Downregulation of miR-199b promotes the acute spinal cord injury through IKKβ-NF-κB signaling pathway activating microglial cells

miR-223 accelerates lipid droplets clearance in microglia following spinal cord injury by upregulating ABCA1

BACKGROUND

Spinal cord injury (SCI) is characterized by extensive demyelination and inflammatory responses. Facilitating the clearance of lipid droplets (LDs) within microglia contributes to creating a microenvironment that favors neural recovery and provides essential materials for subsequent remyelination. Therefore, investigating MicroRNAs (miRNAs) that regulate lipid homeostasis after SCI and elucidating their potential mechanisms in promoting LDs clearance in microglia have become focal points of SCI research.

METHODS

We established a subacute C5 hemicontusion SCI model in mice and performed transcriptomic sequencing on the injury epicenter to identify differentially expressed genes and associated pathways. Confocal imaging was employed to observe LDs accumulation. Multi-omics analyses were conducted to identify differentially expressed mRNA and miRNA post-SCI. Pathway enrichment analysis and protein-protein interaction network construction were performed using bioinformatics methods, revealing miR-223-Abca1 as a crucial miRNA-mRNA pair in lipid metabolism regulation. BV2 microglia cell lines overexpressing miR-223 were engineered, and immunofluorescence staining, western blot, and other techniques were employed to assess LDs accumulation, relevant targets, and inflammatory factor expression, confirming its role in regulating lipid homeostasis in microglia.

RESULTS

Histopathological results of our hemicontusion SCI model confirmed LDs aggregation at the injury epicenter, predominantly within microglia. Our transcriptomic analysis during the subacute phase of SCI in mice implicated ATP-binding cassette transporter A1 (Abca1) as a pivotal gene in lipid homeostasis, cholesterol efflux and microglial activation. Integrative mRNA-miRNA multi-omics analysis highlighted the crucial role of miR-223 in the neuroinflammation process following SCI, potentially through the regulation of lipid metabolism via Abca1. In vitro experiments using BV2 cells overexpressing miR-223 demonstrated that elevated levels of miR-223 enhance ABCA1 expression in myelin debris and LPS-induced BV2 cells. This promotes myelin debris degradation and LDs clearance, and induces a shift toward an anti-inflammatory M2 phenotype.

CONCLUSIONS

In summary, our study unveils the critical regulatory role of miR-223 in lipid homeostasis following SCI. The mechanism by which this occurs involves the upregulation of ABCA1 expression, which facilitates LDs clearance and myelin debris degradation, consequently alleviating the lipid burden, and inhibiting inflammatory polarization of microglia. These findings suggest that strategies to enhance miR-223 expression and target ABCA1, thereby augmenting LDs clearance, may emerge as appealing new clinical targets for SCI treatment.

Recent advances on signaling pathways and their inhibitors in spinal cord injury

Spinal cord injury (SCI) is a serious and disabling central nervous system injury. Its complex pathological mechanism can lead to sensory and motor dysfunction. It has been reported that signaling pathway plays a key role in the pathological process and neuronal recovery mechanism of SCI. Such as PI3K/Akt, MAPK, NF-κB, and Wnt/β-catenin signaling pathways. According to reports, various stimuli and cytokines activate these signaling pathways related to SCI pathology, thereby participating in the regulation of pathological processes such as inflammation response, cell apoptosis, oxidative stress, and glial scar formation after injury. Activation or inhibition of relevant pathways can delay inflammatory response, reduce neuronal apoptosis, prevent glial scar formation, improve the microenvironment after SCI, and promote neural function recovery. Based on the role of signaling pathways in SCI, they may be potential targets for the treatment of SCI. Therefore, understanding the signaling pathway and its inhibitors may be beneficial to the development of SCI therapeutic targets and new drugs. This paper mainly summarizes the pathophysiological process of SCI, the signaling pathways involved in SCI pathogenesis, and the potential role of specific inhibitors/activators in its treatment. In addition, this review also discusses the deficiencies and defects of signaling pathways in SCI research. It is hoped that this study can provide reference for future research on signaling pathways in the pathogenesis of SCI and provide theoretical basis for SCI biotherapy.

The role of miRNAs in multiple sclerosis pathogenesis, diagnosis, and therapeutic resistance

In recent years, microRNAs (miRNAs) have gained increased attention from researchers around the globe. Although it is twenty nucleotides long, it can modulate several gene targets simultaneously. Their mal expression is a signature of various pathologies, and they provide the foundation to elucidate the molecular mechanisms of each pathology. Among the debilitating central nervous system (CNS) disorders with a growing prevalence globally is the multiple sclerosis (MS). Moreover, the diagnosis of MS is challenging due to the lack of disease-specific biomarkers, and the diagnosis mainly depends on ruling out other disabilities. MS could adversely affect patients' lives through its progression, and only symptomatic treatments are available as therapeutic options, but an exact cure is yet unavailable. Consequently, this review hopes to further the study of the biological features of miRNAs in MS and explore their potential as a therapeutic target.

The microRNAs (miRs) overexpressing mesenchymal stem cells (MSCs) therapy in neurological disorders; hope or hype

Altered expression of multiple miRNAs was found to be extensively involved in the pathogenesis of different neurological disorders including Alzheimer's disease, Parkinson's disease, stroke, epilepsy, multiple sclerosis, amyotrophic lateral sclerosis, and Huntington's disease. One of the biggest concerns within gene-based therapy is the delivery of the therapeutic microRNAs to the intended place, which is obligated to surpass the biological barriers without undergoing degradation in the bloodstream or renal excretion. Hence, the delivery of modified and unmodified miRNA molecules using excellent vehicles is required. In this light, mesenchymal stem cells (MSCs) have attracted increasing attention. The MSCs can be genetically modified to express or overexpress a particular microRNA aimed with promote neurogenesis and neuroprotection. The current review has focused on the therapeutic capabilities of microRNAs-overexpressing MSCs to ameliorate functional deficits in neurological conditions.

Non-Coding RNA in Microglia Activation and Neuroinflammation in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by complex pathophysiological features. Amyloid plaques resulting from extracellular amyloid deposition and neurofibrillary tangles formed by intracellular hyperphosphorylated tau accumulation serve as primary neuropathological criteria for AD diagnosis. The activation of microglia has been closely associated with these pathological manifestations. Non-coding RNA (ncRNA), a versatile molecule involved in various cellular functions such as genetic information storage and transport, as well as catalysis of biochemical reactions, plays a crucial role in microglial activation. This review aims to investigate the regulatory role of ncRNAs in protein expression by directly targeting genes, proteins, and interactions. Furthermore, it explores the ability of ncRNAs to modulate inflammatory pathways, influence the expression of inflammatory factors, and regulate microglia activation, all of which contribute to neuroinflammation and AD. However, there are still significant controversies surrounding microglial activation and polarization. The categorization into M1 and M2 phenotypes may oversimplify the intricate and multifaceted regulatory processes in microglial response to neuroinflammation. Limited research has been conducted on the role of ncRNAs in regulating microglial activation and inducing distinct polarization states in the context of neuroinflammation. Moreover, the regulatory mechanisms through which ncRNAs govern microglial function continue to be refined. The current understanding of ncRNA regulatory pathways involved in microglial activation remains incomplete and may be influenced by spatial, temporal, and tissue-specific factors. Therefore, further in-depth investigations are warranted. In conclusion, there are ongoing debates and uncertainties regarding the activation and polarization of microglial cells, particularly concerning the categorization into M1 and M2 phenotypes. The study of ncRNA regulation in microglial activation and polarization, as well as its mechanisms, is still in its early stages and requires further investigation. However, this review offers new insights and opportunities for therapeutic approaches in AD. The development of ncRNA-based drugs may hold promise as a new direction in AD treatment.

The NF-κB Pathway: a Focus on Inflammatory Responses in Spinal Cord Injury

Spinal cord injury (SCI) is a type of central nervous system trauma that can lead to severe nerve injury. Inflammatory reaction after injury is an important pathological process leading to secondary injury. Long-term stimulation of inflammation can further deteriorate the microenvironment of the injured site, leading to the deterioration of neural function. Understanding the signaling pathways that regulate responses after SCI, especially inflammatory responses, is critical for the development of new therapeutic targets and approaches. Nuclear transfer factor-κB (NF-κB) has long been recognized as a key factor in regulating inflammatory responses. The NF-κB pathway is closely related to the pathological process of SCI. Inhibition of this pathway can improve the inflammatory microenvironment and promote the recovery of neural function after SCI. Therefore, the NF-κB pathway may be a potential therapeutic target for SCI. This article reviews the mechanism of inflammatory response after SCI and the characteristics of NF-κB pathway, emphasizing the effect of inhibiting NF-κB on the inflammatory response of SCI to provide a theoretical basis for the biological treatment of SCI.

