scholarly journals Sirt2 in the Spinal Cord Regulates Chronic Neuropathic Pain Through Nrf2-Mediated Oxidative Stress Pathway in Rats

2021 ◽  
Vol 12 ◽  
Author(s):  
Mengnan Zhao ◽  
Xiaojiao Zhang ◽  
Xueshu Tao ◽  
Bohan Zhang ◽  
Cong Sun ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Spinal Cord ◽  
Neuropathic Pain ◽  
Nerve Injury ◽  
Mechanical Allodynia ◽  
Intrathecal Injection ◽  
Thermal Hyperalgesia ◽  
Oxidative Stress Marker ◽  
Oxidative Stress Pathway ◽  
Stress Pathway

Reduction in Nrf2-mediated antioxidant response in the central nervous system plays an important role in the development and maintenance of neuropathic pain (NP). However, the mechanisms regulating Nrf2 activity in NP remain unclear. A recent in vitro study revealed that Sirt2, a member of the sirtuin family of proteins, affects antioxidant capacity by modulating Nrf2 activity. Here we examined whether central Sirt2 regulates NP through Nrf2-mediated oxidative stress pathway. In a rat model of spared nerve injury (SNI)-induced NP, mechanical allodynia and thermal hyperalgesia were observed on day 1 and up to day 14 post-SNI. The expression of Sirt2, Nrf2 and its target gene NQO1 in the spinal cord in SNI rats, compared with sham rats, was significantly decreased from day 7 and remained lower until the end of the experiment (day 14). The mechanical allodynia and thermal hyperalgesia in SNI rats were ameliorated by intrathecal injection of Nrf2 agonist tBHQ, which normalized expression of Nrf2 and NQO1 and reversed SNI-induced decrease in antioxidant enzyme superoxide dismutase (SOD) and increase in oxidative stress marker 8-hydroxy-2′-deoxyguanosine (8-OHdG) in the spinal cord. Moreover, intrathecal injection of a recombinant adenovirus expressing Sirt2 (Ad-Sirt2) that upregulated expression of Sirt2, restored expression of Nrf2 and NQO1 and attenuated oxidative stress in the spinal cord, leading to improvement of thermal hyperalgesia and mechanical allodynia in SNI rats. These findings suggest that peripheral nerve injury downregulates Sirt2 expression in the spinal cord, which inhibits Nrf2 activity, leading to increased oxidative stress and the development of chronic NP.

Sortilins in neuropathic pain

2012 ◽  
Vol 3 (3) ◽  
pp. 183-184
Author(s):  
M. Richner ◽  
O.J. Bjerrum ◽  
Y. De Koninck ◽  
A. Nykjaer ◽  
C.B. Vaegter
Keyword(s):  
Spinal Cord ◽  
Neuropathic Pain ◽  
Peripheral Nerve ◽  
Nerve Injury ◽  
Peripheral Nerve Injury ◽  
Mechanical Allodynia ◽  
Molecular Mechanisms ◽  
Intrathecal Injection ◽  
Ion Concentration ◽  
Down Regulation

AbstractBackground/aimsThe molecular mechanisms underlying neuropathic pain are incompletely understood, but recent data suggest that down-regulation of the chloride extruding co-transporter KCC2 in spinal cord sensory neurons is critical: Following peripheral nerve injury, activated microglia in the spinal cord release BDNF, which stimulates neuronal TrkB receptors and ultimately results in the reduction of KCC2 levels. Consequently, neuronal intracellular chloride ion concentration increases, impairing GABAA-receptor mediated inhibition. We have previously described how the receptor sortilin modulates neurotrophin signaling by facilitating anterograde transport of Trk receptors. Unpublished data further link SorCS2, another member of the Sortilins family of sorting receptors (sortilin, SorLA and SorCS1–3) to BDNF signaling by regulating presynaptic TrkB trafficking. The purpose of this study is to explore the involvement of Sortilins in neuropathic pain.MethodsWe subjected wild-type (wt), sortilin knockout (Sort1-/-) and SorCS2 knockout (SorCS2-/-) mice to the Spared Nerve Injury (SNI) model of peripheral nerve injury. Mechanical allodynia was measured by von Frey filaments using the up-down-up method and a 3-out-of-5 thresshold.ResultsAs previously described by several groups, wt mice developed significant mechanical allodynia following SNI. Interestingly however, mice lacking sortilin or SorCS2 were fully protected from development of allodynia and did not display KCC2 down-regulation following injury. In addition, a single intrathecal injection of antibodies against sortilin or SorCS2 could delay or rescue mechanical allodynia in wt SNI mice for 2-3 days. Finally, neither sortilin nor SorCS2 deficient mice responded to intrathecal injection of BDNF, in contrast to wt mice which developed transient mechanical allodynia.ConclusionWe hypothesize that sortilin and SorCS2 are involved in neuropathic pain development by regulating TrkB signaling. Alternatively, Sortilins may directly influence the regulation of KCC2 membrane levels following injury. Both hypotheses are currently being investigated by our group.

