Time-specific microRNA changes during spinal motoneuron degeneration in adult rats following unilateral brachial plexus root avulsion: ipsilateral vs. contralateral changes

The Involvement of the microRNAs miR-466c and miR-340 in the Palmitate-Mediated Dysregulation of Gonadotropin-Releasing Hormone Gene Expression

Diets high in saturated fatty acids are associated with obesity and infertility. Palmitate, the most prevalent circulating saturated fatty acid, is sensed by hypothalamic neurons, contributing to homeostatic dysregulation. Notably, palmitate elevates the mRNA levels of gonadotropin-releasing hormone (Gnrh) mRNA and its activating transcription factor, GATA binding protein 4 (Gata4). GATA4 is essential for basal Gnrh expression by binding to its enhancer region, with Oct-1 (Oct1) and CEBP-β (Cebpb) playing regulatory roles. The pre- and post-transcriptional control of Gnrh by palmitate have not been investigated. Given the ability of palmitate to alter microRNAs (miRNAs), we hypothesized that palmitate-mediated dysregulation of Gnrh mRNA involves specific miRNAs. In the mHypoA-GnRH/GFP neurons, palmitate significantly downregulated six miRNAs (miR-125a, miR-181b, miR-340, miR-351, miR-466c and miR-503), and the repression was attenuated by co-treatment with 100 μM of oleate. Subsequent mimic transfections revealed that miR-466c significantly downregulates Gnrh, Gata4, and Chop mRNA and increases Per2, whereas miR-340 upregulates Gnrh, Gata4, Oct1, Cebpb, and Per2 mRNA. Our findings suggest that palmitate may indirectly regulate Gnrh at both the pre- and post-transcriptional levels by altering miR-466c and miR-340, which in turn regulate transcription factor expression levels. In summary, palmitate-mediated dysregulation of Gnrh and, consequently, reproductive function involves parallel transcriptional mechanisms.

Regulation of rat HspB5/alphaB-Crystallin by microRNAs miR-101a-3p, miR-140-5p, miR-330-5p, and miR-376b-3p

HspB5/alphaB-crystallin is an ubiquitously expressed member of the small heat shock protein family which help cells to survive cellular stress conditions and are also implicated in neurodegenerative diseases. MicroRNAs are small non-coding RNAs fine-tuning protein expression mainly by inhibiting the translation of target genes. Our earlier finding of an increase in HspB5/alphaB-crystallin protein amount after heat shock in rat hippocampal neurons without a concomitant increase of mRNA prompted us to look for microRNAs as a posttranscriptional regulatory mechanism. Microarray miRNA expression data of rat hippocampal neurons under control and stress conditions in combination with literature search, miRNA binding site prediction and conservation of target sites yielded nine candidate microRNAs. Of these candidates, five (miR-101a-3p, miR-129-2-3p, miR-330-5p, miR-376b-3p, and miR-491-5p) were able to convey a downregulation by binding to the HspB5 3'- or 5'-UTR in a luciferase reporter gene assay while one (miR-140-5p) led to an upregulation. Overexpression of these six microRNAs in C6 glioma cells showed that three of them (miR-101a-3p, miR-140-5p, and miR-376b-3p) regulated endogenous HspB5 protein amount significantly in the same direction as in the reporter gene assay. In addition, overexpression of miR-330-5p and miR-491-5p in C6 cells resulted in regulation of HspB5 in the opposite direction as expected from the luciferase assay. Analysis of miRNA expression in rat hippocampal neurons after cellular stress by qPCR showed that miR-491-5p was not expressed in these cells. In total, we therefore identified four microRNAs, namely miR-101a-3p, miR-140-5p, miR-330-5p, and miR-376b-3p, which can regulate rat HspB5 directly or indirectly.

Quercetin Ameliorates Neuropathic Pain after Brachial Plexus Avulsion via Suppressing Oxidative Damage through Inhibition of PKC/MAPK/ NOX Pathway

BACKGROUND

Brachial plexus avulsion (BPA) animally involves the separation of spinal nerve roots themselves and the correlative spinal cord segment, leading to formidable neuropathic pain of the upper limb.

METHODS

The right seventh cervical (C7) ventral and dorsal roots were avulsed to establish a neuropathic pain model in rats. After operation, rats were treated with quercetin (QCN) by intragastric administration for 1 week. The effects of QCN were evaluated using mechanical allodynia tests and biochemical assay kits.

RESULTS

QCN treatment significantly attenuated the avulsion-provoked mechanical allodynia, elevated the levels of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) and total antioxidant capacity (TAC) in the C7 spinal dorsal horn. In addition, QCN administration inhibited the activations of macrophages, microglia and astrocytes in the C6 dorsal root ganglion (DRG) and C6-8 spinal dorsal horn, as well as attenuated the release of purinergic 2X (P2X) receptors in C6 DRG. The molecular mechanism underlying the above alterations was found to be related to the suppression of the PKC/MAPK/NOX signal pathway. To further study the anti-oxidative effects of QCN, we applied QCN on the H2O2-induced BV-2 cells in vitro, and the results attested that QCN significantly ameliorated the H2O2-induced ROS production in BV-2 cells, inhibited the H2O2-induced activation of PKC/MAPK/NOX pathway.

CONCLUSION

Our study for the first time provided evidence that QCN was able to attenuate pain hypersensitivity following the C7 spinal root avulsion in rats, and the molecular mechanisms involve the reduction of both neuro-inflammatory infiltration and oxidative stress via suppression of P2X receptors and inhibition of the activation of PKC/MAPK/NOX pathway. The results indicate that QCN is a natural compound with great promise worthy of further development into a novel therapeutic method for the treatment of BPA-induced neuropathic pain.

