Therapeutic Target For Neuropathic Pain Research Articles

Histone deacetylase as emerging pharmacological therapeutic target for neuropathic pain: From epigenetic to selective drugs.

Neuropathic pain remains a formidable challenge for modern medicine. The first-line pharmacological therapies exhibit limited efficacy and unfavorable side effect profiles, highlighting an unmet need for effective therapeutic medications. The past decades have witnessed an explosion in efforts to translate epigenetic concepts into pain therapy and shed light on epigenetics as a promising avenue for pain research. Recently, the aberrant activity of histone deacetylase (HDAC) has emerged as a key mechanism contributing to the development and maintenance of neuropathic pain. In this review, we highlight the distinctive role of specific HDAC subtypes in a cell-specific manner in pain nociception, and outline the recent experimental evidence supporting the therapeutic potential of HDACi in neuropathic pain. We have summarized studies of HDAC in neuropathic pain in Pubmed. HDACs, widely distributed in the neuronal and non-neuronal cells of the dorsal root ganglion and spinal cord, regulate gene expression by deacetylation of histone or non-histone proteins and involving in increased neuronal excitability and neuroinflammation, thus promoting peripheral and central sensitization. Importantly, pharmacological manipulation of aberrant acetylation using HDAC-targeted inhibitors (HDACi) has shown promising pain-relieving properties in various preclinical models of neuropathic pain. Yet, many of which exhibit low-specificity that may induce off-target toxicities, underscoring the necessity for the development of isoform-selective HDACi in pain management. Abnormally elevated HDACs promote neuronal excitability and neuroinflammation by epigenetically modulating pivotal gene expression in neuronal and immune cells, contributing to peripheral and central sensitization in the progression of neuropathic pain, and HDACi showed significant efficacy and great potential for alleviating neuropathic pain.

Tumor necrosis factor α-induced protein 8-like-2 controls microglia phenotype via metabolic reprogramming in BV2 microglial cells and responses to neuropathic pain

Microglial are major players in neuroinflammation that have recently emerged as potential therapeutic targets for neuropathic pain. Glucose metabolic programming has been linked to differential activation state and function in microglia. Tumor necrosis factor α-induced protein 8-like-2 (TNFAIP8L2) is an important component in regulating the anti-inflammatory response. However, the role of TNFAIP8L2 in microglia differential state during neuropathic pain and its interplay with glucose metabolic reprogramming in microglia has not yet been determined. Thus, we aimed to investigate the role of TNFAIP8L2 in the status of microglia in vitro and in vivo. BV2 microglial cells were treated with lipopolysaccharides plus interferon-gamma (LPS/IFNγ) or interleukin-4 (IL-4) to induce the two different phenotypes of microglia in vitro. In vivo experiments were conducted by chronic constriction injury of the sciatic nerve (CCI). We investigated whether TNFAIP8L2 regulates glucose metabolic programming in BV2 microglial cells. The data in vitro showed that TNFAIP8L2 lowers glycolysis and increases mitochondrial oxidative phosphorylation (OXPHOS) in inflammatory microglia. Blockade of glycolytic pathway abolished TNFAIP8L2-mediated differential activation of microglia. TNFAIP8L2 suppresses inflammatory microglial activation and promotes restorative microglial activation in BV2 microglial cells and in spinal cord microglia after neuropathic pain. Furthermore, TNFAIP8L2 controls differential activation of microglia and glucose metabolic reprogramming through the MAPK/mTOR/HIF-1α signaling axis. This study reveals that TNFAIP8L2 plays a critical role in neuropathic pain, providing important insights into glucose metabolic reprogramming and microglial phenotypic transition, which indicates that TNFAIP8L2 may be used as a potential drug target for the prevention of neuropathic pain.

MiR‑488‑3p alleviates neuropathic pain by regulating target gene ROCK1.

