MiR-183-5p Alleviates Chronic Constriction Injury-Induced Neuropathic Pain Through Inhibition of TREK-1

MicroRNA-6954-3p Downregulation Contributes to Orofacial Neuropathic Pain in Mice Via Targeting Voltage-Gated Sodium Channel β2 Subunit Protein

The voltage-gated sodium channel β2 subunit protein (SCN2B) plays a crucial role in neuropathic pain. However, the role and mechanisms of SCN2B in orofacial neuropathic pain are still unclear. This study aimed to investigate the upstream regulatory mechanisms of SCN2B in the trigeminal ganglion (TG) underlying orofacial neuropathic pain. Chronic constriction injury of the infraorbital nerve (CCI-ION) of mice was performed to establish the model of orofacial neuropathic pain. Von Frey filament test was performed to detect the head withdrawal threshold (HWT) of mice. Quantitative reverse transcription-polymerase chain, western blotting (WB), fluorescence in situ hybridization, and immunofluorescence (IF) staining were used to detect the expression and distribution of SCN2B and miR-6954-3p in the TG of mice. A luciferase activity assay was carried out to prove the binding between SCN2B messenger ribonucleic acid (mRNA) and miR-6954-3p. After the CCI-ION surgery, the levels of Scn2b mRNA and protein significantly increased and miR-6954-3p decreased in the TG of mice with decreasing HWT. IF staining revealed that SCN2B was expressed specifically in the TG neurons. Silencing SCN2B in the TG of CCI-ION mice significantly increased the HWT. Importantly, the 3'-untranslated region of Scn2b mRNA was proved to bind with miR-6954-3p. Fluorescence in situ hybridization and IF staining demonstrated that miR-6954-3p was expressed in TG neurons and co-expressed with SCN2B. Furthermore, intraganglionic injection of miR-6954-3p agomir into the TG of CCI-ION mice resulted in the downregulation of SCN2B and increased the HWT. These findings suggest that the downregulation of miR-6954-3p in the TG promotes orofacial neuropathic pain by promoting SCN2B expression following trigeminal nerve injury. PERSPECTIVE: This study points to the important role of SCN2B in orofacial neuropathic pain. Furthermore, miR-6954-3p is proven to regulate the expression of SCN2B by binding to the 3'-untranslated region of Scn2b mRNA. These findings indicate that SCN2B and miR-6954-3p are potential therapeutic targets for the treatment of orofacial neuropathic pain.

Newly discovered functions of miRNAs in neuropathic pain: Transitioning from recent discoveries to innovative underlying mechanisms

Neuropathic pain is a widespread clinical issue caused by somatosensory nervous system damage, affecting numerous individuals. It poses considerable economic and public health challenges, and managing it can be challenging due to unclear underlying mechanisms. Nevertheless, emerging evidence suggests that neurogenic inflammation and neuroinflammation play a role in developing pain patterns. Emerging evidence suggests that neurogenic inflammation and neuroinflammation play significant roles in developing neuropathic pain within the nervous system. Increased/decreased miRNA expression patterns could affect the progression of neuropathic and inflammatory pain by controlling nerve regeneration, neuroinflammation, and the expression of abnormal ion channels. However, our limited knowledge of miRNA targets hinders a complete grasp of miRNA's functions. Meanwhile, exploring exosomal miRNA, a recently uncovered role, has significantly advanced our comprehension of neuropathic pain's pathophysiology in recent times. In this review, we present a comprehensive overview of the latest miRNA studies and explore the possible ways miRNAs might play a role in the development of neuropathic pain.

NLR family pyrin domain containing 3 (NLRP3) inflammasomes and peripheral neuropathic pain - Emphasis on microRNAs (miRNAs) as important regulators

