Neuronal calcium signaling pathways are associated with the development of epilepsy

Modeling seizure networks in neuron-glia cultures using microelectrode arrays

Epilepsy is a common neurological disorder, affecting over 65 million people worldwide. Unfortunately, despite resective surgery, over 30 % of patients with drug-resistant epilepsy continue to experience seizures. Retrospective studies considering connectivity using intracranial electrocorticography (ECoG) obtained during neuromonitoring have shown that treatment failure is likely driven by failure to consider critical components of the seizure network, an idea first formally introduced in 2002. However, current studies only capture snapshots in time, precluding the ability to consider seizure network development. Over the past few years, multiwell microelectrode arrays have been increasingly used to study neuronal networks in vitro. As such, we sought to develop a novel in vitro MEA seizure model to allow for study of seizure networks. Specifically, we used 4-aminopyridine (4-AP) to capture hyperexcitable activity, and then show increased network changes after 2 days of chronic treatment. We characterize network changes using functional connectivity measures and a novel technique using dimensionality reduction. We find that 4-AP successfully captures persistently elevated mean firing rate and significant changes in underlying connectivity patterns. We believe this affords a robust in vitro seizure model from which longitudinal network changes can be studied, laying groundwork for future studies exploring seizure network development.

Regulation of specific abnormal calcium signals in the hippocampal CA1 and primary cortex M1 alleviates the progression of temporal lobe epilepsy

Temporal lobe epilepsy is a multifactorial neurological dysfunction syndrome that is refractory, resistant to antiepileptic drugs, and has a high recurrence rate. The pathogenesis of temporal lobe epilepsy is complex and is not fully understood. Intracellular calcium dynamics have been implicated in temporal lobe epilepsy. However, the effect of fluctuating calcium activity in CA1 pyramidal neurons on temporal lobe epilepsy is unknown, and no longitudinal studies have investigated calcium activity in pyramidal neurons in the hippocampal CA1 and primary motor cortex M1 of freely moving mice. In this study, we used a multi-channel fiber photometry system to continuously record calcium signals in CA1 and M1 during the temporal lobe epilepsy process. We found that calcium signals varied according to the grade of temporal lobe epilepsy episodes. In particular, cortical spreading depression, which has recently been frequently used to represent the continuously and substantially increased calcium signals, was found to correspond to complex and severe behavioral characteristics of temporal lobe epilepsy ranging from grade II to grade V. However, vigorous calcium oscillations and highly synchronized calcium signals in CA1 and M1 were strongly related to convulsive motor seizures. Chemogenetic inhibition of pyramidal neurons in CA1 significantly attenuated the amplitudes of the calcium signals corresponding to grade I episodes. In addition, the latency of cortical spreading depression was prolonged, and the above-mentioned abnormal calcium signals in CA1 and M1 were also significantly reduced. Intriguingly, it was possible to rescue the altered intracellular calcium dynamics. Via simultaneous analysis of calcium signals and epileptic behaviors, we found that the progression of temporal lobe epilepsy was alleviated when specific calcium signals were reduced, and that the end-point behaviors of temporal lobe epilepsy were improved. Our results indicate that the calcium dynamic between CA1 and M1 may reflect specific epileptic behaviors corresponding to different grades. Furthermore, the selective regulation of abnormal calcium signals in CA1 pyramidal neurons appears to effectively alleviate temporal lobe epilepsy, thereby providing a potential molecular mechanism for a new temporal lobe epilepsy diagnosis and treatment strategy.

Molecular tools for the characterization of seizure susceptibility in genetic rodent models of epilepsy

Epilepsy is a chronic neurological disorder characterized by abnormal neuronal activity that arises from imbalances between excitatory and inhibitory synapses, which are highly correlated to functional and structural changes in specific brain regions. The difference between the normal and the epileptic brain may harbor genetic alterations, gene expression changes, and/or protein alterations in the epileptogenic nucleus. It is becoming increasingly clear that such differences contribute to the development of distinct epilepsy phenotypes. The current major challenges in epilepsy research include understanding the disease progression and clarifying epilepsy classifications by searching for novel molecular biomarkers. Thus, the application of molecular techniques to carry out comprehensive studies at deoxyribonucleic acid, messenger ribonucleic acid, and protein levels is of utmost importance to elucidate molecular dysregulations in the epileptic brain. The present review focused on the great diversity of technical approaches available and new research methodology, which are already being used to study molecular alterations underlying epilepsy. We have grouped the different techniques according to each step in the flow of information from DNA to RNA to proteins, and illustrated with specific examples in animal models of epilepsy, some of which are our own. Separately and collectively, the genomic and proteomic techniques, each with its own strengths and limitations, provide valuable information on molecular mechanisms underlying seizure susceptibility and regulation of neuronal excitability. Determining the molecular differences between genetic rodent models of epilepsy and their wild-type counterparts might be a key in determining mechanisms of seizure susceptibility and epileptogenesis as well as the discovery and development of novel antiepileptic agents. This article is part of the Special Issue "NEWroscience 2018".