The function of microRNA (miRNA) in neuropathic pain (NP) has received widespread attention. The current research sought to address the contribution of miR‑488‑3p in NP and its downstream mechanisms. The NP rat model was constructed by chronic constriction injury (CCI) surgery in rats. Regulation of miR‑488‑3p or Rho‑associated coiled‑coil‑containing protein kinase 1 (ROCK1) in rats by intrathecal injection of lentivirus or plasmid. Real‑time quantitative reverse transcription polymerase chain reaction (RT‑qPCR) to examine the levels of miR‑488‑3p and ROCK1 in the dorsal root ganglion (DRG). Enzyme‑linked immunosorbent assay (ELISA) to monitor the secretion of pro‑inflammatory and anti‑inflammatory factors. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) for the evaluation of mechanosensitive and thermal nociceptive hypersensitivity of NP behaviors. Validation of molecular mechanism between miR‑488‑3p and ROCK1 using RNA immunoprecipitation assay and dual‑luciferase reporter (DLR) assay. miR‑488‑3p was vigorously less expressed in the DRGs of CCI rats, while ROCK1 was upregulated. Elevated miR‑488‑3p alleviated the decrease of PWL and PWT in CCI rats, inhibited the secretion of pro‑inflammatory factors, and enhanced anti‑inflammatory factors levels. Mechanistically, ROCK1 was the target of miR‑488‑3p. Raised ROCK1 partially attenuated the mitigating effect of miR‑488‑3p on NP behavior and the suppression of inflammatory responses in rats. Current research demonstrated that miR‑488‑3p may be a novel therapeutic target for NP.

TSLP in DRG neurons causes the development of neuropathic pain through T cells

BackgroundPeripheral nerve injury to dorsal root ganglion (DRG) neurons develops intractable neuropathic pain via induction of neuroinflammation. However, neuropathic pain is rare in the early life of rodents. Here, we aimed to identify a novel therapeutic target for neuropathic pain in adults by comprehensively analyzing the difference of gene expression changes between infant and adult rats after nerve injury.MethodsA neuropathic pain model was produced in neonatal and young adult rats by spared nerve injury. Nerve injury-induced gene expression changes in the dorsal root ganglion (DRG) were examined using RNA sequencing. Thymic stromal lymphopoietin (TSLP) and its siRNA were intrathecally injected. T cells were examined using immunofluorescence and were reduced by systemic administration of FTY720.ResultsDifferences in changes in the transcriptome in injured DRG between infant and adult rats were most associated with immunological functions. Notably, TSLP was markedly upregulated in DRG neurons in adult rats, but not in infant rats. TSLP caused mechanical allodynia in adult rats, whereas TSLP knockdown suppressed the development of neuropathic pain. TSLP promoted the infiltration of T cells into the injured DRG and organized the expressions of multiple factors that regulate T cells. Accordingly, TSLP caused mechanical allodynia through T cells in the DRG.ConclusionThis study demonstrated that TSLP is causally involved in the development of neuropathic pain through T cell recruitment.

Electroacupuncture Alleviates Neuropathic Pain by Suppressing Ferroptosis in Dorsal Root Ganglion via SAT1/ALOX15 Signaling.

Neuropathic pain affects globally about 7-10% of the general population. Electroacupuncture (EA) effectively relieves neuropathic pain symptoms without causing any side effects; however, the underlying molecular mechanisms remain unclear. We established a chronic constriction injury (CCI)-induced rat model of neuropathic pain. RNA sequencing was used to screen for differentially expressed genes in the dorsal root ganglion after CCI and EA treatment. We identified gene markers of ferroptosis spermidine/spermine N1-acetyltransferase 1 (Sat1) and arachidonate 15-lipoxygenase (Alox15) to be dysregulated in the CCI-induced neuropathic pain model. Furthermore, EA relieved CCI-induced pain as well as ferroptosis-related symptoms in the dorsal root ganglion, including lipid peroxidation and iron overload. Finally, SAT1 knockdown also alleviated mechanical and thermal pain hypersensitivity and reversed ferroptosis damage. In conclusion, we showed that EA inhibited ferroptosis by regulating the SAT1/ALOX15 pathway to treat neuropathic pain. Our findings provide insight into the mechanisms of EA and suggest a novel therapeutic target for neuropathic pain.

4-Cyanamido-substituted benzenesulfonamides act as dual carbonic anhydrase and cathepsin inhibitors

A set of novel N-cyano-N-substituted 4-aminobenzenesulfonamide derivatives were synthesized and investigated for their inhibitory activity against four cytosolic carbonic anhydrase (CA, EC 4.2.1.1) isoforms (hCA I, II, VII and XIII) and two cathepsins (S and B). N-alkyl/benzyl-substituted derivatives were revealed to be very potent inhibitors against brain-associated hCA VII, but inactive against both cathepsins. On the other hand, N-acyl-substituted derivatives displayed significant inhibitory activities against cathepsin S, but only moderate to poor inhibitory potency against hCA VII. Both hCA VII and cathepsin S have recently been validated as therapeutic targets in neuropathic pain. This study provided an excellent starting point for further structural optimization of this class of bifunctional compounds to enhance their inhibitory activity and selectivity against hCA VII and cathepsin S and to achieve new compounds with an attractive dual mechanism of action as anti-neuropathic agents.

