MicroRNA-34a upregulation during seizure-induced neuronal death

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

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

Is the peroxisome proliferator-activated receptor gamma a putative target for epilepsy treatment? Current evidence and future perspectives

The peroxisome proliferator-activated receptor gamma (PPARγ), which belongs to the family of nuclear receptors, has been mainly studied as an important factor in metabolic disorders. However, in recent years the potential role of PPARγ in different neurological diseases has been increasingly investigated. Especially, in the search of therapeutic targets for patients with epilepsy the question of the involvement of PPARγ in seizure control has been raised. Epilepsy is a chronic neurological disorder causing a major impact on the psychological, social, and economic conditions of patients and their families, besides the problems of the disease itself. Considering that the world prevalence of epilepsy ranges between 0.5% - 1.0%, this condition is the fourth for importance among the other neurological disorders, following migraine, stroke, and dementia. Among others, temporal lobe epilepsy (TLE) is the most common form of epilepsy in adult patients. About 65% of individuals who receive antiseizure medications (ASMs) experience seizure independence. For those in whom seizures still recur, investigating PPARγ could lead to the development of novel ASMs. This review focuses on the most important findings from recent investigations about the potential intracellular PPARγ-dependent processes behind different compounds that exhibited anti-seizure effects. Additionally, recent clinical investigations are discussed along with the promising results found for PPARγ agonists and the ketogenic diet (KD) in various rodent models of epilepsy.

Stage- and Subfield-Associated Hippocampal miRNA Expression Patterns after Pilocarpine-Induced Status Epilepticus

OBJECTIVE

To investigate microRNA (miRNA) expression profiles before and after pilocarpine-induced status epilepticus (SE) in the cornu ammonis (CA) and dentated gyrus (DG) areas of the mouse hippocampus, and to predict the downstream proteins and related pathways based on bioinformatic analysis.

METHODS

An epileptic mouse model was established using a pilocarpine injection. Brain tissues from the CA and DG were collected separately for miRNA analysis. The miRNAs were extracted using a kit, and the expression profiles were generated using the SurePrint G3 Mouse miRNA microarray and validated. The intersecting genes of TargetScan and miRanda were selected to predict the target genes of each miRNA. For gene ontology (GO) studies, the parent-child-intersection (pci) method was used for enrichment analysis, and Benjamini-Hochberg was used for multiple test correction. The Kyoto Encyclopedia of Genes and Genomes (KEGG) was used to detect disease-related pathways among the large list of miRNA-targeted genes. All analyses mentioned above were performed at the time points of control, days 3, 14, and 60 post-SE.

RESULTS

Control versus days 3, 14, and 60 post-SE: in the CA area, a total of 131 miRNAs were differentially expressed; 53, 49, and 26 miRNAs were upregulated and 54, 10, and 22 were downregulated, respectively. In the DG area, a total of 171 miRNAs were differentially expressed; furthermore, 36, 32, and 28 miRNAs were upregulated and 78, 58, and 44 were downregulated, respectively. Of these, 92 changed in both the CA and DG, 39 only in the CA, and 79 only in the DG area. The differentially expressed miRNAs target 11-1630 genes. Most of these proteins have multiple functions in epileptogenesis. There were 15 common pathways related to altered miRNAs: nine different pathways in the CA and seven in the DG area.

CONCLUSIONS

Stage- and subfield-associated hippocampal miRNA expression patterns are closely related to epileptogenesis, although the detailed mechanisms need to be explored in the future.

Expression Profile of miRs in Mesial Temporal Lobe Epilepsy: Systematic Review

Temporal lobe epilepsy (TLE) is one of the most common forms of focal epilepsy in children and adults. TLE is characterized by variable onset and seizures. Moreover, this form of epilepsy is often resistant to pharmacotherapy. The search for new mechanisms for the development of TLE may provide us with a key to the development of new diagnostic methods and a personalized approach to the treatment. In recent years, the role of non-coding ribonucleic acids (RNA) has been actively studied, among which microRNA (miR) is of the greatest interest. (1) Background: The purpose of the systematic review is to analyze the studies carried out on the role of miRs in the development of mesial TLE (mTLE) and update the existing knowledge about the biomarkers of this disease. (2) Methods: The search for publications was carried out in the databases PubMed, Springer, Web of Science, Clinicalkeys, Scopus, OxfordPress, Cochrane. The search was carried out using keywords and combinations. We analyzed publications for 2016–2021, including original studies in an animal model of TLE and with the participation of patients with TLE, thematic and systemic reviews, and Cochrane reviews. (3) Results: this thematic review showed that miR‒155, miR‒153, miR‒361‒5p, miR‒4668‒5p, miR‒8071, miR‒197‒5p, miR‒145, miR‒181, miR‒199a, miR‒1183, miR‒129‒2‒3p, miR‒143‒3p (upregulation), miR–134, miR‒0067835, and miR‒153 (downregulation) can be considered as biomarkers of mTLE. However, the roles of miR‒146a, miR‒142, miR‒106b, and miR‒223 are questionable and need further study. (4) Conclusion: In the future, it will be possible to consider previously studied miRs, which have high specificity and sensitivity in mTLE, as prognostic biomarkers (predictors) of the risk of developing this disease in patients with potentially epileptogenic structural damage to the mesial regions of the temporal lobe of the brain (congenital disorders of the neuronal migration and neurogenesis, brain injury, neuro-inflammation, tumor, impaired blood supply, neurodegeneration, etc.).

New Insights Into the Role of Aberrant Hippocampal Neurogenesis in Epilepsy

Data accumulated over the past four decades have confirmed that adult hippocampal neurogenesis (HN) plays a key role in the wide spectrum of hippocampal pathology. Epilepsy is a disorder of the central nervous system characterized by spontaneous recurrent seizures. Although neurogenesis in persistent germinative zones is altered in the adult rodent models of epilepsy, the effects of seizure-induced neurogenesis in the epileptic brain, in terms of either a pathological or reparative role, are only beginning to be explored. In this review, we described the most recent advances in neurogenesis in epilepsy and outlooked future directions for neural stem cells (NSCs) and epilepsy-in-a-dish models. We proposed that it may help in refining the underlying molecular mechanisms of epilepsy and improving the therapies and precision medicine for patients with epilepsy.