Comprehensive analysis of neurobehavior associated with histomorphological alterations in a chronic constrictive nerve injury model through use of the CatWalk XT system

2014 ◽  
Vol 120 (1) ◽  
pp. 250-262 ◽  
Author(s):  
Chien-Yi Chiang ◽  
Meei-Ling Sheu ◽  
Fu-Chou Cheng ◽  
Chun-Jung Chen ◽  
Hong-Lin Su ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Neuropathic Pain ◽  
Nerve Injury ◽  
Mechanical Allodynia ◽  
S100 Protein ◽  
Thermal Hyperalgesia ◽  
Nerve Damage ◽  
Dorsal Spinal Cord ◽  
Sensory Evoked ◽  
Dorsal Spinal

Object Neuropathic pain is debilitating, and when chronic, it significantly affects the patient physically, psychologically, and socially. The neurobehavior of animals used as a model for chronic constriction injury seems analogous to the neurobehavior of humans with neuropathic pain. However, no data depicting the severity of histomorphological alterations of the nervous system associated with graded changes in neurobehavior are available. To determine the severity of histomorphological alteration related to neurobehavior, the authors created a model of chronic constrictive injury of varying intensity in rats and used the CatWalk XT system to evaluate neurobehavior. Methods A total of 60 Sprague-Dawley rats, weighing 250–300 g each, were randomly assigned to 1 of 5 groups that would receive sham surgery or 1, 2, 3, or 4 ligatures of 3-0 chromic gut loosely ligated around the left sciatic nerve. Neurobehavior was assessed by CatWalk XT, thermal hyperalgesia, and mechanic allodynia before injury and periodically after injury. The nerve tissue from skin to dorsal spinal cord was obtained for histomorphological analysis 1 week after injury, and brain evoked potentials were analyzed 4 weeks after injury. Results. Significant differences in expression of nerve growth factor existed in skin, and the differences were associated with the intensity of nerve injury. After injury, expression of cluster of differentiation 68 and tumor necrosis factor–α was increased, and expression of S100 protein in the middle of the injured nerve was decreased. Increased expression of synaptophysin in the dorsal root ganglion and dorsal spinal cord correlated with the intensity of injury. The amplitude of sensory evoked potential increased with greater severity of nerve damage. Mechanical allodynia and thermal hyperalgesia did not differ significantly among treatment groups at various time points. CatWalk XT gait analysis indicated significant differences for print areas, maximum contact maximum intensity, stand phase, swing phase, single stance, and regular index, with sham and/or intragroup comparisons. Conclusions. Histomorphological and electrophysiological alterations were associated with severity of nerve damage. Subtle neurobehavioral differences were detected by the CatWalk XT system but not by mechanical allodynia or thermal hyperalgesia. Thus, the CatWalk XT system should be a useful tool for monitoring changes in neuropathic pain, especially subtle alterations.

scholarly journals Nuclear PPAR-γ Activation Modulates Inflammation and Oxidative Stress in Attenuating Chemotherapy-Induced Neuropathic Pain in Vivo

2021 ◽  
pp. 167-179
Author(s):  
Haritha Pasupulati ◽  
Satyanarayana S. V. Padi ◽  
Sujatha Dodoala ◽  
Prasad V. S. R. G. Koganti
Keyword(s):  
Oxidative Stress ◽  
Spinal Cord ◽  
Neuropathic Pain ◽  
Peripheral Neuropathy ◽  
Mechanical Allodynia ◽  
Antinociceptive Effect ◽  
Thermal Hyperalgesia ◽  
Ppar Γ ◽  
Markers Of Inflammation ◽  
And Oxidative Stress