Non-Coding RNAs Regulate Spinal Cord Injury-Related Neuropathic Pain via Neuroinflammation

Secondary chronic neuropathic pain (NP) in addition to sensory, motor, or autonomic dysfunction can significantly reduce quality of life after spinal cord injury (SCI). The mechanisms of SCI-related NP have been studied in clinical trials and with the use of experimental models. However, in developing new treatment strategies for SCI patients, NP poses new challenges. The inflammatory response following SCI promotes the development of NP. Previous studies suggest that reducing neuroinflammation following SCI can improve NP-related behaviors. Intensive studies of the roles of non-coding RNAs in SCI have discovered that ncRNAs bind target mRNA, act between activated glia, neuronal cells, or other immunocytes, regulate gene expression, inhibit inflammation, and influence the prognosis of NP.

MALAT1 knockdown alleviates the pyroptosis of microglias in diabetic cerebral ischemia via regulating STAT1 mediated NLRP3 transcription

BACKGROUND

Dysregulated long non-coding RNAs participate in the development of diabetic cerebral ischemia. This study aimed to investigate the underlying mechanism of lncRNA MALAT1 in diabetic cerebral ischemia.

METHOD

Middle cerebral artery occlusion (MCAO) was performed to establish diabetic cerebral I/R in vivo. TTC and neurological deficits assessment were performed to assess cerebral ischemic injury. LDH was conducted to detect cytotoxicity. RT-qPCR and western blotting assays were applied to determine mRNA and protein expression. Flow cytometry was performed to detect the pyroptosis of BV2 cells. Immunofluorescence and FISH were conducted for subcellular localization of MALAT1 and STAT1. ELISA was performed to determine cytokine release. Dual luciferase reporter, RIP, and ChIP assays were used to validate the interaction between STAT1 and MALAT1/NLRP3. Diabetes aggravated cerebral injury in vivo and in vitro. Diabetic cerebral ischemia induced inflammatory response and inflammation-induced cell pyroptosis.

RESULT

MALAT1 was overexpressed in diabetic cerebral ischemia models in vivo and in vitro. However, knockdown of MALAT1 suppressed inflammatory response and the pyroptosis of BV2 cells. Moreover, MALAT1 interacted with STAT1 to transcriptionally activate NLRP3. Knockdown of STAT1 significantly reversed the effects of MALAT1. Furthermore, STAT1 promotes the MALAT1 transcription. MALAT1 interacts with STAT1 to promote the pyroptosis of microglias induced by diabetic cerebral ischemia through activating NLRP3 transcription.

CONCLUSION

Thus, knockdown of MALAT1 may be a potential promising therapy target for diabetic cerebral ischemia.

The Common LncRNAs of Neuroinflammation-Related Diseases

Spatio-temporal specific long noncoding RNAs (lncRNAs) play important regulatory roles not only in the growth and development of the brain but also in the occurrence and development of neurologic diseases. Generally, the occurrence of neurologic diseases is accompanied by neuroinflammation. Elucidation of the regulatory mechanisms of lncRNAs on neuroinflammation is helpful for the clinical treatment of neurologic diseases. This paper focuses on recent findings on the regulatory effect of lncRNAs on neuroinflammatory diseases and selects 10 lncRNAs that have been intensively studied to analyze their mechanism action. The clinical treatment status of lncRNAs as drug targets is also reviewed. SIGNIFICANCE STATEMENT: Gene therapies such as clustered regularly interspaced short palindrome repeats technology, antisense RNA technology, and RNAi technology are gradually applied in clinical treatment, and the development of technology is based on a large number of basic research investigations. This paper focuses on the mechanisms of lncRNAs regulation of neuroinflammation, elucidates the beneficial or harmful effects of lncRNAs in neurosystemic diseases, and provides theoretical bases for lncRNAs as drug targets.

Induced pluripotent stem cells as natural biofactories for exosomes carrying miR-199b-5p in the treatment of spinal cord injury

Background: Induced pluripotent stem cells-derived exosomes (iPSCs-Exo) can effectively treat spinal cord injury (SCI) in mice. But the role of iPSCs-Exo in SCI mice and its molecular mechanisms remain unclear. This research intended to study the effects and molecular mechanism of iPSCs-Exo in SCI mice models. Methods: The feature of iPSCs-Exo was determined by transmission electron microscope (TEM), nanoparticle tracking analysis (NTA), and western blot. The effects of iPSCs-Exo in the SCI mice model were evaluated by Basso Mouse Scale (BMS) scores and H&E staining. The roles of iPSCs-Exo and miR-199b-5p in LPS-treated BMDM were verified by immunofluorescence, RT-qPCR, and Cytokine assays. The target genes of miR-199b-5p were identified, and the function of miR-199b-5p and its target genes on LPS-treated BMDM was explored by recuse experiment. Results: iPSCs-Exo improved motor function in SCI mice model in vivo, shifted the polarization from M1 macrophage to M2 phenotype, and regulated related inflammatory factors expression to accelerate the SCI recovery in LPS-treated BMDM in vitro. Meanwhile, miR-199b-5p was a functional player of iPSCs-Exo, which could target hepatocyte growth factor (Hgf). Moreover, miR-199b-5p overexpression polarized M1 macrophage into M2 phenotype and promoted neural regeneration in SCI. The rescue experiments confirmed that miR-199b-5p induced macrophage polarization and SCI recovery by regulating Hgf and Phosphoinositide 3-kinase (PI3K) signaling pathways. Conclusion: The miR-199b-5p-bearing iPSCs-Exo might become an effective method to treat SCI.

Promising Advances in Pharmacotherapy for Patients with Spinal Cord Injury-A Review of Studies Performed In Vivo with Modern Drugs

Spinal cord injury (SCI) is a pathological neurological condition that leads to significant motor dysfunction. It is a condition that occurs as a result of tragic accidents, violent acts, or as a consequence of chronic diseases or degenerative changes. The current treatments for patients with SCI have moderate efficacy. They improve the quality of life of patients, but they are still doomed to long-term disability. In response to the modern directions of research on possible therapeutic methods that allow for the recovery of patients with SCI, a scientific review publication is needed to summarize the recent developments in this topic. The following review is focused on the available pharmacological treatments for SCIs and the problems that patients face depending on the location of the injury. In the following review, the research team describes problems related to spasticity and neuropathic pain; possible therapeutic pathways are also described for neuroprotection and the improvement of neurotransmission within the injured spinal cord, and the review focuses on issues related to oxidative stress.

Resveratrol Glycosides Impede Microglial Apoptosis and Oxidative Stress in Rats for Spinal Cord Injury

Spinal cord injury (SCI) usually occurs after severe trauma, which can lead to detrimental and unpredictable secondary diseases, including dyskinesia, paraplegia and even quadriplegia, resulting in seriously reduced quality of life among these patients. Oxidative damage is one of the major pathogenic factors of SCI. Resveratrol biologically exerts a significant antioxidant activity by increasing the levels of antioxidants and sequentially scavenging free radicals, so as to protect multiple organs from damage. This study investigates whether resveratrol can function as a protective mediator in SCI and the underlying mechanisms, aiming to provide a theoretical hint for the treatment of SCI. After establishment of SCI model in rats, serial doses of resveratrol were administrated. Afterwards, the therapeutic effects of resveratrol glycosides were evaluated by analyzing the motor function, spinal cord edema, cellular apoptosis and oxidative reaction in rats. Eventually, the potential mechanisms of resveratrol glycosides were studied via Western blotting. Our results showed that the pro-apoptosis proteins were highly expressed in the spinal cord tissue of rats after SCI. In comparison with healthy rats, those with SCI exhibited significant widespread dead neurons, glial cell apoptosis, oxidative stress and more serious functional defects. Nevertheless, resveratrol glycosides can ameliorate oxidative stress, inhibit the apoptosis of glial cells and neuronal death after SCI. Importantly, it can induce the activation of the Nrf2/HO-1 signal transduction pathway that mediated the alleviation of SCI in rats. Resveratrol can improve motor dysfunction after SCI, which may be a result of its anti-oxidation and anti-apoptotic effects via modulating the Nrf2 signal transduction pathway of microglia, which provides a new idea for the treatment of SCI.