Neuropathic pain is caused by the lesion or disease of the somatosensory system and can be initiated and/or maintained by both central and peripheral mechanisms. Nerve injury leads to neuronal damage and apoptosis associated with the release of an array of pathogen- or damage-associated molecular patterns to activate inflammasomes. The activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome contributes to neuropathic pain and may represent a novel target for pain therapeutic development. In the current review, we provide an up-to-date summary of the recent findings on the involvement of NLRP3 inflammasome in modulating neuropathic pain development and maintenance, focusing on peripheral neuropathic conditions. Here we provide a detailed review of the mechanisms whereby NLRP3 inflammasomes contribute to neuropathic pain via (1) neuroinflammation, (2) apoptosis, (3) pyroptosis, (4) proinflammatory cytokine release, (5) mitochondrial dysfunction, and (6) oxidative stress. We then present the current research literature reporting on the antinociceptive effects of several natural products and pharmacological interventions that target activation, expression, and/or regulation of NLRP3 inflammasome. Furthermore, we emphasize the effects of microRNAs as another regulator of NLRP3 inflammasome. In conclusion, we summarize the possible caveats and future perspectives that might provide successful therapeutic approaches against NLRP3 inflammasome for treating or preventing neuropathic pain conditions.

The Role of miRNAs in Neuropathic Pain

Neuropathic pain is a debilitating condition affecting around 8% of the adult population in the UK. The pathophysiology is complex and involves a wide range of processes, including alteration of neuronal excitability and synaptic transmission, dysregulated intracellular signalling and activation of pro-inflammatory immune and glial cells. In the past 15 years, multiple miRNAs–small non-coding RNA–have emerged as regulators of neuropathic pain development. They act by binding to target mRNAs and preventing the translation into proteins. Due to their short sequence (around 22 nucleotides in length), they can have hundreds of targets and regulate several pathways. Several studies on animal models have highlighted numerous miRNAs that play a role in neuropathic pain development at various stages of the nociceptive pathways, including neuronal excitability, synaptic transmission, intracellular signalling and communication with non-neuronal cells. Studies on animal models do not always translate in the clinic; fewer studies on miRNAs have been performed involving human subjects with neuropathic pain, with differing results depending on the specific aetiology underlying neuropathic pain. Further studies using human tissue and liquid samples (serum, plasma, saliva) will help highlight miRNAs that are relevant to neuropathic pain diagnosis or treatment, as biomarkers or potential drug targets.

Emerging roles of miRNAs in neuropathic pain: From new findings to novel mechanisms

Neuropathic pain, which results from damage to the somatosensory nervous system, is a global clinical condition that affects many people. Neuropathic pain imposes significant economic and public health burdens and is often difficult to manage because the underlying mechanisms remain unclear. However, mounting evidence indicates a role for neurogenic inflammation and neuroinflammation in pain pattern development. There is increasing evidence that the activation of neurogenic inflammation and neuroinflammation in the nervous system contribute to neuropathic pain. Altered miRNA expression profiles might be involved in the pathogenesis of both inflammatory and neuropathic pain by regulating neuroinflammation, nerve regeneration, and abnormal ion channel expression. However, the lack of knowledge about miRNA target genes prevents a full understanding of the biological functions of miRNAs. At the same time, an extensive study on exosomal miRNA, a newly discovered role, has advanced our understanding of the pathophysiology of neuropathic pain in recent years. This section provides a comprehensive overview of the current understanding of miRNA research and discusses the potential mechanisms of miRNAs in neuropathic pain.

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.

Microvascular Barrier Protection by microRNA-183 via FoxO1 Repression: A Pathway Disturbed in Neuropathy and Complex Regional Pain Syndrome

Blood nerve barrier disruption and edema are common in neuropathic pain as well as in complex regional pain syndrome (CRPS). MicroRNAs (miRNA) are epigenetic multitarget switches controlling neuronal and non-neuronal cells in pain. The miR-183 complex attenuates hyperexcitability in nociceptors, but additional non-neuronal effects via transcription factors could contribute as well. This study explored exosomal miR-183 in CRPS and murine neuropathy, its effect on the microvascular barrier via transcription factor FoxO1 and tight junction protein claudin-5, and its antihyperalgesic potential. Sciatic miR-183 decreased after CCI. Substitution with perineural miR-183 mimic attenuated mechanical hypersensitivity and restored blood nerve barrier function. In vitro, serum from CCI mice und CRPS patients weakened the microvascular barrier of murine cerebellar endothelial cells, increased active FoxO1 and reduced claudin-5, concomitant with a lack of exosomal miR-183 in CRPS patients. Cellular stress also compromised the microvascular barrier which was rescued either by miR-183 mimic via FoxO1 repression or by prior silencing of Foxo1. PERSPECTIVE: Low miR-183 leading to barrier impairment via FoxO1 and subsequent claudin-5 suppression is a new aspect in the pathophysiology of CRPS and neuropathic pain. This pathway might help untangle the wide symptomatic range of CRPS and nurture further research into miRNA mimics or FoxO1 inhibitors.