Background: Paclitaxel-induced painful neuropathy is a major dose-limiting side effect and can persist for up to two years after completing treatment that greatly affects both the course of chemotherapy and quality of life in cancer patients. Peroxisome proliferator-activated receptor (PPAR)-γ belongs to a family of nuclear receptors known for their transcriptional and regulatory roles in metabolism, inflammation, and oxidative stress. However, the role of PPAR-γ activation on paclitaxel-induced neuropathic pain is not yet known. Objective: To investigate whether pioglitazone, a PPAR-γ agonist reduce paclitaxel-induced neuropathic pain and to elucidate underlying mechanisms. Methodology: Peripheral neuropathy was induced by administration of paclitaxel (2 mg/kg per injection) intraperitoneally on four alternate days (days 0, 2, 4, 6). Thermal hyperalgesia and mechanical allodynia were assessed and the markers of inflammation and nitroso-oxidative stress were estimated. Results: Pioglitazone did not induce hypoalgesia and had no effect on locomotor activity. Repeated oral administration of pioglitazone (10 and 20 mg/kg,) for 2 weeks started 14 days after paclitaxel injection markedly attenuated paw withdrawal responses to thermal (hyperalgesia) and mechanical (allodynia) stimuli. Further, pioglitazone administration significantly reduced elevated level of pro-inflammatory cytokine, TNF-α, in both the dorsal root ganglia and the spinal cord accompanied by marked decrease in oxidative stress parameters as well as increase in activity of antioxidant defense enzyme, superoxide dismutase, in the spinal cord after paclitaxel injection. Conclusion: The results of the present study demonstrate that pioglitazone, a PPAR-γ agonist exerted antinociceptive effect in paclitaxel-induced neuropathic pain through inhibiting neuroimmune inflammation in both the periphery and spinal cord and by reducing nitroso-oxidative stress in spinal cord. Our findings strongly suggest pharmacological activation of PPAR-g as a promising therapeutic target in paclitaxel-induced peripheral neuropathy and provide rationale for the clinical evaluation.

scholarly journals Gut Microbiota Depletion by Antibiotics Ameliorates Somatic Neuropathic Pain Induced by Nerve Injury, Chemotherapy and Diabetes in Mice

2021 ◽  
Author(s):  
Pingchuan Ma ◽  
Ru-Fan Mo ◽  
Hua-Bao Liao ◽  
Yun-Xiao Zhang ◽  
Cai-Xia Yang ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Neuropathic Pain ◽  
Gut Microbiota ◽  
Nerve Injury ◽  
Mechanical Allodynia ◽  
Cell Activation ◽  
Thermal Hyperalgesia ◽  
Fecal Bacteria ◽  
High Blood Glucose ◽  
Diabetes In Mice

Abstract Background: Gut microbiota has been found involved in neuronal functions and neurological disorders. Whether and how gut microbiota impacts chronic somatic pain disorders remain elusive.Methods: Neuropathic pain was produced by different forms of injury or diseases, the chronic constriction injury (CCI) of the sciatic nerves, oxaliplatin (OXA) chemotherapy, and streptozocin (STZ)-induced diabetes in mice. Continuous feeding of antibiotics (ABX) cocktail was used to cause major depletion of the gut microbiota. Fecal microbiota, biochemical changes in the spinal cord and dorsal root ganglion (DRG), and the behaviorally expressed painful syndromes were assessed.Results: Under condition of gut microbiota depletion, CCI, OXA, or STZ treatment-induced thermal hyperalgesia or mechanical allodynia were prevented or completely suppressed. Gut microbiota depletion also prevented CCI or STZ treatment-induced glial cell activation in the spinal cord and inhibited cytokine production in DRG in OXA model. Interestingly, STZ treatment failed to induce the diabetic high blood glucose and painful hypersensitivity in animals with the gut microbiota depletion. ABX feeding starting simultaneously with CCI, OXA, or STZ treatment resulted in instant analgesia in all the animals. ABX feeding starting after establishment of the neuropathic pain in CCI- and STZ-, but not OXA-treated animals produced significant alleviation of the thermal hyeralgesia or mechanical allodynia. Transplantation of fecal bacteria from SPF mice to ABX treated mice partially restored the gut microbiota and fully rescued the behaviorally expressed neuropathic pain, of which, Akkermansia, Bacteroides, and Desulfovibrionaceae phylus may play a key role. Conclusion: This study demonstrates distinct roles of gut microbiota in the pathogenesis of chronic painful conditions with nerve injury, chemotherapy and diabetic neuropathy and supports the clinical significance of fecal bacteria transplantation.

