scholarly journals Effect of PKC/NF-κB on the Regulation of P2X3 Receptor in Dorsal Root Ganglion in Rats with Sciatic Nerve Injury

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Xue Li ◽  
Jie Yuan ◽  
Xuan Yu ◽  
Qin Zhang ◽  
Bangyong Qin
Keyword(s):  
Neuropathic Pain ◽  
Dorsal Root ◽  
Regulatory Mechanism ◽  
Intrathecal Injection ◽  
Intrathecal Administration ◽  
Pyrrolidine Dithiocarbamate ◽  
Withdrawal Threshold ◽  
Protein Levels ◽  
Kinase C ◽  
Mutual Regulation

Background. Protein kinase C (PKC), nuclear factor-kappa B p65 (NF-κB p65), and P2X3 receptor (P2X3R) play significant roles in the sensitization and transduction of nociceptive signals, which are considered as potential targets for the treatment of neuropathic pain. However, the mechanisms and relationships among them have not been clearly clarified. Methods. 80 rats were randomized and divided into 10 groups (n = 8). Sciatic chronic constriction injury (CCI) rats were intrathecally administered with bisindolylmaleimide I (GF109203X), a PKC-selective antagonist once a day, or pyrrolidine dithiocarbamate (PDTC), an NF-κB inhibitor twice a day. Sham-operated rats were intrathecally administered with saline. Thermal withdrawal latency (TWL) and mechanical withdrawal threshold (MWT) were evaluated in all the groups before CCI operation (baseline) and on the 1st, 3rd, 7th, 10th, and 14th day after CCI operation. Protein levels of p-PKCα, p-NF-κB p65, and P2X3R were analyzed in the CCI ipsilateral L4–6 dorsal root ganglions (DRGs). Results. Intrathecal injection of GF109203X or PDTC alleviated the TWL and MWT in the following 2 weeks after CCI surgery. The protein levels of p-PKCα, p-NF-κB p65, and P2X3R in the ipsilateral DRGs significantly increased after CCI operation, which could be partly reversed by intrathecal administration of GF109203X or PDTC. Conclusion. The upregulation of p-PKCα, p-NF-κB p65, and P2X3R expression in the DRGs of CCI rats was involved in the occurrence and development of neuropathic pain. Phosphorylated PKCα and phosphorylated NF-κB p65 regulated with each other. Phosphorylated NF-κB p65 and PKCα have a mutual regulation relationship with P2X3R, respectively, while the specific regulatory mechanism needs further research.

Oxaliplatin Regulates Chemotherapy Induced Peripheral Neuropathic Pain in the Dorsal Horn and Dorsal Root Ganglion via the Calcineurin/NFAT Pathway

2018 ◽  
Vol 18 (8) ◽  
pp. 1197-1207 ◽  
Author(s):  
Wan Huang ◽  
Jingxiu Huang ◽  
Yu Jiang ◽  
Xuanwei Huang ◽  
Wei Xing ◽  
...  
Keyword(s):  
Neuropathic Pain ◽  
Dorsal Root Ganglion ◽  
Dorsal Horn ◽  
Rat Model ◽  
Dorsal Root ◽  
Mrna Level ◽  
Control Group ◽  
Activated T Cells ◽  
Withdrawal Threshold ◽  
Protein Levels

Objective: The aim of this study was to investigate the mechanism of oxaliplatin in the induction of neuropathic pain as a symptom of Chemotherapy-Induced Peripheral Neuropathy (CIPN). Methods: The CIPN rat model was induced with a one-time injection of oxaliplatin, and the paw withdrawal response was determined using von Frey filaments. The Paw Withdrawal Threshold (PWT) value was recorded and the Dorsal Horn (DH) and Dorsal Root Ganglion (DRG) tissues were collected. The mRNA and protein levels of Calcineurin (CaN), Nuclear Factor of Activated T cells (NFAT), and other relevant cytokines were determined. CaN and NFAT inhibition reagents, FK506 and 11R-VIVIT, were applied in order to investigate the functions of the CaN/NFAT pathway in the neuropathic pain processes. The levels of the downstream inflammatory cytokines, TNF-α and IL-1β, were assessed by ELISA. Results: The application of oxaliplatin reduced the value of PWT by 4 times on days 7（4±1.33）and 14（5.13±3.07）compared with the control group(14±0.91; 13.67±0.76). After treatment, the CaN mRNA level decreased and that of NFAT increased in DH and DRG tissues (P<0.05). However, treatment with FK506 and 11R-VIVIT decreased the value of PWT that had increased after oxaliplatin treatment. The expression of downstream cytokines related to the CaN/NFAT pathway increased, including CCR2, COX2, p-ERK, and p-P38 (all p<0.05). In addition, when the CaN/NFAT pathway was activated, the concentration of TNFα increased to 40pg/mg in DH tissues and 60pg/mg in DRG tissues compared with the control group, while the concentration of IL-1β increased to over 60pg/mg in DH and DRG tissues. Conclusion: It was the first time to prove that oxaliplatin-induced neuropathic pain was correlated to the activation of the CaN/NFAT pathway in our rat model. This finding can provide a new direction to explore the mechanism of oxaliplatin-induced neuropathic pain.