Quercetin enhances survival and axonal regeneration of motoneurons after spinal root avulsion and reimplantation: experiments in a rat model of brachial plexus avulsion

BACKGROUND

Brachial plexus avulsion (BPA) physically involves the detachment of spinal nerve roots themselves and the associated spinal cord segment, leading to permanent paralysis of motor function of the upper limb. Root avulsion induces severe pathological changes, including inflammatory reaction, oxidative damage, and finally massive motoneuron apoptosis. Quercetin (QCN), a polyphenolic flavonoid found in abundance in fruit and vegetables, has been reported to possess anti-oxidative, anti-inflammatory, and neuroprotective effects in many experimental models of both central nervous system (CNS) and peripheral nervous system (PNS) disorders. The purpose of this study was to investigate whether QCN could improve motor function recovery after C5-7 ventral root avulsion and C6 reimplantation in a rat model of BPA.

METHODS

The right fifth cervical (C5) to C7 ventral roots were avulsed followed by re-implantation of only C6 to establish the spinal root avulsion plus re-implantation model in rats. After surgery, rats were treated with QCN (25, 50, and 100 mg/kg) by gavage for 2 or 8 consecutive weeks. The effects of QCN were assessed using behavior test (Terzis grooming test, TGT) and histological evaluation. The molecular mechanisms were determined by immunohistochemistry analysis and western blotting.

RESULTS

Our results demonstrated that QCN significantly expedited motor function recovery in the forelimb as shown by the increased Terzis grooming test score, and accelerated motor axon regeneration as evidenced by the ascending number of Fluoro-Ruby-labeled and P75-positive regenerative motoneurons. The raised ChAT-immunopositive and cresyl violet-stained neurons indicated the enhanced survival of motoneurons by QCN administration. Furthermore, QCN treatment markedly alleviated muscle atrophy, restored functional motor endplates in biceps and inhibited the microglial and astroglia activation via modulating Nrf2/HO-1 and neurotrophin/Akt/MAPK signaling pathway.

CONCLUSIONS

Taken together, these findings have for the first time unequivocally indicated that QCN has promising potential for further development into a novel therapeutic in conjunction with reimplantation surgery for the treatment of BPA. .

Identification of a circRNA-mediated comprehensive ceRNA network in spinal cord injury pathogenesis

RNAs are closely associated with human diseases; however, immune-related genes (IRGs) and their potential regulatory networks in relation to spinal cord injury (SCI) are still poorly understood. Here, we investigated the key IRGs as well as the competing endogenous RNA (ceRNA) mechanisms that are associated with SCI pathogenesis based on microarray datasets and the use of a rat SCI model. Specifically, four independent SCI microarray datasets from Gene Expression Omnibus (GEO) database were analyzed and, thereafter, differentially expressed IRGs were annotated via Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. Furthermore, based on the GEO datasets, differentially expressed RNAs (DERNAs), including DEcircRNAs, DEmiRNAs, and DEmRNAs were identified and interactions between them were also predicted using online databases, and to construct a circular RNA (circRNA) mediated ceRNA network, candidate RNAs were also identified. Furthermore, the support vector machine (SVM) and least absolute shrinkage and selection operator (LASSO) methods were used for the identification of critical DERNAs, while differential gene expression was validated using the GSE20907 dataset. Our results were as follows. In the SCI microarray datasets, 32, 58, and 74 DEIRGs, DEcircRNAs, and DEmiRNAs were identified, respectively. In addition, GO and KEGG analyses showed that the DEIRGs were primarily enriched in neutrophil-mediated immunity and nuclear factor-kappa B (NF-κB) and hypoxia-inducible factor-1 (HIF-1) signaling pathways, and based on LASSO and SVM screening, PLXNB2 was identified as a DEIRG, while hsa_circ_0026646 was identified as the key circRNA, showing a higher SCI expression. Furthermore, our results proved that PLXNB2 and hsa_circ_0026646 were upregulated in SCI, whereas miR-331-3p was downregulated, and, interestingly, similar expression profiles were confirmed using the rat SCI model. Furthermore, fluorescent reporter assay indicated that both hsa_circ_0026646 and PLXNB2 have miR-331-3p target sites, and the ceRNA hypothesis suggested the dysregulation of hsa_circ_0026646, miR-331-3p, and PLXNB2 in SCI. Thus, our results suggested that in SCI pathogenesis, hsa_circ_0026646 correlates with PLXNB2 by targeting miR-331-3p.

Artemisinin Facilitates Motor Function Recovery by Enhancing Motoneuronal Survival and Axonal Remyelination in Rats Following Brachial Plexus Root Avulsion

Artemisinin (ART), a well-known antimalarial medicine originally isolated from the plant Artemisia annua, exerts neuroprotective effects in the nervous system owing to an antioxidant effect. Here, we determined whether ART is capable of inhibiting the oxidative stress to enhance motoneuronal (MN) survival to promote motor function recovery of rats following brachial plexus root avulsion (BPRA) with reimplantation surgery. Rats following BPRA and reimplantation were subcutaneously injected with 500 μL of PBS or 16 mg/mL ART once daily for 7 days after surgery. Terzis grooming test (TGT), histochemical staining, real-time polymerase chain reaction, and Western blot were conducted to determine the recovery of motor function of the upper limb, the survival rate of MNs, the oxidative stress levels in the ventral horn of the spinal cord, the morphology of abnormal musculocutaneous nerve fibers, the remyelination of axons in musculocutaneous nerves, and the degree of bicep atrophy. ART significantly increased TGT score, improved the survival of MNs, inhibited the oxidative stress, ameliorated the abnormal morphology of fibers in the musculocutaneous nerve, promoted the remyelination of axons, and alleviated muscle atrophy. Take together, ART can improve the survival of MNs and axonal remyelination to promote the motor function recovery via inhibiting oxidative stress, suggesting that ART may represent a new approach to the therapy of spinal root avulsion.

