Advances With Non-coding RNAs in Neuropathic Pain

Roles of non-coding RNAs and exosomal non-coding RNAs, particularly microRNAs, long non-coding RNAs, and circular RNAs, in pathogenic mechanisms behind chronic pain: A review

Chronic pain is a significant public health concern that diminishes patients' quality of life and imposes considerable socioeconomic costs. Effective pharmacological treatments for ongoing pain are limited. Recent studies have indicated that various models of chronic pain-such as neuropathic pain, inflammatory pain, and pain associated with cancer-have abnormal levels of long noncoding RNAs (lncRNAs). Research has explored how these abnormal lncRNAs influence the activation of inflammatory cytokines, microRNAs, and other related molecules, which are crucial to the development of chronic pain. These findings suggest that these lncRNAs are vital in chronic pain mechanisms within the spinal cord and dorsal root ganglion following nerve injury. Additionally, exosomes, which can traverse the blood-brain barrier, are considered carriers of noncoding RNAs (ncRNAs) from neurons to systemic circulation. This study aims to summarize the existing knowledge on ncRNAs and exosomal ncRNAs in the context of chronic pain, highlighting potential biomarkers for diagnosis, regulatory roles in disease progression, therapeutic strategies, and clinical implications.

Transcriptome Analysis of Non-coding RNAs and mRNAs in the Dorsal Root Ganglion of Peripheral Nerve Injury-Induced Neuropathic Pain

Maladaptive changes in gene expression at transcriptional level in dorsal root ganglia (DRGs) after nerve injury are critical for neuropathic pain genesis. Emerging evidence reveals the important role of non-coding RNAs (ncRNAs) in regulating gene transcription. Recent studies also have showed the contribution of ncRNAs to neuropathic pain. However, the expression profile of ncRNAs in the DRGs and potential regulatory mechanism in peripheral nerve injury-induced neuropathic pain are not fully clear. We used bCCI neuropathic pain model induced by chronic constriction injury of bilateral sciatic nerves to study the expression profile and potential functional mechanism of micro RNAs (miRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs) and messenger RNA (mRNA) in the DRGs by RNA sequencing and bioinformatics analysis. A total of 47 miRNAs, 337 lncRNAs, 32 circRNAs, and 2269 mRNAs were differentially expressed (DE) in the DRGs of CCI mice 14 days after surgery. KEGG analysis demonstrated nociception-related signaling pathways were significantly enriched for DEncRNAs, including Rap1, Ras, and Hippo signaling pathway. GO analysis showed neuron related biological process, membrane related cell components, and binding related molecular functions were significantly enriched. The competing endogenous RNA (ceRNA) regulatory network of DEmiRNA-DEmRNA, DElncRNA-DEmRNA, and DEcircRNA-DEmiRNA existed in the DRGs of mice with neuropathic pain induced by peripheral nerve injury. In addition, 81 pain-related DE genes had protein-protein interactions (PPI) with each other. Our findings indicated that ncRNAs are involved in the development of peripheral nerve injury-induced neuropathic pain. DEncRNAs may provide us with a new perspective in chronic neuropathic pain research and may become a potential target for pain treatment.

RNA Interference Unleashed: Current Perspective of Small Interfering RNA (siRNA) Therapeutics in the Treatment of Neuropathic Pain

Neuropathic pain (NP) is one of the debilitating pain phenotypes that leads to the progressive degeneration of the central as well as peripheral nervous system. NP is often associated with hyperalgesia, allodynia, paresthesia, tingling, and burning sensations leading to disability, motor dysfunction, and compromised psychological state of the patients. Most of the conventional pharmacological agents are unable to improve the devastating conditions of pain because of their limited efficacy, undesirable side effects, and multifaceted pathophysiology of the diseased condition. A rapid rise in new cases of NP warrants further research for identifying the potential novel therapeutic modalities for treating NP. Recently, small interfering RNA (siRNA) approach has shown therapeutic potential in many disease conditions including NP. Delivery of siRNAs led to potential and selective downregulation of target mRNA and abolished the pain-related behaviors/pathophysiological pain response. The crucial role of siRNA in the treatment of NP by considering all of the pathways associated with NP that could be managed by siRNA therapeutics has been discussed. However, their therapeutic use is limited by several hurdles such as instability in systemic circulation due to their negative charge and membrane impermeability, off-target effects, immunogenicity, and inability to reach the intended site of action. This review also emphasizes several strategies and techniques to overcome these hurdles for translating these therapeutic siRNAs from bench to bedside by opening a new avenue for obtaining a potential therapeutic approach for treating NP.