Integrated Analysis of Transcriptome mRNA and miRNA Profiles Reveals Self-Protective Mechanism of Bovine MECs Induced by LPS

Many studies have investigated the molecular crosstalk between mastitis-pathogens and cows by either miRNA or mRNA profiles. Here, we employed both miRNA and mRNA profiles to understand the mechanisms of the response of bovine mammary epithelial cells (bMECs) to lipopolysaccharide (LPS) by RNA-Seq. The total expression level of miRNAs increased while mRNAs reduced after LPS treatment. About 41 differentially expressed mRNAs and 45 differentially expressed miRNAs involved in inflammation were screened out. We found the NFκB-dependent chemokine, CXCL1, CXCL3, CXCL6, IL8, and CX3CL1 to be strongly induced. The anti-apoptosis was active because BCL2A1 and BIRC3 significantly increased with a higher expression. The effects of anti-microbe and inflammation were weakly activated because TNF, IL1, CCL20, CFB, S100A, MMP9, and NOS2A significantly increased but with a low expression, IL6 and β-defensin decreased. These activities were supervised by the NFKBIA to avoid excessive damage to bMECs. The bta-let-7a-5p, bta-miR-30a-5p, bta-miR-125b, and bta-miR-100 were essential to regulate infection process in bMECs after LPS induction. Moreover, the lactation potential of bMECs was undermined due to significantly downregulated SOSTDC1, WNT7B, MSX1, and bta-miR-2425-5p. In summary, bMECs may not be good at going head-to-head with the pathogens; they seem to be mainly charged with sending out signals for help and anti-apoptosis for maintaining lives after LPS induction.

Adult Neural Stem Cell Regulation by Small Non-coding RNAs: Physiological Significance and Pathological Implications

The adult neurogenic niches are complex multicellular systems, receiving regulatory input from a multitude of intracellular, juxtacrine, and paracrine signals and biological pathways. Within the niches, adult neural stem cells (aNSCs) generate astrocytic and neuronal progeny, with the latter predominating in physiological conditions. The new neurons generated from this neurogenic process are functionally linked to memory, cognition, and mood regulation, while much less is known about the functional contribution of aNSC-derived newborn astrocytes and adult-born oligodendrocytes. Accumulating evidence suggests that the deregulation of aNSCs and their progeny can impact, or can be impacted by, aging and several brain pathologies, including neurodevelopmental and mood disorders, neurodegenerative diseases, and also by insults, such as epileptic seizures, stroke, or traumatic brain injury. Hence, understanding the regulatory underpinnings of aNSC activation, differentiation, and fate commitment could help identify novel therapeutic avenues for a series of pathological conditions. Over the last two decades, small non-coding RNAs (sncRNAs) have emerged as key regulators of NSC fate determination in the adult neurogenic niches. In this review, we synthesize prior knowledge on how sncRNAs, such as microRNAs (miRNAs) and piwi-interacting RNAs (piRNAs), may impact NSC fate determination in the adult brain and we critically assess the functional significance of these events. We discuss the concepts that emerge from these examples and how they could be used to provide a framework for considering aNSC (de)regulation in the pathogenesis and treatment of neurological diseases.

Inhibition of miR-145-5p Reduces Spinal Cord Injury-Induced Inflammatory and Oxidative Stress Responses via Affecting Nurr1-TNF-α Signaling Axis

Inflammation and oxidative stress feature prominently in the secondary spinal cord injury (SCI). The present work is targeted at deciphering miR-145-5p's role and underlying mechanism in SCI. We randomly divided Sprague-Dawley rats into SCI group and control group. Microglial BV2 cells were separated into control group and lipopolysaccharide (LPS) treatment group. Enzyme-linked immunosorbent assay was carried out for determining the concentrations of interleukin-6, interleukin-1β, and tumor necrosis factor-α (TNF-α). The expressions of malondialdehyde, glutathione peroxidase, superoxide dismutase, and reactive oxygen species were also detected. TNF-α, miR-145-5p, and Nurr1 expressions were examined by western blot and quantitative real-time polymerase chain reaction. Western blotting and dual-luciferase reporter gene assay were conducted to examine the regulating impact that miR-145-5p had on Nurr1 and TNF-α. MiR-145-5p was remarkably upregulated in the SCI rat model's spinal cord tissues and BV2 cells treated with LPS, and Nurr1 expression was dramatically lowered. Furthermore, miR-145-5p inhibition markedly repressed inflammatory and oxidative stress responses. Moreover, it was proved that Nurr1 was a direct miR-145-5p target. The inhibition of miR-145-5p helped promote Nurr1 expression to block TNF-α signaling. MiR-145-5p inhibition mitigates inflammation and oxidative stress via targeting Nurr1 to regulate TNF-α signaling, which ameliorates SCI.

The Role of Formyl Peptide Receptors in Neurological Diseases via Regulating Inflammation

Formyl peptide receptors (FPRs) are a group of G protein-coupled cell surface receptors that play important roles in host defense and inflammation. Owing to the ubiquitous expression of FPRs throughout different cell types and since they interact with structurally diverse chemotactic agonists, they have a dual function in inflammatory processes, depending on binding with different ligands so that accelerate or inhibit key intracellular kinase-based regulatory pathways. Neuroinflammation is closely associated with the pathogenesis of neurodegenerative diseases, neurogenic tumors and cerebrovascular diseases. From recent studies, it is clear that FPRs are important biomarkers for neurological diseases as they regulate inflammatory responses by monitoring glial activation, accelerating neural differentiation, regulating angiogenesis, and controlling blood brain barrier (BBB) permeability, thereby affecting neurological disease progression. Given the complex mechanisms of neurological diseases and the difficulty of healing, we are eager to find new and effective therapeutic targets. Here, we review recent research about various mechanisms of the effects generated after FPR binding to different ligands, role of FPRs in neuroinflammation as well as the development and prognosis of neurological diseases. We summarize that the FPR family has dual inflammatory functional properties in central nervous system. Emphasizing that FPR2 acts as a key molecule that mediates the active resolution of inflammation, which binds with corresponding receptors to reduce the expression and activation of pro-inflammatory composition, govern the transport of immune cells to inflammatory tissues, and restore the integrity of the BBB. Concurrently, FPR1 is essentially related to angiogenesis, cell proliferation and neurogenesis. Thus, treatment with FPRs-modulation may be effective for neurological diseases.

Overexpression of miR-149-5p Attenuates Cerebral Ischemia/Reperfusion (I/R) Injury by Targeting Notch2

Ischemic stroke is one of the leading causes of death and disability worldwide. Although miR-149-5p downregulation is observed in rats after ischemia/reperfusion (I/R) injury, its function and role in ischemic stroke remain unclear. This study aimed to investigate the roles of miR-149-5p in I/R injury. The results showed that miR-149-5p was significantly downregulated in brain tissues of rats subjected to middle cerebral artery occlusion (MCAO) and primary cortical neurons subject to oxygen and glucose deprivation (OGD). MiR-149-5p overexpression effectively reduced MCAO/R-induced infarct volume, neurological score, and brain water content as well as OGD/R-induced cortical neurons apoptosis and OGD/R-induced expression of TNF-α, IL-4, IL-6, IL-1β, and COX-2. Moreover, Notch2 was identified as a target of miR-149-5p and Notch2 overexpression significantly attenuated the inhibitory effects of miR-149-5p mimics on inflammation and apoptosis. Taken together, our study revealed that miR-149-5p overexpression protects the rat brain against I/R injury by regulating Notch2-mediated inflammation and apoptosis pathway.

MicroRNA-182 improves spinal cord injury in mice by modulating apoptosis and the inflammatory response via IKKβ/NF-κB

Spinal cord injury (SCI) is one common neurological condition which involves primary injury and secondary injury. Neuron inflammation and apoptosis after SCI is the most important pathological process of this disease. Here, we tried to explore the influence and mechanism of miRNAs on the neuron inflammatory response and apoptosis after SCI. First, by re-analysis of Gene Expression Omnibus dataset (accession GSE19890), miR-182 was selected for further study because of its suppressive effects on the inflammatory response in the various types of injuries. Functional experiments demonstrated that miR-182 overexpression promoted functional recovery, reduced histopathological changes, and alleviated spinal cord edema in mice. It was also observed that miR-182 overexpression reduced apoptosis and attenuated the inflammatory response in spinal cord tissue, as evidenced by the reduction of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β, and the induction of IL-10. Using a lipopolysaccharide (LPS)-induced SCI model in BV-2 cells, we found that miR-182 was downregulated in the BV-2 cells following LPS stimulation, and upregulation of miR-182 improved LPS-induced cell damage, as reflected by the inhibition of apoptosis and the inflammatory response. IκB kinase β (IKKβ), an upstream target of the NF-κB pathway, was directly targeted by miR-182 and miR-182 suppressed its translation. Further experiments revealed that overexpression of IKKβ reversed the anti-apoptosis and anti-inflammatory effects of miR-182 in LPS stimulated BV-2 cells. Finally, we found that miR-182 overexpression blocked the activation of the NF-κB signaling pathway in vitro and in vivo, as demonstrated by the downregulation of phosphorylated (p‑) IκB-α and nuclear p-p65. Taken together, these data indicate that miR-182 improved SCI-induced secondary injury through inhibiting apoptosis and the inflammatory response by blocking the IKKβ/NF-κB pathway. Our findings suggest that upregulation of miR-182 may be a novel therapeutic target for SCI.