scholarly journals Oral Gabapentin Activates Spinal Cholinergic Circuits to Reduce Hypersensitivity after Peripheral Nerve Injury and Interacts Synergistically with Oral Donepezil

2007 ◽  
Vol 106 (6) ◽  
pp. 1213-1219 ◽  
Author(s):  
Ken-ichiro Hayashida ◽  
Renée Parker ◽  
James C. Eisenach
Keyword(s):  
Neuropathic Pain ◽  
Nerve Injury ◽  
Intrathecal Injection ◽  
Spinal Nerve ◽  
Male Rats ◽  
Additive Interaction ◽  
Alzheimer Dementia ◽  
Routes Of Administration ◽  
Withdrawal Threshold ◽  
The Brain

Background Gabapentin administration into the brain of mice reduces nerve injury-induced hypersensitivity and is blocked by intrathecal atropine and enhanced by intrathecal neostigmine. The authors tested the relevance of these findings to oral therapy by examining the efficacy of oral gabapentin to reduce hypersensitivity after nerve injury in rats and its interaction with the clinically used cholinesterase inhibitor, donepezil. Methods Male rats with hypersensitivity after spinal nerve ligation received gabapentin orally, intrathecally, and intracerebroventricularly with or without intrathecal atropine, and withdrawal threshold to paw pressure was determined. The effects of oral gabapentin and donepezil alone and in combination on withdrawal threshold were determined in an isobolographic design. Results Gabapentin reduced hypersensitivity to paw pressure by all routes of administration, and was more potent and with a quicker onset after intracerebroventricular than intrathecal injection. Intrathecal atropine reversed the effect of intracerebroventricular and oral gabapentin. Oral gabapentin and donepezil interacted in a strongly synergistic manner, with an observed efficacy at one tenth the predicted dose of an additive interaction. The gabapentin-donepezil combination was reversed by intrathecal atropine. Conclusions Although gabapentin may relieve neuropathic pain by actions at many sites, these results suggest that its actions in the brain to cause spinal cholinergic activation predominate after oral administration. Side effects, particularly nausea, cannot be accurately determined on rats. Nevertheless, oral donepezil is well tolerated by patients in the treatment of Alzheimer dementia, and the current study provides the rationale for clinical study of combination of gabapentin and donepezil to treat neuropathic pain.

scholarly journals Microglial BDNF, PI3K, and p-ERK in the Spinal Cord Are Suppressed by Pulsed Radiofrequency on Dorsal Root Ganglion to Ease SNI-Induced Neuropathic Pain in Rats

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Xueru Xu ◽  
Shaoxiong Fu ◽  
Xiaomei Shi ◽  
Rongguo Liu
Keyword(s):  
Spinal Cord ◽  
Neuropathic Pain ◽  
Dorsal Root Ganglion ◽  
Nerve Injury ◽  
Calcium Binding ◽  
Dorsal Root ◽  
Intrathecal Injection ◽  
Pulsed Radiofrequency ◽  
Erk Phosphorylation ◽  
Extracellular Signal

