Long noncoding RNA (lncRNA): a target in neuropathic pain

Study on analgesic effect of Shentong Zhuyu Decoction in neuropathic pain rats by network pharmacology and RNA-Seq

ETHNOPHARMACOLOGICAL RELEVANCE

Shentong Zhuyu Decoction (STZYD) is a traditional prescription for promoting the flow of Qi and Blood which is often used in the treatment of low back and leg pain clinicall with unclear mechanism. Neuropathic pain (NP) is caused by disease or injury affecting the somatosensory system. LncRNAs may play a key role in NP by regulating the expression of pain-related genes through binding mRNAs or miRNAs sponge mechanisms.

AIM OF THE STUDY

To investigate the effect and potential mechanism of STZYD on neuropathic pain.

METHODS

Chronic constriction injury (CCI) rats, a commonly used animal model, were used in this study. The target of STZYD in NP was analyzed by network pharmacology, and the analgesic effect of STZYD in different doses (H-STZYD, M-STZYD, L-STZYD) on CCI rats was evaluated by Mechanical withdrawal thresholds (MWT) and thermal withdrawal latency (TWL). Meanwhile, RNA-seq assay was used to detect the changed mRNAs and lncRNAs in CCI rats after STZYD intervention. GO analysis, KEGG pathway analysis, and IPA analysis were used to find key target genes and pathways, verified by qPCR and Western Blot. The regulatory effect of lncRNAs on target genes was predicted by co-expression analysis and ceRNA network construction.

RESULTS

We found that STZYD can improve hyperalgesia in CCI rats, and H-STZYD has the best analgesic effect. The results of network pharmacological analysis showed that STZYD could play an analgesic role in CCI rats through the MAPK/ERK/c-FOS pathway. By mRNA-seq and lncRNA-seq, we found that STZYD could regulate the expression of Cnr1, Cacng5, Gucy1a3, Kitlg, Npy2r, and Grm8, and inhibited the phosphorylation level of ERK in the spinal cord of CCI rats. A total of 27 lncRNAs were associated with the target genes and 30 lncRNAs, 83 miRNAs and 5 mRNAs participated in the ceRNA network.

CONCLUSION

STZYD has the effect of improving hyperalgesia in CCI rats through the MAPK/ERK/c-FOS pathway, which is related to the regulation of lncRNAs to Cnr1 and other key targets.

LncRNA-PCat19 acts as a ceRNA of miR-378a-3p to facilitate microglia activation and accelerate chronic neuropathic pain in rats by promoting KDM3A-mediated BDNF demethylation

The pathogenesis of neuropathic pain (NP) is complex, and there are various pathological processes. Previous studies have suggested that lncRNA PCAT19 is abnormally expressed in NP conduction and affects the occurrence and development of pain. The aim of this study is to analyze the role and mechanism of PCAT19 in NP induced by chronic compressive nerve injury (CCI) in mice. In this study, C57BL/6 mice were applied to establish the CCI model. sh-PCAT19 was intrathecally injected once a day for 5 consecutive days from the second day after surgery. We discovered that PCat19 level was gradually up-regulated with the passage of modeling time. Downregulation of Iba-1-positive expression, M1/M2 ratio of microglia, and pro-inflammatory factors in the spinal cords of CCI-mice after PCat19 knock-downed was observed. Mechanically, the expression of miR-378a-3p was negatively correlated with KDM3A and PCat19. Deletion of KDM3A prevented H3K9me2 demethylation of BDNF promoter and suppressed BDNF expression. Further, KDM3A promotes CCI-induced neuroinflammation and microglia activation by mediating Brain-derived neurotrophic factor (BDNF) demethylation. Together, the results suggest that PCat19 may be involved in the development of NP and that PCat19 shRNA injection can attenuate microglia-induced neuroinflammation by blocking KDM3A-mediated demethylation of BDNF and BDNF release.

Long noncoding RNA small nucleolar RNA host gene 5 facilitates neuropathic pain in spinal nerve injury by promoting SCN9A expression via CDK9

This study aims to explore the functions and mechanisms of long noncoding RNA small nucleolar RNA host gene 5 (SNHG5) in chronic constriction injury (CCI)-induced neuropathic pain (NP). An NP rat model was established using the CCI method and the NP severity was evaluated by paw withdrawal threshold (PWT) and paw withdrawal latency (PWL). The expression of SNHG5, CDK9, and SCN9A was quantified in rat dorsal root ganglion, in addition to the detections of apoptosis, pathological changes, neuron number, and the co-localization of Nav1.7 and cleaved caspase-3 with NeuN. In ND7/23 cells, the apoptosis and lactate dehydrogenase concentration were assessed, as well as the relationship between SNHG5, CDK9, and SCN9A. In the dorsal root ganglion of CCI-treated rats, SNHG5 and SCN9A were upregulated and downregulation of SNHG5 suppressed SCN9A expression, increased the PWT and PWL, blocked neuroinflammation and neuronal apoptosis, and alleviated NP. Mechanistically, SNHG5 recruited CDK9 to enhance SCN9A-encoded Nav1.7 expression and promoted peripheral neuronal apoptosis and injury. In addition, SCN9A overexpression nullified the alleviative effects of SNHG5 deficiency on NP and neuron loss in CCI rats. In conclusion, SNHG5 promotes SCN9A-encoded Nav1.7 expression by recruiting CDK9, thereby facilitating neuron loss and NP after spinal nerve injury, which may offer a promising target for the management of NP.

RALY participates in nerve trauma-induced nociceptive hypersensitivity through triggering Eif4g2 gene expression in primary sensory neurons

BACKGROUND AND PURPOSE

Peripheral nerve trauma-induced dysregulation of pain-associated genes in the primary sensory neurons of dorsal root ganglion (DRG) contributes to neuropathic pain genesis. RNA-binding proteins participate in gene transcription. We hypothesized that RALY, an RNA-binding protein, participated in nerve trauma-induced dysregulation of DRG pain-associated genes and nociceptive hypersensitivity.

METHODS AND RESULTS

Immunohistochemistry staining showed that RALY was expressed exclusively in the nuclei of DRG neurons. Peripheral nerve trauma caused by chronic constriction injury (CCI) of unilateral sciatic nerve produced time-dependent increases in the levels of Raly mRNA and RALY protein in injured DRG. Blocking this increase through DRG microinjection of adeno-associated virus 5 (AAV5)-expressing Raly shRNA reduced the CCI-induced elevation in the amount of eukaryotic initiation factor 4 gamma 2 (Eif4g2) mRNA and Eif4g2 protein in injured DRG and mitigated the development and maintenance of CCI-induced nociceptive hypersensitivity, without altering basal (acute) response to noxious stimuli and locomotor activity. Mimicking DRG increased RALY through DRG microinjection of AAV5 expressing Raly mRNA up-regulated the expression of Eif4g2 mRNA and Eif4g2 protein in the DRG and led to hypersensitive responses to noxious stimuli in the absence of nerve trauma. Mechanistically, CCI promoted the binding of RALY to the promoter of Eif4g2 gene and triggered its transcriptional activity.

CONCLUSION AND IMPLICATIONS

Our findings indicate that RALY participates in nerve trauma-induced nociceptive hypersensitivity likely through transcriptionally triggering Eif4g2 expression in the DRG. RALY may be a potential target in neuropathic pain management.

Transcription factor EBF1 mitigates neuropathic pain by rescuing Kv1.2 expression in primary sensory neurons

Nerve injury-induced alternations of gene expression in primary sensory neurons of the dorsal root ganglion (DRG) are molecular basis of neuropathic pain genesis. Transcription factors regulate gene expression. In this study, we examined whether early B cell factor 1 (EBF1), a transcription factor, in the DRG, participated in neuropathic pain caused by chronic constriction injury (CCI) of the sciatic nerve. EBF1 was distributed exclusively in the neuronal nucleus and coexpressed with cytoplasmic/membrane Kv1.2 in individual DRG neurons. The expression of Ebf1 mRNA and protein was time-dependently downregulated in the ipsilateral lumbar (L) 3/4 DRGs after unilateral CCI. Rescuing this downregulation through microinjection of the adeno-associated virus 5 expressing full-length Ebf1 mRNA into the ipsilateral L3/4 DRGs reversed the CCI-induced decrease of DRG Kv1.2 expression and alleviated the development and maintenance of mechanical, heat and cold hypersensitivities. Conversely, mimicking the downregulation of DRG EBF1 through microinjection of AAV5-expressing Ebf1 shRNA into unilateral L3/4 DRGs produced a reduction of Kv1.2 expression in the ipsilateral L3/4 DRGs, spontaneous pain, and the enhanced responses to mechanical, heat and cold stimuli in naive mice. Mechanistically, EBF1 not only bound to the Kcna2 gene (encoding Kv1.2) promoter but also directly activated its activity. CCI decreased the EBF1 binding to the Kcna2 promoter in the ipsilateral L3/4 DRGs. Our findings suggest that DRG EBF1 downregulation contributes to neuropathic pain likely by losing its binding to Kcna2 promoter and subsequently silencing Kv1.2 expression in primary sensory neurons. Exogenous EBF1 administration may mitigate neuropathic pain by rescuing DRG Kv1.2 expression.

Multiple novel functions of circular RNAs in diabetes mellitus

Circular RNAs (circRNAs), as an emerging group of non-coding RNAs (ncRNAs), have received the attention given evidence indicating that these novel ncRNAs are implicated in various biological processes. Due to the absence of 5' and 3' ends in circ-RNAs, their two ends are covalently bonded together, and they are synthesised from pre-mRNAs in a process called back-splicing, which makes them more stable than linear RNAs. There is accumulating evidence showing that circRNAs play a critical role in the pathogenesis of diabetes mellitus (DM). Moreover, it has been indicated that dysregulation of circRNAs has made them promising diagnostic biomarkers for the detection of DM. Recently, increasing attention has been paid to investigate the mechanisms underlying the DM process. It has been demonstrated that there is a strong correlation between the expression of circRNAs and DM. Hence, our aim is to discuss the crosstalk between circRNAs and DM and its complications.