MicroRNA-199a-5p accelerates nucleus pulposus cell apoptosis and IVDD by inhibiting SIRT1-mediated deacetylation of p21

Intervertebral disc degeneration (IVDD) is a multifactorial pathological process associated with low back pain in which nucleus pulposus cell senescence is disrupted. Increasing evidence reveals that IVDD can be modulated by microRNAs (miRNAs or miRs). In the current study, we set out to elucidate the role of miR-199a-5p in nucleus pulposus cell apoptosis and IVDD progression. After sample collection, we found highly expressed miR-199a-5p in nucleus pulposus tissues of both patients diagnosed with IVDD and in IVDD rat models. Next, normal and degenerated nucleus pulposus cells were isolated and transfected with miR-199a-5p mimic, miR-199a-5p inhibitor, overexpressed sirtuin 1 (oe-SIRT1), and oe-p21, followed by detection of nucleus pulposus cell apoptosis and proliferation. In addition, the binding of miR-199a-5p and SIRT1, the interaction between p21 and SIRT1, and the regulation of p21 acetylation by SIRT1 were analyzed. We found that miR-199a-5p overexpression promoted nucleus pulposus cell apoptosis and IVDD. Overexpression of SIRT1 countered the effect of miR-199a-5p overexpression, while overexpression of p21 reversed the effect of miR-199a-5p silencing. Also, miR-199a-5p inhibited SIRT1, promoted p21 acetylation, and upregulated p21 expression, thus accelerating nucleus pulposus cell apoptosis and IVDD. Overall, miR-199a-5p promotes nucleus pulposus cell apoptosis and IVDD by suppressing SIRT1-dependent deacetylation of p21.

Silencing of miR-324-5p alleviates rat spinal cord injury by Sirt1

MicroRNAs (miRNAs) are implicated in the pathogenesis of spinal cord injury (SCI) as primary regulators. Previous studies have reported that miR-324-5p is involved in the modulation of neural injury, while the underlying mechanisms of miR-324-5p in SCI remain unclear. In a SCI rat model, miR-324-5p was significantly upregulated in the spinal cord tissues after SCI. Downregulation of miR-324-5p via injection of adeno-associated viruses (AAV) expressing miR-324-5p inhibitor relieved animal motor deficits and pathological changes in the tissues. Furthermore, downregulation of miR-324-5p significantly altered the expression of genes regulating neural growth, apoptosis, and the inflammatory and antioxidant response, which are implicated in SCI pathogenesis. In a H₂O₂-induced cell injury model, miR-324-5p silencing rescued the elevated apoptosis of PC12 cells. Finally, miR-324-5p directly targeted the 3'-untranslated region of NAD-dependent protein deacetylase sirtuin-1 (Sirt1) and negatively regulated the levels of Sirt1, an anti-inflammatory protein involved in SCI. Silencing of Sirt1 aggravated SCI and rescued the effects of miR-324-5p downregulation in rats. Overall, our findings indicated that silencing of miR-324-5p alleviates the loss of animal locomotion and concurrently mediates several degenerative processes relevant to the pathogenesis of SCI by Sirt1, which may provide clues for SCI treatment.

MicroRNA-145-Mediated KDM6A Downregulation Enhances Neural Repair after Spinal Cord Injury via the NOTCH2/Abcb1a Axis

Spinal cord injury (SCI) causes a significant physical, emotional, social, and economic burden to millions of people. MicroRNAs are known players in the regulatory circuitry of the neural repair in SCI. However, most microRNAs remain uncharacterized. Here, we demonstrate the neuroprotection of microRNA-145 (miR-145) after SCI in vivo and in vitro. In silico analysis predicted the target gene KDM6A of miR-145. The rat SCI model was developed by weight drop, and lipopolysaccharide- (LPS-) induced PC12 cell inflammatory injury model was also established. We manipulated the expression of miR-145 and/or KDM6A both in vivo and in vitro to explain their roles in rat neurological functional recovery as well as PC12 cell activities and inflammation. Furthermore, we delineated the mechanistic involvement of NOTCH2 and Abcb1a in the neuroprotection of miR-145. According to the results, miR-145 was poorly expressed and KDM6A was highly expressed in the spinal cord tissue of the SCI rat model and LPS-induced PC12 cells. Overexpression of miR-145 protects PC12 cells from LPS-induced cell damage and expedites neurological functional recovery of SCI in rats. miR-145 was validated to target and downregulate the demethylase KDM6A expression, thus abrogating the expression of Abcb1a by promoting the methylation of NOTCH2. Additionally, in vivo findings verified that miR-145 expedites neuroprotection after SCI by regulating the KDM6A/NOTCH2/Abcb1a axis. Taken together, miR-145 confers neuroprotective effects and enhances neural repair after SCI through the KDM6A-mediated NOTCH2/Abcb1a axis.

Research progress on the regulatory role of microRNAs in spinal cord injury

Spinal cord injury (SCI) is a severe CNS injury that results in abnormalities in, or loss of, motor, sensory and autonomic nervous function. miRNAs belong to a new class of noncoding RNA that regulates the production of proteins and biological function of cells by silencing translation or interfering with the expression of target mRNAs. Following SCI, miRNAs related to oxidative stress, inflammation, autophagy, apoptosis and many other secondary injuries are differentially expressed, and these miRNAs play an important role in the progression of secondary injuries after SCI. The purpose of this review is to elucidate the differential expression and functional roles of miRNAs after SCI, thus providing references for further research on miRNAs in SCI.

Systematic evaluation, verification and comparison of tuberculosis-related non-coding RNA diagnostic panels

We systematically summarized tuberculosis (TB)‐related non‐coding RNA (ncRNA) diagnostic panels, validated and compared panel performance. We searched TB‐related ncRNA panels in PubMed, OVID and Web of Science up to 28 February 2020, and available datasets in GEO, SRA and EBI ArrayExpress up to 1 March 2020. We rebuilt models and synthesized the results of each model in validation sets by bivariate mixed models. Specificity at 90% sensitivity, area under curve (AUC) and inconsistence index (I²) were calculated. NcRNA biofunctions were analysed. Nineteen models based on 18 ncRNA panels (miRNA, lncRNA, circRNA and snoRNA panels) and 18 datasets were included. Limited available datasets only allowed to evaluate miRNA panels further. Cui 2017 and Latorre 2015 exhibited specificity >70% at 90% sensitivity and AUC >80% in all validation sets. Cui 2017 showed higher specificity at 90% sensitivity (92%) and AUC (95%) and lower heterogeneity (I² = 0%) in ethological‐confirmation validation sets. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis indicated that most ncRNAs in panels involved in immune cell activation, oxidative stress, and Wnt and MAPK signalling pathway. Cui 2017 outperformed other models in both all available and aetiological‐confirmed validation sets, meeting the criteria of target product profile of WHO. This work provided a basis for clinical choice of TB‐related ncRNA diagnostic panels to a certain extent.