Therapeutic Implication of miRNAs as an Active Regulatory Player in the Management of Pain: A Review

Chronic pain is frequently associated with neuropathy, inflammation, or the malfunctioning of nerves. Chronic pain is associated with a significant burden of morbidity due to opioid use, associated with addiction and tolerance, and disability. MicroRNAs (miRs) are emerging therapeutic targets to treat chronic pain through the regulation of genes associated with inflammation, neuronal excitability, survival, or de-differentiation. In this review, we discuss the possible involvement of miRs in pain-related molecular pathways. miRs are known to regulate high-conviction pain genes, supporting their potential as therapeutic targets.

Communicating pain: emerging axonal signaling in peripheral neuropathic pain

Peripheral nerve damage often leads to the onset of neuropathic pain (NeuP). This condition afflicts millions of people, significantly burdening healthcare systems and putting strain on families' financial well-being. Here, we will focus on the role of peripheral sensory neurons, specifically the Dorsal Root Ganglia neurons (DRG neurons) in the development of NeuP. After axotomy, DRG neurons activate regenerative signals of axons-soma communication to promote a gene program that activates an axonal branching and elongation processes. The results of a neuronal morphological cytoskeleton change are not always associated with functional recovery. Moreover, any axonal miss-targeting may contribute to NeuP development. In this review, we will explore the epidemiology of NeuP and its molecular causes at the level of the peripheral nervous system and the target organs, with major focus on the neuronal cross-talk between intrinsic and extrinsic factors. Specifically, we will describe how failures in the neuronal regenerative program can exacerbate NeuP.

Pharmacogenetic landscape of pain management variants among Mediterranean populations

Background

Chronic pain is a major socioeconomic burden in the Mediterranean region. However, we noticed an under-representation of these populations in the pharmacogenetics of pain management studies. In this context, we aimed 1) to decipher the pharmacogenetic variant landscape among Mediterranean populations compared to worldwide populations in order to identify therapeutic biomarkers for personalized pain management and 2) to better understand the biological process of pain management through in silico investigation of pharmacogenes pathways.

Materials and Methods

We collected genes and variants implicated in pain response using the Prisma guidelines from literature and PharmGK database. Next, we extracted these genes from genotyping data of 829 individuals. Then, we determined the variant distribution among the studied populations using multivariate (MDS) and admixture analysis with R and STRUCTURE software. We conducted a Chi2 test to compare the interethnic frequencies of the identified variants. We used SNPinfo web server, miRdSNP database to identify miRNA-binding sites. In addition, we investigated the functions of the identified genes and variants using pathway enrichment analysis and annotation tools. Finally, we performed docking analysis to assess the impact of variations on drug interactions.

Results

We identified 63 variants implicated in pain management. MDS analysis revealed that Mediterranean populations are genetically similar to Mexican populations and divergent from other populations. STRUCTURE analysis showed that Mediterranean populations are mainly composed of European ancestry. We highlighted differences in the minor allele frequencies of three variants (rs633, rs4680, and rs165728) located in the COMT gene. Moreover, variant annotation revealed ten variants with potential miRNA-binding sites. Finally, protein structure and docking analysis revealed that two missense variants (rs4680 and rs6267) induced a decrease in COMT protein activity and affinity for dopamine.

Conclusion

Our findings revealed that Mediterranean populations diverge from other ethnic groups. Furthermore, we emphasize the importance of pain-related pathways and miRNAs to better implement these markers as predictors of analgesic responses in the Mediterranean region.