Pervasive compartment-specific regulation of gene expression during homeostatic synaptic scaling

Synaptic scaling is a form of homeostatic plasticity which allows neurons to adjust their action potential firing rate in response to chronic alterations in neural activity. Synaptic scaling requires profound changes in gene expression, but the relative contribution of local and cell‐wide mechanisms is controversial. Here we perform a comprehensive multi‐omics characterization of the somatic and process compartments of primary rat hippocampal neurons during synaptic scaling. We uncover both highly compartment‐specific and correlating changes in the neuronal transcriptome and proteome. Whereas downregulation of crucial regulators of neuronal excitability occurs primarily in the somatic compartment, structural components of excitatory postsynapses are mostly downregulated in processes. Local inhibition of protein synthesis in processes during scaling is confirmed for candidate synaptic proteins. Motif analysis further suggests an important role for trans‐acting post‐transcriptional regulators, including RNA‐binding proteins and microRNAs, in the local regulation of the corresponding mRNAs. Altogether, our study indicates that, during synaptic scaling, compartmentalized gene expression changes might co‐exist with neuron‐wide mechanisms to allow synaptic computation and homeostasis.

Increased hippocampal excitability in miR-324-null mice

MicroRNAs are non-coding RNAs that act to downregulate the expression of target genes by translational repression and degradation of messenger RNA molecules. Individual microRNAs have the ability to specifically target a wide array of gene transcripts, therefore allowing each microRNA to play key roles in multiple biological pathways. miR-324 is a microRNA predicted to target thousands of RNA transcripts and is expressed far more highly in the brain than in any other tissue, suggesting that it may play a role in one or multiple neurological pathways. Here we present data from the first global miR-324-null mice, in which increased excitability and interictal discharges were identified in vitro in the hippocampus. RNA sequencing was used to identify differentially expressed genes in miR-324-null mice which may contribute to this increased hippocampal excitability, and 3'UTR luciferase assays and western blotting revealed that two of these, Suox and Cd300lf, are novel direct targets of miR-324. Characterisation of microRNAs that produce an effect on neurological activity, such as miR-324, and identification of the pathways they regulate will allow a better understanding of the processes involved in normal neurological function and in turn may present novel pharmaceutical targets in treating neurological disease.

Prospects and Limitations Related to the Use of MicroRNA as a Biomarker of Epilepsy in Children: A Systematic Review

Epilepsy is one of the most common neurological diseases in children. There is an unmet need for new objective methods that would facilitate and accelerate the diagnostic process, thus improving the prognosis. In many studies, the participation of microRNA in epileptogenesis has been confirmed. Therefore, it seems to be a promising candidate for this role. Scientists show the possibility of using microRNAs as diagnostic and predictive biomarkers as well as novel therapeutic targets. Children with epilepsy would benefit particularly from the use of this innovative method. However, the number of studies related to this age group is very limited. This review is based on 10 studies in children and summarizes the information collected from studies on animal models and the adult population. A total of 136 manuscripts were included in the analysis. The aim of the review was to facilitate the design of studies in children and to draw attention to the challenges and traps related to the analysis of the results. Our review suggests a high potential for the use of microRNAs and the need for further research.

The potential role of micro-RNA-211 in the pathogenesis of sleep-related hypermotor epilepsy

Sleep-related hypermotor epilepsy (SHE) is a rare epileptic syndrome characterized by epileptic seizures which occur during the non-rapid eye movement (NREM) stage of sleep. It manifests with hypermotor semiology resembling violent limb movements and an asymmetric tonic-dystonic posture. The genes which are responsible for the autosomal dominant form of SHE (ADSHE) and whose function is to code the sub-unit of the neuronal acetylcholine receptor are well known. Considering that ADSHE is a prototype of SHE, it is thought that the dysfunction of the cortico-subcortical cholinergic network, which regulates the cycle of sleep, has a key role in the epileptogenesis of this syndrome. Namely, studies to date, have shown that the hypercholinergic activity is sufficient for the development of epileptic seizures, even though the exact mechanism remains to be elucidated. NREM parasomnias are sleep disorders that are the most difficult to differentiate from SHE due to a similar clinical presentation. Considering the clinical similarities, NREM occurrence and probable genetic connection, it is considered that fundamentally, both of these conditions share a common pathophysiological mechanism i.e. cholinergic dysfunction. The main difference between SHE and NREM parasomnias are the genuine epileptic seizures that are responsible for the semiology in SHE. These genuine seizures are not present in NREM parasomnias. Why this is so, remains to be elucidated. Considering that animal studies have shown that dynamic changes and the decreased levels of microRNA-211 contribute to epileptic seizures and to changes in cholinergic pathways, our hypothesis is that epileptic seizures and the development of epileptogenesis in SHE are a consequence of cholinergic dysfunction and decreased levels of microRNA-211 as opposed to NREM parasomnias where there is a stable level of microRNA-211, preventing epileptogenesis despite the cholinergic system dysfunction.

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.

A microRNA signature of toxic extrasynaptic N-methyl-D-aspartate (NMDA) receptor signaling

The cellular consequences of N-Methyl-D-Aspartate receptor (NMDAR) stimulation depend on the receptors' subcellular localization. Synaptic NMDARs promote plasticity and survival whereas extrasynaptic NMDARs mediate excitotoxicity and contribute to cell death in neurodegenerative diseases. The mechanisms that couple activation of extrasynaptic NMDARs to cell death remain incompletely understood. We here show that activation of extrasynaptic NMDARs by bath application of NMDA or L-glutamate leads to the upregulation of a group of 19 microRNAs in cultured mouse hippocampal neurons. In contrast, none of these microRNAs is induced upon stimulation of synaptic activity. Increased microRNA expression depends on the pri-miRNA processing enzyme Drosha, but not on de novo gene transcription. These findings suggest that toxic NMDAR signaling involves changes in the expression levels of particular microRNAs.