Involvement of the miR-137-3p/CAPN-2 Interaction in Ischemia-Reperfusion-Induced Neuronal Apoptosis through Modulation of p35 Cleavage and Subsequent Caspase-8 Overactivation

Background

Neuron survival after ischemia-reperfusion (IR) injury is the primary determinant of motor function prognosis. MicroRNA- (miR-) based gene therapy has gained attention recently. Our previous work explored the mechanisms by which miR-137-3p modulates neuronal apoptosis in both in vivo and in vitro IR models.

Methods

IR-induced motor dysfunction and spinal calpain (CAPN) subtype expression and subcellular localization were detected within 12 h post IR. Dysregulated miRs, including miR-137-3p, were identified by miR microarray analysis and confirmed by PCR. A luciferase assay confirmed CAPN-2 as a corresponding target of miR-137-3p, and their modulation of motor function was evaluated by intrathecal injection with synthetic miRs. CAPN-2 activity was measured by the intracellular Ca²⁺ concentration and mean fluorescence intensity in vitro. Neuronal apoptosis was detected by flow cytometry and TUNEL assay. The activities of p35, p25, Cdk5, and caspase-8 were evaluated by ELISA and Western blot after transfection with specific inhibitors and miRs.

Results

The IR-induced motor dysfunction time course was closely associated with upregulated expression of the CAPN-2 protein, which was mainly localized in neurons. The miR-137-3p/CAPN-2 interaction was confirmed by luciferase assay. The miR-137-3p mimic significantly improved IR-induced motor dysfunction and decreased CAPN-2 expression, even in combination with recombinant rat calpain-2 (rr-CALP2) injection, whereas the miR-137-3p inhibitor reversed these effects. Similar changes in the intracellular Ca²⁺ concentration, CAPN-2 expression, and CAPN-2 activity were observed when cells were exposed to oxygen-glucose deprivation and reperfusion (OGD/R) and transfected with synthetic miRs in vitro. Moreover, double fluorescence revealed identical neuronal localization of CAPN-2, p35, p25, and caspase-8. The decrease in CAPN-2 expression and activity was accompanied by the opposite changes in p35 activity and protein expression in cells transfected with the miR-137-3p mimic, roscovitine (a Cdk5 inhibitor), or Z-IETD-FMK (a caspase-8 inhibitor). Correspondingly, the abovementioned treatments resulted in a higher neuron survival rate than that of untreated neurons, as indicated by decreases in the apoptotic cell percentage and p25, Cdk5, caspase-8, and caspase-3 protein expression.

Conclusions

The miR-137-3p/CAPN-2 interaction modulates neuronal apoptosis during IR injury, possibly by inhibiting CAPN-2, which leads to p35 cleavage and inhibition of subsequent p25/Cdk5 and caspase-8 overactivation.

MicroRNA-466c-3p exerts protective effect on neuronal apoptosis and improves functional recovery post spinal cord injury via mitochondrial apoptotic pathway

Spinal cord injury (SCI) is involved with abnormal expression of miRNAs (miRs) which are responsible for some II^ry injury responses which include apoptosis, inflammation and oxidative stress. Mechanisms involving miRs induced apoptosis still needs to be investigated. In the present work we developed a rat model of SCI, followed by microarray analysis for expression of miRs at various time points after SCI. The locomotor activity was assessed by Basso, Beattie and Bresnahan score, lesion volume was analyzed by cresyl violet staining and TUNEL staining for extent of apoptosis at various time points of post SCI. Numbers of miRs were altered after 2 weeks of SCI among which miR-466c-3p was the most significantly down-regulated. Transfection with miR-466c-3p mimics caused overexpression of miR-466c-3p, also improvement in functional recovery, decrease in apoptosis of neuronal cells and lesion size was observed in SCI rats. The Luciferase assay suggested that miR-466c-3p suppressed the expression of Bcl-2 (apoptosis regulator). It was also evidenced that upon restoring the levels of Bcl-2 with the help of pc-DNA3-Bcl-2 halted the attenuating action of miR-466c-3p in hydrogen peroxide exposed N9 microglia cells. The findings suggested that miR-466c-3p may inhibit mitochondrial apoptotic pathway via blocking Bcl-2 and cleaved capase-9/-3in rats after SCI. Altogether, the results suggested that miR-466c-3p may exert attenuating effect on functional recovery and inhibit the apoptosis of neuronal cells via halting the mitochondrial apoptosis cascade in SCI rats indicating that miR-466c-3p can be attractive therapeutic candidate in treating SCI.

ERRγ is downregulated in injured motor neuron subpopulations following brachial plexus root avulsion

Estrogen-related receptor γ (ERRγ) is a member of a small group of orphan nuclear receptor transcription factors that have been implicated in several physiological and pathological processes, including placental development, regulation of metabolic genes or disease. The pattern of expression of ERRγ, its role in neuronal injury and its co-localization with other transcription factors in the spinal cord of rats with brachial plexus injury has not been determined. The expression profile of ERRγ and its co-localization with RNA binding protein fox-1 homolog 3 (NeuN) or cyclic AMP-dependent transcription factor 3 (ATF-3) in the motor neurons of rats that underwent brachial plexus root avulsion were assessed using western blot analysis, immunohistochemistry and immunofluorescence. Fluorogold (FG) was used to mark neurons whose axons were severed. ATF-3 was expressed in the nuclei of motor neurons whose axons were severed by root avulsion. On day 3 post-avulsion, FG and ATF-3 were all co-localized in the injured motor neurons. The level of ERRγ protein in the ipsilateral half of injured spinal cords was significantly decreased compared with that in the contralateral half on days 3, 14 and 28 post-avulsion (all P<0.05). The numbers of ERRγ-positive motor neurons (ERRγ^on) were also notably decreased in the ipsilateral side compared with that in the contralateral side on days 14 and 28 post-avulsion, implying that the expression occurred in α motor neurons that were progressively being lost, a phenomenon that was expected post-brachial plexus avulsion. Almost all large and small ERRγ-positive motor neurons were also NeuN-positive (NeuN^on). However, a few of these were ERRγ^on/NeuN^off (no NeuN signal). Therefore, these results suggested that ERRγ is a non-specific marker of γ motor neurons in rats, and therefore, this specific transcriptional program cannot be used to define functionally distinct motor neuron sub-populations. However, its downregulation on the injured side suggests that it is an important component of the response to injury in motor neurons.