CB2/miR-124 signaling down-regulate the expression of purinergic P2X4 and P2X7 receptor in dorsal spinal cord of CCI rats

2020 ◽  
Author(s):  
Rui Xu ◽  
Fan Yang ◽  
Lijuan Li ◽  
Xiaohong Liu ◽  
Xiaolu Lei ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Neuropathic Pain ◽  
Sciatic Nerve ◽  
Nerve Injury ◽  
Intrathecal Injection ◽  
Receptor Activation ◽  
Cb2 Receptor ◽  
Dorsal Spinal Cord ◽  
P38mapk Pathway ◽  
Dorsal Spinal

Abstract Background: The importance of P2X purinoceptors, CB2 receptor and microRNA-124(miR-124) in spinal cord microglia to the development of neuropathic pain was demonstrated in numerous previous studies. The upregulation of P2X4 and P2X7 receptors in spinal dorsal horn microglia is involved in the development of pain behavior caused by peripheral nerve injury. However, it is not clear whether the expression of P2X4 and P2X7 receptors at dorsal spinal cord will be influenced by CB2 receptor or miR-124 in rats after chronic sciatic nerve injury.Methods: Chronic constriction injury (CCI) of the sciatic nerve was performed in rats to induce neuropathic pain. Tests of the mechanical withdrawal threshold (MWT) were carried out to assess the response of the paw to mechanical stimulus. The expression of miR-124, P2X4, P2X7 and CB2 receptor were detected with RT-PCR. The protein expression of P2X4, P2X7 and CB2 receptor, RhoA, ROCK1, ROCK2, p-p38MAPK and p-NF-kappaBp65 was detected with Western blotting analysis. Results: Intrathecal administration of CB2 receptor agonist AM1241 significantly attenuated CCI-induced mechanical allodynia and significantly inhibited the increased expression of P2X4 and P2X7 receptors at the mRNA and protein levels, which imply that P2X4 and P2X7 receptors expression are down-regulated by AM1241 in CCI rats. Western blot analysis showed that AM1241 suppressed the elevated expression of RhoA, ROCK1, ROCK2, p-p38MAPK and NF-κBp65 in the dorsal spinal cord induced by CCI. After administration with Y-27632 (ROCK inhibitor), SB203580 (P38MAPK inhibitor) or PDTC (NF-κB inhibitor), the levels of P2X4 and P2X7 receptors expression in the dorsal spinal cord were lower than those in CCI rats, which imply that the ROCK/P38MAPK pathway and NF-κB activation may contribute to the increased expression of P2X4 and P2X7 receptor. On the other hand, in CCI rats, AM1241 treatment evoked the increased expression of CB2 receptor and miRNA-124, which can be inhibited by intrathecal injection of CB2 receptor antagonist AM630, which indicate that the increased expression of miRNA-124 may be medicated by CB2 receptor activation. In addition, the increased expression of P2X4 and P2X7 receptors in the dorsal spinal cord of CCI rats were inhibited by miRNA-124 agomir. Furthermore, intrathecal injection of miRNA-124 agomir could efficiently inhibit the ROCK/P38MAPK pathway and NF-κB activation in CCI rats. Moreover, AM1241 treatment significantly inhibited the expression of P2X4 and P2X7 receptors, and this suppression is enhanced by pretreatment with miRNA-124 agomir. On the contrast, the inhibitory effect of AM1241 on the expression of P2X4 and P2X7 receptor can be reversed by pretreatment with miRNA-124 antagomir.Conclusions: In CCI rats, intrathecal injection of AM1241 could efficiently induce the increased expression of miRNA-124, while inhibiting the ROCK/P38MAPK pathway and NF-κB activation in dorsal spinal cord. CB2 receptor/miRNA-124 signaling induced the decreased P2X4 and P2X7 receptors expression via inhibit the ROCK/P38MAPK pathway and NF-κB activation.