Background. Pulsed radiofrequency (PRF) on the dorsal root ganglion (DRG) has been applied to alleviate neuropathic pain effectively, yet the mechanisms underlying pain reduction owing to this treatment are not clarified completely. The activated microglia, brain-derived neurotrophic factor (BDNF), phosphatidylinositol 3-kinase (PI3K), and phosphorylated extracellular signal-regulated kinase (p-ERK) in the spinal cord were demonstrated to be involved in developing neuropathic pain. Also, it has been just known that PRF on DRG inhibits the microglial activation in nerve injury rats. Here, we aim to investigate whether PRF treatment could regulate the levels of BDNF, PI3K, and p-ERK in the spinal cord of rats with spared nerve injury (SNI) via suppressing the spinal microglia activation to ease neuropathic pain. Methods. The rats with SNI were intrathecally treated with minocycline (specific microglia inhibitor) or same volume of dimethyl sulfoxide once daily, beginning from 1 h before nerve transection to 7 days. PRF was applied adjacent to the L4-L5 DRG of rats with SNI at 45 V for 6 min on the seventh postoperative day, whereas the free-PRF rats were treated without PRF. The withdrawal thresholds were studied, and the spinal levels of ionized calcium-binding adapter molecule 1 (Iba1), BDNF, PI3K, and p-ERK were calculated by western blot analysis, reverse transcription-polymerase chain reaction, and immunofluorescence. Results. The paw withdrawal mechanical threshold and paw withdrawal thermal latency decreased in the ipsilateral hind paws after SNI, and the spinal levels of Iba1, BDNF, PI3K, and p-ERK increased on day 21 after SNI compared with baseline (P<0.01). An intrathecal injection of minocycline led to the reversal of SNI-induced allodynia and increase in levels of Iba1, BDNF, PI3K, and p-ERK. Withdrawal thresholds recovered partially after a single PRF treatment for 14 days, and SNI-induced microglia hyperactivity, BDNF upregulation, and PI3K and ERK phosphorylation in the spinal cord reduced on D14 due to the PRF procedure. Conclusion. Microglial BDNF, PI3K, and p-ERK in the spinal cord are suppressed by the therapy of PRF on DRG to ease SNI-induced neuropathic pain in rats.

scholarly journals The fibroblast-derived protein PI16 controls neuropathic pain

2020 ◽  
Vol 117 (10) ◽  
pp. 5463-5471 ◽  
Author(s):  
Pooja Singhmar ◽  
Ronnie The Phong Trinh ◽  
Jiacheng Ma ◽  
XiaoJiao Huo ◽  
Bo Peng ◽  
...  
Keyword(s):  
Neuropathic Pain ◽  
Dorsal Root ◽  
Clinical Problem ◽  
Endothelial Barrier ◽  
Leukocyte Infiltration ◽  
Spared Nerve Injury ◽  
Protein Levels ◽  
Major Clinical Problem

Chronic pain is a major clinical problem of which the mechanisms are incompletely understood. Here, we describe the concept that PI16, a protein of unknown function mainly produced by fibroblasts, controls neuropathic pain. The spared nerve injury (SNI) model of neuropathic pain increases PI16 protein levels in fibroblasts in dorsal root ganglia (DRG) meninges and in the epi/perineurium of the sciatic nerve. We did not detect PI16 expression in neurons or glia in spinal cord, DRG, and nerve. Mice deficient in PI16 are protected against neuropathic pain. In vitro, PI16 promotes transendothelial leukocyte migration. In vivo, Pi16−/− mice show reduced endothelial barrier permeability, lower leukocyte infiltration and reduced activation of the endothelial barrier regulator MLCK, and reduced phosphorylation of its substrate MLC2 in response to SNI. In summary, our findings support a model in which PI16 promotes neuropathic pain by mediating a cross-talk between fibroblasts and the endothelial barrier leading to barrier opening, cellular influx, and increased pain. Its key role in neuropathic pain and its limited cellular and tissue distribution makes PI16 an attractive target for pain management.

scholarly journals Intrathecal injection of bone marrow stromal cells attenuates neuropathic pain via inhibition of P2X4R in spinal cord microglia

2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Yongbo Teng ◽  
Yang Zhang ◽  
Shouwei Yue ◽  
Huanwen Chen ◽  
Yujuan Qu ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Bone Marrow ◽  
Neuropathic Pain ◽  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Purinergic Receptor ◽  
Intrathecal Injection ◽  
Transient Receptor Potential Vanilloid ◽  
Drg Neurons ◽  
Analgesic Effects