Mitochondrial-Derived Peptide MOTS-c Ameliorates Spared Nerve Injury-Induced Neuropathic Pain in Mice by Inhibiting Microglia Activation and Neuronal Oxidative Damage in the Spinal Cord via the AMPK Pathway.

MOTS-c, a recently discovered mitochondrial-derived peptide, plays an important role in many physiological and pathological functions via adenosine monophosphate-activated protein kinase (AMPK) activation. Numerous studies have demonstrated that AMPK is an emerging target for the modulation of neuropathic pain. Meanwhile, microglia-activation-evoked neuroinflammation is known to contribute to the development and progression of neuropathic pain. MOTS-c is also known to inhibit microglia activation, chemokine and cytokine expression, and innate immune responses. Accordingly, in this study, we evaluated the effects of MOTS-c on neuropathic pain and investigated the putative underlying mechanisms. We found that MOTS-c levels in plasma and spinal dorsal horn were significantly lower in mice with spared nerve injury (SNI)-induced neuropathic pain than in control animals. Accordingly, MOTS-c treatment produced pronounced dose-dependent antinociceptive effects in SNI mice; however, these effects were blocked by dorsomorphin, an AMPK inhibitor, but not naloxone, a nonselective opioid receptor antagonist. Moreover, intrathecal (i.t.) injection of MOTS-c significantly enhanced AMPKα1/2 phosphorylation in the lumbar spinal cord of SNI mice. MOTS-c also significantly inhibited proinflammatory cytokine production and microglia activation in the spinal cord. The antinociceptive effects of MOTS-c were retained even when microglia activation in the spinal cord was inhibited by minocycline pretreatment, indicating that spinal cord microglia are dispensable for the antiallodynic effects of MOTS-c. In the spinal dorsal horn, MOTS-c treatment inhibited c-Fos expression and oxidative damage mainly in neurons rather than microglia. Finally, in contrast to morphine, i.t. administration of MOTS-c resulted in limited side effects relating to antinociceptive tolerance, gastrointestinal transit inhibition, locomotor function, and motor coordination. Collectively, the present study is the first to provide evidence that MOTS-c may be a promising therapeutic target for neuropathic pain.

LncRNA Kcnq1ot1relieves neuropathic pain through downregulation of Myd88.

Long non-coding RNAs (lncRNAs) have already been documented to become the therapeutic targets for neuropathic pain. Here, this work focused on exploring the specific mechanism underlying Kcnq1 overlapping transcript 1 (kcnq1ot1) in neuropathic pain. Sciatic nerve chronic constriction injury (CCI) in vivo and LPS-stimulated microglia BV2 cell injury in vitro were adopted to construct neuropathic pain models. Expressions of kcnq1ot1, MyD88, and microglia activation marker Iba-1 were measured. In this study, we carried out fluorescence in-situ Hybridization (FISH) and immunofluorescence for examining Kcnq1ot1 localization within microglial cells in mouse spinal dorsal horn. Subsequently, we evaluated binding between Kcnq1ot1 and Myd88, together with the expressions of IL-1β, IL-6, TNF-α, and Myd88 ubiquitination. Kcnq1ot1 levels decreased within CCI mice and LPS-induced BV2 cells. According to the results of FISH and immunofluorescence, Kcnq1ot1 is located in microglia. Overexpression of Kcnq1ot1 suppressed Iba-1, IL-1β, IL-6 together with TNF-α expression. RNA pull-down and RIP assay confirmed that Kcnq1ot1 bound to Myd88. In addition, Kcnq1ot1 overexpression promoted the degradation, enhanced the ubiquitination, and reduced protein level of Myd88. Overexpression of Myd88 eliminated the effects of Kcnq1ot1 overexpression on Iba-1level and production of pro-inflammatory cytokines. Further in vivo results revealed that increased Kcnq1ot1 level alleviated neuropathic pain and myelinated nerve fiber injury of CCI mice. Kcnq1ot1 downregulated Myd88 protein expression by binding to Myd88 and promoting its ubiquitination, which in turn suppressed microglia activation, pro-inflammatory cytokine production, and relieved neuropathic pain.