Neuronal Excitability in Epileptogenic Zones Regulated by the Wnt/ Β-Catenin Pathway

Epilepsy is a neurological disorder that involves abnormal and recurrent neuronal discharges, producing epileptic seizures. Recently, it has been proposed that the Wnt signaling pathway is essential for the central nervous system development and function because it modulates important processes such as hippocampal neurogenesis, synaptic clefting, and mitochondrial regulation. Wnt/β- catenin signaling regulates changes induced by epileptic seizures, including neuronal death. Several genetic studies associate Wnt/β-catenin signaling with neuronal excitability and epileptic activity. Mutations and chromosomal defects underlying syndromic or inherited epileptic seizures have been identified. However, genetic factors underlying the susceptibility of an individual to develop epileptic seizures have not been fully studied yet. In this review, we describe the genes involved in neuronal excitability in epileptogenic zones dependent on the Wnt/β-catenin pathway.

A genome-wide screen reveals microRNAs in peripheral sensory neurons driving painful diabetic neuropathy

ABSTRACT

Diabetes is a leading cause of peripheral neuropathy (diabetic peripheral neuropathy, DPN), and uncontrolled long-lasting hyperglycemia leads to severe complications. A major proportion of diabetics develop excruciating pain with a variable course. Mechanisms leading to painful DPN are not completely understood and treatment options limited. We hypothesized that epigenetic modulation at the level of microRNA (miRNA) expression triggered by metabolic imbalance and nerve damage regulates the course of pain development. We used clinically relevant preclinical models, genome-wide screening, in silico analyses, cellular assays, miRNA fluorescent in situ hybridization, in vivo molecular manipulations, and behavioral analyses in the current study. We identified miRNAs and their targets that critically impact on nociceptive hypersensitivity in painful DPN. Our analyses identify miR-33 and miR-380 expressed in nociceptive neurons as critical denominators of diabetic pain and miR-124-1 as a mediator of physiological nociception. Our comprehensive analyses on the putative mRNA targets for miR-33 or miR-124-1 identified a set of mRNAs that are regulated after miR-33 or miR-124-1 overexpression in dorsal root ganglia in vivo. Our results shed light on the regulation of DPN pathophysiology and implicate specific miRNAs as novel therapeutic targets for treating painful DPN.

Involvement of nNOS, and α1, α2, β1, and β2 Subunits of Soluble Guanylyl Cyclase Genes Expression in Anticonvulsant Effect of Sumatriptan on Pentylenetetrazole-Induced Seizure in Mice

Epileptic seizure is phenomenon of abnormal synchronous neuronal discharge of a set of neurons in brain as a result of neuronal excitation. Evidence shows the nitric oxide (NO) involvement in neuronal excitability. Moreover, the role of cyclic guanosine monophosphate (cGMP) activation in seizure pathogenesis is well-established. Sumatriptan is a selective agonist of 5-Hydroxytryptamine1B/D auto-receptor, has been reassessed for its neuroprotection. This study was aimed to explore the anticonvulsant effect of sumatriptan through possible involvement of NO-cGMP pathway in mice. For this purpose, the protective effect of sumatriptan on PTZ-induced clonic seizure threshold (CST) was measured using NO-cGMP pathway inhibitors including N(G)-nitro-L-arginine (L-NNA, 1, 5, and 10 mg/kg), 7-nitroindazole (7-NI, 30, 45, and 60 mg/kg), aminoguanidine (AG, 30, 50, and 100 mg/kg), methylene blue (MB, 0.1, 0.5, and 1 mg/kg) and sildenafil (5, 10, and 20 mg/kg). The involvement of nitrergic system was further confirmed by measurement of nitrite levels by Griess reaction. The gene expression of neuronal nitric oxide synthase (nNOS) and subunits of soluble guanylyl cyclase (sGC) was studied using qRT-PCR analysis. Acute administration of sumatriptan (1.2 and 0.3 mg/kg) in combination with subeffective doses of NOS, sGC, and phosphodiesterase 5 inhibitors significantly reversed the PTZ-induced CST (P ≤ 0.001). The nitrite level in prefrontal cortex was significantly attenuated by sumatriptan (P ≤ 0.01). Furthermore, sumatriptan downregulated the PTZ-induced mRNA expression of nNOS (P ≤ 0.01), α1 (P ≤ 0.001), α2 (P ≤ 0.05), and β1 (P ≤ 0.05) genes in cerebral cortex of mice. In conclusion, the anticonvulsant activity of sumatriptan at least, in part, is mediated through inhibiting NO-cGMP pathway.