LncRNA NONRATT014888.2 contributes to cancer-induced bone pain through downregulation of natriuretic peptide receptor 3 in rats

Long noncoding RNA (lncRNA) is implicated in both cancer development and pain process. However, the role of lncRNA in the development of cancer-induced bone pain (CIBP) is unclear. LncRNA NONRATT014888.2 is highly expressed in tibia related dorsal root ganglions (DRGs) in CIBP rats which function is unknown. CIBP was induced by injection of Walker 256 mammary gland tumor cells into the tibia canal of female SD rats. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) of rats were measured. Down-regulation of NONRATT014888.2 by siRNA in CIBP rats markedly attenuated hind-paw mechanical pain hypersensitivity. LncRNA-predicted target mRNAs analysis and mRNA sequencing results cued Socs3, Npr3 were related with NONRATT014888.2. Intrathecal injection of NONRATT014888.2-siR206 upregulated Npr3 both in mRNA and protein level. Npr3 was co-expressed in NONRATT014888.2-positive DRGs neurons and mainly located in cytoplasm, but not in Glial fibrillary acidic protein (GFAP)-positive cells. Intrathecal injection of ADV-Npr3 upregulated Npr3 expression and enhanced the PWT of CIBP rats. Our results suggest that upregulated lncRNA NONRATT014888.2 contributed to hyperalgesia in CIBP rats, and the mechanism may through downregulation of Npr3.

Sensory neuron-specific long noncoding RNA in small non-peptidergic dorsal root ganglion neurons selectively impairs nerve injury-induced mechanical hypersensitivity

AIMS

Nerve injury-induced mechanical hypersensitivity is one of major clinical symptoms in neuropathic pain patients. Understanding molecular mechanisms underlying this symptom is crucial for developing effective therapies. The present study was to investigate whether sensory neuron-specific long noncoding RNA (SS-lncRNA) predominantly expressed in small non-peptidergic dorsal root ganglion (DRG) neurons repaired nerve injury-induced mechanical hypersensitivity.

MATERIALS AND METHODS

SS-lncRNA downregulation in the mas-related G protein-coupled receptor member D (Mrgprd)-expressed DRG neurons was rescued and mimicked by crossbreeding MrgprdCreERT2/+ lines with Rosa26SS-lncRNA knock-in mice and SS-lncRNAfl/fl mice, respectively, followed by tamoxifen injection.

KEY FINDINGS

Rescuing SS-lncRNA downregulation in the Mrgprd-expressed DRG neurons significantly reversed the spinal nerve ligation (SNL)-induced reduction of the calcium-activated potassium channel subfamily N member 1 (KCNN1) in these DRG neurons and alleviated the SNL-induced mechanical hypersensitivity, without affecting the SNL-induced heat and cold nociceptive hypersensitivities, on the ipsilateral side. Conversely, mimicking SS-lncRNA downregulation in the Mrgprd-expressed DRG neurons reduced basal KCNN1 expression in these DRG neurons and produced the enhanced response to mechanical stimulation, but not thermal and cold stimuli, on bilateral sides. Mechanistically, SS-lncRNA downregulation caused a reduction in its binding to lysine-specific demethylase 6B (KDM6B) and consequent recruitment of less KDM6B to Kcnn1 promoter and an increase of H3K27me3 enrichment in this promoter in injured DRG.

SIGNIFICANCE

Our findings suggest that SS-lncRNA downregulation in small non-peptidergic sensory neurons is required specifically for nerve injury-induced mechanical hypersensitivity likely through silencing KCNN1 expression caused by KDM6B-gated increase of H3K27me3 enrichment in Kcnn1 promoter in these neurons.

Peripheral mechanisms of peripheral neuropathic pain

Peripheral neuropathic pain (PNP), neuropathic pain that arises from a damage or disease affecting the peripheral nervous system, is associated with an extremely large disease burden, and there is an increasing and urgent need for new therapies for treating this disorder. In this review we have highlighted therapeutic targets that may be translated into disease modifying therapies for PNP associated with peripheral neuropathy. We have also discussed how genetic studies and novel technologies, such as optogenetics, chemogenetics and single-cell RNA-sequencing, have been increasingly successful in revealing novel mechanisms underlying PNP. Additionally, consideration of the role of non-neuronal cells and communication between the skin and sensory afferents is presented to highlight the potential use of drug treatment that could be applied topically, bypassing drug side effects. We conclude by discussing the current difficulties to the development of effective new therapies and, most importantly, how we might improve the translation of targets for peripheral neuropathic pain identified from studies in animal models to the clinic.

A sensory neuron-specific long non-coding RNA reduces neuropathic pain by rescuing KCNN1 expression

Nerve injury to peripheral somatosensory system causes refractory neuropathic pain. Maladaptive changes of gene expression in primary sensory neurons are considered molecular basis of this disorder. Long non-coding RNAs (lncRNAs) are key regulators of gene transcription; however, their significance in neuropathic pain remains largely elusive.Here, we reported a novel lncRNA, named sensory neuron-specific lncRNA (SS-lncRNA), for its expression exclusively in dorsal root ganglion (DRG) and trigeminal ganglion. SS-lncRNA was predominantly expressed in small DRG neurons and significantly downregulated due to a reduction of early B cell transcription factor 1 in injured DRG after nerve injury. Rescuing this downregulation reversed a decrease of the calcium-activated potassium channel subfamily N member 1 (KCNN1) in injured DRG and alleviated nerve injury-induced nociceptive hypersensitivity. Conversely, DRG downregulation of SS-lncRNA reduced the expression of KCNN1, decreased total potassium currents and afterhyperpolarization currents and increased excitability in DRG neurons and produced neuropathic pain symptoms.Mechanistically, downregulated SS-lncRNA resulted in the reductions of its binding to Kcnn1 promoter and heterogeneous nuclear ribonucleoprotein M (hnRNPM), consequent recruitment of less hnRNPM to the Kcnn1 promoter and silence of Kcnn1 gene transcription in injured DRG.These findings indicate that SS-lncRNA may relieve neuropathic pain through hnRNPM-mediated KCNN1 rescue in injured DRG and offer a novel therapeutic strategy specific for this disorder.

Long non-coding RNA Snhg16 Lessens Ozone Curative Effect on Chronic Constriction Injury mice via microRNA-719/SCN1A axis

We investigated the function and molecular mechanism of long non-coding RNA (lncRNA) small nucleolar RNA host gene 16 (Snhg16) in modifying ozone treatment for neuropathic pain (NP) in a mouse model of chronic constriction injury (CCI). Pain-related behavioral responses were evaluated using paw withdrawal threshold (PWT), paw lifting number (PLN), and paw withdrawal latency (PWL) tests. Interleukin (IL)-1β, IL-10, IL-6, and tumor necrosis factor-alpha (TNF-α) were measured by ELISA and qRT-PCR to evaluate neuroinflammation. qRT-PCR was performed to detect expressions of Snhg16, microRNA (miR)-719, sodium voltage-gated channel alpha subunit 1 (SCN1A), and inflammatory factors. Bioinformatics, dual-luciferase reporter assay, and RNA pull-down verified the underlying molecular mechanisms. Snhg16 expression increased in CCI mice. Snhg16 overexpression retarded the curative effect of ozone and induced NP. miR-719 was sponged by Snhg16. SCN1A was a target of miR-719. Inhibition of miR-719 markedly reversed the effects of Snhg16 on pain-related behavioral responses and neuroinflammation. Upregulation of SCN1A partly abrogated the effects of elevated miR-719 levels on the occurrence of NP. The findings demonstrate that lncRNA Snhg16 promotes NP progression in CCI mice by binding to miR-719 to increase SCN1A expression. The Snhg16/miR-719/SCN1A axis may influence the curative effects of ozone therapy in treating NP.

High-throughput transcriptome sequencing reveals the critical role of long non-coding RNA Gm14376 in the occurrence of neuropathic pain

Long noncoding RNAs (lncRNAs) have been suggested as important regulators in neuropathic pain. Our study aims to explore the possible molecular mechanism underlying the role of long non-coding RNA (lncRNA) Gm14376 in neuropathic pain in mice by high-throughput transcriptome sequencing. A mouse model of spared nerve injury (SNI) was constructed for mechanical, thermal and spontaneous pain testing. Transcriptomic changes in lncRNAs and mRNAs in the dorsal root ganglion (DRG) of SNI mice were analyzed using RNA-sequencing techniques in conjunction with public data analysis. AAV5 viral vector was constructed to assess the effect of Gm14376 on SNI-induced pain hypersensitivity and inflammatory response. Cis-target genes of Gm14376 were obtained and the functions of Gm14376 were analyzed by GO and KEGG pathway enrichment analyses. Results from bioinformatic analysis identified a conserved Gm14376, which was up-regulated in the DRG of SNI mice, specifically in response to nerve injury. Overexpression of Gm14376 in DRG induced neuropathic pain-like symptoms in mice. Furthermore, the functions of Gm14376 were related to the phosphatidylinositol 3-kinase (PI3K)/Akt pathway and fibroblast growth factor 3 (Fgf3) was identified as the cis-target gene of Gm14376. Gm14376 could directly up-regulate Fgf3 expression to activate the PI3K/Akt pathway, which alleviated pain hypersensitivity to mechanical and thermal stimuli and reduced the release of inflammatory factors in SNI mice. From our data, we conclude that SNI-induced up-regulation of Gm14376 expression in DRG activates the PI3K/Akt pathway through up-regulation of Fgf3 expression, thereby promoting the development of neuropathic pain in mice.