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 Urotensin II inhibitor eases neuropathic pain by suppressing the JNK/NF-κB pathway

2017 ◽  
Vol 232 (2) ◽  
pp. 165-174 ◽  
Author(s):  
Jing Li ◽  
Pan-Pan Zhao ◽  
Ting Hao ◽  
Dan Wang ◽  
Yu Wang ◽  
...  
Keyword(s):  
Neuropathic Pain ◽  
Dorsal Horn ◽  
Mechanical Allodynia ◽  
Cyclic Peptide ◽  
Intrathecal Injection ◽  
Thermal Hyperalgesia ◽  
Nuclear Factor Κb ◽  
Neurosecretory System ◽  
Urotensin Ii ◽  
Caudal Neurosecretory System

Urotensin II (U-II), a cyclic peptide originally isolated from the caudal neurosecretory system of fishes, can produce proinflammatory effects through its specific G protein-coupled receptor, GPR14. Neuropathic pain, a devastating disease, is related to excessive inflammation in the spinal dorsal horn. However, the relationship between U-II and neuropathic pain has not been reported. This study was designed to investigate the effect of U-II antagonist on neuropathic pain and to understand the associated mechanisms. We reported that U-II and its receptor GPR14 were persistently upregulated and activated in the dorsal horn of L4–6 spinal cord segments after chronic constriction injury (CCI) in rats. Intrathecal injection of SB657510, a specific antagonist against U-II, reversed CCI-induced thermal hyperalgesia and mechanical allodynia. Furthermore, we found that SB657510 reduced the expression of phosphorylated c-Jun N-terminal kinase (p-JNK) and nuclear factor-κB (NF-κB) p65 as well as subsequent secretion of interleukin-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α). It was also showed that both the JNK inhibitor SP600125 and the NF-κB inhibitor PDTC significantly attenuated thermal hyperalgesia and mechanical allodynia in CCI rats. Our present research showed that U-II receptor antagonist alleviated neuropathic pain possibly through the suppression of the JNK/NF-κB pathway in CCI rats, which will contribute to the better understanding of function of U-II and pathogenesis of neuropathic pain.

scholarly journals The Protective Effect of Bergamot Polyphenolic Fraction (BPF) on Chemotherapy-Induced Neuropathic Pain

2021 ◽  
Vol 14 (10) ◽  
pp. 975
Author(s):  
Sara Ilari ◽  
Filomena Lauro ◽  
Luigino Antonio Giancotti ◽  
Valentina Malafoglia ◽  
Concetta Dagostino ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Neuropathic Pain ◽  
Mechanical Allodynia ◽  
Glutamate Transporter ◽  
Thermal Hyperalgesia ◽  
Chemotherapeutic Agents ◽  
Preventive Strategy ◽  
Polyphenolic Extract ◽  
Thermal Hypersensitivity

Paclitaxel is a chemotherapeutic drug used for cancer treatment. Chemotherapy-induced peripheral neuropathy (CIPN) is a common major dose-limiting side effect of many chemotherapeutic agents, including paclitaxel. CIPN is accompanied by mechanical and thermal hypersensitivity that resolves within weeks, months, or years after drug termination. To date, there is no available preventive strategy or effective treatment for CIPN due to the fact that its etiology has not been fully explained. It is clear that free radicals are implicated in many neurodegenerative diseases and recent studies have shown the important role of oxidative stress in development of CIPN. Here, we observed how, in rats, the administration of a natural antioxidant such as the bergamot polyphenolic extract (BPF), can play a crucial role in reducing CIPN. Paclitaxel administration induced mechanical allodynia and thermal hyperalgesia, which began to manifest on day seven, and reached its lowest levels on day fifteen. Paclitaxel-induced neuropathic pain was associated with nitration of proteins in the spinal cord including MnSOD, glutamine synthetase, and glutamate transporter GLT-1. This study showed that the use of BPF, probably by inhibiting the nitration of crucial proteins involved in oxidative stress, improved paclitaxel-induced pain behaviors relieving mechanical allodynia, thermal hyperalgesia, thus preventing the development of chemotherapy-induced neuropathic pain.

scholarly journals Nrf2 Activation Attenuates Chronic Constriction Injury-induced Neuropathic Pain via Induction of PGC-1α-mediated Mitochondrial Biogenesis in the Spinal Cord

2021 ◽  
Author(s):  
Jia Sun ◽  
Jia-Yan Li ◽  
Long-Qing Zhang ◽  
Dan-Yang Li ◽  
Jia-Yi Wu ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Spinal Cord ◽  
Neuropathic Pain ◽  
Mitochondrial Dysfunction ◽  
Mitochondrial Biogenesis ◽  
Chronic Constriction Injury ◽  
Clinical Investigation ◽  
Thermal Hyperalgesia ◽  
Related Factor ◽  
Dependent Manner

