lncRNA MEG3 restrained the M1 polarization of microglia in acute spinal cord injury through the HuR/A20/NF-κB axis

Conventional type 1 dendritic cells in the lymph nodes aggravate neuroinflammation after spinal cord injury by promoting CD8+ T cell expansion

BACKGROUND

Adaptive immune response is at the core of the mechanism of secondary spinal cord injury (SCI). This study aims to explore the molecular mechanism by which classical dendritic cells (cDC1s) influence CD8+ T cell expansion in SCI.

METHODS

Peripheral blood samples from patients with SCI and spinal cord tissues from SCI mice were collected, and the population of cDC1 subset was analyzed by flow cytometry. In vivo, the fms-like tyrosine kinase 3 (Flt3) inhibitor quizartinib was administered to deplete cDC1s, while intraperitoneal injection of recombinant Flt3L and immunosuppressive drug FTY-720 was used to expand cDC1s and prevent T cell egress from lymph nodes (LNs), respectively. In vitro, the conditioned medium (CM) of isolated LN fibroblastic stromal cells (FSCs) and pre-DCs were co-cultured. Subsequently, FSC CM-induced DCs were stimulated and co-cultured with CD8+ T cells for proliferation assay.

RESULTS

The cDC1 subset was increased in the peripheral blood of SCI patients and in the injured spinal cord of SCI mice. Depletion of cDC1s decreased the proportion of infiltrating CD8+ T cells in the injured spinal cord of SCI mice and reduced the inflammatory response. The Basso Mouse Scale score of SCI mice was increased and the proportion of CD8+ T cells in blood and spinal cord tissue was decreased after FTY-720 injection. Both migratory cDC1s (CD103+) and resident cDC1s (CD8α+) were present in the LNs surrounding the injured spinal cord of SCI mice. Among them, CD103+ cells were derived from the migration of cDC1s in spinal cord tissues, and CD8α+ cDC1s were directionally differentiated from pre-DCs after co-culture with LN-FSCs. Interferon-γ promoted the secretion of Flt3L by LN-FSCs through the activation of JAK/STAT signaling pathway and enhanced the differentiation of pre-DCs into CD8α+ cells.

CONCLUSION

Migratory cDC1s and resident cDC1s promote the expansion of CD8+ T cells in LNs around the injured spinal cord and mediate the adaptive immune response to aggravate neuroinflammation in SCI.

m6A-modified lncRNA GAS5 promotes M1-polarization of microglia in alcohol use disorder

Long noncoding RNA (lncRNA) are essential for modulating the onset and progression of alcohol use disorder (AUD). In this study, we investigated the molecular pathways through which lncRNA may contribute to AUD development. We assessed the expression levels of long noncoding RNA GAS5 (lncRNA GAS5) and microRNA-136-5p (miR-136-5p) in AUD tissue samples and cell lines using reverse transcription-quantitative polymerase chain reaction. Detection of GAS5 N6-methyladenosine (m6A) modifications, facilitated by alkylation repair homolog 5 (ALKBH5), was performed using RNA immunoprecipitation and RNA pull-down assays. The effect of GAS5 on the functionality of SH-SY5Y cells was evaluated using CCK-8 and Transwell assays. Our findings showed high levels of GAS5 expression in both AUD tissues and cell lines. Overexpression of GAS5 decreased the migratory capability of SH-SY5Y cells, whereas silencing GAS5 increased this ability. Bioinformatics analyses predicted a relationship between expression levels of miR-136-5p and GAS5, which was subsequently confirmed using dual-luciferase reporter assays. Additionally, we discovered that GAS5 acts as a sponge for miR-136-5p, leading to the upregulation of ATF2. Elevated levels of ATF2 are associated with M1 microglial polarization. In summary, m6A-modified GAS5 may influence the M1 polarization of microglia via the miR-136-5p/ATF2 pathway. Statistical evaluations were performed using GraphPad Prism V8.0, employing the student's t-test for comparisons between two groups, assuming a normal distribution and equal variances. When variances were unequal, but normality was maintained, the corrected Student's t-test was applied. The non-parametric Wilcoxon rank-sum test was used to analyze non-normally distributed data, and one-way ANOVA was used to compare three or more groups. Independent replication was ensured in the studies, with each experiment repeated at least three times and statistical significance was set at P < 0.05.