Abstract Background Neuropathic pain is one of the most debilitating of all chronic pain syndromes. Intrathecal (i.t.) bone marrow stromal cell (BMSC) injections have a favorable safety profile; however, results have been inconsistent, and complete understanding of how BMSCs affect neuropathic pain remains elusive. Methods We evaluated the analgesic effect of BMSCs on neuropathic pain in a chronic compression of the dorsal root ganglion (CCD) model. We analyzed the effect of BMSCs on microglia reactivity and expression of purinergic receptor P2X4 (P2X4R). Furthermore, we assessed the effect of BMSCs on the expression of transient receptor potential vanilloid 4 (TRPV4), a key molecule in the pathogenesis of neuropathic pain, in dorsal root ganglion (DRG) neurons. Results I.t. BMSC transiently but significantly ameliorated neuropathic pain behavior (37.6% reduction for 2 days). We found no evidence of BMSC infiltration into the spinal cord parenchyma or DRGs, and we also demonstrated that intrathecal injection of BMSC-lysates provides similar relief. These findings suggest that the analgesic effects of i.t. BMSC were largely due to the release of BMSC-derived factors into the intrathecal space. Mechanistically, we found that while i.t. BMSCs did not change TRPV4 expression in DRG neurons, there was a significant reduction of P2X4R expression in the spinal cord microglia. BMSC-lysate also reduced P2X4R expression in activated microglia in vitro. Coadministration of additional pharmacological interventions targeting P2X4R confirmed that modulation of P2X4R might be a key mechanism for the analgesic effects of i.t. BMSC. Conclusion Altogether, our results suggest that i.t. BMSC is an effective and safe treatment of neuropathic pain and provides novel evidence that BMSC’s analgesic effects are largely mediated by the release of BMSC-derived factors resulting in microglial P2X4R downregulation.

Effects of low- and high-frequency electroacupuncture on protein expression and distribution of TRPV1 and P2X3 in rats with peripheral nerve injury

2020 ◽  
pp. 096452842096884
Author(s):  
Junying Du ◽  
Junfan Fang ◽  
Xuaner Xiang ◽  
Jie Yu ◽  
Xiaoqin Le ◽  
...  
Keyword(s):  
Neuropathic Pain ◽  
Protein Expression ◽  
Nerve Injury ◽  
Transient Receptor Potential ◽  
Intrathecal Injection ◽  
Receptor Potential ◽  
P2x Receptor ◽  
Sprague Dawley ◽  
Withdrawal Threshold ◽  
Analgesic Effects

Background: Whether electroacupuncture (EA) stimulation at different frequencies has a similar effect on spared nerve injury (SNI) as other neuropathic pain models, and how EA at different frequencies causes distinct analgesic effects on neuropathic pain is still not clear. Methods: Adult male Sprague-Dawley rats were randomly divided into sham SNI, SNI, 2 Hz, 100 Hz and sham EA groups. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) were measured. EA was performed once a day on days 1 to 14 after SNI. The expressions of transient receptor potential cation subfamily V member 1 (TRPV1) and peripheral purinergic P2X receptor 3 (P2X3) were determined by western blotting and immunofluorescence. TRPV1 siRNA and P2X3 siRNA were administered by intrathecal injection. TRPV1 or P2X3 agonists were combined with EA. Results: There were significant decreases in PWT, but no changes in PWL in the 14 days after SNI. EA using 2- or 100-Hz stimulation similarly increased PWT at every time point. The cytosol protein expression of P2X3 in the L4–L6 dorsal root ganglia (DRG) increased, but the expression of TRPV1 decreased in the SNI model. Both these effects were ameliorated by EA, with 2-Hz stimulation having a stronger effect than 100-Hz stimulation. Blocking either TRPV1 or P2X3 specific siRNAs attenuated the decreased PWT induced by SNI. Administration of either a TRPV1 or P2X3 agonist inhibited EA analgesia. Conclusion: 2- and 100-Hz EA similarly induced analgesic effects in SNI. This effect was related to up-regulation and down-regulation, respectively, of cytosol protein expression of P2X3 and TRPV1 in L4–L6 DRG, with 2 Hz having a better effect than 100 Hz.

scholarly journals Effect of TRPV4-p38 MAPK Pathway on Neuropathic Pain in Rats with Chronic Compression of the Dorsal Root Ganglion

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Yu-Juan Qu ◽  
Xiao Zhang ◽  
Zhen-Zhen Fan ◽  
Juan Huai ◽  
Yong-Bo Teng ◽  
...  
Keyword(s):  
Neuropathic Pain ◽  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Mechanical Allodynia ◽  
Mapk Pathway ◽  
Intrathecal Injection ◽  
Ruthenium Red ◽  
Protein Expressions ◽  
Intermediary Role ◽  
Ectopic Discharges