Narrative Review of the Complex Interaction between Pain and Trauma in Children: A Focus on Biological Memory, Preclinical Data, and Epigenetic Processes

The incidence and collective impact of early adverse experiences, trauma, and pain continue to increase. This underscores the urgent need for translational efforts between clinical and preclinical research to better understand the underlying mechanisms and develop effective therapeutic approaches. As our understanding of these issues improves from studies in children and adolescents, we can create more precise preclinical models and ultimately translate our findings back to clinical practice. A multidisciplinary approach is essential for addressing the complex and wide-ranging effects of these experiences on individuals and society. This narrative review aims to (1) define pain and trauma experiences in childhood and adolescents, (2) discuss the relationship between pain and trauma, (3) consider the role of biological memory, (4) decipher the relationship between pain and trauma using preclinical data, and (5) examine the role of the environment by introducing the importance of epigenetic processes. The ultimate scope is to better understand the wide-ranging effects of trauma, abuse, and chronic pain on children and adolescents, how they occur, and how to prevent or mitigate their effects and develop effective treatment strategies that address both the underlying causes and the associated physiological and psychological effects.

Global research trends on epigenetics and neuropathic pain: A bibliometric analysis

Objective

Neuropathic pain (NP) is a common disease that manifests with pathological changes in the somatosensory system. In recent years, the interactions of NP with the epigenetic mechanism have been increasingly elucidated. However, only a few studies have used bibliometric tools to systematically analyze knowledge in this field. The objective of this study is to visually analyze the trends, hotspots, and frontiers in epigenetics and NP research by using a bibliometric method.

Methods

Studies related to epigenetics and NP were searched from the Science Citation Index-Expanded of the Web of Science Core Collection database. Search time is from inception to November 30, 2022. No restrictions were placed on language. Only articles and reviews were included as document types. Data on institutions, countries, authors, journal distribution, and keywords were imported into CiteSpace software for visual analysis.

Results

A total of 867 publications met the inclusion criteria, which spanned the period from 2000 to 2022. Over the years, the number of publications and the frequency of citations exhibited a clear upward trend in general, reaching a peak in 2021. The major contributing countries in terms of the number of publications were China, the United States, and Japan. The top three institutions were Rutgers State University, Xuzhou Medical University, and Nanjing Medical University. Molecular Pain, Pain, and Journal of Neuroinflammation contributed significantly to the volume of issues. Among the top 10 authors in terms of the number of publications, Tao Yuan-Xiang contributed 30 entries, followed by Zhang Yi with 24 and Wu Shao-Gen with 20. On the basis of the burst and clusters of keywords, "DNA methylation," "Circular RNA," "acetylation," "long non-coding RNA," and "microglia" are global hotspots in the field.

Conclusion

The bibliometric analysis indicates that the number of publications related to epigenetics and NP is exhibiting a rapid increase. Keyword analysis shows that "DNA methylation," "Circular RNA," "acetylation," "long non-coding RNA" and "microglia" are the most interesting terms for researchers in the field. More rigorous clinical trials and additional studies that explore relevant mechanisms are required in the future.

The emerging power and promise of non-coding RNAs in chronic pain

Chronic pain (CP) is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage lasting longer than 3 months. CP is the main reason why people seek medical care and exerts an enormous economic burden. Genome-wide expression analysis has revealed that diverse essential genetic elements are altered in CP patients. Although many possible mechanisms of CP have been revealed, we are still unable to meet all the analgesic needs of patients. In recent years, non-coding RNAs (ncRNAs) have been shown to play essential roles in peripheral neuropathy and axon regeneration, which is associated with CP occurrence and development. Multiple key ncRNAs have been identified in animal models of CP, such as microRNA-30c-5p, ciRS-7, and lncRNA MRAK009713. This review highlights different kinds of ncRNAs in the regulation of CP, which provides a more comprehensive understanding of the pathogenesis of the disease. It mainly focuses on the contributions of miRNAs, circRNAs, and lncRNAs to CP, specifically peripheral neuropathic pain (NP), diabetic NP, central NP associated with spinal cord injury, complex regional pain syndrome, inflammatory pain, and cancer-induced pain. In addition, we summarize some potential ncRNAs as novel biomarkers for CP and its complications. With an in-depth understanding of the mechanism of CP, ncRNAs may provide novel insight into CP and could become new therapeutic targets in the future.