Effects of febrile seizures in mesial temporal lobe epilepsy with hippocampal sclerosis on gene expression using bioinformatical analysis

Background

To investigate the effect of long-term febrile convulsions on gene expression in mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) and explore the molecular mechanism of MTLE-HS.

Methods

Microarray data of MTLE-HS were obtained from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) between MTLE-HS with and without febrile seizure history were screened by the GEO2R software. Pathway enrichment and gene ontology of the DEGs were analyzed using the DAVID online database and FunRich software. Protein–protein interaction (PPI) networks among DEGs were constructed using the STRING database and analyzed by Cytoscape.

Results

A total of 515 DEGs were identified in MTLE-HS samples with a febrile seizure history compared to MTLE-HS samples without febrile seizure, including 25 down-regulated and 490 up-regulated genes. These DEGs were expressed mostly in plasma membrane and synaptic vesicles. The major molecular functions of those genes were voltage-gated ion channel activity, extracellular ligand-gated ion channel activity and calcium ion binding. The DEGs were mainly involved in biological pathways of cell communication signal transduction and transport. Five genes (SNAP25, SLC32A1, SYN1, GRIN1,andGRIA1) were significantly expressed in the MTLE-HS with prolonged febrile seizures.

Conclusion

The pathogenesis of MTLE-HS involves multiple genes, and prolonged febrile seizures could cause differential expression of genes. Thus, investigations of those genes may provide a new perspective into the mechanism of MTLE-HS.

Autophagy-Associated lncRNAs: Promising Targets for Neurological Disease Diagnosis and Therapy

Neurological diseases are a major threat to global public health and prosperity. The number of patients with neurological diseases is increasing due to the population aging and increasing life expectancy. Autophagy is one of the crucial mechanisms to maintain nerve cellular homeostasis. Numerous studies have demonstrated that autophagy plays a dual role in neurological diseases. Long noncoding RNAs (lncRNAs) are a vital class of noncoding RNAs with a length of more than 200 nucleotides and cannot encode proteins themselves but are expressed in most neurological diseases. An early phase, emerging knowledge has revealed that long noncoding RNAs (lncRNAs) are crucial in autophagy regulation. Furthermore, autophagy-associated lncRNAs can promote the development of neurological diseases or slow their progression. In this review, we introduce a general overview of lncRNA functional mechanisms and summarizes the recent progress of lncRNAs on autophagy regulation in neurological diseases to reveal possible novel therapeutic targets or useful biomarkers.

Downregulation of MicroRNA-33-5p Protected Bupivacaine-Induced Apoptosis in Murine Dorsal Root Ganglion Neurons Through GDNF

In this work, we evaluated the functional role of microRNA-33-5p (miR-33-5p) in regulating bupivacaine (Bv)-induced neural apoptosis in dorsal root ganglion (DRG) cells. DRG was extracted from adult mice and treated with BV in vitro. A TUNEL assay was applied to assess neural apoptosis among DRG cells. A qRT-PCR assay was applied to assess miR-33-5p expression among BV-treated DRG cells. MiR-33-5p was genetically knocked down in DRG cells. Its effect on BV-induced neural apoptosis was further evaluated by TUNEL assay. Correlation between miR-33-5p and its putative downstream target gene, glial cell-derived neurotrophic factor (GDNF), was assessed by dual-luciferase activity and qRT-PCR assays, respectively. GDNF was then inhibited in miR-33-5p-downregulated DRG cells to further assess its functional regulation in BV-induced neural apoptosis. BV induced significant neural apoptosis, in a dose-dependent manner, in DRG cells in vitro. MiR-33-5p was upregulated by BV treatment, also in a dose-dependent manner in DRG cells. On the other hand, downregulation of miR-33-5p protected BV-induced DRG neural apoptosis. GDNF was shown to be inversely correlated with miR-33-5p in BV-treated DRG cells. Moreover, inhibiting GDNF was able to reverse the protection of miR-33-5p-downregulation on BV-induced DRG neural apoptosis. MiR-33-5p, through its inverse regulation on DGNF gene, modulates anesthesia-induced neural apoptosis in DRG cells.

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.

The microRNA miR-21 conditions the brain to protect against ischemic and traumatic injuries

Ischemic and traumatic injuries to CNS remain leading causes of death and disability worldwide, despite decades of research into risk factors, therapies, and preventative measures. Recent studies showed that CNS injuries significantly alter the cerebral microRNAome that impact the secondary brain damage as well as plasticity and recovery. Many microRNA based therapies are currently in various clinical trials for different pathologic conditions indicating their therapeutic potential. In the present review, we discuss the role of miR-21 in acute CNS injuries which is currently thought to be a potent neuroprotective microRNA. We emphasize on the potential of miR-21 in promoting cell and tissue survival and preventing inflammation and apoptosis. We also discussed the role of miR-21 in conditioning the brain to promote ischemic tolerance. Finally, we discussed some of the challenges and difficulties to develop miR-21 as a neuroprotective therapy in humans.