Differential expression of miR-34a, 451, 1260, 1275 and 1298 in the neocortex of patients with mesial temporal lobe epilepsy

Mesial temporal lobe epilepsy (mTLE) is the most common epilepsy syndrome which will eventually become pharmacologically intractable partial-onset seizures. Regulation of gene expression is an important process in the development of this pathology where microRNAs (miRs) are involved. The role of miRs has been widely studied in the hippocampus of rodents and patients. However, little is known about its differential expression in other brain regions such as the neocortex. The temporal neocortex plays a major role in the generation and propagation of seizures and in synaptic disruption, impairing the excitatory and inhibitory balance. Therefore, we assessed the expression of miR-146a, 34a, 1260, 1275, 1298, 451, 132 and 142-3p in the neocortex of 12 patients with mTLE and compared them with miRs expression found in 10 control samples. We noted a significant decrease in the expression of miR-34a and 1298 in patients with mTLE and a -1.49 to -7.0 fold change respectively compared with controls. Conversely, we observed a significant increase in the expression of miR-451, 1260 and 1275 in patients with a 25.67, 4.09 and a 7.07 fold change respectively compared to controls. Using Pearson correlation, we explored the association between the clinical features of mTLE patients and controls with miRs expression. In the control group we found a significant correlation only with age and miR-146a expression (r = 0.733). The analysis of mTLE patients showed a negative correlation between expression of miR-1260 (r = -0.666) and miR-1298 (r = -0.651) and age. Furthermore, we found a positive correlation between miR-146a expression with seizure frequency (r = 0.803) and a positive correlation between miR-146a and 451 expression with number of antiepileptic drugs used for presurgical treatment (r = 0.715 and 0.611 respectively), thus suggesting a positive correlation with disease severity. These miRs are associated with biological processes such as apoptosis, drug resistance, inflammation, inhibitory and excitatory synaptic transmission, axonal guidance and signaling of neurotrophins. Therefore, deepening our understanding of the targets involved in these miRs will help to elucidate the role of the neocortex in epilepsy.

Emerging Biomarkers in Vascular Cognitive Impairment and Dementia: From Pathophysiological Pathways to Clinical Application

Vascular pathology is the second most common neuropathology of dementia after Alzheimer’s disease (AD), with small vessels disease (SVD) being considered the major cause of vascular cognitive impairment and dementia (VCID). This review aims to evaluate pathophysiological pathways underlying a diagnosis of VCID. Firstly, we will discuss the role of endothelial dysfunction, blood-brain barrier disruption and neuroinflammation in its pathogenesis. Then, we will analyse different biomarkers including the ones of inflammatory responses to central nervous system tissue injuries, of coagulation and thrombosis and of circulating microRNA. Evidences on peripheral biomarkers for VCID are still poor and large-scale, prospectively designed studies are needed to translate these findings into clinical practice, in order to set different combinations of biomarkers to use for differential diagnosis among types of dementia.

Long-Term Effects of Myoinositol on Behavioural Seizures and Biochemical Changes Evoked by Kainic Acid Induced Epileptogenesis

Epilepsy is one of the most devastating neurological diseases and despite significant efforts there is no cure available. Occurrence of spontaneous seizures in epilepsy is preceded by numerous functional and structural pathophysiological reorganizations in the brain—a process called epileptogenesis. Treatment strategies targeting this process may be efficient for preventing spontaneous recurrent seizures (SRS) in epilepsy, or for modification of disease progression. We have previously shown that (i) myoinositol (MI) pretreatment significantly decreases severity of acute seizures (status epilepticus: SE) induced by kainic acid (KA) in experimental animals and (ii) that daily post-SE administration of MI for 4 weeks prevents certain biochemical changes triggered by SE. However it was not established whether such MI treatment also exerts long-term effects on the frequency of SRS. In the present study we have shown that, in KA-induced post-SE epilepsy model in rats, MI treatment for 28 days reduces frequency and duration of behavioural SRS not only during the treatment, but also after its termination for the following 4 weeks. Moreover, MI has significant effects on molecular changes in the hippocampus, including mi-RNA expression spectrum, as well as mRNA levels of sodium-MI transporter and LRRC8A subunit of the volume regulated anionic channel. Taken together, these data suggest that molecular changes induced by MI treatment may counteract epileptogenesis. Thus, here we provide data indicating antiepileptogenic properties of MI, which further supports the idea of developing new antiepileptogenic and disease modifying drug that targets MI system.

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.

Role of non-coding RNAs in non-aging-related neurological disorders

Protein coding sequences represent only 2% of the human genome. Recent advances have demonstrated that a significant portion of the genome is actively transcribed as non-coding RNA molecules. These non-coding RNAs are emerging as key players in the regulation of biological processes, and act as "fine-tuners" of gene expression. Neurological disorders are caused by a wide range of genetic mutations, epigenetic and environmental factors, and the exact pathophysiology of many of these conditions is still unknown. It is currently recognized that dysregulations in the expression of non-coding RNAs are present in many neurological disorders and may be relevant in the mechanisms leading to disease. In addition, circulating non-coding RNAs are emerging as potential biomarkers with great potential impact in clinical practice. In this review, we discuss mainly the role of microRNAs and long non-coding RNAs in several neurological disorders, such as epilepsy, Huntington disease, fragile X-associated ataxia, spinocerebellar ataxias, amyotrophic lateral sclerosis (ALS), and pain. In addition, we give information about the conditions where microRNAs have demonstrated to be potential biomarkers such as in epilepsy, pain, and ALS.