The Cytidine N-Acetyltransferase NAT10 Participates in Peripheral Nerve Injury-Induced Neuropathic Pain by Stabilizing SYT9 Expression in Primary Sensory Neurons.

RNA N4-acetylcytidine (ac4C) modification is increasingly recognized as an important layer of gene regulation; however, the involvement of ac4C in pain regulation has not been studied. Here, we report that N-acetyltransferase 10 protein (NAT10; the only known ac4C "writer") contributes to the induction and development of neuropathic pain in an ac4C-dependent manner. Peripheral nerve injury increases the levels of NAT10 expression and overall ac4C in injured dorsal root ganglia (DRGs). This upregulation is triggered by the activation of upstream transcription factor 1 (USF1), a transcription factor that binds to the Nat10 promoter. Knock-down or genetic deletion of NAT10 in the DRG abolishes the gain of ac4C sites in Syt9 mRNA and the augmentation of SYT9 protein, resulting in a marked antinociceptive effect in nerve-injured male mice. Conversely, mimicking NAT10 upregulation in the absence of injury evokes the elevation of Syt9 ac4C and SYT9 protein and induces the genesis of neuropathic-pain-like behaviors. These findings demonstrate that USF1-governed NAT10 regulates neuropathic pain by targeting Syt9 ac4C in peripheral nociceptive sensory neurons. Our findings establish NAT10 as a critical endogenous initiator of nociceptive behavior and a promising new target for treating neuropathic pain.SIGNIFICANCE STATEMENT The cytidine N4-acetylcytidine (ac4C), a new epigenetic RNA modification, is crucial for the translation and stability of mRNA, but its role for chronic pain remains unclear. Here, we demonstrate that N-acetyltransferase 10 (NAT10) acts as ac4C N-acetyltransferase and plays an important role in the development and maintenance of neuropathic pain. NAT10 was upregulated via the activation of the transcription factor upstream transcription factor 1 (USF1) in the injured dorsal root ganglion (DRG) after peripheral nerve injury. Since pharmacological or genetic deleting NAT10 in the DRG attenuated the nerve injury-induced nociceptive hypersensitivities partially through suppressing Syt9 mRNA ac4C and stabilizing SYT9 protein level, NAT10 may serve as an effective and novel therapeutic target for neuropathic pain.

Transcription factor ETS proto-oncogene 1 contributes to neuropathic pain by regulating histone deacetylase 1 in primary afferent neurons.

Nerve injury can induce aberrant changes in ion channels, enzymes, and cytokines/chemokines in the dorsal root ganglia (DRGs); these changes are due to or at least partly governed by transcription factors that contribute to the genesis of neuropathic pain. However, the involvement of transcription factors in neuropathic pain is poorly understood. In this study, we report that transcription factor (TF) ETS proto-oncogene 1 (ETS1) is required for the initiation and development of neuropathic pain. Sciatic nerve chronic constrictive injury (CCI, a clinical neuropathic pain model) increases ETS1 expression in the injured male mouse DRG. Blocking this upregulation alleviated CCI-induced mechanical allodynia and thermal hyperalgesia, with no apparent effect on locomotor function. Mimicking this upregulation results in the genesis of nociception hypersensitivity; mechanistically, nerve injury-induced ETS1 upregulation promotes the expression of histone deacetylase 1 (HDAC1, a key initiator of pain) via enhancing its binding activity to the HDAC1 promotor, leading to the elevation of spinal central sensitization, as evidenced by increased expression of p-ERK1/2 and GFAP in the dorsal spinal horn. It appears that the ETS1/HDAC1 axis in DRG may have a critical role in the development and maintenance of neuropathic pain, and ETS1 is a potential therapeutic target in neuropathic pain.

Gene expression signature of human neuropathic pain identified through transcriptome analysis.

Introduction: Neuropathic pain is a type of chronic pain that is characterized by ongoing discomfort and can be challenging to manage effectively. This study aimed to identify genes associated with neuropathic pain through transcriptome analysis in order to gain a better understanding of the mechanisms underlying this chronic, difficult-to-treat pain. Methods: We conducted transcriptome analysis using a training datasetof 202 individuals, including patients with neuropathic pain and healthy controls. Results: Our analysis identified five genes (GTF2H2, KLHL5, LRRC37A4P, PRR24, and MRPL23) that were significantly differentially expressed in the tissue of patients with neuropathic pain compared to controls. We constructed a neuropathic pain signature using these five genes and validated it using an independent dataset of 25 individuals. Receiver operating characteristic (ROC) curve analysis demonstrated that this signature had a high level of accuracy in differentiating between neuropathic pain patients and healthy controls, with an area under the curve (AUC) of 0.83 (95% CI 0.65-1). Discussion: These findings suggest that these five genes may be potential therapeutic targets for neuropathic pain.