Epigenetic regulation of chemokine (CC-motif) ligand 2 in inflammatory diseases

Appropriate responses to inflammation are conducive to pathogen elimination and tissue repair, while uncontrolled inflammatory reactions are likely to result in the damage of tissues. Chemokine (CC-motif) Ligand 2 (CCL2) is the main chemokine and activator of monocytes, macrophages, and neutrophils. CCL2 played a key role in amplifying and accelerating the inflammatory cascade and is closely related to chronic non-controllable inflammation (cirrhosis, neuropathic pain, insulin resistance, atherosclerosis, deforming arthritis, ischemic injury, cancer, etc.). The crucial regulatory roles of CCL2 may provide potential targets for the treatment of inflammatory diseases. Therefore, we presented a review of the regulatory mechanisms of CCL2. Gene expression is largely affected by the state of chromatin. Different epigenetic modifications, including DNA methylation, post-translational modification of histones, histone variants, ATP-dependent chromatin remodelling, and non-coding RNA, could affect the 'open' or 'closed' state of DNA, and then significantly affect the expression of target genes. Since most epigenetic modifications are proven to be reversible, targeting the epigenetic mechanisms of CCL2 is expected to be a promising therapeutic strategy for inflammatory diseases. This review focuses on the epigenetic regulation of CCL2 in inflammatory diseases.

Identification of autophagy-related genes in neuropathic pain through bioinformatic analysis

BACKGROUND

Neuropathic pain (NP) is one of the most common types of chronic pain and significantly compromises the quality of life. Autophagy is an intracellular catabolic process that is required to maintain cellular homeostasis in response to various stresses. The role of autophagy-related genes in the diagnosis and treatment of neuropathic pain remains unclear.

METHODS

We identified autophagy-related differentially expressed genes (ARDEGs) and differentially expressed miRNAs (DE-miRNAs) in neuropathic pain by bioinformatics analysis of the GSE145226 and GSE145199 datasets. These ARDEGs and their co-expressed genes were subjected to Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, Gene Set Enrichment Analysis (GSEA) and friends analysis. Meanwhile, we constructed TFs-ARDEGs, miRNA-ARDEGs regulatory network through ChIPBase database and the HTFtarget database, multiMir R package. Finally, we performed immune infiltration analysis of ARDEGs by Single Sample Gene Set Enrichment Analysis (ssGSEA).

RESULTS

We identified 2 potential autophagy-related differentially expressed genes (Sirt2 and ST7) that may be closely associated with the pathogenesis of neuropathic pain. GO, KEGG and GSEA analysis revealed that these two ARDEGs were mainly enriched in pyridine nucleotide metabolic process, nicotinamide nucleotide metabolic process, Nicotinate and nicotinamide metabolism, NF-κB pathway, KRAS signaling, P53 pathway. In the TFs-ARDEGs and miRNA-ARDEGs regulatory network, miR-140-5p and Cebpb were predicted to be as crucial regulators in the progression of NP. For the ssGSEA results, Sirt2 was positively correlated with Eosinophil and Effector memory CD8⁺ T cell infiltration, which suggested that it may be involved in the regulation of neuroimmune-related signaling.

CONCLUSION

Two autophagy-related differentially expressed genes, especially Sirt2, may be potential biomarkers for NP, providing more evidence about the crucial role of autophagy in neuropathic pain.

LncRNA XR_351665 Contributes to Chronic Pain-Induced Depression by Upregulating DNMT1 via Sponging miR-152-3p

Chronic pain is frequently comorbid with depression. However, the mechanisms underlying chronic pain-induced depression remain unclear. Here, we found that DNA methyltransferase 1 (DNMT1) was upregulated in the central amygdala (CeA) of spared nerve injury (SNI)-induced chronic pain-depression rats, and knockdown of DNMT1 could improve the depression-like behaviors in SNI rats. Additionally, a panel of differentially expressed lncRNAs, including 38 upregulated and 12 downregulated lncRNAs, were identified by microarray analysis. Bioinformatics analysis suggested that the upregulated lncRNA XR_351665 was the upstream molecule to regulate DNMT1 expression. The knockdown of XR_351665 significantly alleviated the depression-like behaviors in SNI rats, whereas overexpression of XR_351665 induced the depression-like behaviors in naïve rats. Further mechanism-related researches uncovered that XR_351665 functioned as a competing endogenous RNA (ceRNA) to upregulate DNMT1 by competitively sponging miR-152-3p, and subsequently promoted the development of chronic pain-induced depression. Our findings suggest that lncRNA XR_351665 is involved in the development of chronic pain-induced depression by upregulating DNMT1 via sponging miR-152-3p. These data provide novel insight into understanding the pathogenesis of chronic pain-induced depression and identify a potential therapeutic target. PERSPECTIVE: LncRNA XR_351665 in CeA functions as a ceRNA to block the inhibitory effect of miR-152-3p on DNMT1 and contributes to the development of chronic pain-induced depression. These data suggest that manipulation of XR_351665/miR-152-3p/DNMT1 axis may be a potential method to attenuate chronic pain-induced depression.

COVID-19-Related Neuropathic Pain: A Systematic Review and Meta-Analysis

INTRODUCTION

SARS-CoV-2, responsible for the coronavirus disease (COVID-19) pandemic, may impact other systems apart from the respiratory system, including the nervous system. In this systematic review, we aimed to establish the prevalence and determinants of neuropathic pain amongst COVID-19-infected individuals.

METHODOLOGY

A literature search in the PubMed database was performed and 11 papers were eligible for inclusion in this systematic review and meta-analysis.

RESULTS

The pooled prevalence of COVID-19-related neuropathic pain was 6.7% (95% CI: 4.7-9.5%) for hospitalised patients during the acute phase and 34.3% (95% CI: 14.3-62%) for long COVID patients. The identified risk factors for COVID-19-related neuropathic pain development included depression, COVID-19 severity and azithromycin use.

CONCLUSIONS

Neuropathic pain is a very common symptom in long COVID, indicating the urgency for further research in this direction.

FUS Contributes to Nerve Injury-Induced Nociceptive Hypersensitivity by Activating NF-κB Pathway in Primary Sensory Neurons

Dysregulation of pain-associated genes in the dorsal root ganglion (DRG) is considered to be a molecular basis of neuropathic pain genesis. Fused in sarcoma (FUS), a DNA/RNA-binding protein, is a critical regulator of gene expression. However, whether it contributes to neuropathic pain is unknown. This study showed that peripheral nerve injury caused by the fourth lumbar (L4) spinal nerve ligation (SNL) or chronic constriction injury (CCI) of the sciatic nerve produced a marked increase in the expression of FUS protein in injured DRG neurons. Blocking this increase through microinjection of the adeno-associated virus (AAV) 5-expressing Fus shRNA into the ipsilateral L4 DRG mitigated the SNL-induced nociceptive hypersensitivities in both male and female mice. This microinjection also alleviated the SNL-induced increases in the levels of phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2) and glial fibrillary acidic protein (GFAP) in the ipsilateral L4 dorsal horn. Furthermore, mimicking this increase through microinjection of AAV5 expressing full-length Fus mRNA into unilateral L3/4 DRGs produced the elevations in the levels of p-ERK1/2 and GFAP in the dorsal horn, enhanced responses to mechanical, heat and cold stimuli, and induced the spontaneous pain on the ipsilateral side of both male and female mice in the absence of SNL. Mechanistically, the increased FUS activated the NF-κB signaling pathway by promoting the translocation of p65 into the nucleus and phosphorylation of p65 in the nucleus from injured DRG neurons. Our results indicate that DRG FUS contributes to neuropathic pain likely through the activation of NF-κB in primary sensory neurons.SIGNIFICANCE STATEMENT In the present study, we reported that fused in sarcoma (FUS), a DNA/RNA-binding protein, is upregulated in injured dorsal root ganglion (DRG) following peripheral nerve injury. This upregulation is responsible for nerve injury-induced translocation of p65 into the nucleus and phosphorylation of p65 in the nucleus from injured DRG neurons. Because blocking this upregulation alleviates nerve injury-induced nociceptive hypersensitivity, DRG FUS participates in neuropathic pain likely through the activation of NF-κB in primary sensory neurons. FUS may be a potential target for neuropathic pain management.

Somatosensory neurons express specific sets of lincRNAs, and lincRNA CLAP promotes itch sensation in mice

Somatosensory neurons are highly heterogeneous with distinct types of neural cells responding to specific stimuli. However, the distribution and roles of cell-type-specific long intergenic noncoding RNAs (lincRNAs) in somatosensory neurons remain largely unexplored. Here, by utilizing droplet-based single-cell RNA-seq (scRNA-seq) and full-length Smart-seq2, we show that lincRNAs, but not coding mRNAs, are enriched in specific types of mouse somatosensory neurons. Profiling of lincRNAs from single neurons located in dorsal root ganglia (DRG) identifies 200 lincRNAs localized in specific types or subtypes of somatosensory neurons. Among them, the conserved cell-type-specific lincRNA CLAP associates with pruritus and is abundantly expressed in somatostatin (SST)-positive neurons. CLAP knockdown reduces histamine-induced Ca2+ influx in cultured SST-positive neurons and in vivo reduces histamine-induced scratching in mice. In vivo knockdown of CLAP also decreases the expression of neuron-type-specific and itch-related genes in somatosensory neurons, and this partially depends on the RNA binding protein MSI2. Our data reveal a cell-type-specific landscape of lincRNAs and a function for CLAP in somatosensory neurons in sensory transmission.

