remodeling. We provide an up-to-date listing of miRNAs altered in epileptogenesis and assess recent functional studies that have interrogated their role in epilepsy. Last, we discuss potential applications of these findings for the future development of disease-modifying therapeutic strategies for antiepileptogenesis.

Targeting of microRNA-199a-5p protects against pilocarpine-induced status epilepticus and seizure damage via SIRT1-p53 cascade

OBJECTIVE

MicroRNAs (miRNAs) are noncoding small RNAs that control gene expression at the posttranscriptional level. Some dysregulated miRNAs have been shown to play important roles in epileptogenesis. The aim of this study was to determine if miR-199a-5p regulates seizures and seizure damage by targeting the antiapoptotic protein silent information regulator 1 (SIRT1).

METHODS

Hippocampal expression levels of miR-199a-5p, SIRT1, and acetylated p53 were quantified by quantitative real-time polymerase chain reaction (RT-PCR) and Western blotting in the acute, latent, and chronic stages of epilepsy in a rat lithium-pilocarpine epilepsy model. Silencing of miR-199a-5p expression in vivo was achieved by intracerebroventricular injection of antagomirs. The effects of targeting miR-199a-5p and SIRT1 protein on seizure and epileptic damage post-status epilepticus were assessed by electroencephalography (EEG) and immunohistochemistry, respectively.

RESULTS

miR-199a-5p expression was up-regulated, SIRT1 levels were decreased, and neuron loss and apoptosis were induced in epilepsy model rats compared with normal controls, as determined by up-regulation of acetylated p53 and cleaved caspase-3 expression. In vivo knockdown of miR-199a-5p by an antagomir alleviated the seizure-like EEG findings and protected against neuron damage, in accordance with up-regulation of SIRT1 and subsequent deacetylation of p53. Furthermore, the seizure-suppressing effect of the antagomir was partly SIRT1 dependent.

SIGNIFICANCE

The results of this study suggest that silencing of miR-199a-5p exerts a seizure-suppressing effect in rats, and that SIRT1 is a direct target of miR-199a-5p in the hippocampus. The effect of miR-199a-5p on seizures and seizure damage is mediated via down-regulation of SIRT1. The miR-199a-5p/SIRT1 pathway may thus represent a potential target for the prevention and treatment of epilepsy and epileptic damage.

Correlation Between IL-10 and microRNA-187 Expression in Epileptic Rat Hippocampus and Patients with Temporal Lobe Epilepsy

Accumulating evidence is emerging that microRNAs (miRNAs) are key regulators in controlling neuroinflammatory responses that are known to play a potential role in the pathogenesis of temporal lobe epilepsy (TLE). The aim of the present study was to investigate the dynamic expression pattern of interleukin (IL)-10 as an anti-inflammatory cytokine and miR-187 as a post-transcriptional inflammation-related miRNA in the hippocampus of a rat model of status epilepticus (SE) and patients with TLE. We performed a real-time quantitative PCR and western blot on rat hippocampus 2 h, 7 days, 21 days and 60 days following pilocarpine-induced SE, and on hippocampus obtained from TLE patients and normal controls. To detect the relationship between IL-10 and miR-187 on neurons, lipopolysaccharide (LPS) and IL-10-stimulated neurons were performed. Furthermore, we identified the effect of antagonizing miR-187 by its antagomir on IL-10 secretion. Here, we reported that IL-10 secretion and miR-187 expression levels are inversely correlated after SE. In patients with TLE, the expression of IL-10 was also significantly upregulated, whereas miR-187 expression was significantly downregulated. Moreover, miR-187 expression was significantly reduced following IL-10 stimulation in an IL-10-dependent manner. On the other hand, antagonizing miR-187 promoted the production of IL-10 in hippocampal tissues of rat model of SE. Our findings demonstrate a critical role of miR-187 in the physiological regulation of IL-10 anti-inflammatory responses and elucidate the role of neuroinflammation in the pathogenesis of TLE. Therefore, modulation of the IL-10 / miR-187 axis may be a new therapeutic approach for TLE.

miRNAs: biological and clinical determinants in epilepsy

Recently, microRNAs (miRNAs) are reported to be crucial modulators in the pathogenesis and potential treatment of epilepsies. To date, several miRNAs have been demonstrated to be significantly expressed in the epileptic tissues and strongly associated with the development of epilepsy. Specifically, miRNAs regulate synaptic strength, inflammation, neuronal and glial function, ion channels, and apoptosis. Furthermore, peripheral blood miRNAs can also be utilized as diagnostic biomarkers to assess disease risk and treatment responses. Here, we will summarize the recent available literature regarding the role of miRNAs in the pathogenesis and treatment of epilepsy. Moreover, we will provide brief insight into the potential of miRNA as diagnostic biomarkers for early diagnosis and prognosis of epilepsy.