The Challenge of microRNA as a Biomarker of Epilepsy

BACKGROUND

Epilepsy is one of chronic severe neurological disorders possess to recurring seizures. And now anti-epileptic drugs are only effective in less than one third of epilepsy patients, and biomarkers predicting are not available when the specific antiepileptic drugs treated. Advanced studies have showed that miRNA may be a key in the pathogenesis of epilepsy beginning in the early 2000 years. Several target genes and pathways of miRNA which related to the therapeutic methods to epilepsy.

METHOD

We searched PubMed from Jan 1,2000 to Jan 1, 2017, using the terms "epilepsy AND microRNA AND biomarker" and "seizure AND microRNA AND biomarker". We selected articles that featured novel miRNAs in vivo epilepsy models and patients. We then selected the most relevant articles based on a subjective appraisal of their quality and mechanistic insight that could be relevant to epilepsy.

RESULTS

Decrease the expression of has-miR134 could be a potential non-invasive biomarker to use in diagnosis for the epilepsy patients for using hsa-miR-134 also be identified to distinguish patients with and without epilepsy. miR-181a show significant downregulation in the acute stage, but up regulation in the chronic stage and in the latent stage there is no changing and how about this phenomenon appearance in different stage still should be discussed in the future. Besides that, miR- 146a can down-regulated in the patients using genome-wide for serum in circulating miRNAs.miR- 124, miR-199a, and miR-128 etc. could be a candidate for the biomarker in future. miR-15a-5p and -194-5p down-regulated in epilepsy patients, in the future, it may be used as a novel biomarker for improve diagnosis.

CONCLUSION

These observations give a chance that new development for diagnosis and treatment of epilepsy patients. Advanced technique and miRNA combination may product more effective roles in epilepsy and other disease. These reports will be available to solve the application of miRNAs as biomarkers and novel therapy approaches for epilepsy. In summary, researcher who focus on miRNAs should be understanding of the causes, treatment, and diagnosis of epilepsy. exploration of any of these effects on the efficacy of these drugs is worthwhile.

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.

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.

Epigenetic interventions for epileptogenesis: A new frontier for curing epilepsy

This article highlights the emerging therapeutic potential of specific epigenetic modulators as promising antiepileptogenic or disease-modifying agents for curing epilepsy. Currently, there is an unmet need for antiepileptogenic agents that truly prevent the development of epilepsy in people at risk. There is strong evidence that epigenetic signaling, which exerts high fidelity regulation of gene expression, plays a crucial role in the pathophysiology of epileptogenesis and chronic epilepsy. These modifications are not hard-wired into the genome and are constantly reprogrammed by environmental influences. The potential epigenetic mechanisms, including histone modifications, DNA methylation, microRNA-based transcriptional control, and bromodomain reading activity, can drastically alter the neuronal gene expression profile by exerting their summative effects in a coordinated fashion. Such an epigenetic intervention appears more rational strategy for preventing epilepsy because it targets the primary pathway that initially triggers the numerous downstream cellular and molecular events mediating epileptogenesis. Among currently approved epigenetic drugs, the majority are anticancer drugs with well-established profiles in clinical trials and practice. Evidence from preclinical studies supports the premise that these drugs may be applied to a wide range of brain disorders. Targeting histone deacetylation by inhibiting histone deacetylase enzymes appears to be one promising epigenetic therapy since certain inhibitors have been shown to prevent epileptogenesis in animal models. However, developing neuronal specific epigenetic modulators requires rational, pathophysiology-based optimization to efficiently intercept the upstream pathways in epileptogenesis. Overall, epigenetic agents have been well positioned as new frontier tools towards the national goal of curing epilepsy.

miRNA-34b is directly involved in the aging of macrophages

BACKGROUND

MicroRNAs (miRNAs) are a class of short noncoding RNA that play important regulatory roles in living organisms. These RNA molecules are implicated in the development and progression of malignant diseases such as cancer and are closely associated with cell aging. Findings demonstrating that microRNA is associated with aging in macrophages have nevertheless rarely been reported.

AIMS

This study's objective was to investigate if miRNA-34 is linked to aging process of macrophages.

METHODS

We built a cell aging model in mouse RAW264.7 macrophages using D-galactose and determined the expression levels of miRNA-34a, miRNA-34b, and miRNA-34c in aging and normal macrophages by fluorescence quantitative polymerase chain reaction (q-PCR). We predicted a target gene of miRNA-34 using biological information techniques and constructed the recombinant plasmid pGL3-E2f3 for the putative target gene E2f3.

RESULTS

The expression level of miRNA-34b was 5.23 times higher in aging macrophages than in normal macrophages. The luciferase activity decreased by nearly 50 % in cells transfected with miRNA-34b mimics, while no significant decrease in luciferase activity was noted in cells transfected with the miRNA-34b inhibitor or unrelated sequences.

DISCUSSION

Our findings provide the groundwork for further research into the molecular mechanisms whereby miRNA-34b regulates the aging of macrophages.

CONCLUSIONS

miRNA-34b is associated with the aging of RAW264.7 macrophages, and E2f3 is a target gene of miRNA-34b.

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.

