Complement Receptor 3 Pathway and NMDA Receptor 2B Subunit Involve Neuropathic Pain Associated with Spinal Cord Injury.

Background: Neuropathic pain (NP) after spinal cord injury (SCI-evoked NP) is clinically challenging; the underlying mechanisms are not fully understood, leading to a lack of promising treatment options. NP occurs in only a subset of patients with SCI. The injured spinal cord exhibits a series of histopathological changes, and the complement system has been shown to play an important role in these processes. In addition, NMDA receptor subunit 2B (NR2B) is involved in the development and maintenance of NP. This preliminary study was performed to investigate the correlations of the complement receptor 3/complement component 3 (CR3/C3) pathway and NR2B with SCI-evoked NP. Methods: A trauma-induced SCI animal model was established and SCI-evoked NP was evaluated by behavioural analysis. Transcriptome analysis was performed to identify genes in the CR3/C3 pathway related to synaptic modification, while the expression and distribution of NR2B in the injured spinal cord, and the relation to NP, were examined by immunohistochemical analysis. Results: Nine of seventeen SCI rats (52.9%) developed NP. C3 mRNA expression was significantly decreased in SCI-evoked NP rats and significantly increased in the non-NP SCI rats. C1q mRNA and CR3 mRNA expression were significantly increased in all SCI rats, but higher levels of expression were observed in the non-NP SCI rats. NR2B mRNA expression was significantly increased in the SCI-evoked NP rats and significantly decreased in the non-NP SCI rats. In addition, significantly elevated expression of NR2B-positive cells was seen in lamina II of the superficial dorsal horn in SCI-evoked NP rats in comparison with non-NP SCI rats. Conclusion: NP occurred in only a subset of SCI rats, and the CR3/C3 pathway and NR2B were involved in SCI-evoked NP. Further studies are required to determine the mechanisms underlying the SCI-evoked NP associated with the CR3/C3 pathway and NR2B.

Caveolin-1 in spinal cord modulates type-2 diabetic neuropathic pain through the Rac1/NOX2/NR2B signaling pathway.

OBJECTIVE: The present study determines whether Cav-1 modulates the initiation, development and maintenance of type-2 DNP via the Rac1/NOX2-NR2B signaling pathway. METHODS: After regular feeding for three days, these rats were randomly divided into two groups: control group with normal-diet (maintenance feed) (n=8); type-2 DM group (n=8). In the type-2 DM group, the rats were fed with a high-fat and high-sugar diet, and received a single intraperitoneal streptozotocin (STZ) injection (35 mg/kg). At two weeks after STZ injection, these diabetic neuropathic pain (DNP) rats were treated with daidzein (0.4 mg/kg/day) and N-tert-Butyl-α-phenylnitrone (PBN, 100 mg/kg/day) for 14 days. After the type-2 DNP model was successfully established, the rats were assigned into four groups: DNP group, DNP+Da group (DNP rats with Cav-1 specific inhibitor daidzein), DNP+PBN group (DNP rats treated with ROS scavenger PBN), and SC group (solvent control group). Then, the mechanical and thermal hyperalgesia were assayed to evaluate the function of the caveolin 1-Recombinant Human Ras-Related C1/nicotinamide adenosine diphosphate oxidase 2-NR2B gene (Cav-1-Rac1/NOX2-NR2B) signaling pathway. In the mechanism study, the protein expression levels of p-Caveolin-1, Rac1, NOX2, p-NR2B and t-NR2B, the production of ROS, and the distribution of Cav-1 and NOX2 in the spinal cord were observed. RESULTS: The present study revealed that p-Cav-1 was persistently upregulated and activated in the spinal cord microglia in type-2 DNP rats. The use of the pharmacological inhibitor of Cav-1 and a ROS scavenger resulted to a significantly relieved mechanical allodynia and thermal hyperalgesia. In addition, it was demonstrated that Cav-1 promoted ROS generation via the activation of Rac1-dependent NADPH oxidase (NOX). CONCLUSION: The present data suggests that Cav-1 in the spinal cord modulates type-2 DNP via regulating the Rac1/NOX2-NR2B pathway.

The effects of sodium butyrate on ethanol-seeking behavior and H3K9 acetylation in NMDA receptor 2B subunit promotor region in the hippocampus of rats / 中华行为医学与脑科学杂志