Pretreatment with kaempferol attenuates microglia-mediate neuroinflammation by inhibiting MAPKs-NF-κB signaling pathway and pyroptosis after secondary spinal cord injury

Spinal cord injury (SCI) is a devastating injury that characterized by oxidative stress and inflammatory response. Kaempferol is reported to be an anti-neuroinflammation in neurologic disorders. Nevertheless, the role and mechanism of kaempferol in SCI remains unclear. The present study aims to investigate effects of kaempferol on SCI and its possible underlying mechanisms in in vivo and in vitro models. A C5 hemi-contusion injury was induced in Sprague-Dawley rats to investigate the neuroprotective effects of kaempferol after SCI. For in vitro study, the BV2 microglia cell lines were pretreated with or without kaempferol. A combination of molecular and histological methods was used to clarify the mechanism and explore the signaling pathway both in vivo and in vitro. One-way analysis of variance (ANOVA) was conducted with Bonferroni post hoc tests to examine the differences between groups. The in vivo studies showed that kaempferol could improve the recovery of hindlimb motor function and ameliorate tissue damage in the spinal cord after SCI. Moreover, administration of kaempferol reduced microglia activation and oxidative stress level in the spinal cord. The in vitro studies showed that kaempferol suppressed the microglia activation resulting from the administration of LPS with ATP to BV-2 cells. Pretreated BV2 cells with kaempferol reduced the generation of reactive oxygen species (ROS) by inhibiting NADPH oxidase 4, and then, suppressed the phosphorylation of p38 MAPK and JNK, which subsequently inhibited nuclear translocation of NF-κB p65 to express pro-inflammatory factors. We also observed that kaempferol could inhibite the pyroptosis related proteins (NLRP3 Caspase-1 p10 ASC N-GSDMD) and reduce the release of IL-18 and IL-1β. In conclusion, kaempferol was able to reduce oxidative stress and inflammatory response through down-regulation of ROS dependent MAPKs- NF-κB and pyroptosis signaling pathway, which suggested that kaempferol might be a novel promising therapeutic agent for SCI.

MicroRNA-129-5p alleviates spinal cord injury in mice via suppressing the apoptosis and inflammatory response through HMGB1/TLR4/NF-κB pathway

Secondary injury after spinal cord injury (SCI) is one reversible pathological change mainly involving excessive inflammatory response and neuro-apoptosis. Since in recent years, microRNAs (miRNAs) have been proposed as novel regulators of inflammation in different disease conditions. However, the role of miRNAs in the inflammatory response and apoptosis of secondary injury after SCI remains to be fully elucidated. Here, we tried to explore the influence and mechanism of miRNAs on the neuron inflammatory response and apoptosis after SCI. The expression profiles of miRNA were examined using miRNA microarray, and among the candidate miRNAs, miR-129-5p was found to be the most down-regulated miRNA in spinal tissues. Overexpression of miR-129-5p using agomir-miR-129-5p promoted injury mice functional recovery, suppressed the apoptosis and alleviated inflammatory response in spinal tissues. Using LPS-induced BV-2 cell model, we found miR-129-5p was also proved in protecting inflammatory response and cell apoptosis in vitro. High-mobility group protein B1 (HMGB1), a well-known inflammatory mediator, was found to be directly targeted by miR-129-5p and it was associated with the inhibitory effect of miR-129-5p on the activation of toll-like receptor (TLR)-4 (TLR4)/ nuclear factor-κB (NF-κB) pathway in vitro and in vivo. Further experiments revealed that the anti-apoptosis and anti-inflammatory effects of miR-129-5p were reversed by HMGB1 overexpression in BV-2 cells. Collectively, these data revealed that miR-129-5p alleviated SCI in mice via suppressing the apoptosis and inflammatory response through HMGB1//TLR4/NF-κB pathway. Our data suggest that up-regulation of miR-129-5p may be a novel therapeutic target for SCI.

Decreased miR-214-3p activates NF-κB pathway and aggravates osteoarthritis progression

Background

Osteoarthritis (OA), a disease with whole-joint damage and dysfunction, is the leading cause of disability worldwide. The progressive loss of hyaline cartilage extracellular matrix (ECM) is considered as its hallmark, but its exact pathogenesis needs to be further clarified. MicroRNA(miRNA) contributes to OA pathology and may help to identify novel biomarkers and therapies against OA. Here we identified miR-214–3p as an important regulator of OA.

Methods

qRT-PCR and in situ hybridization were used to detect the expression level of miR-214–3p. The function of miR-214–3p in OA, as well as the interaction between miR-214–3p and its downstream mRNA target (IKBKB), was evaluated by western blotting, immunofluorescence, qRT-PCR and luciferase assay. Mice models were introduced to examine the function and mechanism of miR-214–3p in OA in vivo.

Findings

In our study, we found that miR-214–3p, while being down-regulated in inflamed chondrocytes and OA cartilage, regulated ECM metabolism and cell apoptosis in the cartilage. Mechanically, the protective effect of miR-214–3p downregulated the IKK-β expression and led to the dysfunction of NF-κB signaling pathway. Furthermore, intra-articular injection of miR-214–3p antagomir in mice joints triggered spontaneous cartilage loss while miRNA-214–3p agomir alleviated OA in the experimental mouse models.

Interpretation

Decreased miR-214–3p activates the NF-κB signaling pathway and aggravates OA development through targeting IKKβ, suggesting miR-214–3p may be a novel therapeutic target for OA.

Funding

This study was financially supported by grants from the National Natural Science Foundation of China (81,773,532, 81,974,342).

MicroRNAs in central nervous system disorders: current advances in pathogenesis and treatment

MicroRNAs (miRNAs) are a class of short, non-coding, regulatory RNA molecules that function as post transcriptional regulators of gene expression. Altered expression of multiple miRNAs was found to be extensively involved in the pathogenesis of different neurological disorders including Alzheimer’s disease, Parkinson’s disease, stroke, epilepsy, multiple sclerosis, amyotrophic lateral sclerosis, and Huntington’s disease. miRNAs are implicated in the pathogenesis of excitotoxicity, apoptosis, oxidative stress, inflammation, neurogenesis, angiogenesis, and blood–brain barrier protection. Consequently, miRNAs can serve as biomarkers for different neurological disorders. In recent years, advances in the miRNA field led to identification of potentially novel prospects in the development of new therapies for incurable CNS disorders. MiRNA-based therapeutics include miRNA mimics and inhibitors that can decrease or increase the expression of target genes. Better understanding of the mechanisms by which miRNAs are implicated in the pathogenesis of neurological disorders may provide novel targets to researchers for innovative therapeutic strategies.

miRNAs in Microglia: Important Players in Multiple Sclerosis Pathology

Microglia are the resident immune cells of the central nervous system and important regulators of brain homeostasis. Central to this role is a dynamic phenotypic plasticity that enables microglia to respond to environmental and pathological stimuli. Importantly, different microglial phenotypes can be both beneficial and detrimental to central nervous system health. Chronically activated inflammatory microglia are a hallmark of neurodegeneration, including the autoimmune disease multiple sclerosis (MS). By contrast, microglial phagocytosis of myelin debris is essential for resolving inflammation and promoting remyelination. As such, microglia are being explored as a potential therapeutic target for MS. MicroRNAs (miRNAs) are short non-coding ribonucleic acids that regulate gene expression and act as master regulators of cellular phenotype and function. Dysregulation of certain miRNAs can aberrantly activate and promote specific polarisation states in microglia to modulate their activity in inflammation and neurodegeneration. In addition, miRNA dysregulation is implicated in MS pathogenesis, with circulating biomarkers and lesion specific miRNAs identified as regulators of inflammation and myelination. However, the role of miRNAs in microglia that specifically contribute to MS progression are still largely unknown. miRNAs are being explored as therapeutic agents, providing an opportunity to modulate microglial function in neurodegenerative diseases such as MS. This review will focus firstly on elucidating the complex role of microglia in MS pathogenesis. Secondly, we explore the essential roles of miRNAs in microglial function. Finally, we focus on miRNAs that are implicated in microglial processes that contribute directly to MS pathology, prioritising targets that could inform novel therapeutic approaches to MS.

Promoting functions of microRNA-29a/199B in neurological recovery in rats with spinal cord injury through inhibition of the RGMA/STAT3 axis

Background

The prognostic and therapeutic potential of microRNAs (miRNAs) in spinal cord injury (SCI) has aroused increasing concerns. This study aims to research the functions of miR-29a/199B in the neurological function recovery after SCI and the mechanical mechanism.

Methods

A rat model with SCI was induced with sham-operated ones as control. The locomotor function and coordination of rat hindlimbs were determined by a Basso, Beattie, and Bresnahan (BBB) locomotor rating scale and a ladder-climbing test, respectively. Expression of a neurofilament protein NF-200 and synaptophysin in gray matter of rats was determined to evaluate neuronal recovery in a cellular perspective. Binding relationships between miR-29a/199B with RGMA were predicted and validated using luciferase assays. Altered expression of miR-29a/199B and RGMA was introduced to explore their functions in rat neurological functions. The protein level and phosphorylation of STAT3 in gray matter were measured by western blot analysis.