The aim of this study was to investigate the relationships among TRPV4, p38, and neuropathic pain in a rat model of chronic compression of the dorsal root ganglion. Mechanical allodynia appeared after CCD surgery, enhanced via the intrathecal injection of 4α-phorbol 12,13-didecanoate (4α-PDD, an agonist of TRPV4) and anisomycin (an agonist of p38), but was suppressed by Ruthenium Red (RR, an inhibitor of TRPV4) and SB203580 (an inhibitor of p38). The protein expressions of p38 and P-p38 were upregulated by 4α-PDD and anisomycin injection but reduced by RR and SB203580. Moreover, TRPV4 was upregulated by 4α-PDD and SB203580 and downregulated by RR and anisomycin. In DRG tissues, the numbers of TRPV4- or p38-positive small neurons were significantly changed in CCD rats, increased by the agonists, and decreased by the inhibitors. The amplitudes of ectopic discharges were increased by 4α-PDD and anisomycin but decreased by RR and SB203580. Collectively, these results support the link between TRPV4 and p38 and their intermediary role for neuropathic pain in rats with chronic compression of the dorsal root ganglion.

scholarly journals Divanillyl sulfone suppresses NLRP3 inflammasome activation via inducing mitophagy to ameliorate chronic neuropathic pain in mice

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Shuai Shao ◽  
Cheng-Bo Xu ◽  
Cheng-Juan Chen ◽  
Gao-Na Shi ◽  
Qing-Lan Guo ◽  
...  
Keyword(s):  
Neuropathic Pain ◽  
Nlrp3 Inflammasome ◽  
Intrathecal Injection ◽  
Beclin 1 ◽  
Inflammasome Activation ◽  
Chronic Neuropathic Pain ◽  
Withdrawal Threshold ◽  
Caspase 1 ◽  
Nlrp3 Inflammasome Activation ◽  
Related Proteins

Abstract Background Chronic neuropathic pain is a frequent sequel to peripheral nerve injury and maladaptive nervous system function. Divanillyl sulfone (DS), a novel structural derivative of 4,4′-dihydroxydibenzyl sulfoxide from a traditional Chinese medicine Gastrodia elata with anti-nociceptive effects, significantly alleviated neuropathic pain following intrathecal injection. Here, we aimed to investigate the underlying mechanisms of DS against neuropathic pain. Methods A chronic constrictive injury (CCI) mouse model of neuropathic pain induced by sciatic nerve ligation was performed to evaluate the effect of DS by measuring the limb withdrawal using Von Frey filament test. Immunofluorescence staining was used to assess the cell localizations and expressions of Iba-1, ASC, NLRP3, and ROS, the formation of autolysosome. The levels of NLRP3-related proteins (caspase-1, NLRP3, and IL-1β), mitophagy-related proteins (LC3, Beclin-1, and p62), and apoptosis-related proteins (Bcl-XL and Bax) were detected by Western blotting. The apoptosis of BV-2 cell and caspase activity were evaluated by flow cytometry. Results DS significantly alleviated the neuropathic pain by increasing the mechanical withdrawal threshold and inhibiting the activation of NLRP3 in CCI-induced model mice. Our findings indicated that DS promoted the mitophagy by increasing the LC3II and Beclin 1 and decreasing the levels of p62 protein in BV-2 cell. This is accompanied by the inhibition of NLRP3 activation, which was shown as inhibited the expression of NLRP3 in lysates as well as the secretion of mature caspase-1 p10 and IL-1β p17 in supernatants in cultured BV-2 microglia. In addition, DS could promote mitophagy-induced improvement of dysfunctional mitochondria by clearing intracellular ROS and restoring mitochondrial membrane potential. Conclusion Together, our findings demonstrated that DS ameliorate chronic neuropathic pain in mice by suppressing NLRP3 inflammasome activation induced by mitophagy in microglia. DS may be a promising therapeutic agent for chronic neuropathic pain.

scholarly journals Pulsed Radiofrequency on Dorsal Root Ganglion Improves Neuropathic Pain-induced Depression in SNI Rats by Regulating Hippocampal BDNF and Neuroinflammation via Spinal IRF8 Inactivation

2021 ◽  
Author(s):  
Xueru Xu ◽  
Zhisen Dai ◽  
Chun Lin ◽  
Fan Lin ◽  
Rongguo Liu
Keyword(s):  
Neuropathic Pain ◽  
Dorsal Root Ganglion ◽  
Nerve Injury ◽  
Dorsal Root ◽  
Intrathecal Injection ◽  
Free Water ◽  
Sucrose Preference ◽  
Pulsed Radiofrequency ◽  
Tnf Α ◽  
Immobility Time