Neuronal C-Reactive Protein/FcγRI Positive Feedback Proinflammatory Signaling Contributes to Nerve Injury Induced Neuropathic Pain.

Neuropathic pain is difficult to treat in clinical practice, and the underlying mechanisms are insufficiently elucidated. Previous studies have demonstrated that the neuronal Fc-gamma-receptor type I (FcγRI) of the dorsal root ganglion (DRG) mediates antigen-specific pain. However, the mechanisms of neuronal FcγRI in neuropathic pain remain to be explored. Here, it is found that the activation of FcγRI-related signals in primary neurons induces neuropathic pain in a rat model. This work first reveals that sciatic nerve injury persistently activates neuronal FcγRI-related signaling in the DRG, and conditional knockout (CKO) of the FcγRI-encoding gene Fcgr1 in rat DRG neurons significantly alleviates neuropathic pain after nerve injury. C-reactive protein (CRP) is increased in the DRG after nerve injury, and CRP protein of the DRG evokes pain by activating neuronal FcγRI-related signals. Furthermore, microinjection of naive IgG into the DRG alleviates neuropathic pain by suppressing the activation of neuronal FcγRI. These results indicate that the activation of neuronal CRP/FcγRI-related signaling plays an important role in the development of neuropathic pain in chronic constriction injury (CCI) rats. The findings may provide novel insights into the neuroimmune responses after peripheral nerve injury and suggest potential therapeutic targets for neuropathic pain.

Somatostatin Neurons from Periaqueductal Gray to Medulla Facilitate Neuropathic Pain in Male Mice

Projections from the periaqueductal gray (PAG) to the rostral ventromedial medulla (RVM) are known to engage in descending pain modulation, but how the neural substrates of the PAG-RVM projections contribute to neuropathic pain remains largely unknown. In this study, we showed somatostatin-expressing glutamatergic neurons in the lateral/ventrolateral PAG that facilitate mechanical and thermal hypersensitivity in a mouse model of chemotherapy-induced neuropathic pain. We found that these neurons form direct excitatory connections with neurons in the RVM region. Inhibition of this PAG-RVM projection alleviates mechanical and thermal hypersensitivity associated with neuropathy, whereas its activation enhances hypersensitivity in the mice. Thus, our findings revealed that somatostatin neurons within the PAG-RVM axial are crucial for descending pain facilitation and can potentially be exploited as a useful therapeutic target for neuropathic pain. PerspectiveWe report the profound contribution of somatostatin neurons within the PAG-RVM projections to descending pain facilitation underlying neuropathic pain. These results may help to develop central therapeutic strategies for neuropathic pain.

Investigating the Molecular Mechanisms Driving 7α,25‐dihydroxycholesterol‐GPR183‐Induced Hypersensitivity

Neuropathic pain is a debilitating health concern and there is an urgent need for non‐opioid analgesic targets. Our group has identified GPR183 as a novel potential therapeutic target for neuropathic pain. GPR183 is a G‐protein coupled receptor that promotes the migration of immune cells in response to its ligand, 7α,25‐dihydroxycholesterol (7α,25‐OHC). We have shown that GPR183 is upregulated in the dorsal horn spinal cord during neuropathic pain states in rodents and intrathecal injections of 7α,25‐OHC is able to induce allodynia in mice in a GPR183‐dependent manner. However, the mechanism by which GPR183 activation leads to pain is unknown. These studies aim to elucidate the molecular signaling pathways that contribute to 7α,25‐OHC‐induced hypersensitivity. Based on previous literature, we hypothesized that GPR183 activation in the spinal cord would activate mitogen‐activated protein kinases (MAPKs), extracellular signal‐regulated kinase (ERK) and p38, leading to the production of neuroexcitatory cytokines contributing to hypersensitivity.MethodsTo investigate the signaling pathways downstream of GPR183 activation in the spinal cord, we performed unbiased RNA‐Sequencing following intrathecal injections of 7α,25‐OHC with or without the GPR183 antagonist, SAE‐14, in male and female ICR mice. We then performed follow‐up studies giving pharmacological inhibitors of the identified pathways prior to intrathecal 7α,25‐OHC to confirm functional relevance. We also took spinal cord tissue for western blot and enzyme‐linked immunoassay (ELISA) analysis following intrathecal injections.ResultsThrough our unbiased RNA‐sequencing we found that many of the genes that were differentially regulated by GPR183 activation contain binding sites for NF‐κB or transcription factors that are regulated by the MAPK’s, ERK or p38. Additionally, we found that small molecule inhibitors of these pathways delayed 7α,25‐OHC‐induced mechanical allodynia. Importantly, the GPR183 antagonist, SAE‐14, blocked the 7α,25‐OHC‐induced upregulation of these pathways, including the upregulation of neuroexcitatory cytokines interleukin‐1β and tumor necrosis factor α.ConclusionThese findings provide novel insight into how spinal GPR183 signaling produces hypersensitivity and can contribute to neuropathic pain states.