Results

miR-29a and miR-199B were poorly expressed, while RGMA was abundantly expressed in gray matter at injury sites. Either miR-29a or miR-199B could bind to RGMA. Overexpression of miR-29a/199B or silencing of RGMA led to an increase in BBB locomotor scores, hindlimb coordination ability, and the expression of NF-200 and synaptophysin in gray matter. Further inhibition in miR-29a/199B blocked the promoting roles of RGMA silencing in neurological recovery. Upregulation of miR-29a/199B or downregulation of RGMA suppressed the phosphorylation of STAT3.

Conclusion

This study evidenced that miR-29a and miR-199B negatively regulated RGMA to suppress STAT3 phosphorylation, therefore promoting the neurological function recovery in rats following SCI.

TNFAIP8 influences the motor function in mice after spinal cord injury (SCI) through meditating inflammation dependent on AKT

Spinal cord injury (SCI) is a devastating disease and causes tissue loss and neurologic dysfunction, contributing to high morbidity and disability among human. However, the underlying molecular mechanisms still remain unclear. Tumor necrosis factor-α-induced protein 8 (TNFAIP8) is a member of the TNFAIP8/TIPE family, and has been implicated in different diseases associated with inflammation, infection, and immunity. Nevertheless, its effects on SCI have not been well investigated. In our study, we found time course of TNFAIP8 following SCI in mice, along with time-dependent increases of pro-inflammatory cytokines. The in vitro results confirmed the up-regulation of TNFAIP8 induced by lipopolysaccharide (LPS). Subsequently, we found that reducing TNFAIP8 by transfection with its specific siRNA (siTNFAIP8) markedly alleviated cell viability and inflammatory response caused by LPS in mouse microglial BV2 cells. Importantly, LPS-enhanced activation of inhibitor of κBα/nuclear factor-κB (IκBα/NF-κB) and phosphoinositide 3-kinase/serine-threonine kinase (PI3K/AKT) signaling pathways was considerably blunted by siTNFAIP8. Intriguingly, our results further showed that siTNFAIP8-restrained inflammation and IκBα/NF-κB in LPS-stimulated BV2 cells were almost abolished by the pre-treatment of AKT activator SC-79, demonstrating that TNFAIP8-regulated inflammatory response was largely dependent on AKT activation. Then, the in vivo studies were performed using the wild type (WT) and TNFAIP8-knockout (KO) mice with or without SCI operation. Results showed that TNFAIP8-KO mice exhibited improved neuron injury and locomotor function along with decreased microglial activity. Furthermore, compared with the WT/SCI mice, the expression of pro-inflammatory cytokines in spinal cords was markedly down-regulated by TNFAIP8-deficiency through blocking IκBα/NF-κB and PI3K/AKT signaling pathways. Taken together, these findings elucidated the novel role of TNFAIP8 in regulating SCI via the AKT signaling, and thus TNFAIP8 may be served as a promising therapeutic target for SCI treatment.

Advanced oxidation protein products induce microglia-mediated neuroinflammation via MAPKs-NF-κB signaling pathway and pyroptosis after secondary spinal cord injury

Background

Inflammatory response mediated by oxidative stress is considered as an important pathogenesis of spinal cord injury (SCI). Advanced oxidation protein products (AOPPs) are novel markers of oxidative stress and their role in inflammatory response after SCI remained unclear. This study aimed to investigate the role of AOPPs in SCI pathogenesis and explore the possible underlying mechanisms.

Methods

A C5 hemi-contusion injury was induced in Sprague-Dawley rats to confirm the involvement of AOPPs after SCI. For in vivo study, apocynin, the NADPH oxidase inhibitor was used to study the neuroprotective effects after SCI. For in vitro study, the BV2 microglia cell lines were pretreated with or without the inhibitor or transfected with or without small interference RNA (siRNA) and then stimulated with AOPPs. A combination of molecular and histological methods was used to clarify the mechanism and explore the signaling pathway both in vivo and in vitro. One-way analysis of variance (ANOVA) was conducted with Bonferroni post hoc tests to examine the differences between groups.

Results

The levels of AOPPs in plasma and cerebrospinal fluid as well as the contents in the spinal cord showed significant increase after SCI. Meanwhile, apocynin ameliorated tissue damage in the spinal cord after SCI, improving the functional recovery. Immunofluorescence staining and western blot analysis showed activation of microglia after SCI, which was in turn inhibited by apocynin. Pretreated BV2 cells with AOPPs triggered excessive generation of reactive oxygen species (ROS) by activating NADPH oxidase. Increased ROS induced p38 MAPK and JNK phosphorylation, subsequently triggering nuclear translocation of NF-κB p65 to express pro-inflammatory cytokines. Also, treatment of BV2 cells with AOPPs induced NLRP3 inflammasome activation and cleavage of Gasdermin-d (GSDMD), causing pyroptosis. This was confirmed by cleavage of caspase-1, production of downstream mature interleukin (IL)-1β and IL-18 as well as rupture of rapid cell membrane.

Conclusions

Collectively, these data indicated AOPPs as biomarkers of oxidative stress, modulating inflammatory response in SCI by multiple signaling pathways, which also included the induction of NADPH oxidase dependent ROS, and NLRP3-mediated pyroptosis, and activation of MAPKs and NF-κB.

RNA interference in glial cells for nerve injury treatment

Drivers of RNA interference are potent for manipulating gene and protein levels, which enable the restoration of dysregulated mRNA expression that is commonly associated with injuries and diseases. This review summarizes the potential of targeting neuroglial cells, using RNA interference, to treat nerve injuries sustained in the central nervous system. In addition, the various methods of delivering these RNA interference effectors will be discussed.

Curcumin Alleviates Lipopolysaccharide (LPS)-Activated Neuroinflammation via Modulation of miR-199b-5p/IκB Kinase β (IKKβ)/Nuclear Factor Kappa B (NF-κB) Pathway in Microglia

BACKGROUND Microglia reside in the spinal cord plays a key role in the onset, progression of post-spinal cord injury (SCI) neuroinflammation. Curcumin has been shown to exhibit diverse anti-inflammatory and anti-tumor activities. The aim of this study was to explore the effect of curcumin on the inflammatory response in lipopolysaccharide (LPS)-activated microglia and its mechanism. MATERIAL AND METHODS The expression levels of phosphorylated-p65 (p-p65), tumor necrosis factor (TNF)-alpha, interleukin (IL)-1ß, and IkappaB kinase ß (IKKß) were examined by western blot assay. MiR-199b-5p expression was detected by quantitative real-time polymerase chain reaction assay. The putative binding sites of miR-199b-5p in IKKß 3'UTR were predicted by bioinformatics, and direct interaction between miR-199b-5p and IKKß was verified by dual-luciferase reporter assay and RNA-immunoprecipitation assay. RESULTS Curcumin significantly suppressed inflammatory response induced by LPS by inactivation of nuclear factor kappa B (NF-kappaB) in microglial cells, as reflected by the decreased levels of p-p65, as well as the pro-inflammatory mediators, including inducible nitric oxide synthase (iNOS), TNF-alpha, and IL-1ß. Moreover, curcumin increased the level of miR-199b-5p and decreased IKKß expression in activated microglial cells. Knockdown of miR-199b-5p or overexpression of IKKß reversed the inhibitory effect of curcumin on inflammatory response and NF-kappaB activation. MiR-199b-5p directly targeted IKKß and suppressed its expression. Silencing of IKKß abolished miR-199b-5p-stimulated inflammatory cytokines production and NF-kappaB activation. CONCLUSIONS Curcumin attenuated neuroinflammation induced by LPS through regulating miR-199b-5p/IKKß/NF-kappaB axis in microglia.