Exploring Ubiquitination in Spinal Cord Injury Therapy: Multifaceted Targets and Promising Strategies

Spinal cord injury (SCI) is a severely debilitating neurological condition that often results in significant functional impairment and is associated with poor long-term prognosis. Edema, oxidative stress, inflammatory responses, and cell death are the primary factors contributing to secondary injury following spinal cord damage. Ubiquitination is a crucial intracellular mechanism for protein regulation that has garnered significant attention as a therapeutic target in a variety of diseases. Numerous studies have shown that ubiquitination plays a key role in modulating processes such as inflammatory responses, apoptosis, and nerve regeneration following SCI, thereby influencing injury repair. Accordingly, targeting ubiquitination has the potential for mitigating harmful inflammatory responses, inhibiting dysregulated programmed cell death, and protecting the integrity of the blood-spinal cord barrier, thereby providing a novel therapeutic strategy for SCI. In this review, we discuss the role of ubiquitination and its potential as a therapeutic target in SCI, aiming to offer a foundation for developing ubiquitination-targeted therapies for this condition.

DANCR knockdown alleviates neuroinflammation and functional recovery after spinal cord injury via regulating the ACTN4 / STAT3 axis

Polarization of microglia following spinal cord injury (SCI) is a pivotal pathological process of secondary injury. Although differentiation antagonistic nonprotein coding RNA (DANCR) has been implicated in immune and inflammatory responses across various diseases, its role in SCI still unclear. This research aimed to clarify the underlying mechanisms of DANCR in SCI recovery by investigating its expression pattern in microglia. Our findings indicate that the DANCR level in microglia is increased after SCI and that its knockdown can promote microglial M2-type polarization; suppress inflammatory cytokines, oxidative stress, and neuronal apoptosis; and facilitate nerve regeneration as well as spinal cord functional recovery. Further investigations suggest that DANCR's effects are mediated through the ACTN4/STAT3 axis. These results provide potential targets for enhancing functional recovery following SCI.

The potential of long non-coding RNAs for motor function recovery after spinal cord injury in rodents: A systematic review and meta-analysis

OBJECTIVE

Long non-coding RNAs (LncRNAs) have garnered significant attention in preclinical studies for their potential in treating spinal cord injury (SCI). This meta-analysis aimed to assess the overall efficacy of lncRNA treatments in improving motor function in rodent models of SCI.

METHODS

The Embase, PubMed, Web of Science, and Scopus databases were searched. Meta-analysis was performed using STATA 14.0. The standardized mean difference (SMD) was employed to combine various motor function scores.

RESULTS

A total of 33 studies were included in this review. Key findings indicated that lncRNA treatments could markedly enhance locomotor function in rodents with SCI compared to control groups (SMD = 4.20, 95% CI: 3.35 to 5.05, I2 = 80.0%, P < 0.0001). Furthermore, in male rats with contusion/compression injuries, targeting specific cytosol-enriched lncRNAs to downregulate their expression may significantly improve motor function recovery. Specifically, intrathecal injection of non-viral vectors for lncRNA delivery proved to be the most effective method in this study.

CONCLUSIONS

LncRNA treatments have demonstrated the potential to improve motor function in rodent models with SCI. However, the therapeutic efficacy may be overestimated. Future research should rigorously assess the clinical translational efficacy and safety of lncRNA treatments.

Temporal changes of spinal microglia in murine models of neuropathic pain: a scoping review

Neuropathic pain (NP) is an ineffectively treated, debilitating chronic pain disorder that is associated with maladaptive changes in the central nervous system, particularly in the spinal cord. Murine models of NP looking at the mechanisms underlying these changes suggest an important role of microglia, the resident immune cells of the central nervous system, in various stages of disease progression. However, given the number of different NP models and the resource limitations that come with tracking longitudinal changes in NP animals, many studies fail to truly recapitulate the patterns that exist between pain conditions and temporal microglial changes. This review integrates how NP studies are being carried out in murine models and how microglia changes over time can affect pain behavior in order to inform better study design and highlight knowledge gaps in the field. 258 peer-reviewed, primary source articles looking at spinal microglia in murine models of NP were selected using Covidence. Trends in the type of mice, statistical tests, pain models, interventions, microglial markers and temporal pain behavior and microglia changes were recorded and analyzed. Studies were primarily conducted in inbred, young adult, male mice having peripheral nerve injury which highlights the lack of generalizability in the data currently being collected. Changes in microglia and pain behavior, which were both increased, were tested most commonly up to 2 weeks after pain initiation despite aberrant microglia activity also being recorded at later time points in NP conditions. Studies using treatments that decrease microglia show decreased pain behavior primarily at the 1- and 2-week time point with many studies not recording pain behavior despite the involvement of spinal microglia dysfunction in their development. These results show the need for not only studying spinal microglia dynamics in a variety of NP conditions at longer time points but also for better clinically relevant study design considerations.