METTL3 suppresses neuropathic pain via modulating N6-methyladenosine-dependent primary miR-150 processing

Methyltransferase-like 3 (METTL3)-modulated N6-methyladenosine (m6A) was recently identified as an important epigenetic regulation type during RNA processing and contributes to multiple pathological processes. Neuropathic pain (NP) is induced by a lesion of the somatosensory nervous system, and the detailed pathways by which METTL3/m6A regulated to modulate gene dysregulation and enable NP have remained unclear. Therefore, this study investigated the function of METTL3-mediated m6A methylation on miRNA maturation, and investigated how this regulation contributes to NP progression. A rat model characterized with typical NP was established by a spared nerve-injury (SNI) method. By analyzing the expression levels of METTL3 and m6A methylation, we found that METTL3, along with m6A methylation, was dramatically downregulated in NP rats in contrast to the sham ones. Functionally, enhanced METTL3 promoted the m6A methylation in total RNAs and inhibited NP progression, whereas silencing METTL3 suppressed m6A methylation and increased NP severity. Mechanistically, METTL3 accelerated miR-150 maturation via mediating m6A methylation of primiR-150 at locus 498, cooperating with the “m6A reader” YTHDF2. Meanwhile, miR-150 could directly target brain-derived neurotrophic factor (BDNF) mRNA, and the METTL3/miR-150/BDNF regulatory pathway was finally established. Clinically, we proved that serum METTL3 mRNA was also downregulated in Shingles patients with NP, suggesting its diagnostic potential. In conclusion, we demonstrated an essential function of METTL3-regulated N6-methyladenosine during NP progression via modulating primiR-150 maturation. Serum METTL3 could effectively differentiate NP patients from healthy people, and is useful for dynamic monitoring of diseases after treatment. Therefore, the METTL3/miR-150/BDNF pathway may be a promising therapeutic target for NP patients.

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

In numerous studies, microRNAs (miRNAs) have been authenticated to play vital roles in the pathophysiology of neuropathic pain and other neurological diseases. In our study, we focused on evaluating miR-378 and its potential effects in neuropathic pain development, as well as the underlying molecular mechanisms. Primarily, a chronic sciatic nerve injury (CCI) rat model was established. Next, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was employed to measure the expression levels of miR-378 and EZH2 mRNA; the EZH2 protein expression levels were detected by western blot. A luciferase activity assay monitored the interaction of miR-378 and EZH2. Mechanical and thermal hyperalgesia was also performed to quantitate the effects of overexpression of miR-378 or EZH2 on the CCI rats. We found that miR-378 was down-regulated in the CCI rats, and the overexpression of miR-378 produced significant relief in their pain management. EZH2 was the downstream gene of miR-378 and was negatively regulated by miR-378. The up-regulation of EZH2 reduced the inhibitory effects of miR-378 on the development of neuropathic pain in the CCI rats. miR-378 acts as an inhibitor in the progression of neuropathic pain via targeting EZH2; the miR-378/EZH2 axis may be a novel target for the diagnosis and therapy of neuropathic pain in clinical treatment.

TREK-1 potassium channels participate in acute and long-lasting nociceptive hypersensitivity induced by formalin in rats

TREK-1 channels are expressed in small nociceptive dorsal root ganglion (DRG) neurons where they participate in acute inflammatory and neuropathic pain. However, the role of TREK-1 in persistent pain is not well understood. The aim of this study was to investigate the local peripheral and spinal participation of TREK-1 in formalin-induced acute and long-lasting nociceptive hypersensitivity. Local peripheral or intrathecal pre-treatment with spadin, selective blocker of TREK-1, increased acute flinching behavior and secondary mechanical allodynia and hyperalgesia behavior observed 6 days after formalin injection. Local peripheral or intrathecal pre-treatment with BL-1249, selective opener of TREK-1, decreased long-lasting secondary mechanical allodynia and hyperalgesia induced by formalin. Pre-treatment with BL-1249 prevented the pro-nociceptive effect of spadin on acute nociception and long-lasting mechanical allodynia and hyperalgesia in rats. Pre-treatment with two recombinant channels that produce a high TREK-1 current, S300A and S333A (non-phosphorylated state of TREK-1), reduced formalin-induced acute pain and long-lasting mechanical allodynia and hyperalgesia. Besides, post-treatment with S300A, S333A or BL-1249 reversed long-lasting mechanical allodynia and hyperalgesia induced by formalin. Formalin increased TREK-1 expression at 1 and 6 days in DRG and dorsal spinal cord in rats, whereas that it increased c-fos expression at the DRG. Intrathecal repeated transfection of rats with S300A and S333A or injection with BL-1249 reduced formalin-induced enhanced c-fos expression. Data suggest that TREK-1 activity at peripheral and spinal sites reduces neuronal excitability in the process of acute and long-lasting nociception induced by formalin in rats.