The involvement of Eag1 potassium channels and miR-34a in rotenone-induced death of dopaminergic SH-SY5Y cells

The loss of dopaminergic neurons and the resultant motor impairment are hallmarks of Parkinson's disease. The SH‑SY5Y cell line is a model of dopaminergic neurons, and allows for the study of dopaminergic neuronal injury. Previous studies have revealed changes in Ether à go‑go 1 (Eag1) potassium channel expression during p53-induced SH‑SY5Y apoptosis, and the regulatory involvement of microRNA‑34a (miR‑34a) was demonstrated. In the present study, the involvement of Eag1 and miR‑34a in rotenone‑induced SH‑SY5Y cell injury was investigated. Rotenone is a neurotoxin, which is often used to generate models of Parkinson's disease, since it causes the death of nigrostriatal neurons by inducing intracellular aggregation of alpha synuclein and ubiquitin. In the present study, rotenone resulted in a dose‑dependent decrease in cell viability, as revealed by 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide (MTT) and trypan blue cell counting assays. In addition, Eag1 was demonstrated to be constitutively expressed by SH‑SY5Y cells, and involved in cell viability. Suppression of Eag1 with astemizole resulted in a dose‑dependent decrease in cell viability, as revealed by MTT assay. Astemizole also enhanced the severity of rotenone‑induced injury in SH‑SY5Y cells. RNA interference against Eag1, using synthetic small interfering RNAs (siRNAs), corroborated this finding, as siRNAs potentiated rotenone‑induced injury. Eag1‑targeted siRNAs (kv10.1‑3 or EAG1hum_287) resulted in a statistically significant 16.4‑23.5% increase in vulnerability to rotenone. An increased number of apoptotic nuclei were observed in cells transfected with EAG1hum_287. Notably, this siRNA intensified rotenone‑induced apoptosis, as revealed by an increase in caspase 3/7 activity. Conversely, a miR‑34a inhibitor was demonstrated to exert neuroprotective effects. The viability of cells exposed to rotenone for 24 or 48 h and treated with miR‑34a inhibitor was restored by 8.4‑8.8%. In conclusion, Eag1 potassium channels and miR‑34a are involved in the response to rotenone-induced injury in SH‑SY5Y cells. The neuroprotective effect of mir‑34a inhibitors merits further investigations in animal models of Parkinson's disease.

Molecular Links and Biomarkers of Stroke, Vascular Dementia, and Alzheimer's Disease

Stroke is a very common neurological disease, and it occurs when the blood supply to part of the brain is interrupted and the subsequent shortage of oxygen and nutrients causes damage to the brain tissue. Stroke is the second leading cause of death and the third leading cause of disability-adjusted life years. The occurrence of stroke increases with age, but anyone at any age can suffer a stroke. Stroke can be broadly classified in two major clinical types: ischemic stroke (IS) and hemorrhagic stroke. Research also revealed that stroke, vascular dementia (VaD), and Alzheimer's disease (AD) increase with a number of modifiable factors, and most strokes can be prevented and/or controlled through pharmacological or surgical interventions and lifestyle changes. The pathophysiology of stroke, VaD, and AD is complex, and recent molecular and postmortem brain studies have revealed that multiple cellular changes have been implicated, including inflammatory responses, microRNA alterations, and marked changes in brain proteins. These molecular and cellular changes provide new information for developing therapeutic strategies for stroke and related vascular disorders treatment. IS is the major risk factor for VaD and AD. This chapter summarizes the (1) links among stroke-VaD-AD; (2) updates the latest developments of research in identifying protein biomarkers in peripheral and central nervous system tissues; and (3) critically evaluates miRNA profile and function in human blood samples, animal, and postmortem brains.

microRNAs in the pathophysiology of epilepsy

Temporal lobe epilepsy is a common and often drug-resistant seizure disorder. The underlying pathological processes which give rise to the development of spontaneous seizures include neuroinflammation, cell loss, neurogenesis and dendritic abnormalities and many of these are driven by insult-induced changes in gene expression and gene expression regulation. MicroRNAs are powerful modulators of post-transcriptional gene expression which are dysregulated during epileptogenesis. The advent of locked nucleic acid (LNA) based inhibitory methods and mimic technology has facilitated in vivo functional assessment of these molecules in epilepsy. Here we review recent advances in our understanding of the role of these short non-coding RNAs in the pathophysiology of epilepsy.

MicroRNA expression profiles in chronic epilepsy rats and neuroprotection from seizures by targeting miR-344a

MicroRNA (miRNA) is believed to play a crucial role in the cause and treatment of epilepsy by controlling gene expression. However, it is still unclear how miRNA profiles change after multiple prolonged seizures and aggravation of brain injury in chronic epilepsy (CE). To investigate the role of miRNA in epilepsy, we utilized the CE rat models with pentylenetetrazol (PTZ) and miRNA profiles in the hippocampus. miRNA profiles were characterized using miRNA microarray analysis and were compared with the rats in the sham group, which received 0.9% physiological saline treatment at the same dose. Four up-regulated miRNAs (miR-139-3p, -770-5p, -127-5p, -331-3p) and 5 down-regulated miRNAs (miR-802-5p, -380-5p, -183-5p, -547-5p, -344a/-344a-5p) were found in the CE rats (fold change >1.5, P<0.05). Three of the dysregulated miRNAs were validated by quantitative real-time polymerase chain reaction, which revealed an outcome consistent with the initial results of the miRNA microarray analyses. Then, miR-344a agomir was intracerebroventricularly injected and followed by PTZ induction of CE models to investigate the effect of miR-344a in chronic neocortical epileptogenesis. After miRNA-344a agomir and scramble treatment, results showed a restoration of seizure behavior and a reduction in neuron damage in the cortex in miRNA-334a agomir treated rats. These data suggest that miRNA-344a might have a small modulatory effect on seizure-induced apoptosis signaling pathways in the cortex.