The role of long noncoding ribonucleic acids in the central nervous system injury

Central nervous system (CNS) injury involves complex pathophysiological molecular mechanisms. Long noncoding ribonucleic acids (lncRNAs) are an important form of RNA that do not encode proteins but take part in the regulation of gene expression and various biological processes. Multitudinous studies have evidenced lncRNAs to have a significant role in the process of progression and recovery of various CNS injuries. Herein, we review the latest findings pertaining to the role of lncRNAs in CNS, both normal and diseased state. We aim to present a comprehensive clinical application prospect of lncRNAs in CNS, and thus, discuss potential strategies of lncRNAs in treating CNS injury.

Effect of Electrical Stimulation of the Vagus Nerve on Inflammation in Rats With Spinal Cord Injury

OBJECTIVE

The purpose of this study was to assess the effect of electroacupuncture stimulation (EAS) of the vagus nerve on the inflammatory response in rat models of spinal cord injury (SCI).

METHODS

The T10 SCI model in adult male Sprague Dawley rats was established using the modified Allen's method. The EAS group was treated with the therapy on the vagus nerve of rat ear nails, while the SCI group did not receive any EAS treatment. The degree of inflammatory infiltration was reflected by hematoxylin-eosin staining. The inflammatory cytokines in spinal cord tissues, cerebrospinal fluid inflammation, and peripheral blood were detected by enzyme-linked immunosorbent assay. Changes in astrocytes and microglia were assessed using an immunofluorescence assay.

RESULTS

Electroacupuncture stimulation treatment inhibited inflammatory infiltration, as well as the concentrations of interleukin-6, interleukin-1β, tumor necrosis factor-α, astrocytes, and microglia at 1, 6, and 24 hours after 1 EAS treatment. Multiple EAS treatments had an obvious effect on SCI inflammation.

CONCLUSION

A single EAS treatment had a limited effect on inflammation, but multiple treatments had a significant inhibitory effect on inflammation.

Sp1 Regulates the M1 Polarization of Microglia Through the HuR/NF-κB Axis after Spinal Cord Injury

The M1 polarization of microglia, followed by the production of pro-inflammatory mediators, hinders functional recovery after spinal cord injury (SCI). Our previous study has illuminated that specificity protein 1 (Sp1) expression is increased following SCI, whereas the function and regulatory mechanism of Sp1 during M1 polarization of microglia following SCI remain unknown. RNA binding protein, HuR, has been shown to be up-regulated in the injured spinal cord through analysis of the GEO database. Further investigation using Chip-Atlas data suggests a binding between Sp1 and HuR. Emerging evidence indicates that HuR plays a pivotal role in neuroinflammation after SCI. In this research, Sp1 and HuR levels in mice with SCI and BV2 cells treated with lipopolysaccharide (LPS) was determined by using quantitative real-time polymerase chain reaction and Western blotting techniques. A series of in vitro assays were performed to investigate the function of Sp1 during M1 polarization of microglia. The association between Sp1 and its target gene HuR was confirmed through gene transfection and luciferase reporter assay. Enhanced expression of HuR was observed in both SCI mice and LPS-treated BV2 cells, while Sp1 knockdown restrained M1 polarization of microglia and its associated inflammation by inhibiting the NF-κB signaling pathway. Silencing Sp1 also suppressed microglia activation and its mediated inflammatory response, which could be reversed by overexpression of HuR. In conclusion, silencing Sp1 restrains M1 polarization of microglia through the HuR/NF-κB axis, leading to neuroprotection, and thus promotes functional restoration following SCI.

LncRNA MEG3 Reduces the Ratio of M2/M1 Macrophages Through the HuR/CCL5 Axis in Hepatocellular Carcinoma

Objective

Tumor-associated macrophages play a crucial role in the development of hepatocellular carcinoma (HCC). Our study aimed to investigate the relationship between long coding RNA (lncRNA) maternally expressed gene 3 (MEG3), RNA-binding protein human antigen R (HuR), and messenger RNA C-C motif chemokine 5 (CCL5) in the modulation of M1 and M2 macrophage polarization in HCC.

Methods

To induce M1 or M2 polarization, LPS/IFNγ- or IL4/IL13 were used to treat bone marrow derived macrophages (BMDMs). The localization of MEG3 in M1 and M2 macrophages was assessed using fluorescence in situ hybridization assay. Expression levels of MEG3, HuR, CCL5, M1, and M2 markers were measured by RT-qPCR or immunofluorescence staining. Flow cytometry was performed to determine the proportion of F4/80+CD206+ and F4/80+CD68+ cells. RNA pulldown assay was performed to detect the binding of lncRNA MEG3 and HuR. The impacts of HuR on CCL5 stability and activity of CCL5 promoter were evaluated using actinomycin D treatment and luciferase reporter assay. Cell migration, invasiveness, and angiogenesis were assessed using transwell migration and invasion assays and a tube formation assay. A mixture of Huh-7 cells and macrophages were injected into nude mice to explore the effect of MEG3 on tumorigenesis.

