Overexpression of miR-378 Alleviates Chronic Sciatic Nerve Injury by Targeting EZH2

Ultrahigh frequency transcutaneous electrical nerve stimulation for neuropathic pain alleviation and neuromodulation

A challenging complication in patients with peripheral compressive neuropathy is neuropathic pain. Excessive neuroinflammation at the injury site worsens neuropathic pain and impairs function. Currently, non-invasive modulation techniques like transcutaneous electrical nerve stimulation (TENS) have shown therapeutic promise with positive results. However, the underlying regulatory molecular mechanism for pain relief remains complex and unexplored. This study aimed to validate the therapeutic effect of ultrahigh frequency (UHF)-TENS in chronic constriction injury of the rat sciatic nerve. Alleviation of mechanical allodynia was achieved through the application of UHF-TENS, lasting for 3 days after one session of therapy and 4 days after two sessions, without causing additional damage to the myelinated axon structure. The entire tissue collection schedule was divided into four time points: nerve exposure surgery, 7 days after nerve ligation, and 1 and 5 days after one session of UHF therapy. Significant reductions in pain-related neuropeptides, MEK, c-Myc, c-FOS, COX2, and substance P, were observed in the injured DRG neurons after UHF therapy. RNA sequencing of differential gene expression in sensory neurons revealed significant downregulation in Cables, Pik3r1, Vps4b, Tlr7, and Ezh2 after UHF therapy, while upregulation was observed in Nfkbie and Cln3. UHF-TENS effectively and safely relieved neuropathic pain without causing further nerve damage. The decreased production of pain-related neuropeptides within the DRG provided the therapeutic benefit. Possible molecular mechanisms behind UHF-TENS may result from the modulation of the NF-κB complex, toll-like receptor-7, and phosphoinositide 3-kinase/Akt signaling pathways. These results suggest the neuromodulatory effects of UHF-TENS in rat sciatic nerve chronic constriction injury, including alleviation of neuropathic pain, amelioration of pain-related neuropeptides, and regulation of neuroinflammatory gene expression. In combination with the regulation of related neuroinflammatory genes, UHF-TENS could become a new modality for enhancing the treatment of neuropathic pain in the future.

Modulation of experimental acute lung injury by exosomal miR-7704 from mesenchymal stromal cells acts through M2 macrophage polarization

Acute lung injury (ALI) is a life-threatening condition with limited treatment options. The pathogenesis of ALI involves macrophage-mediated disruption and subsequent repair of the alveolar barriers, which ultimately results in lung damage and regeneration, highlighting the pivotal role of macrophage polarization in ALI. Although exosomes derived from mesenchymal stromal cells have been established as influential modulators of macrophage polarization, the specific role of exosomal microRNAs (miRNAs) remains underexplored. This study aimed to elucidate the role of specific exosomal miRNAs in driving macrophage polarization, thereby providing a reference for developing novel therapeutic interventions for ALI. We found that miR-7704 is the most abundant and efficacious miRNA for promoting the switch to the M2 phenotype in macrophages. Mechanistically, we determined that miR-7704 stimulates M2 polarization by inhibiting the MyD88/STAT1 signaling pathway. Notably, intra-tracheal delivery of miR-7704 alone in a lipopolysaccharide-induced murine ALI model significantly drove M2 polarization in lung macrophages and remarkably restored pulmonary function, thus increasing survival. Our findings highlight miR-7704 as a valuable tool for treating ALI by driving the beneficial M2 polarization of macrophages. Our findings pave the way for deeper exploration into the therapeutic potential of exosomal miRNAs in inflammatory lung diseases.

EZH2 Methyltransferase Regulates Neuroinflammation and Neuropathic Pain

Recent studies by us and others have shown that enhancer of zeste homolog-2 (EZH2), a histone methyltransferase, in glial cells regulates the genesis of neuropathic pain by modulating the production of proinflammatory cytokines and chemokines. In this review, we summarize recent advances in this research area. EZH2 is a subunit of polycomb repressive complex 2 (PRC2), which primarily serves as a histone methyltransferase to catalyze methylation of histone 3 on lysine 27 (H3K27), ultimately resulting in transcriptional repression. Animals with neuropathic pain exhibit increased EZH2 activity and neuroinflammation of the injured nerve, spinal cord, and anterior cingulate cortex. Inhibition of EZH2 with DZNep or GSK-126 ameliorates neuroinflammation and neuropathic pain. EZH2 protein expression increases upon activation of Toll-like receptor 4 and calcitonin gene-related peptide receptors, downregulation of miR-124-3p and miR-378 microRNAs, or upregulation of Lncenc1 and MALAT1 long noncoding RNAs. Genes suppressed by EZH2 include suppressor of cytokine signaling 3 (SOCS3), nuclear factor (erythroid-derived 2)-like-2 factor (NrF2), miR-29b-3p, miR-146a-5p, and brain-specific angiogenesis inhibitor 1 (BAI1). Pro-inflammatory mediators facilitate neuronal activation along pain-signaling pathways by sensitizing nociceptors in the periphery, as well as enhancing excitatory synaptic activities and suppressing inhibitory synaptic activities in the CNS. These studies collectively reveal that EZH2 is implicated in signaling pathways known to be key players in the process of neuroinflammation and genesis of neuropathic pain. Therefore, targeting the EZH2 signaling pathway may open a new avenue to mitigate neuroinflammation and neuropathic pain.

