MicroRNA in glutamate receptor-dependent neurological diseases.

Glutamate-mediated excitotoxicity is the major neuropathological process contributing to numerous neurological diseases. Recently, emerging evidence indicates that microRNAs (miRNAs) play essential roles in the pathophysiology of a wide range of neurological diseases. Notably, there have been significant developments in understanding the biogenesis of miRNAs, their regulatory mechanisms, and their potential as effective biomarkers and therapies. In the present review, we summarize the recent literature that highlights the versatile roles played by miRNAs in glutamate receptor (GluR)-dependent neurological diseases. Based on the reported studies to date, modulation of miRNAs could emerge as a promising therapeutic target for a variety of neurological diseases that were discussed in this review.

MicroRNA-139-5p negatively regulates NR2A-containing NMDA receptor in the rat pilocarpine model and patients with temporal lobe epilepsy.

OBJECTIVES: Regulation of N-methyl-d-aspartate (NMDA) subunits NR2A and NR2B expression during status epilepticus (SE) remains incompletely understood. Here we explored the role of brain-enriched microRNA (miR)-139-5p in this process. METHODS: miRNA microarray was performed to examine changes in miRNA expression in the rat pilocarpine model following NMDA-receptor blockade. The dynamic expression patterns of miR-139-5p, NR2A, and NR2B levels were measured in rats during the three phases of temporal lobe epilepsy (TLE) development using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot. Similar expression methods were applied to hippocampi obtained from patients with TLE and from normal controls. Moreover, miR-139-5p agomir and antagomir were utilized to explore the role of miR-139-5p in determining NMDA-receptor subunit expression patterns. RESULTS: We identified 18 miRNAs that were significantly altered in the rat pilocarpine model following NMDA-receptor blockade. Of these, miR-139-5p was significantly up-regulated and Grin2A was predicted as its potential putative target. In patients with TLE, miR-139-5p expression was significantly down-regulated, whereas NR2A and NR2B levels were significantly up-regulated. In the rat model of SE, miR-139-5p expression was down-regulated while NR2A was up-regulated in the acute and chronic phases, but not in the latent phase. NR2B expression was up-regulated during the three phases of TLE development. Overexpression of miR-139-5p decreased, whereas depletion of miR-139-5p enhanced the expression levels of NR2A, but not NR2B, induced by pilocarpine treatment. Of interest, NMDA nonselective antagonist and NR2A selective antagonist enhanced miR-139-5p levels suppressed by pilocarpine treatment, whereas the NR2B selective antagonist was ineffective. SIGNIFICANCE: These findings elucidate the potential role of miR-139-5p in NMDA-receptor involvement in TLE development and may provide novel therapeutic targets for the future treatment of TLE.

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.

Dynamic Expression of MicroRNAs (183, 135a, 125b, 128, 30c and 27a) in the Rat Pilocarpine Model and Temporal Lobe Epilepsy Patients.

Recently, microRNAs (miRNAs) are emerging as new regulators in the pathogenesis of temporal lobe epilepsy (TLE) and playing a major role in the inflammatory and immune processes. The aim of the present study was to evaluate the dynamic expression of brain-specific miR-183 and miR-135a, brain-enriched miR-125b and miR-128 and inflammation-related miR-30c and miR-27a. Status epilepticus evoked by pilocarpine administeration was used to induce epilepsy in rats. Quantitative polymerase chain reaction was performed on rat hippocampus 2 hours, 3 weeks and 2 months following pilocarpine-induced status epilepticus, representing the acute, latent, and chronic phases, respectively. Expression levels were also measured in hippocampus obtained from TLE patients and normal controls. In the rat model, miR-183, miR-135a and miR-125b were detected upregulated during the acute and chronic phases compared to controls, but not during the latent phase. miR-30c and miR-27a were upregulated in the acute and chronic phases of TLE, while in the latent phase miR-30c was downregulated and miR-27a was upregulated. On the other hand, miR-128 showed significantly downregulated in all phases of TLE development. In TLE patients, miR-183, miR- 135a, miR-125b, miR-30c and miR-27a were upregulated, whereas miR-128 was downregulated. Our study revealed upregulation of miR-183, miR-135a and miR-125b in the seizure-related phases and TLE patients, suggesting that all may provide a potential therapeutic approach for the treatment of TLE, whereas the dysregulation of miR-128, miR-30c and miR-27a may suggest different functions during the process of TLE development.