Effect of intrathecal NIS-lncRNA antisense oligonucleotides on neuropathic pain caused by nerve trauma, chemotherapy, or diabetes mellitus

BACKGROUND

Blocking increased expression of nerve injury-specific long non-coding RNA (NIS-lncRNA) in injured dorsal root ganglia (DRG) through DRG microinjection of NIS-lncRNA small hairpin interfering RNA or generation of NIS-lncRNA knockdown mice mitigates neuropathic pain. However, these strategies are impractical in the clinic. This study employed a Food and Drug Administration (FDA)-approved antisense oligonucleotides strategy to examine the effect of NIS-lncRNA ASOs on neuropathic pain.

METHODS

Effects of intrathecal injection of NIS-lncRNA antisense oligonucleotides on day 7 or 14 after chronic constriction injury (CCI) of the sciatic nerve, fourth lumbar (L4) spinal nerve ligation, or intraperitoneal injection of paclitaxel or streptozotocin on the expression of DRG NIS-lncRNA and C-C chemokine ligand 2 (CCL2, an NIS-lncRNA downstream target) and nociceptive hypersensitivity were examined. We also assessed whether NIS-lncRNA antisense oligonucleotides produced cellular toxicity.

RESULTS

Intrathecal NIS-lncRNA antisense oligonucleotides attenuated CCI-induced mechanical allodynia, heat hyperalgesia, cold hyperalgesia, and ongoing nociceptive responses, without changing basal or acute nociceptive responses and locomotor function. Intrathecal NIS-lncRNA antisense oligonucleotides also blocked CCI-induced increases in NIS-lncRNA and CCL2 in the ipsilateral L3 and L4 DRG and hyperactivities of neurones and astrocytes in the ipsilateral L3 and L4 spinal cord dorsal horn. Similar results were found in antisense oligonucleotides-treated mice after spinal nerve ligation or intraperitoneal injection of paclitaxel or streptozotocin. Normal morphologic structure and no cell loss were observed in the DRG and spinal cord of antisense oligonucleotides-treated mice.

CONCLUSION

These findings further validate the role of NIS-lncRNA in trauma-, chemotherapy-, or diabetes-induced neuropathic pain and demonstrate potential clinical application of NIS-lncRNA antisense oligonucleotides for neuropathic pain management.

Tetramethylpyrazine and Astragaloside IV have synergistic effects against spinal cord injury-induced neuropathic pain via the OIP5-AS1/miR-34a/Sirt1/NF-κB axis

BACKGROUND

Both Tetramethylpyrazine (TMPZ) and Astragaloside IV (AGS-IV) can ameliorate neuronal apoptosis and neuroinflammation in CNS diseases. This study revolves around the underlying mechanism of TMPZ and AGS-IV in spinal cord injury (SCI)-associated neuropathic pain (NP).

MATERIALS AND METHODS

An in-vivo NP model was constructed in Sprague-Dawley (SD) rats via SCI. qRT-PCR was employed to detect OIP5-AS1 and miR-34a. The paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) of the rats were evaluated. Neuronal apoptosis in the spinal cord of rats was examined by Nissl staining and TUNEL staining. The interactions between OIP5-AS1 and miR-34a as well as miR-34a and Sirt1 were investigated through dual luciferase assay and RIP assay. The protein expressions of Bad, Bax, Caspase-3, iNOS, COX2, NF-κB, and Sirt1 were examined by western blot.

RESULTS

TMPZ and AGS-IV combination relieved behavioral symptoms of neuropathic pain in the SCI rat model, enhanced the levels of OIP5-AS1 and Sirt1, and lowered the profile of miR-34a. OIP5-AS1 downregulation weakened the neuroprotective function of TMPZ and AGS-IV in SCI rats and reversed their anti-inflammatory and anti-apoptotic effects on LPS-elicited primary spinal cord neurons. miR-34a was identified as a target of OIP5-AS1. Upregulated miR-34a partly abated the protective functions of TMPZ and AGS-IV in primary spinal cord neurons. Additionally, miR-34a targeted and repressed Sirt1, thus activating the NF-κB pathway and inflammatory reactions. Sirt1 inhibition reduced the protective effects mediated by OIP5-AS1.

CONCLUSION

TMPZ and AGS-IV ameliorate SCI-elicited NP via the OIP5-AS1/miR-34a/Sirt1/NF-κB pathway.

Noncoding RNAs: Novel Targets for Opioid Tolerance

As a global health problem, chronic pain is one of the leading causes of disability, and it imposes a huge economic and public health burden on families and society. Opioids represent the cornerstone of analgesic drugs. However, opioid tolerance caused by long-term application of opioids is a major factor leading to drug withdrawal, serious side effects caused by dose increases, and even the death of patients, placing an increasing burden on individuals, medicine, and society. Despite efforts to develop methods to prevent and treat opioid tolerance, no effective treatment has yet been found. Therefore, understanding the mechanism underlying opioid tolerance is crucial for finding new prevention and treatment strategies. Noncoding RNAs (ncRNAs) are important parts of mammalian gene transcriptomes, and there are thousands of unique noncoding RNA sequences in cells. With the rapid development of high-throughput genome technology, research on ncRNAs has become a hot topic in biomedical research. In recent years, studies have shown that ncRNAs mediate physiological and pathological processes, including chromatin remodeling, transcription, posttranscriptional modification and signal transduction, which are key regulators of physiological processes in developmental and disease environments and have become biomarkers and potential therapeutic targets for various diseases. An increasing number of studies have found that ncRNAs are closely related to the development of opioid tolerance. In this review, we have summarized the evidence that ncRNAs play an important role in opioid tolerance and that ncRNAs may be novel targets for opioid tolerance.

Upregulation of LncRNA71132 in the spinal cord regulates hypersensitivity in a rat model of bone cancer pain

ABSTRACT

Bone cancer pain (BCP) is a pervasive clinical symptom which impairs the quality life. Long noncoding RNAs (lncRNAs) are enriched in the central nervous system and play indispensable roles in numerous biological processes, while its regulatory function in nociceptive information processing remains elusive. Here, we reported that functional modulatory role of ENSRNOT00000071132 (lncRNA71132) in the BCP process and sponging with miR-143 and its downstream GPR85-dependent signaling cascade. Spinal lncRNA71132 was remarkably increased in the rat model of bone cancer pain. The knockdown of spinal lncRNA71132 reverted BCP behaviors and spinal c-Fos neuronal sensitization. Overexpression of spinal lncRNA71132 in naive rat generated pain behaviors, which were accompanied by increased spinal c-Fos neuronal sensitization. Furthermore, it was found that lncRNA71132 participates in the modulation of BCP by inversely regulating the processing of miR-143-5p. In addition, an increase in expression of spinal lncRNA71132 resulted in the decrease in expression of miR-143 under the BCP state. Finally, it was found that miR-143-5p regulates pain behaviors by targeting GPR85. Overexpression of miR-143-5p in the spinal cord reverted the nociceptive behaviors triggered by BCP, accompanied by a decrease in expression of spinal GPR85 protein, but no influence on expression of gpr85 mRNA. The findings of this study indicate that lncRNA71132 works as a miRNA sponge in miR-143-5p-mediated posttranscriptional modulation of GPR85 expression in BCP. Therefore, epigenetic interventions against lncRNA71132 may potentially work as novel treatment avenues in treating nociceptive hypersensitivity triggered by bone cancer.

E74-like factor 1 contributes to nerve trauma-induced nociceptive hypersensitivity through transcriptionally activating matrix metalloprotein-9 in dorsal root ganglion neurons

ABSTRACT

Nerve trauma-induced alternations of gene expression in the neurons of dorsal root ganglion (DRG) participate in nerve trauma-caused nociceptive hypersensitivity. Transcription factors regulate gene expression. Whether the transcription factor E74-like factor 1 (ELF1) in the DRG contributes to neuropathic pain is unknown. We report here that peripheral nerve trauma caused by chronic constriction injury (CCI) of unilateral sciatic nerve or unilateral fourth lumbar spinal nerve ligation led to the time-dependent increases in the levels of Elf1 mRNA and ELF1 protein in injured DRG, but not in the spinal cord. Preventing this increase through DRG microinjection of adeno-associated virus 5 expressing Elf1 shRNA attenuated the CCI-induced upregulation of matrix metallopeptidase 9 (MMP9) in injured DRG and induction and maintenance of nociceptive hypersensitivities, without changing locomotor functions and basal responses to acute mechanical, heat, and cold stimuli. Mimicking this increase through DRG microinjection of AAV5 expressing full-length Elf1 upregulated DRG MMP9 and produced enhanced responses to mechanical, heat, and cold stimuli in naive mice. Mechanistically, more ELF1 directly bond to and activated Mmp9 promoter in injured DRG neurons after CCI. Our data indicate that ELF1 participates in nerve trauma-caused nociceptive hypersensitivity likely through upregulating MMP9 in injured DRG. E74-like factor 1 may be a new target for management of neuropathic pain.

Segmental Upregulation of ASIC1 Channels in the Formalin Acute Pain Mouse Model

BACKGROUND

Hindpaw injection of formalin in rodents is used to assess acute persistent pain. The response to formalin is biphasic. The initial response (first minutes) is thought to be linked to inflammatory, peripheral mechanisms, while the latter (around 30 min after the injection), is linked to central mechanisms. This model is useful to analyze the effect of drugs at one or both phases, and the involvement of ion channels in the response. Acid-sensing ion channels (ASICs) regulate synaptic activities and play important roles in pain conditions. Recently, psalmotoxin-1 (Pctx-1), a toxin that inhibits ASIC1a-constituted channels, and antisense ASIC1a-RNA, intrathecal administered in mice were shown to affect both phases of the test.