Development of Non-opioid Analgesics Targeting Two-pore Domain Potassium Channels

Two-pore domain potassium (K2P) channels are a diverse family of potassium channels. K2P channels generate background leak potassium currents to regulate cellular excitability and are thereby involved in a wide range of neurological disorders. K2P channels are modulated by a variety of physicochemical factors such as mechanical stretch, temperature, and pH. In the the peripheral nervous system (PNS), K2P channels are widely expressed in nociceptive neurons and play a critical roles in pain perception. In this review, we summarize the recent advances in the pharmacological properties of K2P channels, with a focus on the exogenous small-molecule activators targeting K2P channels. We emphasize the subtype-selectivity, cellular and in vivo pharmacological properties of all the reported small-molecule activators. The key underlying analgesic mechanisms mediated by K2P are also summarized based on the data in the literature from studies using small-molecule activators and genetic knock-out animals. We discuss advantages and limitations of the translational perspectives of K2P in pain medicine and provide outstanding questions for future studies in the end.

TRPA1 involved in miR-141-5p-alleviated neuropathic pain induced by oxaliplatin

Oxaliplatin (OXA) is widely used to treat advanced colorectal cancer, but it can induce severe peripheral neuropathy. Accumulating evidence has shown that microRNAs (miRNAs) are closely linked to neuropathic pain induced by sciatic nerve lesion and spinal cord injury. However, the study on the role of miRNAs in OXA-induced neuropathic pain is rare and needs to be further investigated. The study is aiming to investigate the effects of miR-141-5p on OXA-induced neuropathic pain and its underlying mechanisms. The neuropathic pain rat model was built through intraperitoneal injection of OXA. Mechanical withdrawal threshold and tail withdrawal latency were measured. The expressions of miR-141-5p and TRPA1 in dorsal root ganglion were detected by qRT-PCR, western blot, and immunohistochemistry. The results indicated that OXA down-regulated the expression of miR-141-5p. By contrast, OXA significantly up-regulated the expression of TRPA1 mRNA and protein. Besides, intrathecal injection of miR-141-5p mimic attenuated OXA-induced neuropathic pain and reduced the expression of TRPA1, a predicted target of miR-141-5p. Collectively, the results suggest that TRPA1 may mediate miR-141-5p-alleviated neuropathic pain induced by OXA. Our findings provide a potential therapeutic target for OXA-induced neuropathic pain.

PKC- and PKA-dependent phosphorylation modulates TREK-1 function in naïve and neuropathic rats

PKC and PKA phosphorylation inhibit TREK-1 channels downstream of G_s protein-coupled receptor activation in vitro. However, the role of phosphorylation of TREK-1 in neuropathic pain is unknown. The purpose of this study was to investigate whether altered TREK-1 channel function by PKA and PKC modulators contributes to antiallodynia in neuropathic rats. Furthermore, we investigated if the in vitro described sites for PKC and PKA phosphorylation (S300 and S333, respectively) participate in the modulation of TREK-1 in naïve and neuropathic rats. L5/L6 spinal nerve ligation (SNL) induced tactile allodynia. Intrathecal injection of BL-1249 (TREK-1 activator) reversed nerve injury-induced tactile allodynia, whereas spadin (TREK-1 blocker) produced tactile allodynia in naïve rats and reversed the antiallodynic effect induced by BL-1249 in neuropathic rats. Intrathecal administration of rottlerin or Rp-cAMPs (PKC and PKA inhibitors, respectively) enhanced the antiallodynia observed with BL-1249 in neuropathic rats. In contrast, pretreatment with PdBu or forskolin (PKC and PKA activators, respectively) reduced the BL-1249-induced antiallodynia. Intrathecal injection of two high-activity TREK-1 recombinant channels, using a in vivo transfection method with lipofectamine, with mutations at PKC/PKA phosphosites (S300A and S333A) reversed tactile allodynia in neuropathic rats, with no effect in naïve rats. In contrast, transfection of two low-activity TREK-1 recombinant channels with phosphomimetic mutations at those sites (S300D and S333D) produced tactile allodynia in naïve rats and interfered with antiallodynic effects of rottlerin/BL-1249 or Rp-cAMPs/BL-1249. Data suggest that TREK-1 channel activity can be dynamically tuned in vivo by PKC/PKA to provoke allodynia and modulate its antiallodynic role in neuropathic pain.