Abstract Background: Increasing evidence suggests that neuroglia, neuroimmune, and neuroinflammatory processes are involved in the development of nerve injury-induced pain and depression. Interferon regulatory factor 8 (IRF8), a crucial factor for microglial activation, is essential for the development of neuropathic pain. The brain-derived neurotrophic factor (BDNF) and inflammatory mediators (IL-1β, IL-6, and TNF-α) in the hippocampus contribute to the pathophysiology of neuropathic pain-depression comorbidity. Our previous study found that depressive-like behaviors induced by spared nerve injury (SNI) could be improved by applying pulsed radiofrequency (PRF) to the dorsal root ganglion (DRG) (PRF-DRG). However, the anti-depressive mechanisms of PRF-DRG therapy remain largely unknown. Methods: All rats (except for those in the sham group) were subjected to SNI. The nuclease-free water group and the IRF8 siRNA group were intrathecally injected with nuclease-free water and IRF8 siRNA on days 5 and 6 after SNI, respectively. PRF therapy on the L5 DRG was performed in the PRF group on day 7 after SNI, whereas no PRF current was delivered in the Sham-PRF group. The 50% paw withdrawal threshold, forced swimming test, and sucrose preference test were performed. The expression levels of spinal IRF8 and hippocampal BDNF were tested by molecular biochemistry, while IL-1β, IL-6, and TNF-α were tested by ELISA.Results: The depressive-like behaviors induced by SNI were remarkably developed in rats, which was indicated by a significant reduction in the sucrose preference rate and prolonged immobility time on day 42 after SNI. Mechanical allodynia and depression-like behaviors of rats with SNI were remarkably improved after PRF-DRG or intrathecal IRF8 siRNA. Spinal IRF8 overexpression, hippocampal BDNF downregulation, and increased hippocampal IL-1β and TNF-α levels were reversed by PRF-DRG, similar to the intrathecal injection of IRF8 siRNA. Conclusions: PRF-DRG therapy could regulate neuroimmune and neuroinflammatory responses to improve pain-induced depressive-like behaviors. The beneficial effect was correlated with the upregulation of BDNF and inhibition of IL-1β and TNF-α in the hippocampus via spinal IRF8 inactivation.

scholarly journals Intrathecal IGF2 siRNA injection provides long-lasting anti-allodynic effect in a spared nerve injury rat model of neuropathic pain

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0260887
Author(s):  
Wei-Hung Chan ◽  
Nian-Cih Huang ◽  
Yi-Wen Lin ◽  
Feng-Yen Lin ◽  
Chien-Sung Tsai ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Neuropathic Pain ◽  
Protein Expression ◽  
Nerve Injury ◽  
Quantitative Polymerase Chain Reaction ◽  
Response Duration ◽  
Intrathecal Administration ◽  
Significant Inhibition ◽  
Spared Nerve Injury ◽  
Withdrawal Threshold

Previous studies have shown an increase of insulin-like growth factor-2 (IGF2) in animal models of neuropathic pain. We aimed to examine the hypothesis that reducing the expression of IGF2 using intrathecal IGF2 small-interfering RNA (siRNA) would attenuate the development of neuropathic pain in rats after spared nerve injury (SNI). Male Wistar rats were divided into three groups: sham-operated group, in which surgery was performed to cut the muscles without injuring the nerves; SNI group, in which SNI surgery was performed to sever the nerves; and SNI + siRNA IGF2 group, in which SNI surgery was performed, and IGF2-siRNA was administered intrathecally 1 day after SNI. The rats were assessed for mechanical allodynia and cold allodynia 1 day before surgery (baseline), and at 2, 4, 6, 8, and 10 days after siRNA treatment. The rat spinal cord was collected for quantitative polymerase chain reaction and western blot analysis. Compared with the SNI group, rats that received IGF2 siRNA showed a significantly increased SNI-induced paw-withdrawal threshold to metal filament stimulation from Day 4 to Day 10 after SNI surgery. IGF2 siRNA significantly decreased the response duration from the acetone test from Day 2 to Day 10 following SNI surgery. SNI increased IGF2 mRNA expression on Day 2 and increased IGF2 protein expression on Day 8 and Day 10 in the spinal cord of the SNI rats. However, the above-mentioned effects of IGF2 mRNA and protein expression were significantly inhibited in the SNI + IGF2 siRNA group. We demonstrated that intrathecal administration of IGF2 siRNA provided significant inhibition of SNI-induced neuropathic pain via inhibition of IGF2 expression in the spinal cord. The analgesic effect lasted for 10 days. Further exploration of intrathecal IGF2 siRNA administration as a potential therapeutic strategy for neuropathic pain is warranted.

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