Targeting Vascular endothelial growth factor A with soluble vascular endothelial growth factor receptor 1 ameliorates nerve injury-induced neuropathic pain.

Neuropathic pain is a distressing medical condition with few effective treatments. The role of Vascular endothelial growth factor A (VEGFA) in inflammation pain has been confirmed in many researches. However, the mechanism of VEGFA affects neuropathic pain remains unclear. In this study, we demonstrated that VEGFA plays an important role in spare nerve injury (SNI)-induced neuropathic pain, which is mediated by enhanced expression and colocalized of VEGFA, p-AKT and TRPV1 in SNI-induced neuropathic pain model. Soluble VEGFR1 (sFlt1) not only relieved mechanical hyperalgesia and the expression of inflammatory markers, but ameliorated the expression of VEGFA, VEGFR2, p-AKT, and TRPV1 in spinal cord. However, these effects of sFlt1 can be blocked by rpVEGFA and by 740 Y-P. Therefore, our study indication that targeting VEGFA with sFlt1 reduces neuropathic pain development via the AKT/TRPV1 pathway in SNI-induced nerve injury. This study elucidates a new therapeutic target for neuropathic pain.

Current Therapeutic Targets for Neuropathic Pain

Nociceptive ache signals the frame to capability or real tissue harm. By contrast, neuropathic ache, which ends from damage or harm to the worried system, persists lengthy in spite of everything symptoms and symptoms of the authentic damage have disappeared. This kind of maladaptive ache affords a full-size scientific problem, because it responds poorly or unpredictably to classical analgesics. There is likewise no single, uniformly well-tolerated drug this is reliably helpful. Neuropathic ache withinside the popular populace is expected to have a occurrence ranging among 3% and 17%. Most of the remedies for neuropathic ache have slight efficacy and gift aspect consequences that restriction their use; therefore, different healing strategies are wished for patients. In this article, the contemporary trendy of care treatment, the rising pharmacological strategies until date, and the preclinical research on novel promising healing alternatives could be reviewed.

Blocking NLRP3 inflammasome expression by RAS-like protein A mitigates neuropathic pain in chronic constriction injury rat models

Purpose: To investigate the role of RAS-like protein A (RalA) in lipopolysaccharide-induced inflammatory regulation in primary microglia of chronic constriction injury (CCI)-induced neuropathic pain in rat models.
 Methods: In vitro, overexpression (OE) of RalA was performed in rat microglia using transfection procedure, and then LPS was used to provoke the inflammatory phenotype. In vivo, the rat model of neuropathic pain was induced using CCI and treated with LV-RalA. Neuroinflammatory levels including the expressions of IL-1β, IL-6, and TNF-α were detected. Moreover, the expressions of NF-κB p65, thioredoxin-interacting protein (TXNIP) and NLR family pyrin domain-containing 3(NLRP3)were examined in CCI rats and microglial cells. Finally, the functional evaluation was determined via mechanical allodynia and thermal hyperalgesia assays.
 Results: The level of RalA decreased in the dorsal horn following CCI. OE of RalA in microglia after LPS insult and CCI-induced rat model significantly decreased the expressions of inflammation promoters (p < 0.05). Mechanistically, OE of RalA mitigated inflammatory response by inhibiting NF-κB/TXNIP/NLRP3 signaling pathway, thus attenuating neuropathic pain in microglial cells and CCI rats.
 Conclusion: These results indicate that the OE of RalA plays a protective role in CCI-induced neuropathic pain via NF-κB/TXNIP/ NLRP3 axis. These findings may provide a promising therapeutic target for neuropathic pain.