MicroRNA profiling in the dentate gyrus in epileptic rats: The role of miR-187-3p

This study aimed to explore the role of aberrant miRNA expression in epilepsy and to identify more potential genes associated with epileptogenesis.The miRNA expression profile of GSE49850, which included 20 samples from the rat epileptic dentate gyrus at 7, 14, 30, and 90 days after electrical stimulation and 20 additional samples from sham time-matched controls, was downloaded from the Gene Expression Omnibus database. The significantly differentially expressed miRNAs were identified in stimulated samples at each time point compared to time-matched controls, respectively. The target genes of consistently differentially expressed miRNAs were screened from miRDB and microRNA.org databases, followed by Gene Ontology (GO) and pathway enrichment analysis and regulatory network construction. The overlapping target genes for consistently differentially expressed miRNAs were also identified from these 2 databases. Furthermore, the potential binding sites of miRNAs and their target genes were analyzed.Rno-miR-187-3p was consistently downregulated in stimulated groups compared with time-matched controls. The predicted target genes of rno-miR-187-3p were enriched in different GO terms and pathways. In addition, 7 overlapping target genes of rno-miR-187-3p were identified, including NFS1, PAQR4, CAND1, DCLK1, PRKAR2A, AKAP3, and KCNK10. These 7 overlapping target genes were determined to have a different number of matched binding sites with rno-miR-187-3p.Our study suggests that miR-187-3p may play an important role in epilepsy development and progression via regulating numerous target genes, such as NFS1, CAND1, DCLK1, AKAP3, and KCNK10. Determining the underlying mechanism of the role of miR-187-3p in epilepsy may make it a potential therapeutic option.

MicroRNA profiles in hippocampal granule cells and plasma of rats with pilocarpine-induced epilepsy--comparison with human epileptic samples

The identification of biomarkers of the transformation of normal to epileptic tissue would help to stratify patients at risk of epilepsy following brain injury, and inform new treatment strategies. MicroRNAs (miRNAs) are an attractive option in this direction. In this study, miRNA microarrays were performed on laser-microdissected hippocampal granule cell layer (GCL) and on plasma, at different time points in the development of pilocarpine-induced epilepsy in the rat: latency, first spontaneous seizure and chronic epileptic phase. Sixty-three miRNAs were differentially expressed in the GCL when considering all time points. Three main clusters were identified that separated the control and chronic phase groups from the latency group and from the first spontaneous seizure group. MiRNAs from rats in the chronic phase were compared to those obtained from the laser-microdissected GCL of epileptic patients, identifying several miRNAs (miR-21-5p, miR-23a-5p, miR-146a-5p and miR-181c-5p) that were up-regulated in both human and rat epileptic tissue. Analysis of plasma samples revealed different levels between control and pilocarpine-treated animals for 27 miRNAs. Two main clusters were identified that segregated controls from all other groups. Those miRNAs that are altered in plasma before the first spontaneous seizure, like miR-9a-3p, may be proposed as putative biomarkers of epileptogenesis.

Micro RNA expression profiles in peripheral blood cells of rats that were experimentally infected with Trypanosoma congolense and different Trypanosoma brucei subspecies

To identify miRNAs whose expression are differentially regulated during trypanosome infections a microarray targeting more than 600 rat miRNA was used to analyze the miRNA expression profiles between uninfected rats and animals infected by Trypanosoma congolense and Trypanosoma brucei s.l. The potential targets of dysregulated miRNAs as well as their biological pathways and functions were predicted using several bioinformatics software tools. Irrespective of the infecting trypanosome species, eight miRNAs (seven up- and one down-regulated) were dysregulated during infections. Moreover, other miRNAs were differentially regulated in rats infected by specific trypanosome species. Functional analyses of differentially regulated miRNAs indicated their involvement in diverse biological processes. Among these, transcription repressor activity, gene expression control as well as protein transporter activity were predominant. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis of dysregulated miRNAs revealed their involvement in several biological pathways and disease conditions. This suggests possible modulation of such pathways following trypanosome infection; for example, the MAPK signaling pathway which is known to play vital roles in apoptosis, innate immune response and response to viral infections was highly affected. Axon guidance was equally highly impacted and may indicate a cross reactivity between pathogen proteins and guidance molecules representing one pathological mechanism as it has been observed with influenza HA. Furthermore, Ingenuity pathway analyses of dysregulated miRNAs and potential targets indicated strong association with inflammatory responses, cell death and survival as well as infectious diseases. The data generated here provide valuable information to understand the regulatory function of miRNAs during trypanosome infections. They improved our knowledge on host-parasite cross-talks and provide a framework for investigations to understand the development of trypanosomes in their hosts as well as the differences in the clinical and pathological evolutions of the disease.