Modulation of miR-146a/complement factor H-mediated inflammatory responses in a rat model of temporal lobe epilepsy

Increasing evidence supports the involvement of inflammatory and immune processes in temporal lobe epilepsy (TLE). miRNAs represent small regulatory RNA molecules that have been shown to act as negative regulators of gene expression controlling different biological processes, including immune system homoeostasis and function. We investigated the expression and cellular distribution of miRNA-146a (miR-146a) in a rat model of TLE. Prominent up-regulation of miR-146a activation was evident in 1 week after status epilepticus (SE) and persisted in the chronic phase. The predicted miR-146a's target complement factor H (CFH) mRNA and protein expression was also down-regulated in TLE rat model. Furthermore, transfection of miR-146a mimics in neuronal and glial cells down-regulated CFH mRNA and protein levels respectively. Luciferase reporter assays demonstrated that miR-146a down-regulated CFH mRNA expression via 3'-UTR pairing. Down-regulating miR-146a by intracerebroventricular injection of antagomir-146a enhanced the hippocampal expression of CFH in TLE model and decreased seizure susceptibility. These findings suggest that immunopathological deficits associated with TLE can in part be explained by a generalized miR-146a-mediated down-regulation of CFH that may contribute to epileptogenesis in a rat model of TLE.

miRNA-187-3p-Mediated Regulation of the KCNK10/TREK-2 Potassium Channel in a Rat Epilepsy Model

Regulatory RNAs play a key role in the regulation of protein expression patterns in neurological diseases. Here we studied the regulation of miRNAs in a chronic rat model of temporal lobe epilepsy. The analysis was focused on a putative link with pharmacoresponsiveness as well as the functional implications of the regulation of a selected miRNA. The findings did not reveal a difference in hippocampal miRNA expression between phenobarbital responders and nonresponders. However, when comparing rats following status epilepticus with control rats we identified 13 differentially expressed miRNAs with miRNA-187-3p being most strongly regulated. mRNAs encoding KCNK10/TREK-2 as well as DYRK2 were confirmed as targets of miRNA-187-3p. Expression of the potassium channel protein KCNK10/TREK-2 negatively correlated with hippocampal miRNA-187-3p expression and proved to be upregulated in the chronic phase of the epilepsy model. In conclusion, our data do not suggest a relevant impact of miRNA expression patterns on pharmacoresponsiveness. However, we confirmed regulation of miRNA-187-3p and demonstrated that it impacts the expression of the two-pore domain potassium channel protein KCNK10/TREK-2. Considering evidence from brain ischemia models, KCNK10/TREK-2 upregulation might serve a protective function with a beneficial impact on astrocytic potassium and glutamate homeostasis.

A calcium-sensitive feed-forward loop regulating the expression of the ATP-gated purinergic P2X7 receptor via specificity protein 1 and microRNA-22

Cells have developed complex transcriptional regulatory mechanisms to maintain intracellular homeostasis and withstand pathophysiological stressors. Feed-forward loops comprising transcription factors that drive expression of both target gene and a microRNA as negative regulator, are gaining increasing recognition as key regulatory elements of cellular homeostasis. The ATP-gated purinergic P2X7 receptor (P2X7R) is an important driver of inflammation and has been implicated in the pathogenesis of numerous brain diseases including epilepsy. Changes in P2X7R expression have been reported in both experimental models and in epilepsy patients but the mechanism(s) controlling P2X7R levels remain incompletely understood. The specificity protein 1 (Sp1) has been shown to induce P2X7R transcription in vitro and recent data has identified microRNA-22 as a post-transcriptional repressor of P2X7R expression after seizures. In the present study we show that Sp1 can induce the transcription of both microRNA-22 and P2X7R in vitro during increased neuronal activity and in vivo in a mouse model of status epilepticus. We further show that Sp1-driven microRNA-22 transcription is calcium-sensitive and Sp1 occupancy of the microRNA-22 promoter region is blocked under conditions of seizure activity sufficient to elicit neuronal death. Taken together, our results suggest a neuronal activity-dependent P2X7R expression which is induced by the transcription factor Sp1 and repressed in a calcium-dependent manner by microRNA-22.

Identification of serum miRNAs differentially expressed in human epilepsy at seizure onset and post-seizure

MicroRNAs (miRNAs) function as potential novel biomarkers for disease detection due to their marked stability in the blood and the characteristics of their expression profile in several diseases. In the present study, microarray‑based serum miRNA profiling was performed on serum obtained from three patients with epilepsy at diagnosis and from three healthy individuals as controls. This was followed by reverse transcription‑quantitative polymerase chain reaction analysis in a separate cohort of 35 health volunteers and 90 patients with epilepsy. The correlations between miRNAs and clinical parameters were analyzed. The array results showed that 15 miRNAs were overexpressed and 10 miRNAs were underexpressed (>2‑fold) in the patients with epilepsy. In addition, four miRNAs, including miR‑30a, miR‑378, miR‑106b and miR‑15a were found to be overexpressed in the serum of patients at seizure onset, compared with post‑seizure. When the patients were at seizure onset, the expression of miR‑30a was positively associated with seizure frequency. No significant differences were found between miR‑30a and gender, age or number of years following diagnosis. The expression levels of miR‑378, miR‑106b and mir‑15a were not associated with the clinical parameters in the patients with seizures. Calcium/calmodulin‑dependent protein kinase type IV was a target of miR‑30a, and its expression was increased following seizure and was negatively correlated with miR‑30a in the patients with epilepsy. The present study provided the first evidence, to the best of our knowledge, that the expression levels of miR‑378, miR‑30a, miR‑106b and miR‑15a were enhanced in epileptic patients with seizures. miR-30a may be useful for prognostic prediction in epilepsy.

Increased precursor microRNA-21 following status epilepticus can compete with mature microRNA-21 to alter translation

MicroRNA-21 (miR-21) is consistently up-regulated in various neurological disorders, including epilepsy. Here, we show that the biogenesis of miR-21 is altered following pilocarpine-induced status epilepticus (SE) with an increase in precursor miR-21 (pre-miR-21) in rats. We demonstrate that pre-miR-21 has an energetically favorable site overlapping with the miR-21 binding site and competes with mature miR-21 for binding in the 3'UTR of TGFBR2 mRNA, but not NT-3 mRNA in vitro. This binding competition influences miR-21-mediated repression in vitro and correlates with the increase in TGFBR2 and decrease in NT-3 following SE. Polysome profiling reveals co-localization of pre-miR-21 in the ribosome fraction with translating mRNAs in U-87 cells. The current work suggests that pre-miR-21 may post-transcriptionally counteract miR-21-mediated suppression following SE and could potentially lead to prolonged TGF-β receptor expression impacting epileptogenesis. The study further supports that the ratio of the pre to mature miRNA may be important in determining the regulatory effects of a miRNA gene.