Objective To investigate the effects of sodium butyrate on ethanol-seeking behavior and H3K9 acetylation levels in NMDA receptor 2B subunit(NR2B) promoter region in the hippocampus of Wistar rats.To explore the epigenetic mechanism underlying ethanol-seeking behavior.Methods According to random number table,48 male Wistar rats were divided into saline group,sodium butyrate group,ethanol group and sodium butyrate + ethanol group,with 12 rats in each group and administered by intraperitioneal injection respectively.Conditioned place preference (CPP)was used to evaluate the ethanol-seeking behavior.Using Western-blot,real-time PCR and chromatin immunoprecipitation assays,the expression of NR2B protein,NR2BmRNA and the relative level acetylated H3K9 in NR2B promoter region in the hippocampus were determined respectively.Results The CPP test and the CPP score in each group were different (P＜ 0.05).Compared with the CPP test(261.1 ± 102.2) and the CPP score(48.5±94.6) of saline group,the CPP test ((406.8±109.2),(502.7±72.89)) and the CPP score((198.2± 119.4),(277.5±76.2)) of ethanol group and sodium butyrate + ethanol group were significantly higher(P＜0.05),the CPP test(193.4±93.8) and the CPP score (9.7±94.0)of sodium butyrate group were not significantly different(P＞0.05).Compared with the ethanol group,CPP test of sodium butyrate + ethanol group was significantly higher(P＜0.05).The expression of NR2B protein,NR2BmRNA and acetylated level H3K9 in NR2B promoter region in the hippocampus in each group were different (P＜ 0.05).Compared with the expression of NR2B protein (1.00 ± 0.28),NR2BmRNA(1.00±0.14) and H3K9 acetylation in NR2B promoter region(1.00±0.25)in the hippocampus of saline group the expression of NR2B protein((1.40±0.34),(1.79±0.30)),NR2BmRNA((1.26±0.16),(1.50±0.08)) and aeetylated level H3K9 in NR2B promoter region ((1.68±0.16),(2.35±0.45)) of ethanol group and sodium butyrate ± ethanol group were significantly higher(P＜0.05).The expression of NR2B protein(0.85±0.24),NR2BmRNA(1.05±0.13) and acetylated level H3K9 in NR2B promoter region(0.96±0.41) of sodium butyrate group were not significantly different(P＞0.05).Compared with the ethanol group,the expression of NR2B protein,NR2BmRNA and acetylated level H3K9 in NR2B promoter region in the hippocampus of ethanol group,these of sodium butyrate + ethanol group were significantly higher (P＜0.05).The CPP score were positively correlated with the expression of NR2B protein (r=0.474,P＜0.05).The expression of NR2B protein were positively correlated with the expression of NR2BmRNA (r=0.468,P＜0.05).The expression of NR2BmRNA were positively correlated with the expression of H3K9 acetylation in NR2B promoter region(r=0.596,P＜0.05),and the CPP score were positively correlated with the expression of H3K9 acetylation in NR2B promoter region (r=0.542,P＜0.05).Conclusion The increasing acetylation level of H3K9 in NR2B promoter region in the hippocampus may be one of the epigenetic mechanisms of promoting ethanolseeking behavior,and H3K9 deacetylation in NR2B promoter region in the hippocampus is likely to be a new target for controlling ethanol dependence.

Caveolin-1 in the anterior cingulate cortex modulates chronic neuropathic pain via regulation of NMDA receptor 2B subunit.

Chronic pain is still a basic science and clinical challenge. Unraveling of the neurobiological mechanisms involved in chronic pain will offer novel targets for the development of therapeutic strategies. It is well known that central sensitization in the anterior cingulate cortex (ACC) plays a critical role in initiation, development, and maintenance of chronic pain. However, the underlying mechanisms still remain elusive. Here, we reported that caveolin-1 (Cav-1), a scaffolding protein in membrane rafts, was persistently upregulated and activated in the ACC neurons after chronic constriction injury (CCI) in mice. Knockdown or blocking of Cav-1 in the contralateral ACC to the injury side reversed CCI-induced pain behavioral and neuronal sensitization and overexpression of Cav-1 in the ipsilateral ACC-induced pain behavior in the unaffected hindpaw. Furthermore, we found that Cav-1 directly binding with NMDA receptor 2B subunit (NR2B) and promotion of NR2B surface levels in the ACC contributed to modulation of chronic neuropathic pain. Disrupting the interaction of Cav-1 and NR2B through microinjection of a short peptide derived from the C-terminal of NR2B into the ACC exhibited a significant anti-nociception effect associated with decrease of surface NR2B expression. Moreover, Cav-1 increased intracellular Ca(2+) concentration and activated the ERK/CREB signaling pathway in an NR2B-dependent manner in the ACC. Our findings implicate that Cav-1 in the ACC neurons modulates chronic neuropathic pain via regulation of NR2B and subsequent activation of ERK/CREB signaling, suggesting a possible caveolin-mediated process would participate in neuronal transmission pathways implicated in pain modulation.

The effect of rhynchophylline on NR2B mRNA expression in nucleus accubems and amygdaloid of amphetamine-dependent rats / 中国药理学通报

Aim To study the effect of rhynchophylline on NMDA receptor 2B subunit(NR2B) mRNA expression in the nucleus accumbens(NAc) and amygdala(Amy) of amphetamine-induced condictioned place preference(CPP) rats.Method 56 male SPF grade Sprague-Dawley rats were randomly divided into control group,amphetamine-induced model group,model group with ketamine,model group with low,middle,high dose of rhynchophylline,and control group with rhynchophylline(n=8 for each group) The time of rats' staying in white compartment was measured in the 5th day,then NR2B mRNA expression in NAc and Amy of each rat was detected with in situ hybridization technology.Results The rats exhibited CPP after treated with 2 mg?kg-1?d-1 amphetamine for 4 d.Ketamine and rhynchophylline eliminated CPP effect,and the effect of rhychophylline showed a dose-dependence.In amphetamine-induced model group,NR2B mRNA expression in NAc and AMY of rats was significantly increased.Ketamine,middle and high dose of rhynchophylline blocked the increase of NR2B mRNA expression induced by amphetamine.Rhynchophylline had no effect on the basal level of RN2B mRNA expression in normal rats.Conclusion Inhibition of NR2B mRNA expression in NAc and AMY may contribute to the antagonistic effect of rhychophylline on amphetamine-induced CPP.