Nuclear Factor κB Signaling and Its Related Non-coding RNAs in Cancer Therapy

Nuclear factor κB (NF-κB) acts as a nuclear factor that is composed of five main subunits. It is a pluripotent and crucial dimer transcription factor that has a close relationship with many serious illnesses, especially its influences on cell proliferation, inflammation, and cancer initiation and progression. NF-κB acts as part of the signaling pathway and determines its effect on the expression of several other genes, such as epidermal growth factor receptor (EGFR), p53, signal transducer and activator of transcription 3 (STAT3), and non-coding RNA (ncRNA). Continuous activation of the NF-κB signaling pathway has been seen in many cancer types. While the NF-κB signaling pathway is tightly regulated in physiological settings, quite frequently it is constitutively activated in cancer, and the molecular biology mechanism underlying the deregulated activation of NF-κB signaling remains unclear. In this review, we discuss the regulatory role and possible clinical significance of ncRNA (microRNA [miRNA] and long non-coding RNA [lncRNA]) in NF-κB signaling in cancer, including in the conversion of inflammation to carcinogenesis. Non-coding RNA plays an essential and complex role in the NF-κB signaling pathway. NF-κB activation can also induce the ncRNA status. Targeting NF-κB signaling by ncRNA is becoming a promising strategy of drug development and cancer treatment.

miR-636: A Newly-Identified Actor for the Regulation of Pulmonary Inflammation in Cystic Fibrosis

Cystic fibrosis (CF) results from deficient CF transmembrane conductance regulator (CFTR) protein activity leading to defective epithelial ion transport. Pulmonary degradation due to excessive inflammation is the main cause of morbidity and mortality in CF patients. By analysing miRNAs (small RNAseq) in human primary air-liquid interface cell cultures, we measured the overexpression of miR-636 in CF patients compared to non-CF controls. We validated these results in explant biopsies and determined that the mechanism underlying miR-636 overexpression is linked to inflammation. To identify specific targets, we used bioinformatics analysis to predict whether miR-636 targets the 3′-UTR mRNA regions of IL1R1 and RANK (two pro-inflammatory cytokine receptors), IKBKB (a major protein in the NF-κB pathway), and FAM13A (a modifier gene of CF lung phenotype implicated in epithelial remodelling). Using bronchial epithelial cells from CF patients to conduct a functional analysis, we showed a direct interaction between miR-636 and IL1R1, RANK, and IKBKB, but not with FAM13A. These interactions led to a decrease in IL1R1 and IKKβ protein expression levels, while we observed an increase in RANK protein expression levels following the overexpression of miR-636. Moreover, NF-κB activity and IL-8 and IL-6 secretions decreased following the transfection of miR-636 mimics in CF cells. Similar but opposite effects were found after transfection with an antagomiR-636 in the same cells. Furthermore, we demonstrated that miR-636 was not regulated by Pseudomonas aeruginosa in our model. We went on to show that miR-636 is raised in the blood neutrophils, but not in the plasma, of CF patients and may have potential as a novel biomarker. Collectively, our findings reveal a novel actor for the regulation of inflammation in CF, miR-636, which is able to reduce constitutive NF-κB pathway activation when it is overexpressed.

The Emerging Role of lncRNAs in Spinal Cord Injury

Spinal cord injury (SCI) is a highly debilitating disease and is increasingly being recognized as an important global health priority. However, the mechanisms underlying SCI have not yet been fully elucidated, and effective therapies for SCI are lacking. Long noncoding RNAs (lncRNAs), which form a major class of noncoding RNAs, have emerged as novel targets for regulating several physiological functions and mediating numerous neurological diseases. Notably, gene expression profile analyses have demonstrated aberrant changes in lncRNA expression in rats or mice after traumatic or nontraumatic SCI. LncRNAs have been shown to be associated with multiple pathophysiological processes following SCI including inflammation, neural apoptosis, and oxidative stress. They also play a crucial role in the complications associated with SCI, such as neuropathic pain. At the same time, some lncRNAs have been found to be therapeutic targets for neural stem cell transplantation and hydrogen sulfide treatment aimed at alleviating SCI. Therefore, lncRNAs could be promising biomarkers for the diagnosis, treatment, and prognosis of SCI. However, further researches are required to clarify the therapeutic effects of lncRNAs on SCI and the mechanisms underlying these effects. In this study, we reviewed the current progress of the studies on the involvement of lncRNAs in SCI, with the aim of drawing attention towards their roles in this debilitating condition.

Triptolide Suppressed the Microglia Activation to Improve Spinal Cord Injury Through miR-96/IKKβ/NF-κB Pathway

STUDY DESIGN

The effect of triptolide on spinal cord injury (SCI) and inflammatory response was observed by establishing SCI rat model. And in vitro experiments were conducted to determine the underlying mechanism of triptolide-mediated in murine microglial cell line BV2.

OBJECTIVE

To determine the underlying mechanism of triptolide in suppressing the microglia activation to improve SCI.

SUMMARY OF BACKGROUND DATA

Triptolide, as a major active ingredient of Chinese herb Tripterygium wilfordii, can promote spinal cord repair through inhibiting microglia activation, but the underlying mechanism is not clear.

METHODS

Locomotion recovery was accessed by Basso, Beattie, and Bresnahan score, the number of footfalls, stride length, and angle of rotation analysis. Expressions of microRNA 96 (miR-96), microglia activation marker Iba-1, and IκB kinase (IKKβ)/nuclear factor (NF)-κB-related proteins were detected by qRT-PCR or western blot. Inflammatory cytokines tumor necrosis factor-α and interleukin -1β were measured by enzyme-linked immuno sorbent assay. The regulation of miR-96 on IKKβ was confirmed by dual luciferase reporter assay.

RESULTS

Triptolide promoted locomotion recovery of SCI rats, upregulated the expression of miR-96, decreased microglia activation marker Iba-1 and IKKβ/NF-κB-related proteins, and inhibited inflammatory cytokines tumor necrosis factor-α and interleukin-1β levels in spinal cord tissues and lipopolysaccharide -induced microglia. Triptolide suppressed the microglia activation and inflammatory cytokines secretion in BV2 cells through up-regulating miR-96. We confirmed the interaction between miR-96 and IKKβ, and IKKβ expression was negatively regulated by miR-96. Finally, we determined that triptolide suppressed the microglia activation and inflammatory cytokines secretion through miR-96/IKKβ pathway.

CONCLUSION

Triptolide suppressed microglia activation after SCI through miR-96/IKKβ/NF-κB pathway.

LEVEL OF EVIDENCE

N/A.

MicroRNAs in Microglia: How do MicroRNAs Affect Activation, Inflammation, Polarization of Microglia and Mediate the Interaction Between Microglia and Glioma?

The essential roles of microglia in maintaining homeostasis in the healthy brain and contributing to neuropathology are well documented. Emerging evidence suggests that epigenetic modulation regulates microglial behavior in both physiological and pathological conditions. MicroRNAs (miRNAs) are short, non-coding epigenetic regulators that repress target gene expression mostly via binding to 3'-untranslated region (3'-UTR) of mRNA in a Dicer-dependent manner. Dysregulation of certain miRNAs can contribute to microglial hyper-activation, persistent neuroinflammation, and abnormal macrophage polarization in the brain. These abnormal conditions can support the pathogenesis of neurological disorders such as glioma, Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), stroke, ischemia, and spinal cord injury (SCI). However, the roles of miRNAs in microglia in health and neurological disease have not been systematically summarized. This review will first report the role of Dicer, a key endoribonulease that is responsible for most miRNA biogenesis in microglia. Second, we will focus on recent research about the function of miRNAs in activation, inflammation and polarization of microglia, respectively. In addition, potential crosstalk between microglia and glioma cells via miRNAs will be discussed in this part. Finally, the role of two essential miRNAs, miR-124, and miR-155, in microglia will be highlighted.

A Causal Relationship in Spinal Cord Injury Rat Model Between Microglia Activation and EGFR/MAPK Detected by Overexpression of MicroRNA-325-3p

Microglial activation and inflammatory response played an important role in the secondary injury of spinal cord injury (SCI). Several microRNAs were associated with this procedure, but the underlying molecular mechanism was poorly understood. Sprague-Dawley (SD) rats were divided into four groups: SCI group (n = 7), agomiR-325-3p group (n = 7), and their control groups. Expression of miR-325-3p and proteins in epidermal growth factor receptor (EGFR)/mitogen-activated protein kinase (MAPK) signaling pathway was evaluated in microglia from SCI rats and primary microglia/BV2 cells activated by lipopolysaccharide (LPS). Concentrations of interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α) in supernatants were measured by ELISA. Low expression of miR-325-3p and activation of EGFR/MAPK was observed in microglia of SCI and LPS-induced primary microglia. Overexpression of miR-325-3p in LPS-induced BV2 cells inhibited microglial activation and release of TNF-α and IL-1β. Luciferase reporter assay confirmed that miR-325-3p negatively regulated EGFR by targeting its 3'-untranslated regions. Additionally, agomiR-325-3p inhibited the activation of microglia and EGFR/MAPK, alleviating the inflammatory response. These results indicated that miR-325-3p attenuated secondary injury after SCI through inhibition of EGFR/MAPK signaling pathway, the microglial activation, and the release of inflammatory cytokines, suggesting that miR-325-3p may be employed as a therapeutic target for SCI.