Expression of microRNA-129-2-3p and microRNA-935 in plasma and brain tissue of human refractory epilepsy

OBJECTIVE

Numerous microRNAs (miRNAs) are differentially expressed in specific diseases, suggesting possible use as diagnostic or prognostic biomarkers. The purpose of this study is to investigate the expression levels of miR-129-2-3p and miR-935 in cortical brain tissue and plasma samples from controls and refractory temporal lobe epilepsy (TLE) patients to evaluate the utility of these measures as diagnostic biomarkers.

METHODS

The study was divided into three phases. First, cortical brain tissue samples from nine refractory TLE patients and eight controls were screened for differential miRNA expression using the Affymetrix miRNA 4.0 microarray. Second, real-time quantitative PCR (qRT-PCR) was used to verify the microarray results in brain tissue samples from 13 refractory TLE patients and 13 healthy controls (including those studied by microarray analysis). Third, we tested the expression levels of selected miRNAs in plasma samples from 25 refractory TLE patients and 25 healthy volunteers by qRT-PCR. The capacity of miR-129-2-3p and miR-935 expression to distinguish refractory TLE from health controls was tested by receiver operator characteristics (ROC) curve analysis.

RESULTS

(1) High-resolution miRNA arrays indicated that miR-129-2-3p and miR-935 were significantly upregulated in the cortical brain tissues of TLE patients compared to controls. (2) qRT-PCR confirmed upregulated miR-129-2-3p expression in the brain tissue(P<0.0001) and plasma samples(P=0.0008) of refractory TLE patients. (3) The expression of miR-935 in epilepsy patients was higher than control group, however, there are no significant statistical differences between them whether in plasma samples(P=0.644) or in tissue samples(P=0.258). (4) ROC analysis of miRNA-129-2-3p showed that the area under the curve (AUC) was 0.929 (95% CI: 0.833-1.000; p=0.000) for brain tissue and 0.778 (95% CI: 0.640-0.915; p=0.001) for plasma.

CONCLUSION

Expression of miRNA-129-2-3p was upregulated in cortical brain tissue and plasma samples from patients with refractory TLE, but miR-935 not. Plasma miRNA-129-2-3p has great potential as a non-invasive biomarker for early detection and clinical evaluation of refractory TLE.

Increased Expression of mir-34a-5p and Clinical Association in Acute Ischemic Stroke Patients and in a Rat Model

BACKGROUND MiRNA is widely recognized as the most important regulator in various diseases. However, there has been little research regarding miRNA expression and its involvement in ischemic stroke. MATERIAL AND METHODS In this study, we investigated the pattern of miRNA-34a-5p expression along with its clinical application in human ischemic stroke and in an in vivo rat model. We recruited 102 cerebral ischemia patients and 97 health controls for this study. Clinical data were gathered and recorded with the help of questionnaires. Blood samples were obtained from patients within 72 h after cerebral ischemia. National Institutes of Health Stroke Scale (NIHSS), Acute Stroke Treatment (TOAST), and infarct volume were used to analyze the correlation of miRNA-34a-5p expression and clinical information. In addition, blood samples and brain tissues were collected from an established middle cerebral artery occlusion (MCAO) model consisting of 20 adult male mice at 24 h after the MCAO. Expression level of miRNA-34a-5p was detected by real-time polymerase chain reactions. RESULTS Results showed overexpression of miRNA-34a-5p in acute ischemic stroke patients blood samples compared to the controls (p<0.05). Also, large and small arterial strokes types demonstrated elevated miRNA-34a-5p expression levels. Further correlation analysis revealed a negative association between miRNA-34a-5p and NIHSS scores (r=-0.692 p<0.05) and infarct volume (r=-0.719, p<0.05). Moreover, in vivo experiment results showed significant up-regulated expression of miRNA-34a-5p in middle cerebral artery occlusion compared to controls, along with a positive correlation between miRNA-34a-5p in blood and brain (r=0.742, p<0.05). CONCLUSIONS Our results suggest there is a potential regulatory role of miRNA-34a-5p in acute ischemic stroke, which could serve as a therapeutic target or biomarker in stroke prognosis.

An evaluation of the links between microRNA, autophagy, and epilepsy

Epilepsy is a serious chronic neurologic disorder characterized by recurrent unprovoked seizures resulting from abnormal and highly synchronous neuronal discharges within the brain. Small noncoding RNAs, called microRNAs, play vital roles in epileptogenesis, with potential contributions as valuable biomarkers and targets for the treatment of epilepsy. To maintain cellular homeostasis, cellular components, such as organelles, proteins, protein complexes/oligomers, and pathogens, are delivered to the lysosome for degradation through a process called autophagy, which plays either a protective or a harmful role under epileptic stress. Several autophagic mechanisms have been implicated in epileptogenesis, including the mammalian target of rapamycin pathway, aberrant substrate accumulation, and the formation of epileptic networks. In addition, the regulation of autophagy through microRNAs (miRNAs) represents a novel posttranscriptional regulatory mechanism through 'autophagamiRNAs'. The correlation between autophagy and miRNA has increased our understanding of the underlying pathogenesis of human diseases. Here, we review the current findings regarding the correlations between miRNA, autophagy, and epilepsy to provide a solid foundation for further examination of the miRNA-autophagy pathway involved in epilepsy pathophysiology.

MicroRNA-34b mediates hippocampal astrocyte apoptosis in a rat model of recurrent seizures

Background

Recurrent convulsions can cause irreversible astrocyte death, impede neuron regeneration, and further aggravate brain damage. MicroRNAs have been revealed as players in the progression of numerous diseases including cancer and Alzheimer’s disease. Particularly, microRNA has been found linked to seizure-induced neuronal death. In this study, a rat model of recurrent convulsions induced by flurothyl treatments was utilised to assess the alterations of microRNA expressions in hippocampus tissues. We also applied an in vitro model in which primary astrocytes were exposed to kainic acid to verify the targets of miR-34b-5p identified in the animal model.