A High-Throughput Screening Identifies MicroRNA Inhibitors That Influence Neuronal Maintenance and/or Response to Oxidative Stress

Small non-coding RNAs (sncRNAs), including microRNAs (miRNAs) are important post-transcriptional gene expression regulators relevant in physiological and pathological processes. Here, we combined a high-throughput functional screening (HTFS) platform with a library of antisense oligonucleotides (ASOs) to systematically identify sncRNAs that affect neuronal cell survival in basal conditions and in response to oxidative stress (OS), a major hallmark in neurodegenerative diseases. We considered hits commonly detected by two statistical methods in three biological replicates. Forty-seven ASOs targeting miRNAs (miRNA-ASOs) consistently decreased cell viability under basal conditions. A total of 60 miRNA-ASOs worsened cell viability impairment mediated by OS, with 36.6% commonly affecting cell viability under basal conditions. In addition, 40 miRNA-ASOs significantly protected neuronal cells from OS. In agreement with cell viability impairment, damaging miRNA-ASOs specifically induced increased free radical biogenesis. miRNAs targeted by the detrimental ASOs are enriched in the fraction of miRNAs downregulated by OS, suggesting that the miRNA expression pattern after OS contributes to neuronal damage. The present HTFS highlighted potentially druggable sncRNAs. However, future studies are needed to define the pathways by which the identified ASOs regulate cell survival and OS response and to explore the potential of translating the current findings into clinical applications.

MicroRNA Expression Profiles, Target Genes, and Pathways in Intervertebral Disk Degeneration: A Meta-Analysis of 3 Microarray Studies

BACKGROUND

Determining the expression profile and target genes of microRNA (miRNA) would assist in determining the pathophysiologic pathways in intervertebral disk degeneration (IDD). The aim of this study was to determine the expression profile of miRNA in degenerated intervertebral disks compared with normal healthy intervertebral disks.

METHODS

We conducted a meta-analysis of 3 available miRNA expression datasets to identify a panel of co-deregulated miRNA genes and overlapping biological processes in IDD. Degenerated intervertebral disks were compared with normal healthy disks. We selected 35 miRNA features common to all 3 platforms. Then, we calculated differential expression P values from our unpaired data using metaMA package in R statistical software according to the moderated t test method (Limma). Based on the P values (where the threshold was <0.05), a list of differentially expressed miRNAs was identified.

RESULTS

After normalization and selection of common miRNA features across all 3 platforms, we found a total of 5 differentially expressed miRNAs, among which miR-574-3p, miR-199a-5p, and miR-483-5p were not identified in any individual studies. Our results revealed that miR-199a-5p, miR-574-3p, miR-551a, and miR-640 are commonly upregulated in IDDs compared with control disks, whereas miR-483 is commonly downregulated. Pathway analysis of identified dysregulated miRNAs indicated the involvement of extracellular matrix-receptor interaction, adherens junction, and transforming growth factor-beta signaling pathway in the pathogenesis of IDDs. Moreover, the network of predicted targets for these miRNAs identified most affected target genes as ERBB4 and CLTC.

CONCLUSIONS

We found that the identified miRNAs through meta-analysis are candidate predictive markers for IDDs through different pathways.

Neuregulin-1 Accelerates Functional Motor Recovery by Improving Motoneuron Survival After Brachial Plexus Root Avulsion in Mice

Brachial plexus root avulsion (BPRA) results in the complete loss of motor function in the upper limb, mainly due to the death of spinal motoneurons (MNs). The survival of spinal MNs is the key to the recovery of motor function. Neuregulin-1 (Nrg1) plays fundamental roles in nervous system development and nerve repair. However, its functional role in BPRA remains unclear. On the basis of our findings that Nrg1 is down-regulated in the ventral horn in a mouse model of BPRA, Nrg1 may be associated with BPRA. Here, we investigated whether recombinant Nrg1β (rNrg1β) can enhance the survival of spinal MNs and improve functional recovery in mice following BPRA. In vitro studies on primary cultured mouse MNs showed that rNrg1β increased the survival rate in a dose-dependent manner, reaching a peak at 5 nM, which increased the survival rate and enhanced the pERK levels in MNs under H₂O₂-induced oxidative stress. In vivo studies revealed that rNrg1β improved the functional recovery of elbow flexion, promoted the survival of MNs, enhanced the re-innervation of biceps brachii, and decreased the muscle atrophy. These results suggest that Nrg1 may provide a potential therapeutic strategy for root avulsion.

MiR-21 attenuates apoptosis-triggered by amyloid-β via modulating PDCD4/ PI3K/AKT/GSK-3β pathway in SH-SY5Y cells

Alzheimer's disease (AD) remains the most common neurodegenerative disease with amyloid beta (Aβ) formatted and accumulated. Recently, microRNAs have been identified as significant regulators in neurogenesis of the central nervous system (CNS). However, the biological role of miR-21 in AD remains unclear. The purpose of our study was to investigate the mechanism of miR-21 in AD. AD model was established using 20 μM Aβ_1-42 in SH-SY5Y cells. Aβ_1-42 can induce cell apoptosis via increasing Bax and decreasing Bcl-2 protein levels. Meanwhile, we observed that miR-21 was remarkably elevated by indicated Aβ_1-42 in vitro. Subsequently, miR-21 mimics were transfected into SH-SY5Y cells and it was found that miR-21 can inhibit cell apoptosis induced by Aβ_1-42. Programmed cell death protein 4 (PDCD4), an important tumor suppressor in various cancers has been reported to prevent AKT activation. The phosphatidylinositol 3-kinase (PI3K)/AKT/GSK-3β pathway can release a survival signal to protect from multiple injuries. Interestingly, it was found that PDCD4 was involved in miR-21-repressed cell apoptosis in AD models. miR-21 mimics can increase the PI3K, AKT and GSK-3β activity while PDCD4 ovexexpression inhibited their activity respectively. Moreover, knockdown of PDCD4 can rescue PI3K/AKT/GSK-3β pathway in SH-SY5Y cells. Taken these together, it was suggested by our data that miR-21 can exert protective roles in AD, which might be dependent on PDCD4/PI3K/AKT/GSK-3β signaling pathway in vitro.