MiR-185-5p alleviates CCI-induced neuropathic pain by repressing NLRP3 inflammasome through dual targeting MyD88 and CXCR4

MicroRNAs (miRNAs) are important modulators in the evolvement and progression of neuropathic pain (NP). According to reports, miR-185-5p contributes to various diseases and inflammatory responses. However, it is not clear whether miR-185-5p mediates neuroinflammation and NP following chronic constrictive injury (CCI). The CCI model was constructed in rats to induce NP. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) were employed to evaluate pain threshold in CCI rats. The expression of miR-185-5p, GFAP, Iba1, Caspase-3-positive cells, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)-labeled apoptotic neurons, inflammatory mediators, including interleukin (IL)-6, IL-1β and tumor necrosis factor-α (TNF-α) in lumbar portion (L4-L6) of CCI rats were determined. Furthermore, the targets of miR-185-5p were predicted by the Starbase, and the binding association between miR-185-5p and MyD88, miR-185-5p and CXCR4 was verified by the dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. As shown by the data, miR-185-5p was distinctly reduced in L4-L6 spinal cord tissues of rats after CCI. Up-regulating miR-185-5p alleviated mechanical and thermal hyperalgesia, inactivated microglia and astrocytes accumulation, and abated the contents of IL-1β, IL-6 and TNF-α in L4-L6 spinal cord tissues of CCI rats. Bioinformatics analysis suggested that MyD88 and CXCR4 were potential target genes of miR-185-5p. Increasing miR-185-5p expression notably impeded the expression of MyD88, CXCR4 and NLRP3 inflammasome in BV2 microglia, while attenuating miR-185-5p expression exerted the opposite effects. Notably, down-regulating MyD88 and CXCR4 significantly enhanced the miR-185-5p-mediated anti-inflammatory effects, and reversed miR-185-5p inhibitor-mediated proinflammatory effects. Additionally, up-regulating miR-185-5p repressed BV2-induced neuronal apoptosis and increased neuronal viability. In conclusion, this study suggested that miR-185-5p chokes CCI-induced NP and neuroinflammation by targeting MyD88 and CXCR4, indicating that miR-186-5p is an underlying therapeutic target for NP.

Examination of the Novel Sigma-1 Receptor Antagonist, SI 1/28, for Antinociceptive and Anti-allodynic Efficacy against Multiple Types of Nociception with Fewer Liabilities of Use.

Neuropathic pain is a significant problem with few effective treatments lacking adverse effects. The sigma-1 receptor (S1R) is a potential therapeutic target for neuropathic pain, as antagonists for this receptor effectively ameliorate pain in both preclinical and clinical studies. The current research examines the antinociceptive and anti-allodynic efficacy of SI 1/28, a recently reported benzylpiperazine derivative and analog of the S1R antagonist SI 1/13, that was 423-fold more selective for S1R over the sigma-2 receptor (S2R). In addition, possible liabilities of respiration, sedation, and drug reinforcement caused by SI 1/28 have been evaluated. Inflammatory and chemical nociception, chronic nerve constriction injury (CCI) induced mechanical allodynia, and adverse effects of sedation in a rotarod assay, conditioned place preference (CPP), and changes in breath rate and locomotor activity were assessed after i.p. administration of SI 1/28. Pretreatment with SI 1/28 produced dose-dependent antinociception in the formalin test, with an ED50 (and 95% C.I.) value of 13.2 (7.42–28.3) mg/kg, i.p. Likewise, SI 1/28 produced dose-dependent antinociception against visceral nociception and anti-allodynia against CCI-induced neuropathic pain. SI 1/28 demonstrated no impairment of locomotor activity, conditioned place preference, or respiratory depression. In summary, SI 1/28 proved efficacious in the treatment of acute inflammatory pain and chronic neuropathy without liabilities at therapeutic doses, supporting the development of S1R antagonists as therapeutics for chronic pain.

Lysophosphatidic acids in cerebrospinal fluids: Potential biomarkers and therapeutic targets for neuropathic pain

Lysophosphatidic acids in cerebrospinal fluids: Potential biomarkers and therapeutic targets for neuropathic pain