Results

MEG3 promoted M1-like polarization while dampening M2-like polarization of BMDMs. MEG3 bound to HuR in M1 and M2 macrophages. HuR downregulated CCL5 by inhibiting CCL5 transcription in macrophages. In addition, overexpression of MEG3 suppressed cell metastasis, invasion, and angiogenesis by obstructing macrophage M2 polarization. MEG3 inhibited tumorigenesis in HCC via promotion of M1-like polarization and inhibition of M2-like polarization. Rescue experiments showed that depletion of CCL5 in M2 macrophages reversed MEG3-induced suppressive effect on cell migration, invasion, and tube formation.

Conclusion

MEG3 suppresses HCC progression by promoting M1-like while inhibiting M2-like macrophage polarization via binding to HuR and thus upregulating CCL5.

Electroacupuncture Relieves HuR/KLF9-Mediated Inflammation to Enhance Neurological Repair after Spinal Cord Injury

Electroacupuncture (EA) is widely applied in clinical therapy for spinal cord injury (SCI). However, the associated molecular mechanism has yet to be elucidated. The current study aimed to investigate the underlying mechanism of EA in neurologic repair after SCI. First, we investigated the role of EA in the neurologic repair of the SCI rat model. The expression levels of human antigen R (HuR) and Krüppel-like factor 9 (KLF9) in spinal cord tissues were quantified after treatment. Second, we conducted bioinformatics analysis, RNA pull-down assays, RNA immunoprecipitation, and luciferase reporter gene assay to verify the binding of HuR and KLF9 mRNA for mRNA stability. Last, HuR inhibitor CMLD-2 was used to verify the enhanced effect of EA on neurologic repair after SCI via the HuR/KLF9 axis. Our data provided convincing evidence that EA facilitated the recovery of neuronal function in SCI rats by reducing apoptosis and inflammation of neurons. We found that EA significantly diminished the SCI-mediated upregulation of HuR, and HuR could bind to the 3' untranslated region of KLF9 mRNA to protect its decay. In addition, a series of in vivo experiments confirmed that CMLD-2 administration increased EA-mediated pain thresholds and motor function in SCI rats. Collectively, the present study showed that EA improved pain thresholds and motor function in SCI rats via impairment of HuR-mediated KLF9 mRNA stabilization, thus providing a better understanding of the regulatory mechanisms regarding EA-mediated neurologic repair after SCI.

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.

Photobiomodulation promotes spinal cord injury repair by inhibiting macrophage polarization through lncRNA TUG1-miR-1192/TLR3 axis

BACKGROUND

Secondary spinal cord injury (SCI) often causes the aggravation of inflammatory reaction and nerve injury, which affects the recovery of motor function. Bone-marrow-derived macrophages (BMDMs) were recruited to the injured area after SCI, and the M1 polarization is the key process for inducing inflammatory response and neuronal apoptosis. We previously showed that photobiomodulation (PBM) can inhibit the polarization of M1 phenotype of BMDMs and reduce inflammation, but the underlying mechanisms are unclear. The purpose of this study is to explore the potential target and mechanism of PBM in treating SCI.

METHODS

Transcriptome sequencing and bioinformatics analysis showed that long noncoding RNA taurine upregulated gene 1 (lncRNA TUG1) was a potential target of PBM. The expression and specific mechanism of lncRNA TUG1 were detected by qPCR, immunofluorescence, flow cytometry, western blotting, fluorescence in situ hybridization, and luciferase assay. The Basso mouse scale (BMS) and gait analysis were used to evaluate the recovery of motor function in mice.

RESULTS

Results showed that lncRNA TUG1 may be a potential target of PBM, regulating the polarization of BMDMs, inflammatory response, and the axial growth of DRG. Mechanistically, TUG1 competed with TLR3 for binding to miR-1192 and attenuated the inhibitory effect of miR-1192 on TLR3. This effect protected TLR3 from degradation, enabling the high expression of TLR3, which promoted the activation of downstream NF-κB signal and the release of inflammatory cytokines. In vivo, PBM treatment could reduce the expression of TUG1, TLR3, and inflammatory cytokines and promoted nerve survival and motor function recovery in SCI mice.

CONCLUSIONS

Our study clarified that the lncRNA TUG1/miR-1192/TLR3 axis is an important pathway for PBM to inhibit M1 macrophage polarization and inflammation, which provides theoretical support for its clinical application in patients with SCI.