METHODS

The mouse formalin test was performed on C57/BL6 7- to 9-week-old mice. Behavioral tests were conducted and tissue was extracted to detect proteins (ASIC1 and pERK) and ASIC1-mRNA and mir485-5p levels.

RESULTS

The injection of formalin was accompanied by an increase in ASIC1 levels. This was detected at the contralateral anterior cingulate cortex (ACC) compared to the ipsilateral side, and both sides of the ACC of vehicle-injected animals. At the spinal cord and dorsal root ganglia, ASIC1 levels followed a gradient stronger at lumbar (L) 3 and decreased towards L5. Gender differences were detected at the ACC; with female mice showing higher ASIC1a levels at the ACC. No significant changes in ASIC1-mRNA levels were detected. Evidence suggests ASIC1 upregulation depends on regulatory microRNAs.

CONCLUSION

This work highlights the important role of ASIC1 in pain and the potential role of pharmacological therapies aimed at this channel.

Interactions Among Non-Coding RNAs and mRNAs in the Trigeminal Ganglion Associated with Neuropathic Pain

Background

Recent studies have demonstrated the contribution of non-coding RNAs (ncRNAs) to neuropathic pain. However, the expression profile of ncRNAs in the trigeminal ganglion (TG) and their functional mechanism underlying trigeminal neuropathic pain are still unclear.

Methods

In the present study, the trigeminal neuropathic pain model induced by chronic constriction injury of the infraorbital nerve (CCI-ION) was used to study the expression profile and potential regulatory mechanism of miRNAs, lncRNAs, circRNAs, and mRNAs in the TG by RNA-sequencing (RNA-seq) and bioinformatics analysis. CCI-ION mice suffered from mechanical allodynia from 3 days to 28 days after surgery.

Results

The RNA-seq results discovered 67 miRNAs, 216 lncRNAs, 14 circRNAs, 595 mRNAs, and 421 genes were differentially expressed (DE) in the TG of CCI-ION mice 7 days after surgery. And 39 DEGs were known pain genes. Besides, 5 and 35 pain-related DE mRNAs could be targeted by 6 DE miRNAs and 107 DE lncRNAs, respectively. And 23 pain-related DEGs had protein–protein interactions (PPI) with each other. GO analysis indicated membrane-related cell components and binding-related molecular functions were significantly enriched. KEGG analysis showed that nociception-related signaling pathways were significantly enriched for DE ncRNAs and DEGs. Finally, the competing endogenous RNA (ceRNA) regulatory network of DE lncRNA/DE circRNA-DE miRNA-DE mRNA existed in the TG of mice with trigeminal neuropathic pain.

Conclusion

Our findings demonstrate ncRNAs are involved in the development of trigeminal neuropathic pain, possibly through the ceRNA mechanism, which brings a new bright into the study of trigeminal neuropathic pain and the development of novel treatments targeting ncRNAs.

LncRNA Miat promotes neuropathic pain through miR-362-3p/BAMBI signaling axis

The treatment of neuropathic pain (NP) has become an important subject to be studied and solved urgently in clinical practice. The role of long noncoding RNAs (lncRNAs) in NP development is becoming clear. Therefore, this study aimed to investigate the role and mechanism of lncRNA Miat in NP. In this study, chronic contractionary injury (CCI) mouse NP model was performed. Firstly, the effects of Miat on pain behavior in mice and the expression levels of pro-inflammatory cytokines and pro-inflammatory proteins in spinal cord tissue were explored by interfering with the expression of Miat. Then, Miat-targeted signaling pathway was predicted by bioinformatics and verified by dual luciferase reporter gene and RNA pull down. Finally, the mechanism of Miat was confirmed by the rescue experiments. Our results demonstrated that Miat knockdown alleviated paw withdrawal threshold, paw withdrawal latency, cold hyperalgesia frequency and neuroinflammation in CCI mice. MiR-362-3p was able to bind to Miat and BAMBI. Overall, Miat upregulated BAMBI by inhibiting miR-362-3p, thereby promoting the occurrence and development of NP. This study analyzed the possibility and effectiveness of targeting Miat for NP clinical treatment, in order to provide new ideas and technical methods for NP gene therapy.

MITF-Mediated lncRNA CCDC183-As1 Promotes the Tumorigenic Properties and Aerobic Glycolysis of Bladder Cancer via Upregulating TCF7L2

As a primary malignancy tumor of the urology system, bladder cancer (BC) is characterized by its high recurrence and metastasis characteristics. Despite the great improvement in clinical interventions over the past decades, the outcomes of BC patients are still unsatisfactory. Novel molecular mechanisms for developing effective diagnostic and therapeutic strategies are urgently needed; therefore, we screened the lncRNA expression profile in four pairs of BC tissues, showing that CCDC183-AS1 was the most upregulated lncRNA. Subsequently, results of CCK-8, EdU, Transwell, and aerobic glycolysis detection showed that CCDC183-AS1 plays an oncogene role in BC progression. Furthermore, an investigation of the downstream and upstream factors of CCDC183-AS1 identified a novel MITF/CCDC183-AS1/miR-4731-5p/TCF7L2 axis in BC progression, which might furnish novel insights for developing effective diagnostic and therapeutic strategies for BC.

LncRNA, an Emerging Approach for Neurological Diseases Treatment by Regulating Microglia Polarization

Neurological disorders cause untold human disability and death each year. For most neurological disorders, the efficacy of their primary treatment strategies remains suboptimal. Microglia are associated with the development and progression of multiple neurological disorders. Targeting the regulation of microglia polarization has emerged as an important therapeutic strategy for neurological disorders. Their pro-inflammatory (M1)/anti-inflammatory (M2) phenotype microglia are closely associated with neuronal apoptosis, synaptic plasticity, blood-brain barrier integrity, resistance to iron death, and astrocyte regulation. LncRNA, a recently extensively studied non-coding transcript of over 200 nucleotides, has shown great value to intervene in microglia polarization. It can often participate in gene regulation of microglia by directly regulating transcription or sponging downstream miRNAs, for example. Through proper regulation, microglia can exert neuroprotective effects, reduce neurological damage and improve the prognosis of many neurological diseases. This paper reviews the progress of research linking lncRNAs to microglia polarization and neurological diseases.

A nerve injury-specific long noncoding RNA promotes neuropathic pain by increasing Ccl2 expression

Maladaptive changes of nerve injury-associated genes in dorsal root ganglia (DRGs) are critical for neuropathic pain genesis. Emerging evidence supports the role of long noncoding RNAs (lncRNAs) in regulating gene transcription. Here we identified a conserved lncRNA, named nerve injury-specific lncRNA (NIS-lncRNA) for its upregulation in injured DRGs exclusively in response to nerve injury. This upregulation was triggered by nerve injury-induced increase in DRG ELF1, a transcription factor that bound to the NIS-lncRNA promoter. Blocking this upregulation attenuated nerve injury-induced CCL2 increase in injured DRGs and nociceptive hypersensitivity during the development and maintenance periods of neuropathic pain. Mimicking NIS-lncRNA upregulation elevated CCL2 expression, increased CCL2-mediated excitability in DRG neurons, and produced neuropathic pain symptoms. Mechanistically, NIS-lncRNA recruited more binding of the RNA-interacting protein FUS to the Ccl2 promoter and augmented Ccl2 transcription in injured DRGs. Thus, NIS-lncRNA participates in neuropathic pain likely by promoting FUS-triggered DRG Ccl2 expression and may be a potential target in neuropathic pain management.

Identifying a novel KLF2/lncRNA SNHG12/miR-494-3p/RAD23B axis in Spare Nerve Injury-induced neuropathic pain

Spinal cord injury (SCI) is a devastating condition for patients, affecting nearly 2.5 million people globally. Multiple side effects of SCI have resulted in a terrible life experience for SCI patients, of which neuropathic pain has attracted the most scientific interest. Even though many efforts have been made to attenuate or eliminate neuropathic pain induced by SCI, the outcomes for patients are still poor. Therefore, identifying novel diagnosis or therapeutic targets of SCI-induced neuropathic pain is urgently needed. Recently, multiple functions of long non-coding RNA (lncRNA) have been elucidated, including those in SCI-induced neuropathic pain. In this study, lncRNA small nucleolar RNA host gene 12 (SNHG12) was found to be upregulated in the dorsal root ganglion (DRGs) of rats with spare nerve injury (SNI). By constructing SCI rat models, we found that lncRNA SNHG12 expression was increased in the DRGs, and mainly distributed in the cytoplasm of PC12 cells. Paw withdrawal threshold (PWT), paw withdrawal latency (PWL), and enzyme linked immunosorbent assay (ELISA) results indicated that lncRNA SNHG12 knockdown attenuated SNI-induced neuropathic pain, and decreased the expression levels of interleukin (IL)−1β, IL-6, and tumour necrosis factor α (TNF-α) in the DRGs. Bioinformatics analysis, RNA pull-down, chromatin immunoprecipitation (ChIP), and luciferase reporter gene assays showed that lncRNA SNHG12 regulates the RAD23 homologue B, nucleotide excision repair protein (RAD23B) expression, through targeting micro RNA (miR)−494-3p. Furthermore, the study indicated that Kruppel-Like Factor 2 (KLF2) could regulate lncRNA SNHG12 expression in PC12 cells. This study identified a novel KLF2/lncRNA SNHG12/miR-494-3p/RAD23B axis in SNI-induced neuropathic pain, which might provide a new insight for developing novel diagnosis, or therapeutic targets of SCI-induced neuropathic pain in the future.