miR‑183‑5p attenuates cerebral ischemia injury by negatively regulating PTEN

Cerebral ischemia is a common cerebrovascular disease caused by the occlusion of a cerebral blood vessel. MicroRNAs (miRNAs/miRs) are emerging regulators of various human diseases, including cerebral ischemia. Upregulation of miR‑183‑5p has been reported to alleviate liver injury induced by ischemia‑reperfusion (I/R). However, the effect of miR‑183‑5p on cerebral ischemia injury remains unknown. The present study evaluated the effects of miR‑183‑5p on ischemia injury using ischemic models of mouse brains exposed to transient middle cerebral artery occlusion and Neuro‑2A (N2A) neuroblastoma cells exposed to oxygen‑glucose‑deprivation (OGD) and subsequently reoxygenated. Ischemia was evaluated in mice using neurological function scores, cerebral edema, 2,3,5‑triphenyltetrazoliumchloride, Nissl and Fluoro‑Jade B staining assays. In addition, miR‑183‑5p expression, N2A cell viability and the expression levels of apoptosis‑associated proteins were detected by quantitative PCR, Cell Counting Kit‑8 assay, flow cytometry and western blotting. The association between miR‑183‑5p and phosphatase and tensin homolog (PTEN) was also confirmed by a luciferase reporter assay. The results revealed that miR‑183‑5p expression was decreased and brain damage was increased in ischemic mice compared with the sham group. Additionally, miR‑183‑5p levels were reduced, and apoptosis was increased in N2A cells exposed to ischemia compared with the control group. Following transfection with agomiR‑183‑5p, cerebral ischemic injury and apoptosis levels were reduced in the in vivo I/R stroke model and OGD‑induced N2A cells. In addition, PTEN was determined to be a target of miR‑183‑5p following elucidation of a direct binding site. Overexpression of PTEN reversed the miR‑183‑5p‑induced N2A cell apoptosis inhibition and survival after OGD. The results of the present study suggested that miR‑183‑5p reduced ischemic injury by negatively regulating PTEN, which may aid the development of a novel therapeutic strategy for cerebral ischemia.

NF-κB p65-dependent transcriptional regulation of histone deacetylase 2 contributes to the chronic constriction injury-induced neuropathic pain via the microRNA-183/TXNIP/NLRP3 axis

BACKGROUND

Neuropathic pain is related to the sustained activation of neuroglial cells and the production of proinflammatory cytokines in the spinal dorsal horn. However, the clinical efficacy of currently available treatments is very limited. The transcription factor nuclear factor κB (NF-κB) is a ubiquitously expressed protein family and considered to be crucial in autoimmunity. Thus, our study aimed to examine the influence of NF-κB p65 in chronic constriction injury (CCI)-induced neuropathic pain as well as its underlying mechanism.

METHODS

A rat model of neuropathic pain was established by CCI induction followed by isolation of microglial cells. The binding of NF-κB p65 to HDAC2, of miR-183 to TXNIP, and of TXNIP to NLRP3 was investigated. Expression of miR-183, NF-κB p65, HDAC2, TXNIP, and NLRP3 was determined with their functions in CCI rats and microglial cells analyzed by gain- and loss-of-function experiments.

RESULTS

NF-κB p65 and HDAC2 were upregulated while miR-183 was downregulated in the dorsal horn of the CCI rat spinal cord. NF-κB p65 was bound to the HDAC2 promoter and then increased its expression. HDAC2 reduced miR-183 expression by deacetylation of histone H4. Additionally, miR-183 negatively regulated TXNIP. Mechanistically, NF-κB p65 downregulated the miR-183 expression via the upregulation of HDAC2 and further induced inflammatory response by activating the TXNIP-NLRP3 inflammasome axis, thus aggravating the neuropathic pain in CCI rats and microglial cells.