RNA interference-mediated silencing of DNA methyltransferase 1 attenuates neuropathic pain by accelerating microglia M2 polarization

Background

DNA methyltransferase 1 (DNMT1) exerts imperative functions in neuropathic pain (NP). This study explored the action of RNA interference-mediated DNMT1 silencing in NP by regulating microglial M2 polarization.

Methods

NP rat models were established using chronic constriction injury (CCI) and highly aggressive proliferating immortalized (HAPI) microglia were treated with lipopolysaccharide (LPS) to induce microglia M1 polarization, followed by treatment of DNMT1 siRNA or si-DNMT1/oe-DNMT1, respectively. The pain threshold of CCI rats was assessed by determining mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL). Levels of inflammatory factors (TNF-α/IL-1β/IL-6/IL-10) and DNMT1 in rat L4-L6 spinal cord samples and HAPI cells were measured using ELISA, RT-qPCR, and Western blot. iNOS and Arg-1 mRNA levels were measured via RT-qPCR. DNMT1, M1 marker (iNOS), and M2 marker (Arg-1) levels in microglia of CCI rats were detected by immunofluorescence. Percentages of M1 microglia phenotype (CD16) and M2 microglia phenotype (CD206) were detected by flow cytometry. The phosphorylation of PI3K/Akt pathway-related proteins was determined by Western blot.

Results

CCI rats exhibited diminished MWT and TWL values, increased pro-inflammatory cytokines, and decreased anti-inflammatory cytokine IL-10. Additionally, DNMT1 was upregulated in CCI rat microglia. DNMT1 siRNA alleviated CCI-induced NP and facilitated M2 polarization of microglia in CCI rats. DNMT1 knockdown inhibited LPS-induced M1 polarization of HAPI cells and promoted M2 polarization by blocking the PI3K/Akt pathway, but DNMT1 overexpression inhibited the M1-to-M2 polarization of microglia.

Conclusion

RNA interference-mediated DNMT1 silencing accelerates microglia M2 polarization by impeding the PI3K/Akt pathway, thereby alleviating CCI-induced NP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02860-6.

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.

Role of Epigenetic Mechanisms in Chronic Pain

Pain is an unpleasant but essential-to-life sensation, usually resulting from tissue damage. When pain persists long after the injury has resolved, it becomes pathological. The precise molecular and cellular mechanisms causing the transition from acute to chronic pain are not fully understood. A key aspect of pain chronicity is that several plasticity events happen along the neural pathways involved in pain. These long-lasting adaptive changes are enabled by alteration in the expression of relevant genes. Among the different modulators of gene transcription in adaptive processes in the nervous system, epigenetic mechanisms play a pivotal role. In this review, I will first outline the main classes of epigenetic mediators and then discuss their implications in chronic pain.

Expression Profiles of Circulating MicroRNAs in XELOX-Chemotherapy-Induced Peripheral Neuropathy in Patients with Advanced Gastric Cancer

Gastric cancer (GC) is one of the most common cancers and a leading cause of cancer deaths around the world. Chemotherapy is one of the most effective treatments for cancer patients, and has remarkably enhanced survival rates. However, it has many side effects. Recently, microRNAs (miRNAs) have been intensively studied as potential biomarkers for cancer diagnosis and treatment monitoring. However, definitive biomarkers in chemotherapy-induced peripheral neuropathy (CIPN) are still lacking. The aim of this study was to identify the factors significant for neurological adverse events in GC patients receiving XELOX (oxaliplatin and capecitabine) chemotherapy. The results show that XELOX chemotherapy induces changes in the expression of hsa-miR-200c-3p, hsa-miR-885-5p, and hsa-miR-378f. Validation by qRT-PCR demonstrated that hsa-miR-378f was significantly downregulated in CIPN. Hsa-miR-378f was identified as showing a statistically significant correlation in GC patients receiving XELOX chemotherapy according to the analysis of differentially expressed (DE) miRNAs. Furthermore, 34 potential target genes were predicted using a web-based database for miRNA target prognostication and functional annotations. The identified genes are related to the peptidyl-serine phosphorylation and regulation of alternative mRNA splicing with enrichment in the gastric cancer, neurotrophin, MAPK, and AMPK signaling pathways. Collectively, these results provide information useful for developing promising strategies for the treatment of XELOX-chemotherapy-induced peripheral neuropathy.