Long Non-coding RNA and mRNA Expression Change in Spinal Dorsal Horn After Exercise in Neuropathic Pain Rats

Exercise can help inhibition of neuropathic pain (NP), but the related mechanism remains being explored. In this research, we performed the effect of swimming exercise on the chronic constriction injury (CCI) rats. Compared with CCI group, the mechanical withdrawal threshold of rats in the CCI-Swim group significantly increased on the 21st and 28th day after CCI surgery. Second-generation RNA-sequencing technology was employed to investigate the transcriptomes of spinal dorsal horns in the Sham, CCI, and CCI-Swim groups. On the 28th day post-operation, 306 intersecting long non-coding RNAs (lncRNAs) and 173 intersecting mRNAs were observed between the CCI vs Sham group and CCI-Swim vs CCI groups. Then, the biological functions of lncRNAs and mRNAs in the spinal dorsal horn of CCI rats were then analyzed. Taking the results together, this study could provide a novel perspective for the treatment for NP.

CASC7: a LncRNA with potential clinical application

AIM

To explore the novel lncRNA CASC7 and its potential clinical applications.Long non-coding RNAs (IncRNAs) are defined as non-coding genes with a length exceeding 200 nt. As transcripts of RNA polymerase Il, they have limited coding potential due to the lack of an open reading frame in the gene segment. Research has confirmed that lncRNAs are important biological factors that regulate many life processes in the human body through different mechanisms. This work focused on Cancer Susceptibility Candidate 7 (CASC7), a lncRNA with nuclear and cytoplasmic localization. Publicly available databases show that CASC7 is differentially expressed in human organs as well as in tumor tissues. A study confirmed that CASC7 is abnormally expressed in colorectal cancer, glioma, breast cancer, non-small cell lung cancer and thyroid cancer. In male infertility, asthma and heart failure, it may also be a potential therapeutic target and promising biomarker. CASC7 mainly plays a biological effect through direct or indirect effects of promoting or inhibiting the expression of related genes. Currently, only few studies have assessed CASC7, and its mechanisms are not clear. The main purpose of this review was to examine CASC7 and its possible molecular mechanisms and clinical significance in cancer.

CONCLUSION

We reviewed the recent research progress of CASC7 and its potential as a diagnostic marker and therapeutic target, and provide an outlook on its future application in terms of mechanism.Key points:CASC7 is a novel lncRNA, for which there are few reports.Aberrant expression of CASC7 may be associated with the emergence and treatment of many clinical diseases, including malignancy.

Ion channel long non-coding RNAs in neuropathic pain

Neuropathic pain is one of the primary forms of chronic pain and is the consequence of the somatosensory system's direct injury or disease. It is a relevant public health problem that affects about 10% of the world's general population. In neuropathic pain, alteration in neurotransmission occurs at various levels, including the dorsal root ganglia, the spinal cord, and the brain, resulting from the malfunction of diverse molecules such as receptors, ion channels, and elements of specific intracellular signaling pathways. In this context, there have been exciting advances in elucidating neuropathic pain's cellular and molecular mechanisms in the last decade, including the possible role that long non-coding RNAs (lncRNAs) may play, which open up new alternatives for the development of diagnostic and therapeutic strategies for this condition. This review focuses on recent studies associated with the possible relevance of lncRNAs in the development and maintenance of neuropathic pain through their actions on the functional expression of ion channels. Recognizing the changes in the function and spatio-temporal patterns of expression of these membrane proteins is crucial to understanding the control of neuronal excitability in chronic pain syndromes.

Organic anion transporter 1 is an HDAC4-regulated mediator of nociceptive hypersensitivity in mice

Persistent pain is sustained by maladaptive changes in gene transcription resulting in altered function of the relevant circuits; therapies are still unsatisfactory. The epigenetic mechanisms and affected genes linking nociceptive activity to transcriptional changes and pathological sensitivity are unclear. Here, we found that, among several histone deacetylases (HDACs), synaptic activity specifically affects HDAC4 in murine spinal cord dorsal horn neurons. Noxious stimuli that induce long-lasting inflammatory hypersensitivity cause nuclear export and inactivation of HDAC4. The development of inflammation-associated mechanical hypersensitivity, but neither acute nor basal sensitivity, is impaired by the expression of a constitutively nuclear localized HDAC4 mutant. Next generation RNA-sequencing revealed an HDAC4-regulated gene program comprising mediators of sensitization including the organic anion transporter OAT1, known for its renal transport function. Using pharmacological and molecular tools to modulate OAT1 activity or expression, we causally link OAT1 to persistent inflammatory hypersensitivity in mice. Thus, HDAC4 is a key epigenetic regulator that translates nociceptive activity into sensitization by regulating OAT1, which is a potential target for pain-relieving therapies.

Chronic pain is sustained by alterations in gene transcription. Here, the authors show that increased expression of Organic Anionic Transporter 1 in the spinal cord is epigenetically controlled and key to hypersensitivity in pathological pain.

Biomarkers from Secondary Complications in Spinal Cord Injury

PURPOSE OF REVIEW

In the USA, spinal cord injury (SCI) occurs in 40 people per million every year due to events such as car accidents, falls, violence, or sports injury. Secondary complications that arise from SCI are life-threatening and should be treated as early as possible. In some cases, it is not completely obvious what complication a patient may have until it is too late. Therefore, biomarkers are required to assess the levels of secondary complications after SCI. As there are several complications that pose different warning signs, different biomarkers may be beneficial in early detection, maintenance, and long-term care for patients with SCI.

RECENT FINDINGS

Numerous studies have been conducted on biomarkers in various SCI and its related complications, such as neuropathic pain and deep vein thrombosis. In recent years, research has expanded with biomarkers discovered by cellular and molecular, genome-wide transcriptomic analysis, bioinformatics, and clinical studies. Biomarkers have allowed early prediction of the severity of secondary complications due to SCI.

SUMMARY

In this review, we summarize recent studies on the common biomarkers for the secondary complications related to SCI. We highlight the reliable biomarkers that have been tested, e.g., sclerostin, NGF, D-dimer, oncostatin M (OSM), microbiota, and C-reactive protein, which are valuable and with clinical importance. This review also emphasizes continuing research in biomarkers as they can provide valuable cellular and molecular insight into secondary complications after SCI.

Differential Expression of Long Non-Coding RNAs and Their Role in Rodent Neuropathic Pain Models

Neuropathic pain, which is accompanied by an unpleasant sensation, affects the patient’s quality of life severely. Considering the complexity of the neuropathic pain, there are huge unmet medical needs for it while current effective therapeutics remain far from satisfactory. Accordingly, exploration of mechanisms of neuropathic pain could provide new therapeutic insights. While numerous researches have pointed out the contribution of sensory neuron-immune cell interactions, other mechanisms of action, such as long non-coding RNAs (lncRNAs), also could contribute to the neuropathic pain observed in vivo. LncRNAs have more than 200 nucleotides and were originally considered as transcriptional byproducts. However, recent studies have suggested that lncRNAs played a significant role in gene regulation and disease pathogenesis. A substantial number of long non-coding RNAs were expressed differentially in neuropathic pain models. Besides, therapies targeting specific lncRNAs can significantly ameliorate the development of neuropathic pain, which reveals the contribution of lncRNAs in the generation and maintenance of neuropathic pain and provides a new therapeutic strategy. The primary purpose of this review is to introduce recent studies of lncRNAs on different neuropathic pain models.

DNA Methylation and Non-Coding RNAs during Tissue-Injury Associated Pain

While about half of the population experience persistent pain associated with tissue damages during their lifetime, current symptom-based approaches often fail to reduce such pain to a satisfactory level. To provide better patient care, mechanism-based analgesic approaches must be developed, which necessitates a comprehensive understanding of the nociceptive mechanism leading to tissue injury-associated persistent pain. Epigenetic events leading the altered transcription in the nervous system are pivotal in the maintenance of pain in tissue injury. However, the mechanisms through which those events contribute to the persistence of pain are not fully understood. This review provides a summary and critical evaluation of two epigenetic mechanisms, DNA methylation and non-coding RNA expression, on transcriptional modulation in nociceptive pathways during the development of tissue injury-associated pain. We assess the pre-clinical data and their translational implication and evaluate the potential of controlling DNA methylation and non-coding RNA expression as novel analgesic approaches and/or biomarkers of persistent pain.

Long non-coding RNA rhabdomyosarcoma 2-associated transcript contributes to neuropathic pain by recruiting HuR to stabilize DNA methyltransferase 3 alpha mRNA expression in dorsal root ganglion neuron

Introduction

Long non-coding RNAs (lncRNAs) act as key regulators in multiple human diseases. In particular, the dysfunction of lncRNAs in dorsal root ganglion (DRG) contributes to the pathogenesis of neuropathic pain (NP). Nevertheless, the role and mechanism of most lncRNAs in NP remain unclear.

Methods

Two classic chronic NP models, including L4 spinal nerve ligation (SNL) model and chronic constriction injury (CCI) of the sciatic nerve, were performed. Mechanical allodynia and heat hyperalgesia were used to evaluate neuropathic pain. DRG microinjection was used to deliver agents into DRG. qRT-PCR, immunofluorescence, immunoprecipitation, western blotting, siRNA transfection, AAV transduction were performed to investigate the phenotypes and molecular basis.

Results

Here, we discovered that Rmst as a lncRNA was specifically expressed in Atf3 ⁺ injured DRG neurons and significantly upregulated following peripheral nerve damage. Rmst overexpression by direct DRG injection of AAV5-Rmst causes neuropathic symptoms in the absence of nerve damage. Conversely, blocking Rmst expression in injured DRGs alleviated nerve injury-induced pain hypersensitivities and downregulated Dnmt3a expression. Furthermore, we found peripheral nerve damage induced Rmst increase could interact with RNA-binding protein HuR to stabilize the Dnmt3a mRNA.

Conclusion

Our findings reveal a crucial role of Rmst in damaged DRG neurons under NP condition and provide a novel target for drug development against NP.