CONCLUSION

These results revealed a novel transcriptional mechanism of interplay between NF-κB and HDAC2 focusing on neuropathic pain via the miR-183/TXNIP/NLRP3 axis.

Granulocyte Colony Stimulating Factor (GCSF) Can Attenuate Neuropathic Pain by Suppressing Monocyte Chemoattractant Protein-1 (MCP-1) Expression, through Upregulating the Early MicroRNA-122 Expression in the Dorsal Root Ganglia

Our previous animal studies and several human clinical trials have shown that granulocyte-colony stimulating factor (GCSF) can attenuate neuropathic pain through various mechanisms. GCSF itself is also a multipotent cytokine that can modulate microribonucleic acid (microRNA) expression profiles in vitro. In this study, we used the NanoString nCounter analysis system to screen the expression of different rodent microRNAs at early stage after nerve injury and studied the expression of related cytokines/chemokines in the dorsal root ganglia (DRGs) of rats that underwent chronic constriction injury (CCI) to explore the underlying mechanisms of the analgesic effects of GCSF. We found that microRNA-122 expression was downregulated by CCI; in contrast, GCSF treatment significantly upregulated microRNA-122 expression in the DRGs of CCI rats on the 1st day after nerve injury. We further studied the expression of different cytokines/chemokines (IL-1β, IL-6, and monocyte chemoattractant protein-1 (MCP-1)) that were modulated by microRNA-122. MCP-1 has been reported to participate in neuropathic pain development, and its expression on the DRGs of vehicle-treated CCI rats was significantly higher than that on the DRGs of sham-operated rats; in contrast, GCSF-treated rats exhibited significantly lower MCP-1 expression in the DRG than vehicle-treated rats on the 7th day after nerve injury. An early GCSF treatment can suppress MCP-1 expressions, through upregulating microRNA-122 expressions in the DRGs of CCI rats at an earlier stage, thus indirectly attenuating neuropathic pain development.

miR-183-3p suppresses proliferation and migration of keratinocyte in psoriasis by inhibiting GAB1

Background

MicroRNAs (miRNAs) target genes involved in the hyperproliferation of keratinocytes or immune dysfunction of psoriasis. This study prospectively determined the involvement of miR-183-3p in the pathogenesis of psoriasis.

Methods

Differentially expressed miR-183-3p between psoriatic lesional and non-lesional skin were determined by quantitative RT-PCR and in situ hybridization (ISH). CCK8 and wound healing assays were performed to assess cell viability and migration of human keratinocyte cell line (HaCaT). The target of miR-183-3p was validated by luciferase activity assay.

Results

Lower miR-183-3p expression was observed in psoriatic lesional skin compared to psoriatic non-lesional skin. MiR-183-3p over-expression inhibited the viability and migration of HaCaT cells, while inhibition of miR-183-3p promoted the viability and migration of HaCaT cells. Moreover, miR-183-3p could bind to the 3′ UTR of GAB1 (growth factor receptor binding 2-associated binding protein 1) and decrease the mRNA and protein expression of GAB1 in HaCaT cells. In addition, higher GAB1 expression was observed in psoriatic lesional skin than psoriatic non-lesional skin.

Conclusion

MiR-183-3p exhibited inhibition property in the proliferation and migration of HaCaT cells via down-regulation of GAB1, suggesting the potential therapeutic strategy for psoriasis.

Interactions Among lncRNAs/circRNAs, miRNAs, and mRNAs in Neuropathic Pain

Neuropathic pain (NP) is directly caused by an injury or disease of the somatosensory nervous system. It is a serious type of chronic pain that is a burden to the economy and public health. Although recent studies have improved our understanding of NP, its pathogenesis has not been fully elucidated. Noncoding RNAs, including lncRNAs, circRNAs, and miRNAs, are involved in the pathological development of NP through many mechanisms. In addition, extensive evidence suggests that novel regulatory mechanisms among lncRNAs/circRNAs, miRNAs, and mRNAs play a crucial role in the pathophysiological process of NP. In this review, we comprehensively summarize the regulatory relationship among lncRNAs/circRNAs, miRNAs, and mRNAs and emphasize the important role of the lncRNA/circRNA-miRNA-mRNA axis in NP.