Inhibition of KLF7-Targeting MicroRNA 146b Promotes Sciatic Nerve Regeneration

A previous study has indicated that Krüppel-like factor 7 (KLF7), a transcription factor that stimulates Schwann cell (SC) proliferation and axonal regeneration after peripheral nerve injury, is a promising therapeutic transcription factor in nerve injury. We aimed to identify whether inhibition of microRNA-146b (miR-146b) affected SC proliferation, migration, and myelinated axon regeneration following sciatic nerve injury by regulating its direct target KLF7. SCs were transfected with miRNA lentivirus, miRNA inhibitor lentivirus, or KLF7 siRNA lentivirus in vitro. The expression of miR146b and KLF7, as well as SC proliferation and migration, were subsequently evaluated. In vivo, an acellular nerve allograft (ANA) followed by injection of GFP control vector or a lentiviral vector encoding an miR-146b inhibitor was used to assess the repair potential in a model of sciatic nerve gap. miR-146b directly targeted KLF7 by binding to the 3'-UTR, suppressing KLF7. Up-regulation of miR-146b and KLF7 knockdown significantly reduced the proliferation and migration of SCs, whereas silencing miR-146b resulted in increased proliferation and migration. KLF7 protein was localized in SCs in which miR-146b was expressed in vivo. Similarly, 4 weeks after the ANA, anti-miR-146b increased KLF7 and its target gene nerve growth factor cascade, promoting axonal outgrowth. Closer analysis revealed improved nerve conduction and sciatic function index score, and enhanced expression of neurofilaments, P0 (anti-peripheral myelin), and myelinated axon regeneration. Our findings provide new insight into the regulation of KLF7 by miR-146b during peripheral nerve regeneration and suggest a potential therapeutic strategy for peripheral nerve injury.

MicroRNA-34c is regulated by p53 and is involved in sevoflurane-induced apoptosis in the developing rat brain potentially via the mitochondrial pathway

The commonly used inhalation anesthetic, sevoflurane, has been previously demonstrated to induce apoptosis in the developing brain; however, the underlying molecular mechanisms remain largely unknown. MicroRNAs (miRNAs) serve important roles in multiple physiological/pathological processes, such as cell death and survival. In the present study, the miRNA sequence that was most closely associated with sevoflurane‑induced apoptosis in the hippocampus of neonatal rat brains was identified. Seven‑day‑old Sprague Dawley rats were first exposed to 2.3% sevoflurane for 6 h. Hippocampal brain tissues were harvested at 6 h following sevoflurane exposure. Cleaved caspase‑3 levels were examined using an immunofluorescence assay. Alterations in miRNA expression were assessed by microarray analysis and reverse transcription-quantitative polymerase chain reaction. The protein levels of p53, phosphorylated (p)‑p53, B-cell lymphoma-2 (Bcl-2) and Bax were assessed by western blot analysis. Sevoflurane exposure significantly increased the levels of cleaved caspase‑3 in the hippocampus. In addition, among the 688 miRNAs that were observed to be expressed in the hippocampus, sevoflurane exposure altered the expression levels of 266 miRNAs. Among these differentially expressed miRNAs, eight were significantly upregulated and one (miRNA‑34c) was significantly downregulated following sevoflurane exposure. Bioinformatics analyses indicated the miRNA‑34c was a direct downstream target of p53. Sevoflurane exposure induced significant alterations in the level of p‑p53, Bcl‑2 and Bax in the hippocampus of neonatal rats. In conclusion, the results of the present study suggest that miRNA‑34c may be regulated by p53 and is involved in sevoflurane‑induced neural apoptosis in the hippocampus of developing rat brains, potentially via the mitochondrial pathway.

Methotrexate combined with methylprednisolone for the recovery of motor function and differential gene expression in rats with spinal cord injury

Methylprednisolone is a commonly used drug for the treatment of spinal cord injury, but high doses of methylprednisolone can increase the incidence of infectious diseases. Methotrexate has anti-inflammatory activity and immunosuppressive effects, and can reduce inflammation after spinal cord injury. To analyze gene expression changes and the molecular mechanism of methotrexate combined with methylprednisolone in the treatment of spinal cord injury, a rat model of spinal cord contusion was prepared using the PinPoint™ precision cortical impactor technique. Rats were injected with methylprednisolone 30 mg/kg 30 minutes after injury, and then subcutaneously injected with 0.3 mg/kg methotrexate 1 day after injury, once a day, for 2 weeks. TreadScan gait analysis found that at 4 and 8 weeks after injury, methotrexate combined with methylprednisolone significantly improved hind limb swing time, stride time, minimum longitudinal deviation, instant speed, footprint area and regularity index. Solexa high-throughput sequencing was used to analyze differential gene expression. Compared with methylprednisolone alone, differential expression of 316 genes was detected in injured spinal cord treated with methotrexate and methylprednisolone. The 275 up-regulated genes were mainly related to nerve recovery, anti-oxidative, anti-inflammatory and anti-apoptotic functions, while 41 down-regulated genes were mainly related to proinflammatory and pro-apoptotic functions. These results indicate that methotrexate combined with methylprednisolone exhibited better effects on inhibiting the activity of inflammatory cytokines and enhancing antioxidant and anti-apoptotic effects and thereby produced stronger neuroprotective effects than methotrexate alone. The 316 differentially expressed genes play an important role in the above processes.