Intrathecal administration of the fat-mass and obesity-associated protein inhibitor mitigates neuropathic pain in female rats

Several intracellular signals are involved in the sexual dimorphism of chronic pain. Our previous studies demonstrated that the fat-mass and obesity-associated protein (FTO), a demethylase of RNA N6-methyladenosine, in the injured dorsal root ganglion (DRG) contributed to the development and maintenance of nerve injury-induced nociceptive hypersensitivity in male rats and male mice. However, whether these effects of DRG FTO are in a sex-dependent manner is still unknown. The present study sought to investigate the effect of intrathecal administration of a specific FTO inhibitor, meclofenamic acid (MA), on chronic constriction injury (CCI)-induced nociceptive hypersensitivity in female rats. Intrathecal injection of MA attenuated the CCI-induced mechanical allodynia, heat hyperalgesia, and cold hyperalgesia in both the induction and maintenance periods, without changing acute/basal pain and locomotor function, in female rats. Intrathecal MA also blocked the CCI-induced hyperactivations of neurons and astrocytes in the ipsilateral L4 and L5 dorsal horns of female rats. Mechanistically, intrathecal MA prevented the CCI-induced increase in the histone methyltransferase G9a expression and reversed the G9a-controlled downregulation of mu-opioid receptor and Kv1.2 proteins in the ipsilateral L4 and L5 DRGs of female rats. These findings indicate that the effects of the FTO inhibitor on nerve injury-induced nociceptive hypersensitivity in female rats are similar to those in male rats reported previously. Our data also further confirm the role of DRG FTO in neuropathic pain and suggest potential clinical application of the FTO inhibitors for the prevention and treatment of this disorder in both men and women.

Selected Thiadiazine-Thione Derivatives Attenuate Neuroinflammation in Chronic Constriction Injury Induced Neuropathy

Neuropathic pain refers to a lesion or disease of peripheral and/or central somatosensory neurons and is an important body response to actual or potential nerve damage. We investigated the therapeutic potential of two thiadiazine-thione [TDT] derivatives, 2-(5-propyl-6-thioxo-1, 3, 5-thiadiazinan-3-yl) acetic acid [TDT1] and 2-(5-propyl-2-thioxo-1, 3, 5-thiadiazinan-3-yl) acetic acid [TDT2] against CCI (chronic constriction injury)-induced neuroinflammation and neuropathic pain. Mice were used for assessment of acute toxicity of TDT derivatives and no major toxic/bizarre responses were observed. Anti-inflammatory activity was assessed using the carrageenan test, and both TDT1 and TDT2 significantly reduced carrageenan-induced inflammation. We also used rats for the induction of CCI and performed allodynia and hyperalgesia-related behavioral tests followed by biochemical and morphological analysis using RT-qPCR, immunoblotting, immunohistochemistry and immunofluorescence. Our findings revealed that CCI induced clear-cut allodynia and hyperalgesia which was reversed by TDT1 and TDT2. To determine the function of TDT1 and TDT2 in glia-mediated neuroinflammation, Iba1 mRNA and protein levels were measured in spinal cord tissue sections from various experimental groups. Interestingly, TDT1 and TDT2 substantially reduced the mRNA expression and protein level of Iba1, implying that TDT1 and TDT2 may mitigate CCI-induced astrogliosis. In silico molecular docking studies predicted that both compounds had an effective binding affinity for TNF-α and COX-2. The compounds interactions with the proteins were dominated by both hydrogen bonding and van der Waals interactions. Overall, these results suggest that TDT1 and TDT2 exert their neuroprotective and analgesic potentials by ameliorating CCI-induced allodynia, hyperalgesia, neuroinflammation and neuronal degeneration in a dose-dependent manner.

Epigenetic modifications in neuropathic pain

Neuropathic pain (NP) is a common symptom in many diseases of the somatosensory nervous system, which severely affects the patient’s quality of life. Epigenetics are heritable alterations in gene expression that do not cause permanent changes in the DNA sequence. Epigenetic modifications can affect gene expression and function and can also mediate crosstalk between genes and the environment. Increasing evidence shows that epigenetic modifications, including DNA methylation, histone modification, non-coding RNA, and RNA modification, are involved in the development and maintenance of NP. In this review, we focus on the current knowledge of epigenetic modifications in the development and maintenance of NP. Then, we illustrate different facets of epigenetic modifications that regulate gene expression and their crosstalk. Finally, we discuss the burgeoning evidence supporting the potential of emerging epigenetic therapies, which has been valuable in understanding mechanisms and offers novel and potent targets for NP therapy.

MeCP2 Epigenetic Silencing of Oprm1 Gene in Primary Sensory Neurons Under Neuropathic Pain Conditions

Opioids are the last option for the pharmacological treatment of neuropathic pain, but their antinociceptive effects are limited. Decreased mu opioid receptor (MOR) expression in the peripheral nervous system may contribute to this. Here, we showed that nerve injury induced hypermethylation of the Oprm1 gene promoter and an increased expression of methyl-CpG binding protein 2 (MeCP2) in injured dorsal root ganglion (DRG). The downregulation of MOR in the DRG is closely related to the augmentation of MeCP2, an epigenetic repressor, which could recruit HDAC1 and bind to the methylated regions of the Oprm1 gene promoter. MeCP2 knockdown restored the expression of MOR in injured DRG and enhanced the analgesic effect of morphine, while the mimicking of this increase via the intrathecal infusion of viral vector-mediated MeCP2 was sufficient to reduce MOR in the DRG. Moreover, HDAC1 inhibition with suberoylanilide hydroxamic acid, an HDAC inhibitor, also prevented MOR reduction in the DRG of neuropathic pain mice, contributing to the augmentation of morphine analgesia effects. Mechanistically, upregulated MeCP2 promotes the binding of a high level of HDCA1 to hypermethylated regions of the Oprm1 gene promoter, reduces the acetylation of histone H3 (acH3) levels of the Oprm1 gene promoter, and attenuates Oprm1 transcription in injured DRG. Thus, upregulated MeCP2 and HDAC1 in Oprm1 gene promoter sites, negatively regulates MOR expression in injured DRG, mitigating the analgesic effect of the opioids. Targeting MeCP2/HDAC1 may thus provide a new solution for improving the therapeutic effect of opioids in a clinical setting.

KDM6B epigenetically regulated-interleukin-6 expression in the dorsal root ganglia and spinal dorsal horn contributes to the development and maintenance of neuropathic pain following peripheral nerve injury in male rats

The lysine specific demethylase 6B (KDM6B) has been implicated as a coregulator in the expression of proinflammatory mediators, and in the pathogenesis of inflammatory and arthritic pain. However, the role of KDM6B in neuropathic pain has yet to be studied. In the current study, the neuropathic pain was determined by assessing the paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) following lumbar 5 spinal nerve ligation (SNL) in male rats. Immunohistochemistry, Western blotting, qRT-PCR, and chromatin immunoprecipitation (ChIP)-PCR assays were performed to investigate the underlying mechanisms. Our results showed that SNL led to a significant increase in KDM6B mRNA and protein in the ipsilateral L4/5 dorsal root ganglia (DRG) and spinal dorsal horn; and this increase correlated a markedly reduction in the level of H3K27me3 methylation in the same tissue. Double immunofluorescence staining revealed that the KDM6B expressed in myelinated A- and unmyelinated C-fibers in the DRG; and located in neuronal cells, astrocytes, and microglia in the dorsal horn. Behavioral data showed that SNL-induced mechanical allodynia and thermal hyperalgesia were impaired by the treatment of prior to i.t. injection of GSK-J4, a specific inhibitor of KDM6B, or KDM6B siRNA. Both microinjection of AAV2-EGFP-KDM6B shRNA in the lumbar 5 dorsal horn and sciatic nerve, separately, alleviated the neuropathic pain following SNL. The established neuropathic pain was also partially attenuated by repeat i.t. injections of GSK-J4 or KDM6B siRNA, started on day 7 after SNL. SNL also resulted in a remarkable increased expression of interleukin-6 (IL-6) in the DRG and dorsal horn. But this increase was dramatically inhibited by i.t. injection of GSK-J4 and KDM6B siRNA; and suppressed by prior to microinjection of AAV2-EGFP-KDM6B shRNA in the dorsal horn and sciatic nerve. Results of ChIP-PCR assay showed that SNL-induced enhanced binding of STAT3 with IL-6 promoter was inhibited by prior to i.t. injection of GSK-J4. Meanwhile, the level of H3K27me3 methylation was also decreased by the treatment. Together, our results indicate that SNL-induced upregulation of KDM6B via demethylating H3K27me3 facilitates the binding of STAT3 with IL-6 promoter, and subsequently mediated-increase in the expression of IL-6 in the DRG and dorsal horn contributes to the development and maintenance of neuropathic pain. Targeting KDM6B might a promising therapeutic strategy to treatment of chronic pain.

LncRNA CRNDE exacerbates neuropathic pain in chronic constriction injury-induced(CCI) rats through regulating miR-146a-5p/WNT5A pathway

Neuropathic pain (NP) originating from a dysfunction in the nervous system is often intractable and chronic. Many studies have implicated long noncoding RNAs (lncRNAs) in the physiological and pathological development of NP. The lncRNA colorectal neoplasia differentially expressed gene (CRNDE) has been shown to mediate NP progression. However, further investigations are needed to gain deeper understanding of the specific mechanisms governing CRNDE in NP etiopathology. In this study, we successfully used chronic constrictive injury (CCI)-induced rats to establish an NP model with intrathecal injection, and confirmed the upregulation of CRNDE in CCI-induced rats. Moreover, silencing of CRNDE relieved mechanical allodynia, thermal hyperalgesia, and neuroinflammation in the NP model. Bioinformatics analysis predicted that miR-146a-5p binds to CRNDE. Our findings validated that miR-146a-5p was a target of CRNDE and that the expression of miR-146a-5p was decreased in CCI rats. Furthermore, miR-151A-3p was found to exert a negative regulatory effect on WNT5A. In addition, knockdown of WNT5A alleviated the pain-related behavior and inflammatory response of NP in vivo. Finally, we demonstrated that CRNDE contributed to the progression of CCI-induced NP via competitive binding to miR-146a-5p to upregulate WNT5A. The present study offers novel insights that may be translated into improved therapies for NP.

lncRNA MEG3 aggravated neuropathic pain and astrocyte overaction through mediating miR-130a-5p/CXCL12/CXCR4 axis

OBJECTIVE

Long non-coding RNAs (lncRNAs) exert a critical function in mediating neuropathic pain (NP). MEG3, a novel lncRNA, contributes to astrocyte activation and inflammation. However, its role in NP remains unclear.