Comparison of short-term effects of midazolam and lorazepam in the intra-amygdala kainic acid model of status epilepticus in mice

Benzodiazepines remain as the first-line treatment for status epilepticus (SE), but debate continues as to the choice and delivery route of pharmacotherapy. Lorazepam is currently the preferred anticonvulsant for clinical use, but midazolam has become a popular alternative, particularly as it can be given by nonintravenous routes. Anticonvulsants are also commonly used to terminate SE in animal models. Here, we aimed to compare the efficacy of midazolam with that of lorazepam in an experimental model of focal-onset SE. Status epilepticus was induced by intra-amygdala microinjection of kainic acid in 8week old C57Bl/6 mice. Forty minutes later, mice were treated with an intraperitoneal injection of either lorazepam or midazolam (8mg/kg). Electroencephalogram (EEG) activity, histology, and behavioral tests assessing recovery of function were evaluated and compared between groups. Intraperitoneal injection of either lorazepam or midazolam resulted in similar patterns of reduced EEG epileptiform activity during 1-hour recordings. Damage to the hippocampus and presentation of postinsult anxiety-related behavior did not significantly differ between treatment groups at 72h. However, return of normal behaviors such as grooming, levels of activity, and the evaluation of overall recovery of SE mice were all superior at 24h in animals given midazolam compared with lorazepam. Our results indicate that midazolam is as effective as lorazepam as an anticonvulsant in this model while also providing improved animal recovery after SE. These data suggest that midazolam might be considered by researchers as an anticonvulsant in animal models of SE, particularly as it appears to satisfy the requirements of refining procedures involving experimental animals at early time-points after SE.

Differential expression and clinical significance of three inflammation-related microRNAs in gangliogliomas

PURPOSE

miR21, miR146, and miR155 represent a trio of microRNAs which has been shown to play a key role in the regulation of immune and inflammatory responses. In the present study, we investigated the differential expression and clinical significance of these three miRNAs in glioneuronal tumors (gangliogliomas, GGs) which are characterized by prominent activation of the innate immune response.

METHODS

The expression levels of miR21, miR146, and miR155 were evaluated using Taqman PCR in 34 GGs, including 15 cases with sufficient amount of perilesional cortex. Their expression was correlated with the tumor features and the clinical history of epilepsy. In addition, in situ hybridization was used to evaluate their cellular distribution in both tumor and peritumoral cortex.

RESULTS

Increased expression of miR146a was observed in both tumor and peritumoral cortex compared to control samples. miR146a was detected in both neuronal and astroglial cells. Tumor and peritumoral miR146a expression was negatively correlated with frequency of seizures and the density of activated microglial cells. Neuronal and astroglial expression was observed for both miR21 and miR155 with increased expression of miR21 within the tumor and miR155 in the peritumoral region. Negative correlations were observed between the miRNA levels and the expression of putative targets within the astroglial component of the tumor.

CONCLUSION

We report a differential regulation of three miRNAs, known to be related to inflammation, in both tumor and peritumoral cortex of patients with GG. Moreover, our findings suggest a functional relationship between miR146a expression and epilepsy, either directly in epileptogenesis or as modulation of seizure activity.

Role of MicroRNAs in innate neuroprotection mechanisms due to preconditioning of the brain

Insults to the brain that are sub-threshold for damage activate endogenous protective pathways, which can temporarily protect the brain against a subsequent harmful episode. This mechanism has been named as tolerance and its protective effects have been shown in experimental models of ischemia and epilepsy. The preconditioning-stimulus can be a short period of ischemia or mild seizures induced by low doses of convulsant drugs. Gene-array profiling has shown that both ischemic and epileptic tolerance feature large-scale gene down-regulation but the mechanism are unknown. MicroRNAs are a class of small non-coding RNAs of ~20-22 nucleotides length which regulate gene expression at a post-transcriptional level via mRNA degradation or inhibition of protein translation. MicroRNAs have been shown to be regulated after non-harmful and harmful stimuli in the brain and to contribute to neuroprotective mechanisms. This review focuses on the role of microRNAs in the development of tolerance following ischemic or epileptic preconditioning.

Pathway analysis from lists of microRNAs: common pitfalls and alternative strategy

MicroRNAs (miRNAs) are involved in the regulation of gene expression at a post-transcriptional level. As such, monitoring miRNA expression has been increasingly used to assess their role in regulatory mechanisms of biological processes. In large scale studies, once miRNAs of interest have been identified, the target genes they regulate are often inferred using algorithms or databases. A pathway analysis is then often performed in order to generate hypotheses about the relevant biological functions controlled by the miRNA signature. Here we show that the method widely used in scientific literature to identify these pathways is biased and leads to inaccurate results. In addition to describing the bias and its origin we present an alternative strategy to identify potential biological functions specifically impacted by a miRNA signature. More generally, our study exemplifies the crucial need of relevant negative controls when developing, and using, bioinformatics methods.