Results

We discovered that miR-34b-5p, a member of the miR-34 family, increased significantly in flurothyl-treated rat hippocampus tissue. More surprisingly, this upregulation occurred concurrently with accumulating astrocyte apoptosis, indicating the involvement of miR-34b-5p in seizures caused astrocyte apoptosis. Results from the in vitro experiments further demonstrated that miR-34b-5p directly targeted Bcl-2 mRNA, translationally repressed Bcl-2 protein, and thus modulated cell apoptosis by influencing Bcl-2, Bax, and Caspase-3.

Conclusion

Our findings prove microRNAs play a role in mediating recurrent convulsions-induced astrocyte death and further indicate that miR-34b-5p could acts as a regulator for astrocyte apoptosis induced by recurrent seizures.

Electronic supplementary material

The online version of this article (doi:10.1186/s12868-016-0291-6) contains supplementary material, which is available to authorized users.

Inhibition of microRNA 128 promotes excitability of cultured cortical neuronal networks

Cultured neuronal networks monitored with microelectrode arrays (MEAs) have been used widely to evaluate pharmaceutical compounds for potential neurotoxic effects. A newer application of MEAs has been in the development of in vitro models of neurological disease. Here, we directly evaluated the utility of MEAs to recapitulate in vivo phenotypes of mature microRNA-128 (miR-128) deficiency, which causes fatal seizures in mice. We show that inhibition of miR-128 results in significantly increased neuronal activity in cultured neuronal networks derived from primary mouse cortical neurons. These results support the utility of MEAs in developing in vitro models of neuroexcitability disorders, such as epilepsy, and further suggest that MEAs provide an effective tool for the rapid identification of microRNAs that promote seizures when dysregulated.

miRNAs: Key Players in Neurodegenerative Disorders and Epilepsy

MicroRNAs (miRNAs) are endogenous, ∼22 nucleotide, non-coding RNA molecules that function as post-transcriptional regulators of gene expression. miRNA dysregulation has been observed in cancer and in neurodegenerative disorders such as Alzheimer's, Parkinson's, and Huntington's diseases, amyotrophic lateral sclerosis, and the neurological disorder, epilepsy. Neuronal degradation and death are important hallmarks of neurodegenerative disorders. Additionally, abnormalities in metabolism, synapsis and axonal transport have been associated with Alzheimer's disease, Parkinson's disease, and frontotemporal dementia. A number of recently published studies have demonstrated the importance of miRNAs in the nervous system and have contributed to the growing body of evidence on miRNA dysregulation in neurological disorders. Knowledge of the expressions and activities of such miRNAs may aid in the development of novel therapeutics. In this review, we discuss the significance of miRNA dysregulation in the development of neurodegenerative disorders and the use of miRNAs as targets for therapeutic intervention.

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.

Association of the genetic polymorphisms in pre-microRNAs with risk of childhood epilepsy in a Chinese population

PURPOSE

MicroRNA (miRNA), functions as gene regulators, plays crucial roles in pathogenesis of epilepsy. We hypothesized that single nucleotide polymorphisms (SNPs) in miRNA may be associated with childhood epilepsy.

METHOD

We first genotyped the selected four SNPs (miR-146a rs57095329, miR-149 rs2292832, miR-196a2 rs11614913, and miR-499 rs3746444) in 267 paired childhood epilepsy patients and controls using the TaqMan assay, and evaluated the associations of the four SNPs with the risk of epilepsy. In addition, we evaluated the associations of these SNPs with drug-resistance in 95 drug-resistant and 172 drug-responsive epilepsy patients. Furthermore, the genotype-phenotype correlation was assessed in 95 drug-resistant epilepsy patients.

RESULTS

The selected four SNPs (miR-146a rs57095329, miR-149 rs2292832, miR-196a2 rs11614913, and miR-499 rs3746444) were not significantly different between epilepsy patients and controls (P>0.05 for all). However, the miR-146a rs57095329 A/G genotypes were significantly associated with increased drug-resistance risk of epilepsy patients in allelic comparison (OR=2.363, 95%CI=1.608-3.472, P<0.001), heterozygote model (OR=2.341, 95%CI=1.301-4.211, P=0.005), homozygote model (OR=1.791, 95%CI=1.239-2.589, P=0.002), dominant model (OR=2.625, 95%CI=1.558-4.425, P<0.001), and recessive model (OR=2.336, 95%CI=1.166-4.673, P=0.017). Moreover, subjects with the rs57095329 GG genotype had significantly higher NHS3 score than subjects with AA genotype (P<0.001) and AG genotype (P=0.013) in the drug resistant patients.

CONCLUSION

miR-146a rs57095329 polymorphism might be involved in the genetic susceptibility to drug-resistance and seizure severity in childhood epilepsy patients.

Analysis of Altered Micro RNA Expression Profiles in Focal Cortical Dysplasia IIB

Focal cortical dysplasia type IIB is a commonly encountered subtype of developmental malformation of the cerebral cortex and is often associated with pharmacoresistant epilepsy. In this study, to investigate the molecular etiology of focal cortical dysplasia type IIB, the authors performed micro ribonucleic acid (RNA) microarray on surgical specimens from 5 children (2 female and 3 male, mean age was 73.4 months, range 50-112 months) diagnosed of focal cortical dysplasia type IIB and matched normal tissue adjacent to the lesion. In all, 24 micro RNAs were differentially expressed in focal cortical dysplasia type IIB, and the microarray results were validated using quantitative real-time polymerase chain reaction (PCR). Then the putative target genes of the differentially expressed micro RNAs were identified by bioinformatics analysis. Moreover, biological significance of the target genes was evaluated by investigating the pathways in which the genes were enriched, and the Hippo signaling pathway was proposed to be highly related with the pathogenesis of focal cortical dysplasia type IIB.

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.