Bone Mesenchymal Stem Cell-Derived Extracellular Vesicles Promote Recovery Following Spinal Cord Injury via Improvement of the Integrity of the Blood-Spinal Cord Barrier

Mesenchymal stem cell (MSC) transplantation has been shown to represent a potential treatment for traumatic spinal cord injury (SCI). However, there are several obstacles that need to be overcome before MSCs can be considered for clinical application, such as failure of MSCs to reach the spinal cord lesion core and possible tumor formation. Recent studies have suggested that MSC treatment is beneficial owing to paracrine-secreted factors. Extracellular vesicles are considered to be some of the most valuable paracrine molecules. However, the therapeutic mechanism of extracellular vesicles on spinal cord injury has not been studied clearly. Therefore, our study investigated the effect of systemic administration of extracellular vesicles on the loss of motor function after SCI and examined the potential mechanisms underlying their effects. Disruption of the blood-spinal cord barrier (BSCB) is a crucial factor that can be detrimental to motor function recovery. Pericytes are an important component of the neurovascular unit, and play a pivotal role in maintaining the structural integrity of the BSCB. Our study demonstrated that administration of bone mesenchymal stem cell-derived extracellular vesicles (BMSC-EV) reduced brain cell death, enhanced neuronal survival and regeneration, and improved motor function compared with the administration of BMSC-EV free culture media (EV-free CM). Besides, the BSCB was attenuated and pericyte coverage was significantly decreased in vivo. Furthermore, we found that exosomes reduced pericyte migration via downregulation of NF-κB p65 signaling, with a consequent decrease in the permeability of the BSCB. In summary, we identified that extracellular vesicles treatment suppressed the migration of pericytes and further improved the integrity of the BSCB via NF-κB p65 signaling in pericytes. Our data suggest that extracellular vesicles may serve as a promising treatment strategy for SCI.

MicroRNAs in contusion spinal cord injury: pathophysiology and clinical utility

Spinal cord injury (SCI) in humans is a common central nervous system trauma. Pathophysiologically, SCI involves both primary and secondary damages. Therapeutically, targeting secondary damage including inflammation, neuropathic pain, apoptosis, demyelination, and glial reaction to promote functional benefits for SCI patients has long been considered a potential treatment strategy by neuroscientists and clinicians. As a type of small non-coding RNA, microRNAs (miRNAs) have been shown to play essential roles in the regulation of pathophysiologic processes of SCI and are considered to be an effective treatment method for SCI. Dysregulated expression of miRNAs is observed in SCI patients and animal models of SCI. Furthermore, miRNAs might also be used as biomarkers for diagnostic and prognostic purposes in SCI. Given contusion injury is the most clinically relevant type of SCI, this review mainly focuses on the role of miRNAs in the pathophysiology of contusion SCI and the putative utilization of miRNAs as diagnostic biomarkers and therapeutic targets for contusion SCI.

Effect of miR-495 on lower extremity deep vein thrombosis through the TLR4 signaling pathway by regulation of IL1R1

Lower extremity deep vein thrombosis (LEDVT), a common peripheral vascular disease caused by a blood clot in a deep vein is usually accompanied by swelling of the lower limbs. MicroRNAs (miRs) have been reported to play roles in LEDVT. We aimed to investigate the effect of miR-495 on LEDVT via toll-like receptor 4 (TLR4) signaling pathway through interleukin 1 receptor type 1 (IL1R1). LEDVT mouse model was established, and the femoral vein (FV) tissues were collected to detect expressions of miR-495, IL1R1, and TLR4 signaling-related genes. The expressions of both CD31 and CD34 (markers for endothelial progenitor cells) in the FV endothelial cells as well as the proportion of CD31⁺/CD34⁺ cells in peripheral blood were measured in order to evaluate thrombosis. The effect of miR-495 on cell viability, cell cycle, and apoptosis was analyzed. IL1R1 was confirmed as the target gene of miR-495. Besides, inhibiting the miR-495 expression could increase IL1R1 expression along with activating the TLR4 signaling pathway. The total number of the leukocytes along with the ratio of weight to length of thrombus in the FV tissue showed an increase. The overexpression of miR-495 could promote FV endothelial cell viability. By injecting agomiR-495 and antagomiR-495 in vivo, the number of leukocytes in the FV tissues and the ratio of weight to length of thrombus were significantly decreased in the mice injected with the overexpressed miR-495, and the IL1R1/TLR4 signaling pathway was inhibited. Collectively, overexpressed miR-495 directly promotes proliferation while simultaneously inhibiting apoptosis of FV endothelial cells, alleviating FV thrombosis by inhibiting IL1R1 via suppression of TLR4 signaling pathway.

miR-199b-5p Regulates Immune-Mediated Allograft Rejection after Lung Transplantation Through the GSK3β and NF-κB Pathways

Emerging evidence indicates that acute rejection mainly associated with the inflammatory response is an independent risk factor for chronic rejection after lung transplantation. Monocytes are the main pro-inflammatory leukocytes infiltrating around the lesions and play vital roles in triggering the acute rejection. In the rat lung transplantation model, lipopolysaccharide (LPS)-induced severe acute rejection was strongly associated with advanced chronic rejection. The exact regulatory mechanism of pro-inflammation in monocytes is not yet clear. In this study, we identified a novel anti-inflammatory effect of miR-199b-5p (miR-199b) through the GSK3β and NF-κB pathways. THP-1 monocytes treated with LPS showed a significant decrease in miR-199b that is inversely correlated to GSK3β expression and NF-κB activation. Furthermore, the NF-κB-associated inflammatory response was reduced due to the overexpression of miR-199b targeting GSK3β, which was rescued by the inhibition of miR-199b. These results indicated that miR-199b attenuated the inflammatory response at least partly through the GSK3β/NF-κB signaling pathways in monocytes. Our data point toward a potentially important role for miR-199b in the inhibition of rejection after lung transplantation.

Regulation of Inflammatory Cytokines for Spinal Cord Injury Repair Through Local Delivery of Therapeutic Agents

The balance of inflammation is critical to the repair of spinal cord injury (SCI), which is one of the most devastating traumas in human beings. Inflammatory cytokines, the direct mediators of local inflammation, have differential influences on the repair of the injured spinal cord. Some inflammatory cytokines are demonstrated beneficial to spinal cord repair in SCI models, while some detrimental. Various animal researches have revealed that local delivery of therapeutic agents efficiently regulates inflammatory cytokines and promotes repair from SCI. Quite a few clinical studies have also shown the promotion of repair from SCI through regulation of inflammatory cytokines. However, local delivery of a single agent affects only a part of the inflammatory cytokines that need to be regulated. Meanwhile, different individuals have differential profiles of inflammatory cytokines. Therefore, future studies may aim to develop personalized strategies of locally delivered therapeutic agent cocktails for effective and precise regulation of inflammation, and substantial functional recovery from SCI.

Epigenetics Control Microglia Plasticity

Microglia, resident immune cells of the central nervous system, fulfill multiple functions in the brain throughout life. These microglial functions range from participation in innate and adaptive immune responses, involvement in the development of the brain and its homeostasis maintenance, to contribution to degenerative, traumatic, and proliferative diseases; and take place in the developing, the aging, the healthy, or the diseased brain. Thus, an impressive level of cellular plasticity, appears as a requirement for the pleiotropic biological functions of microglia. Epigenetic changes, including histone modifications or DNA methylation as well as microRNA expression, are important modifiers of gene expression, and have been involved in cell phenotype regulation and reprogramming and are therefore part of the mechanisms regulating cellular plasticity. Here, we review and discuss the epigenetic mechanisms, which are emerging as contributors to this microglial cellular plasticity and thereby can constitute interesting targets to modulate microglia associated brain diseases, including developmental diseases, neurodegenerative diseases as well as cancer.

Long noncoding RNA MALAT1 contributes to inflammatory response of microglia following spinal cord injury via the modulation of a miR-199b/IKKβ/NF-κB signaling pathway

Long noncoding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) was widely recognized to be implicated in human cancer, vascular diseases, and neurological disorders. This study was to explore the role and underlying mechanism of MALAT1 in acute spinal cord injury (ASCI). ASCI models in adult rats were established and demonstrated by a numerical decrease in BBB scores. Expression profile of MALAT1 and miR-199b following ASCI in rats and in vitro was determined using quantitative real-time PCR. RNA pull-down assays combined with RIP assays were performed to explore the interaction between MALAT1 and miR-199b. In the present study, MALAT1 expression was significantly increased (2.4-fold that of control) in the spinal cord of the rat contusion epicenter accompanied by activation of IKKβ/NF-κB signaling pathway and an increase in the level of proinflammatory cytokines TNF-α and IL-1β. Upon treatment with LPS, MALAT1 expression dramatically increased in the microglia in vitro, but knockdown of MALAT1 attenuated LPS-induced activation of MGs and TNF-α and IL-1β production. Next, we confirmed that LPS-induced MALAT1 activated IKKβ/NF-κB signaling pathway and promoted the production of proinflammatory cytokines TNF-α and IL-1β through downregulating miR-199b. More importantly, MALAT1 knockdown gradually improved the hindlimb locomotor activity of ASCI rats as well as inhibited TNF-α, IL-1β levels, and Iba-1 protein, the marker of activated microglia in injured spinal cords. Our study demonstrated that MALAT1 was dysregulated in ASCI rats and in LPS-activated MGs, and MALAT1 knockdown was expected to attenuate ASCI through repressing inflammatory response of MGs.