The Role of microRNA Markers in the Diagnosis, Treatment, and Outcome Prediction of Spinal Cord Injury

Spinal cord injury (SCI) is a devastating condition that affects many people worldwide. Treatment focuses on controlling secondary injury cascade and improving regeneration. It has recently been suggested that both the secondary injury cascade and the regenerative process are heavily regulated by microRNAs (miRNAs). The measurement of specific biomarkers could improve our understanding of the disease processes, and thereby provide clinicians with the opportunity to guide treatment and predict clinical outcomes after SCI. A variety of miRNAs exhibit important roles in processes of inflammation, cell death, and regeneration. These miRNAs can be used as diagnostic tools for predicting outcome after SCI. In addition, miRNAs can be used in the treatment of SCI and its symptoms. Significant laboratory and clinical evidence exist to show that miRNAs could be used as robust diagnostic and therapeutic tools for the treatment of patients with SCI. Further clinical studies are warranted to clarify the importance of each subtype of miRNA in SCI management.

Extrinsic and Intrinsic Regulation of Axon Regeneration by MicroRNAs after Spinal Cord Injury

Spinal cord injury is a devastating disease which disrupts the connections between the brain and spinal cord, often resulting in the loss of sensory and motor function below the lesion site. Most injured neurons fail to regenerate in the central nervous system after injury. Multiple intrinsic and extrinsic factors contribute to the general failure of axonal regeneration after injury. MicroRNAs can modulate multiple genes' expression and are tightly controlled during nerve development or the injury process. Evidence has demonstrated that microRNAs and their signaling pathways play important roles in mediating axon regeneration and glial scar formation after spinal cord injury. This article reviews the role and mechanism of differentially expressed microRNAs in regulating axon regeneration and glial scar formation after spinal cord injury, as well as their therapeutic potential for promoting axonal regeneration and repair of the injured spinal cord.

Traumatic brain injury increases levels of miR-21 in extracellular vesicles: implications for neuroinflammation

Traumatic brain injury (TBI) is an important health concern and effective treatment strategies remain elusive. Understanding the complex multicellular response to TBI may provide new avenues for intervention. In the context of TBI, cell–cell communication is critical. One relatively unexplored form of cell–cell communication in TBI is extracellular vesicles (EVs). These membrane‐bound vesicles can carry many different types of cargo between cells. Recently, miRNA in EVs have been shown to mediate neuroinflammation and neuronal injury. To explore the role of EV‐associated miRNA in TBI, we isolated EVs from the brain of injured mice and controls, purified RNA from brain EVs, and performed miRNA sequencing. We found that the expression of miR‐212 decreased, while miR‐21, miR‐146, miR‐7a, and miR‐7b were significantly increased with injury, with miR‐21 showing the largest change between conditions. The expression of miR‐21 in the brain was primarily localized to neurons near the lesion site. Interestingly, adjacent to these miR‐21‐expressing neurons were activated microglia. The concurrent increase in miR‐21 in EVs with the elevation of miR‐21 in neurons, suggests that miR‐21 is secreted from neurons as potential EV cargo. Thus, this study reveals a new potential mechanism of cell–cell communication not previously described in TBI.

Selected gene profiles of stressed NSC-34 cells and rat spinal cord following peripheral nerve reconstruction and minocycline treatment

The present study was conducted to investigate the effects of minocycline on the expression of selected transcriptional and translational profiles in the rat spinal cord following sciatic nerve (SNR) transection and microsurgical coaptation. The mRNA and protein expression levels of B cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), caspase-3, major histocompatibility complex I (MHC I), tumor necrosis factor-α (TNF-α), activating transcription factor 3 (ATF3), vascular endothelial growth factor (VEGF), matrix metalloproteinase 9 (MMP9), and growth associated protein-43 (GAP-43) were monitored in the rat lumbar spinal cord following microsurgical reconstruction of the sciatic nerves and minocycline treatment. The present study used semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. As a PCR analysis of spinal cord tissue enabled the examination of the expression patterns of all cell types including glia, the motorneuron-like NSC-34 cell line was used to investigate expression level changes in motorneurons. As stressors, oxygen glucose deprivation (OGD) and lipopolysaccharide (LPS) treatment were performed. SNR did not induce significant degeneration of ventral horn motorneurons, whereas microglia activation and synaptic terminal retraction were detectable. All genes were constitutively expressed at the mRNA and protein levels in untreated spinal cord and control cells. SNR significantly increased the mRNA expression levels of all genes, albeit only temporarily. In all genes except MMP9 and GAP-43, the induction was seen ipsilaterally and contralaterally. The effects of minocycline were moderate. The expression levels of MMP9, TNF-α, MHC I, VEGF, and GAP-43 were reduced, whereas those of Bax and Bcl-2 were unaffected. OGD, but not LPS, was toxic for NSC-34 cells. No changes in the expression levels of Bax, caspase-3, MHC I or ATF3 were observed. These results indicated that motorneurons were not preferentially or solely responsible for SNR-mediated upregulation of these genes. MMP9, TNF-α, VEGF and Bcl-2 were stress-activated. These results suggest that a substantial participation of motorneurons in gene expression levels in vivo. Minocycline was also shown to have inhibitory effects. The nuclear factor-κB signalling pathway may be a possible target of minocycline.

MicroRNAs Are Involved in the Development of Morphine-Induced Analgesic Tolerance and Regulate Functionally Relevant Changes in Serpini1