METHODS

The chronic constriction injury (CCI) method was employed to construct an NP rat model. Astrocyte activation was induced by lipopolysaccharide (LPS). The profiles of MEG3, microRNA (miR)-130a-5p, CXC motif chemokine receptor 12 (CXCL12)/CXC motif chemokine receptor 4 (CXCR4), and the Rac1/NF-κB pathway in CCI rats' spinal cord tissues and astrocytes were monitored by reverse transcription-quantitative PCR (RT-qPCR) and western blot (WB). Pain scores of CCI rats were assessed. Enzyme-linked immunosorbent assay (ELISA) was adopted to monitor neuroinflammation alteration. The glial fibrillary acidic protein (GFAP)-labeled astrocytes were tested by immunohistochemistry (IHC). Bioinformatics, dual-luciferase reporter assay and RNA immunoprecipitation (RIP) were utilized to verify the molecular mechanism between MEG3 and miR-130a-3p.

RESULTS

MEG3, CXCL12 and CXCR4 were overexpressed and miR-130a-5p was knocked down in CCI rats and LPS-induced astrocytes. Up-regulating MEG3 aggravated NP, enhanced inflammatory cytokines interleukin-1β (IL-1β), tumor necrosis factor (TNF)-α, and interleukin-6 (IL-6) expression and release in CCI rats and LPS-induced astrocytes. Up-regulating miR-130-5p repressed LPS-induced inflammation in astrocytes. AS verified by the dual-luciferase reporter assay and RIP assay, MEG3 sponged miR-130a-5p as a competitive endogenous RNA (ceRNA). What's more, miR-130a-5p up-regulation weakened the MEG3-induced proinflammatory effects on LPS-induced astrocytes.

CONCLUSIONS

MEG3 aggravates NP and astrocyte activation via the miR-130a-5p/CXCL12/CXCR4 axis, which is a potential therapeutic target for NP.

LncRNA SNHG16 promotes Schwann cell proliferation and migration to repair sciatic nerve injury

Background

To investigate the expression of long non-coding RNA (lncRNA) Snorna hostgene16 (SNHG16) in sciatic nerve injury tissues and cells. The molecular mechanism of SNHG16 regulating signal activator of transcription 3 (STAT3) expression through “sponge” adsorption of miR-93-5p was also studied.

Methods

A rat model of sciatic nerve injury was established, and primary Schwann cells (SCs) were extracted. The expression of SNHG16 in animal tissues with sciatic nerve injury and SCs treated with ischemia and hypoxia was detected by qPCR, and CCK-8 assay, cell scratch assay, and Transwell chamber assay were used to detect cell proliferation, migration, and invasion. The targeted binding of SNHG16 to miR-93-5p was verified by double luciferase reporter gene assay and miRNA immunoprecipitation assay. MiR-93-5p mimic, SNHG16 overexpression vector, and sh-STAT3 plasmid were transfected into cells, respectively, and the mRNA expressions of SNHG16, miR-93-5p, and STAT3 in the cells were detected by qPCR.

Results

The expression of lncRNA SNHG16 was decreased after sciatic nerve injury, while overexpression of SNHG16 promoted the proliferation, migration, and invasion of SCs. The results of dual luciferase reporter gene assay and miRNA immunoprecipitation reaction showed miR-93-5p interacted with SNHG16, and the overexpression of miR-93-5p reversed the promoting effects of SNHG16 on the proliferation and invasion of SCs. At the same time, the knockdown of STAT3, which is the target gene of miR-93-5p, reversed the proliferation and invasion promotion effect of SNHG16 on SCs. SNHG16 affected the expression of its downstream target gene STAT3 by adsorbing miR-93-5p via endogenous competitive sponge.

Conclusions

SNHG16 can regulate STAT3 expression by sponge adsorption of miR-93-5p in SCs, and SNHG16 and miR-93-5p can be used as potential targets for the diagnosis and treatment of sciatic nerve injury.

Circular RNA SMEK1 promotes neuropathic pain in rats through targeting microRNA-216a-5p to mediate Thioredoxin Interacting Protein (TXNIP) expression

Neuropathic pain (NP) is a disease induced by damage to the nervous system. A large number of studies have manifested that circular RNAs (circRNAs) are key in the development of neurological diseases. However, the role of circRNA in NP remains ambiguous. In this study, the biological function and molecular mechanism of circSMEK1 were investigated in NP. NP rat and cell models were established by chronic contractile injury (CCI) surgery and lipopolysaccharide (LPS) treatment, separately. The results exposed that circSMEK1 and TXNIP were up-regulated in NP, while miR-216a-5p was down-regulated. The claw retraction threshold and claw retraction latency in rats were elevated and reduced separately via knockdown circSMEK1 and miR-216a-5p. Meanwhile, knockout circSMEK1 or elevated miR-216a-5p declined inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL6 in spinal cord, and the activation of microglia, but promoted the polarization of microglia into anti-inflammatory type, while up-regulation of circSMEK1 or knockdown of miR-216a-5p was opposite. Mechanism studies demonstrated that circSMEK1 mediated TXNIP expression through competitive adsorption of miR-216a-5p. Functional rescue experiments manifested that the suppressive effect of circSMEK1 knockdown on NP was reversed by declined miR-216a-5p simultaneously. In conclusion, the results of this study affirmed that circSMEK1 facilitates NP inflammation and microglia M1 polarization by modulating miR-216a-5p/TXNIP axis, providing a new molecular target for the future treatment of NP.

Dorsal Root Injury-A Model for Exploring Pathophysiology and Therapeutic Strategies in Spinal Cord Injury

Unraveling the cellular and molecular mechanisms of spinal cord injury is fundamental for our possibility to develop successful therapeutic approaches. These approaches need to address the issues of the emergence of a non-permissive environment for axonal growth in the spinal cord, in combination with a failure of injured neurons to mount an effective regeneration program. Experimental in vivo models are of critical importance for exploring the potential clinical relevance of mechanistic findings and therapeutic innovations. However, the highly complex organization of the spinal cord, comprising multiple types of neurons, which form local neural networks, as well as short and long-ranging ascending or descending pathways, complicates detailed dissection of mechanistic processes, as well as identification/verification of therapeutic targets. Inducing different types of dorsal root injury at specific proximo-distal locations provide opportunities to distinguish key components underlying spinal cord regeneration failure. Crushing or cutting the dorsal root allows detailed analysis of the regeneration program of the sensory neurons, as well as of the glial response at the dorsal root-spinal cord interface without direct trauma to the spinal cord. At the same time, a lesion at this interface creates a localized injury of the spinal cord itself, but with an initial neuronal injury affecting only the axons of dorsal root ganglion neurons, and still a glial cell response closely resembling the one seen after direct spinal cord injury. In this review, we provide examples of previous research on dorsal root injury models and how these models can help future exploration of mechanisms and potential therapies for spinal cord injury repair.

Identification of lncRNA and mRNA expression profiles in dorsal root ganglion in rats with cancer-induced bone pain

BACKGROUND

Cancer-induced bone pain (CIBP) is one of the most severe types of chronic pain which the involved mechanisms are largely unknown. LncRNA has been found to play critical roles in chronic pain. However, its function in peripheral nervous system in CIBP remains unknown. Identifying the different lncRNA expression pattern is essential for understanding the genetic mechanisms underlying the pathogenesis of CIBP.

METHODS

The model was induced by injection of Walker 256 cells into the rat tibia canal. Behavior tests and X-ray microtomography (MicroCT) analysis were performed to verify the model's establishment. L2-L5 DRGs were harvested at 14-day post operation and the differential lncRNA and mRNA expression patterns were investigated by microarray analyses. RT-qPCR analysis and RNA interference were performed for expression and function verifications. Bioinformatics analysis was conducted for further function study.

RESULTS

CIBP rats showed hyperalgesia and the MicroCT analysis showed tibia destruction. A total of 73 lncRNAs and 187 mRNAs were dysregulated. The expressions of several lncRNAs and mRNAs were validated by RT-qPCR experiment. Biological analyses showed that the changed mRNAs were mainly related to cellular and single-organism process, cell and cell part, binding function and immune system pathway. The top 30 lncRNA-predicted mRNAs are mainly related to peroxisome, DNA-dependent DNA replication, double-stranded RNA binding, tuberculosis and purine metabolism. 56 lncRNAs (30 downregulated and 26 upregulated) and 179 DEGs (35 downregulated and 144 upregulated) have a significant correlation and constructed a co-expression network. Downregulation of lncRNA NONRATT021203.2 by siRNA intrathecal injection increased PWL and WBD in CIBP rats, alleviating cancer induced bone hyperalgesia.

CONCLUSION

LncRNA played important roles in regulation of CIBP or mRNA expression in peripheral neuropathy in CIBP. These alterd mRNAs and lncRNAs might be potential therapeutic targets for the treatment of CIBP.