Effect of Khat on apoptosis and related gene Smac/DIABLO expression in the cerebral cortex of rats following transient focal ischemia.

BACKGROUND: The leaves of the Khat shrub contain the major alkaloid compounds (cathinone) and cathine. These compounds can induce apoptosis and exacerbate the acute cerebral infarction, but the underlying mechanism is poorly understood. The present study aimed to investigate the effects of Khat treatment on the expression and cellular localization of Smac/Diablo (second mitochondrial activator of caspase) in the cortex of ischemic rat brain. METHODS: Adult male Sprague-Dawley rats were administered Khat (3g/kg) twice daily for 4 weeks, then underwent left middle cerebral artery occlusion (MCAO) for 2h and reperfusion for 3, 6 and 12h, respectively. The infarction area was evaluated with 2,3,5-triphenyltetrazolium chloride (TTC) staining. Apoptosis was assessed by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL). Smac/DIABLO expression levels in experimental and control groups were examined by immunohistochemistry and Western blot. RESULTS: Khat significantly exacerbates the neurological damage compared with control (p<0.05). In addition, Khat-treatment significantly increased the number of TUNEL-positive cells 3h (p<0.01) and 12h (p<0.05) after reperfusion. Ischemia/reperfusion enhanced the release of Smac/DIABLO from the mitochondria to the cytosol after reperfusion. Such release of Smac/DIABLO was elevated after the rats were pretreated with Khat. CONCLUSIONS: Our results indicate that Khat treatment can induce apoptosis through enhancing the release of Smac/DIABLO from the mitochondria to the cytosol after transient focal ischemia which may be an important mechanism of Khat neurotoxicity. Therefore, Khat chewing should be avoided by people who have cerebrovascular problems.

Changes in the numbers and distribution of calretinin in the epileptic rat hippocampus.

OBJECTIVES: To examine calretinin (CR)-containingObjectives: To examine cairetinin (CR)-containingnterneuronsthatdegenerate inthe hippocampus in post statusinterneurons that dege nera te in the hippocampusepilepticus (SE) ratsatdifferent time in post status epilepticus (SE) rats at different time points. METHODS: This study was conducted at the Central South University, Xiangya Hospital, Hunan Province, P.R. China between September 2008 and January 2010. Pilocarpine-induced SE was chosen as a model to generate chronic epileptic rats. To determine whether hippocampal neuronal populations are affected by hippocampal seizures, immunohistochemical assays were performed in brain sections obtained from age-matched control (n=50) and epileptic rats (n=170). Nissl stain was used to observe pathological changes of the hippocampus. RESULTS: Our results revealed the most dramatic cell loss to be in the hilar, cornu Ammonis (CA)1, and CA3 areas in the epileptic rats. Quantitative analysis revealed significant differences between control and epileptic rats in the number of CR-positive interneurons. These interneurons were distributed in the hilar, CA1, and CA3 areas and in thedentate gyrus of both control and epileptic rats, but was more numerous in the hippocampus of normal rats. However, a transient increase of CR-positive interneurons was observed in the CA1 between 7 and 15 days post SE. The CR interneurons were mostly located in the hilar and CA1 for epileptic rats, and in the hilus for control rats. CONCLUSIONS: Our data suggest that a different proportion of inhibitory interneurons was observed in the epileptic rat hippocampus, as their numbers differ from controls. These results indicate that the inhibitory circuits in the hippocampus may represent a compensatory response with a role to balance the enhanced excitatory input in the region.