Long-term opioid treatment results in reduced therapeutic efficacy and in turn leads to an increase in the dose required to produce equivalent pain relief and alleviate break-through or insurmountable pain. Altered gene expression is a likely means for inducing long-term neuroadaptations responsible for tolerance. Studies conducted by our laboratory (Tapocik et al., 2009) revealed a network of gene expression changes occurring in canonical pathways involved in neuroplasticity, and uncovered miRNA processing as a potential mechanism. In particular, the mRNA coding the protein responsible for processing miRNAs, Dicer1, was positively correlated with the development of analgesic tolerance. The purpose of the present study was to test the hypothesis that miRNAs play a significant role in the development of analgesic tolerance as measured by thermal nociception. Dicer1 knockdown, miRNA profiling, bioinformatics, and confirmation of high value targets were used to test the proposition. Regionally targeted Dicer1 knockdown (via shRNA) had the anticipated consequence of eliminating the development of tolerance in C57BL/6J (B6) mice, thus supporting the involvement of miRNAs in the development of tolerance. MiRNA expression profiling identified a core set of chronic morphine-regulated miRNAs (miR's 27a, 9, 483, 505, 146b, 202). Bioinformatics approaches were implemented to identify and prioritize their predicted target mRNAs. We focused our attention on miR27a and its predicted target serpin peptidase inhibitor clade I (Serpini1) mRNA, a transcript known to be intricately involved in dendritic spine density regulation in a manner consistent with chronic morphine's consequences and previously found to be correlated with the development of analgesic tolerance. In vitro reporter assay confirmed the targeting of the Serpini1 3'-untranslated region by miR27a. Interestingly miR27a was found to positively regulate Serpini1 mRNA and protein levels in multiple neuronal cell lines. Lastly, Serpini1 knockout mice developed analgesic tolerance at a slower rate than wild-type mice thus confirming a role for the protein in analgesic tolerance. Overall, these results provide evidence to support a specific role for miR27a and Serpini1 in the behavioral response to chronic opioid administration (COA) and suggest that miRNA expression and mRNA targeting may underlie the neuroadaptations that mediate tolerance to the analgesic effects of morphine.

Identification and Characterization of MicroRNAs from Longitudinal Muscle and Respiratory Tree in Sea Cucumber (Apostichopus japonicus) Using High-Throughput Sequencing

MicroRNAs (miRNAs), as a family of non-coding small RNAs, play important roles in the post-transcriptional regulation of gene expression. Sea cucumber (Apostichopus japonicus) is an important economic species which is widely cultured in East Asia. The longitudinal muscle (LTM) and respiratory tree (RPT) are two important tissues in sea cucumber, playing important roles such as respiration and movement. In this study, we identified and characterized miRNAs in the LTM and RPT of sea cucumber (Apostichopus japonicus) using Illumina HiSeq 2000 platform. A total of 314 and 221 conserved miRNAs were identified in LTM and RPT, respectively. In addition, 27 and 34 novel miRNAs were identified in the LTM and RPT, respectively. A set of 58 miRNAs were identified to be differentially expressed between LTM and RPT. Among them, 9 miRNAs (miR-31a-3p, miR-738, miR-1692, let-7a, miR-72a, miR-100b-5p, miR-31b-5p, miR-429-3p, and miR-2008) in RPT and 7 miRNAs (miR-127, miR-340, miR-381, miR-3543, miR-434-5p, miR-136-3p, and miR-300-3p) in LTM were differentially expressed with foldchange value being greater than 10. A total of 14,207 and 12,174 target genes of these miRNAs were predicted, respectively. Functional analysis of these target genes of miRNAs were performed by GO analysis and pathway analysis. This result provided in this work will be useful for understanding biological characteristics of the LTM and RPT of sea cucumber and assisting molecular breeding of sea cucumber for aquaculture.

Identification of the Avulsion-Injured Spinal Motoneurons

In laboratory studies, counting the spinal motoneurons that survived axonal injury is a major method to estimate the severity and regenerative capacity of the injured motoneurons after the axonal injury and rehabilitation surgery. However, the typical motoneuron marker, the choline acetyltransferase (ChAT), could not be detected in the injured motoneurons within the first 3–4 weeks postinjury. It is necessary to explore the useful and reliable specific phenotypic markers to assess the fate of injured motoneurons in axonal injury. Here, we used the fluorogold to retrograde trace the injured motoneurons in the spinal cord and studied the expression patterns of the alpha-motoneuron marker, the neuronal nuclei DNA-binding protein (NeuN) and the peripheral nerve injury marker, the activating transcriptional factor (ATF-3), and the oxidative stress marker, the neuronal nitric oxide synthase (nNOS) within the first 4 weeks of the root avulsion of the right brachial plexus (BPRA) in the adult male Sprague-Dawley rats. Our results showed that ATF-3 was rapidly induced and sustained to express only in the nuclei of the fluorogold-labeled injured motoneurons but none in the unaffected motoneurons from the 24 h of the injury; meanwhile, the NeuN almost disappeared in the avulsion-affected motoneurons within the first 4 weeks. The nNOS was not detected in the motoneurons until the second week of the injury. On the basis of the present data, we suggest that ATF-3 labels avulsion-injured motoneurons while NeuN and nNOS are poor markers within the first 4 weeks of BPRA.

MicroRNA Expression Profile of Neural Progenitor-Like Cells Derived from Rat Bone Marrow Mesenchymal Stem Cells under the Influence of IGF-1, bFGF and EGF

Insulin-like growth factor 1 (IGF-1) enhances cellular proliferation and reduces apoptosis during the early differentiation of bone marrow derived mesenchymal stem cells (BMSCs) into neural progenitor-like cells (NPCs) in the presence of epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF). BMSCs were differentiated in three groups of growth factors: (A) EGF + bFGF, (B) EGF + bFGF + IGF-1, and (C) without growth factor. To unravel the molecular mechanisms of the NPCs derivation, microarray analysis using GeneChip^® miRNA arrays was performed. The profiles were compared among the groups. Annotated microRNA fingerprints (GSE60060) delineated 46 microRNAs temporally up-regulated or down-regulated compared to group C. The expressions of selected microRNAs were validated by real-time PCR. Among the 46 microRNAs, 30 were consistently expressed for minimum of two consecutive time intervals. In Group B, only miR-496 was up-regulated and 12 microRNAs, including the let-7 family, miR-1224, miR-125a-3p, miR-214, miR-22, miR-320, miR-708, and miR-93, were down-regulated. Bioinformatics analysis reveals that some of these microRNAs (miR-22, miR-214, miR-125a-3p, miR-320 and let-7 family) are associated with reduction of apoptosis. Here, we summarize the roles of key microRNAs associated with IGF-1 in the differentiation of BMSCs into NPCs. These findings may provide clues to further our understanding of the mechanisms and roles of microRNAs as key regulators of BMSC-derived NPC maintenance.