Role of hippocampal circKcnk9 in visceral hypersensitivity and anxiety comorbidity of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder characterized by recurrent visceral pain and altered bowel habits (diarrhea or constipation). However, the molecular and pathological mechanisms are poorly understood. This study found neonatal colorectal distension to induce visceral hypersensitivity and anxiety. The expression of hippocampal circKcnk9, a novel circRNA, was significantly increased in IBS-like rats. Interestingly, CA1 shcircKcnk9 treatment inhibited long-term potentiation (LTP) and alleviated visceral hypersensitivity and anxiety in IBS-like rats, whereas overexpression of CA1 circKcnk9 induced LTP, visceral hypersensitivity, and anxiety in controls. Several experiments indicated that increased CA1 circKcnk9 acted as a miR-124-3p sponge, which resulted in the inhibitory effect of miR-124-3p on gene silencing. There was a negative correlation between circKcnk9 and miR-124-3p expression. As expected, CA1 administration of agomiR-124-3p decreased CA1 LTP, visceral hypersensitivity, and anxiety in the IBS-like rats. In contrast, CA1 treatment with antagomiR-124-3p induced LTP, visceral hypersensitivity, and anxiety in the controls. Furthermore, bioinformatic analysis and experimental data showed that EZH2 is a circKcnk9/miR-124-3p target gene, and increased EZH2 expression was involved in visceral hypersensitivity and anxiety in IBS-like rats by enhancing hippocampal synaptic plasticity. In conclusion, early life stress induces increased expression of circKcnk9 in the CA1 of IBS-like rats. Increased circKcnk9 expression regulates synaptic transmission and enhances LTP, leading to visceral hypersensitivity and anxiety in IBS-like rats. The underlying circKcnk9 signaling pathway is miR124-3p/EZH2. Increased circKcnk9 reinforces its sponging of miR124-3p and strongly suppresses miR124-3p activity, resulting in increased expression of the target gene EZH2. This study provides a new epigenetic mechanism for visceral hypersensitivity and anxiety in IBS-like rats.

The etiological roles of miRNAs, lncRNAs, and circRNAs in neuropathic pain: A narrative review

Background

Non‐coding RNAs (ncRNAs) are involved in neuropathic pain development. Herein, we systematically searched for neuropathic pain‐related ncRNAs expression changes, including microRNAs (miRNAs), long non‐coding RNAs (lncRNAs), and circular non‐coding RNAs (circRNAs).

Methods

We searched two databases, PubMed and GeenMedical, for relevant studies.

Results

Peripheral nerve injury or noxious stimuli can induce extensive changes in the expression of ncRNAs. For example, higher serum miR‐132‐3p, ‐146b‐5p, and ‐384 was observed in neuropathic pain patients. Either sciatic nerve ligation, dorsal root ganglion (DRG) transaction, or ventral root transection (VRT) could upregulate miR‐21 and miR‐31 while downregulating miR‐668 and miR‐672 in the injured DRG. lncRNAs, such as early growth response 2‐antisense‐RNA (Egr2‐AS‐RNA) and Kcna2‐AS‐RNA, were upregulated in Schwann cells and inflicted DRG after nerve injury, respectively. Dysregulated circRNA homeodomain‐interacting protein kinase 3 (circHIPK3) in serum and the DRG, abnormally expressed lncRNAs X‐inactive specific transcript (XIST), nuclear enriched abundant transcript 1 (NEAT1), small nucleolar RNA host gene 1 (SNHG1), as well as ciRS‐7, zinc finger protein 609 (cirZNF609), circ_0005075, and circAnks1a in the spinal cord were suggested to participate in neuropathic pain development. Dysregulated miRNAs contribute to neuropathic pain via neuroinflammation, autophagy, abnormal ion channel expression, regulating pain‐related mediators, protein kinases, structural proteins, neurotransmission excitatory–inhibitory imbalances, or exosome miRNA‐mediated neuron–glia communication. In addition, lncRNAs and circRNAs are essential in neuropathic pain by acting as antisense RNA and miRNA sponges, epigenetically regulating pain‐related molecules expression, or modulating miRNA processing.

Conclusions

Numerous dysregulated ncRNAs have been suggested to participate in neuropathic pain development. However, there is much work to be done before ncRNA‐based analgesics can be clinically used for various reasons such as conservation among species, proper delivery, stability, and off‐target effects.

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.

Advances With Non-coding RNAs in Neuropathic Pain

Neuropathic pain (NP) is one of the most common types of clinical pain. The common causes of this syndrome include injury to the central or peripheral nervous systems and pathological changes. NP is characterized by spontaneous pain, hyperalgesia, abnormal pain, and paresthesia. Because of its diverse etiology, the pathogenesis of NP has not been fully elucidated and has become one of the most challenging problems in clinical medicine. This kind of pain is extremely resistant to conventional treatment and is accompanied by serious complications. Non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), contribute to diverse biological processes by regulating the expression of various mRNAs involved in pain-related pathways, at the posttranscriptional level. Abnormal regulation of ncRNAs is closely related to the occurrence and development of NP. In this review, we summarize the current state of understanding of the roles of different ncRNAs in the development of NP. Understanding these mechanisms can help develop novel therapeutic strategies to prevent or treat chronic pain.