MicroRNA-based therapeutics in central nervous system injuries

Central nervous system (CNS) injuries, such as stroke, traumatic brain injury (TBI) and spinal cord injury (SCI), are important causes of death and long-term disability worldwide. MicroRNA (miRNA), small non-coding RNA molecules that negatively regulate gene expression, can serve as diagnostic biomarkers and are emerging as novel therapeutic targets for CNS injuries. MiRNA-based therapeutics include miRNA mimics and inhibitors (antagomiRs) to respectively decrease and increase the expression of target genes. In this review, we summarize current miRNA-based therapeutic applications in stroke, TBI and SCI. Administration methods, time windows and dosage for effective delivery of miRNA-based drugs into CNS are discussed. The underlying mechanisms of miRNA-based therapeutics are reviewed including oxidative stress, inflammation, apoptosis, blood-brain barrier protection, angiogenesis and neurogenesis. Pharmacological agents that protect against CNS injuries by targeting specific miRNAs are presented along with the challenges and therapeutic potential of miRNA-based therapies.

LncRNA MALAT1 promotes high glucose-induced inflammatory response of microglial cells via provoking MyD88/IRAK1/TRAF6 signaling

Although a large number of studies have confirmed from multiple levels that diabetes mellitus (DM) promotes cerebral ischemic reperfusion (I/R) injury, but the precise mechanism is still unclear. A cerebral I/R injury model in diabetic rats was established. The neurological deficit scores and brain edema were monitored at 24 and 72 hours after injury. The peri-infarct cortical tissues of rats were isolated for molecular biology detection. The rat primary microglia and microglia line HAPI were cultured to establish the cell model of DM-I/R by high glucose (HG) and hypoxia-reoxygenation (H/R). The endogenous expression of MALAT1 and MyD88 was regulated by the transfection with pcDNA-MALAT1, si-MALAT1 and si-MyD88, respectively. The cerebral I/R injury model in diabetic rats had more severe neuronal injury as shown by the significantly higher neurological deficit scores and an obvious increasing brain edema at 24 and 72 hours after injury. Moreover, the microglia were activated and induced a large number of inflammatory cytokines TNF-α, IL-1β and IL-6 in the peri-infarct cortical tissues during cerebral I/R injury associated with DM. The expression of MALAT1, MyD88, IRAK1 and TRAF6 protein were significantly up-regulated by DM-I/R in vitro and in vivo. Furthermore, the HG-H/R-induced MALAT1 promoted the inflammatory response in microglia via MyD88/IRAK1/TRAF6 signaling. Our results suggested that MALAT1 mediated the exacerbation of cerebral I/R injury induced by DM through triggering the inflammatory response in microglia via MyD88 signaling.

miR-411 suppresses acute spinal cord injury via downregulation of Fas ligand in rats

OBJECTIVE

To explore the role of miR-411/FasL in acute spinal cord injury (ASCI).

METHODS

The ASCI rat model was established, and expression of miR-411 and Fas ligand (FasL) was examined. Basso, Beattie and Bresnahan (BBB) score was used to evaluate the rats' neurological function. PC12 oxygen-glucose deprivation (OGD) model was also established. Gene manipulation (including miR-411 mimic or inhibitor) was used to modulate gene expression. Luciferase reporter assay was conducted to confirm the targeting relationship between miR-411 and FasL. Flow cytometry was applied in the measurement of PC12 cell apoptosis. Finally, the miR-411 mimic was injected into the vertebral canal of ASCI rats to determine the effects of miR-411 in vivo.

RESULTS

Compared with sham group, the expression of miR-411 and FasL was significantly decreased and increased in ASCI group, respectively (P < 0.05). Similarly, the expression of miR-411 and FasL was significantly lower and higher in OGD group than that in control group, respectively (P < 0.05). miR-411 directly controlled the FasL expression. miR-411 mimic can dramatically reduce the increased percentage of apoptosis cells caused by OGD when comparing to mimic control, which was greatly reversed by the overexpression of FasL (P < 0.05). Further, the BBB score was significantly elevated in the miR-411 mimic group when comparing to mimic control group, with decreased FasL expression (P < 0.05).

CONCLUSION

miR-411 mimic suppressed PC12 cell apoptosis via FasL, and relieved ASCI in rats.

Down-Regulation of miR-218-5p Promotes Apoptosis of Human Umbilical Vein Endothelial Cells Through Regulating High-Mobility Group Box-1 in Henoch-Schonlein Purpura

BACKGROUND

Apoptosis of human umbilical vein endothelial cells (HUVECs) plays an important role in the progression of Henoch-Schonlein purpura (HSP). In the present study, we explored the function of miR-218-5p in HUVEC apoptosis and HSP development.

MATERIALS AND METHODS

HSP rat model was established and peripheral blood mononuclear cells (PBMC) were isolated. The expression of miR-218-5p and high-mobility group box-1 (HMGB1) protein in HUVECs was determined by quantitative real-time polymerase chain reaction and western blot, respectively. Cell apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling assay. The association between miR-218-5p and HMGB1 was determined by luciferase assay. The endogenous expression of related genes was modulated with recombinant plasmids and cell transfection.

RESULTS

MiR-218-5p was down-regulated and HMGB1 was up-regulated in vessels of the lower limb of HSP rats and in HUVECs co-cultured in HSP PBMC supernatant. MiR-218-5p negatively regulated HMGB1 by targeting its 3'-untranslated regions. Over expression of miR-218-5p reversed the increased apoptosis and HMGB1 expression observed in HUVECs co-cultured in PBMC supernatant, whereas miR-218-5p knockdown showed the opposite outcomes. Furthermore, the miR-218-5p mimic demonstrated an inhibitory effect on the apoptosis of HUVECs co-cultured in PBMC supernatant, which was reversed by over expression of HMGB1. In HSP rats, over expression of miR-218-5p attenuated HSP and decreased the level of HMGB1.

CONCLUSIONS

MiR-218-5p attenuated HSP at least partly through regulating HMGB1 expression and affecting the function of HUVECs.

Protective role of microRNA-219-5p inhibitor against spinal cord injury via liver receptor homolog-1/Wnt/β-catenin signaling pathway regulation

The present study aimed to investigate the role of microRNA (miR)-219-5p in spinal cord injury (SCI) and to examine the underlying molecular mechanism. SCI rat and cell models were conducted in the current study, while reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect the level of miR-219-5p in the SCI mice and neurons. Bioinformatics analysis was applied to predict the target genes of miR-219-5p, and dual-luciferase reporter assay was performed to verify the prediction. In addition, MTT assay and flow cytometry were conducted to determine the cell viability and cell apoptosis of the neurons, respectively. Western blot analysis was also performed to detect the expression of associated proteins. The study results demonstrated that miR-219-5p was highly expressed in SCI mice and neurons, and directly targets liver receptor homolog-1 (LRH-1). The neuron viability was significantly reduced by SCI, however, it was recovered upon transfection with an miR-219-5p inhibitor. Neuron apoptosis was notably induced by SCI and inhibited by miR-219-5p inhibition. The LRH-1/Wnt/β-catenin signaling pathway was also inhibited by SCI, while it was significantly enhanced by the miR-219-5p inhibitor. Furthermore, LRH-1 overexpression eliminated the effects of the miR-219-5p inhibitor on SCI. In conclusion, these data indicated that the miR-219-5p inhibitor served a protective role in SCI via regulating the LRH-1/Wnt/β-catenin signaling pathway.

The Destiny of Glucose from a MicroRNA Perspective

Glucose serves as a primary, and for some tissues the unique, fuel source in order to generate and maintain the biological functions. Hyperglycemia is a hallmark of type 2 diabetes and is the direct consequence of perturbations in the glucose homeostasis. Insulin resistance, referred to as a reduced response of target tissues to the hormone, contributes to the development of hyperglycemia. The molecular mechanisms responsible for the altered glucose homeostasis are numerous and not completely understood. MicroRNAs (miRNAs) are now recognized as regulators of the lipid and glucose metabolism and are involved in the onset of metabolic diseases. Indeed, these small non-coding RNA molecules operate in the RNA silencing and posttranscriptional regulation of gene expression and may modulate the levels of kinases and enzymes in the glucose metabolism. Therefore, a better characterization of the function of miRNAs and a deeper understanding of their role in disease may represent a fundamental step toward innovative treatments addressing the causes, not only the symptoms, of hyperglycemia, using approaches aimed at restoring either miRNAs or their specific targets. In this review, we outline the current understanding regarding the impact of miRNAs in the glucose metabolism and highlight the need for further research focused on altered key kinases and enzymes in metabolic diseases.