Oxaliplatin-induced peripheral neuropathy: clinical features, mechanisms, prevention and treatment

Oxaliplatin (OXA) is a commonly used platinum-based chemotherapy drug for colorectal cancer. OXA-induced peripheral neurotoxcity (OIPN) is a comprehensive adverse reaction of OXA. OIPN can be divided into acute and chronic types according to clinical features and different mechanisms. The main clinical features of acute OIPN are cold-sensitive sensory symptoms and neuropathic pain in limbs. In addition to the above symptoms, chronic OIPN also produces autonomic nerve dysfunction. The most important mechanism involved in acute OIPN is the alteration of voltage-gated Na + channels, and nuclear DNA damage in chronic OIPN. There are some methods like reducing exposure to cold, calcium and magnesium salts, amifostine could be beneficial in acute OIPN prevention and dose modification, changing in schedule glutathione, duloxetine, selective serotonin reuptake inhibitors, carbonic anhydrase inhibitor in chronic OIPN prevention. Recent updates are provided in this article in relation to the clinical features, potential mechanisms, prevention and treatment of OIPN.

Non-coding RNAs in neuropathic pain

Neuro-immune alterations in the peripheral and central nervous system play a role in the pathophysiology of chronic pain in general, and members of the non-coding RNA (ncRNA) family, specifically the short, 22 nucleotide microRNAs (miRNAs) and the long non-coding RNAs (lncRNAs) act as master switches orchestrating both immune as well as neuronal processes. Several chronic disorders reveal unique ncRNA expression signatures, which recently generated big hopes for new perspectives for the development of diagnostic applications. lncRNAs may offer perspectives as candidates indicative of neuropathic pain in liquid biopsies. Numerous studies have provided novel mechanistic insight into the role of miRNAs in the molecular sequelae involved in the pathogenesis of neuropathic pain along the entire pain pathway. Specific processes within neurons, immune cells, and glia as the cellular components of the neuropathic pain triad and the communication paths between them are controlled by specific miRNAs. Therefore, nucleotide sequences mimicking or antagonizing miRNA actions can provide novel therapeutic strategies for pain treatment, provided their human homologues serve the same or similar functions. Increasing evidence also sheds light on the function of lncRNAs, which converge so far mainly on purinergic signalling pathways both in neurons and glia, and possibly even other ncRNA species that have not been explored so far.

MicroRNA-144 relieves chronic constriction injury-induced neuropathic pain via targeting RASA1

MicroRNAs (miRNAs) have been shown to participate in development of neuropathic pain. However, the role of microRNA-144 (miR-144) in neuropathic pain remains unclear. In the present study, we established a neuropathic pain mouse model via chronic constriction injury (CCI)-induction. The successful establishment of this model was confirmed via evaluation of paw withdrawal threshold (PWT) and paw withdrawal latency (PWL). By using this model, we found that miR-144 was significantly downregulated in CCI-induced neuropathic pain mice. In addition, intrathecal injection of miR-144 agomiR alleviated mechanical and thermal hyperalgesia in neuropathic pain mice as shown by the increased of PWT and PWL. Moreover, miR-144 negatively regulated neuroinflammation by decreasing the expression of proinflammatory mediators, including TNF-α (tumor necrosis factor-α), IL (interleukin)-1β, and IL-6, thus facilitating the inhibition of neuropathic pain development. Mechanistically, RASA1 (RAS P21 Protein Activator 1) was downregulated following the injection of agomiR-144, and was verified to be a target of miR-144. Furthermore, overexpression of RASA1 reversed the inhibitory effect of miR-144 on neuropathic pain. Therefore, the present study suggested that miR-144 has the potential to be explored as therapeutic target for treatment of neuropathic pain.