Abstract BackgroundNeuropathic pain is a debilitating disease with few effective treatments. Emerging evidence indicates the involvement of mitochondrial dysfunction and oxidative stress in neuropathic pain. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a potent regulator of antioxidant response system. In this study, we investigated whether RTA-408 (a novel synthetic triterpenoid under clinical investigation) could activate Nrf2 and promote mitochondrial biogenesis (MB) to reverse neuropathic pain and the underlying mechanisms.MethodsNeuropathic pain was induced by chronic constriction injury (CCI) of the sciatic nerve. Pain behaviors were measured via the von-Frey test and Hargreaves plantar test. The L4-6 spinal cord was collected to examine the activation of Nrf2 and MB.ResultsRTA-408 treatment significantly reversed mechanical allodynia and thermal hyperalgesia in CCI mice in a dose-dependent manner. Furthermore, RTA-408 increased the activity of Nrf2 and significantly restored MB that was impaired in CCI mice in an Nrf2 dependent manner. Peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1α) is the key regulator of MB. We found that PGC-1α activator also exhibited a potent analgesic effect in CCI mice. Moreover, the antinociceptive effect of RTA-408 was reversed by the pre-injection of PGC-1α inhibitor.ConclusionsNrf2 activation attenuates chronic constriction injury-induced neuropathic pain via induction of PGC-1α-mediated mitochondrial biogenesis in the spinal cord. Our results indicate that Nrf2 may be a potential therapeutic strategy to ameliorate neuropathic pain and many other disorders with oxidative stress and mitochondrial dysfunction.

scholarly journals Long-term Application of Glycine Transporter Inhibitors Acts Antineuropathic and Modulates Spinal N-methyl-d-aspartate Receptor Subunit NR-1 Expression in Rats

2014 ◽  
Vol 121 (1) ◽  
pp. 160-169 ◽  
Author(s):  
Franziska Barthel ◽  
Andrea Urban ◽  
Lukas Schlösser ◽  
Volker Eulenburg ◽  
Robert Werdehausen ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Neuropathic Pain ◽  
Side Effects ◽  
Mechanical Allodynia ◽  
Chronic Constriction Injury ◽  
Thermal Hyperalgesia ◽  
Receptor Expression ◽  
Dependent Manner ◽  
Receptor Subunit ◽  
Aspartate Receptor

Abstract Background: Dysfunction of spinal glycinergic neurotransmission is a major pathogenetic factor in neuropathic pain. The synaptic glycine concentration is controlled by the two glycine transporters (GlyT) 1 and 2. GlyT inhibitors act antinociceptive in various animal pain models when applied as bolus. Yet, in some studies, severe neuromotor side effects were reported. The aim of the current study was to elucidate whether continuous inhibition of GlyT ameliorates neuropathic pain without side effects and whether protein expression of GlyT1, GlyT2, or N-methyl-d-aspartate receptor subunit NR-1 in the spinal cord is affected. Methods: In the chronic constriction injury model of neuropathic pain, male Wistar rats received specific GlyT1 and GlyT2 inhibitors (ALX5407 and ALX1393; Sigma-Aldrich®, St. Louis, MO) or vehicle for 14 days via subcutaneous osmotic infusion pumps (n = 6). Mechanical allodynia and thermal hyperalgesia were assessed before, after chronic constriction injury, and every 2 days during substance application. At the end of behavioral assessment, the expression of GlyT1, GlyT2, and NR-1 in the spinal cord was determined by Western blot analysis. Results: Both ALX5407 and ALX1393 ameliorated thermal hyperalgesia and mechanical allodynia in a time- and dose-dependent manner. Respiratory or neuromotor side effects were not observed. NR-1 expression in the ipsilateral spinal cord was significantly reduced by ALX5407, but not by ALX1393. The expression of GlyT1 and GlyT2 remained unchanged. Conclusions: Continuous systemic inhibition of GlyT significantly ameliorates neuropathic pain in rats. Thus, GlyT represent promising targets in pain research. Modulation of N-methyl-d-aspartate receptor expression might represent a novel mechanism for the antinociceptive action of GyT1 inhibitors.

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