Upregulation of miR-183 represses neuropathic pain through inhibiton of MAP3K4 in CCI rat models

Many studies have verified that microRNAs contribute a lot to neuropathic pain progression. Furthermore, nerve-related inflammatory cytokines play vital roles in neuropathic pain progression. miR-183 has been identified to have a common relationship with multiple pathological diseases. However, the potential effects of miR-183 in the process of neuropathic pain remain undetermined. Therefore, we performed the current study with the purpose of finding the functions of miR-183 in neuropathic pain progression using a chronic sciatic nerve injury (CCI) rat model. We demonstrated that miR-183 expression levels were evidently reduced in CCI rats in contrast with the control group. Overexpression of miR-183 produced significant relief of mechanical hyperalgesia, as well as thermal hyperalgesia in CCI rats. Furthermore, neuropathic pain-correlated inflammatory cytokine expression levels containing interleukin-6 (IL-6) and interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2) were obviously inhibited by upregulation of miR-183. Meanwhile, dual-luciferase reporter assays showed MAP3K4 was a direct downstream gene of miR-183. The expression levels of MAP3K4 were modulated by the increased miR-183 negatively, which lead to the downregulation of IL-6, IL-1β, and COX-2, and then reduced neuropathic pain progression, respectively. Overall, our study pointed out that miR-183 was a part of the negative regulator which could relieve neuropathic pain by targeting MAP3K4. Thus it may provide a new clinical treatment for neuropathic pain patients clinical therapy.

Network and pathway-based analysis of microRNA role in neuropathic pain in rat models

The molecular mechanisms underlying neuropathic pain (NP) remain poorly understood. Emerging evidence has suggested the role of microRNAs (miRNAs) in the initiation and development of NP, but the specific effects of miRNAs in NP are largely unknown. Here, we use network- and pathway-based methods to investigate NP-induced miRNA changes and their biological functions by conducting a systematic search through multiple electronic databases. Thirty-seven articles meet the inclusion criteria. Venn analysis and target gene forecasting are performed and the results indicate that 167 overlapping target genes are co-regulated by five down-regulated miRNAs (rno-miR-183, rno-miR-96, rno-miR-30b, rno-miR-150 and rno-miR-206). Protein-protein interaction network analysis shows that 77 genes exhibit interactions, with cyclic adenosine monophosphate (cAMP)-dependent protein kinase catalytic subunit beta (degree = 11) and cAMP-response element binding protein 1 (degree = 10) having the highest connectivity degree. Gene ontology analysis shows that these target genes are enriched in neuron part, neuron projection, somatodendritic compartment and nervous system development. Moreover, analysis of Kyoto Encyclopedia of Genes and Genomes reveals that three pathways, namely, axon guidance, circadian entrainment and insulin secretion, are significantly enriched. In addition, rno-miR-183, rno-miR-96, rno-miR-30b, rno-miR-150 and rno-miR-206 are consistently down-regulated in the NP models, thus constituting the potential biomarkers of this disease. Characterizing these miRNAs and their target genes paves way for their future use in clinical practice.

Role of TREK-1 in Health and Disease, Focus on the Central Nervous System

TREK-1 is the most studied background K_2P channel. Its main role is to control cell excitability and maintain the membrane potential below the threshold of depolarization. TREK-1 is multi-regulated by a variety of physical and chemical stimuli which makes it a very promising and challenging target in the treatment of several pathologies. It is mainly expressed in the brain but also in heart, smooth muscle cells, endocrine pancreas, and prostate. In the nervous system, TREK-1 is involved in many physiological and pathological processes such as depression, neuroprotection, pain, and anesthesia. These properties explain why many laboratories and pharmaceutical companies have been focusing their research on screening and developing highly efficient modulators of TREK-1 channels. In this review, we summarize the different roles of TREK-1 that have been investigated so far in attempt to characterize pharmacological tools and new molecules to modulate cellular functions controlled by TREK-1.

MiR-206-3p alleviates chronic constriction injury-induced neuropathic pain through targeting HDAC4

It was identified that microRNAs were involved in the regulation of chronic neuropathic pain. However, the role of miR-206-3p in neuropathic pain was still unclear. In the current study, the role of miR-206-3p, a type of mature miR-206, in neuropathic pain was investigated. The potential mechanisms were also explored. We found that the expression of miR-206-3p decreased in the dorsal root ganglion (DRG) of chronic constriction sciatic nerve injury (CCI) rats, whereas the While histone deacetylase 4 (HDAC4) level increased. Further exploration showed that administration of a miR-206-3p mimic alleviated neuropathic pain and reduced the level of HDAC4, a predicted target of miR-206-3p. Overexpression of HDAC4 attenuated the effects of miR-206-3p on neuropathic pain. Our data revealed a miR-206-3p-HDAC4 signal that played a potentially important role in CCI-induced neuropathic pain.