Spinal α2-Adrenoceptor-mediated Analgesia in Neuropathic Pain Reflects Brain-derived Nerve Growth Factor and Changes in Spinal Cholinergic Neuronal Function

Introduction Spinal alpha2-adrenoceptor stimulation produces analgesia in neuropathic pain states, and this effect in animals is blocked by the inhibitors of brain-derived neurotrophic factor (BDNF) function. In rats, alpha2-adrenoceptor stimulation normally inhibits acetylcholine release, but it excites release after nerve injury. The authors examined the roles of BDNF and excitatory Gs-protein in this change. Methods Male rats underwent L5-L6 spinal nerve ligation (SNL), and their lumbar spinal dorsal horns with or without spinal BDNF infusion were used for either synaptosome preparation for acetylcholine release or immunostaining for choline acetyltransferase. Results SNL did not alter spontaneous release from synaptosomes or choline acetyltransferase immunoreactivity in the spinal dorsal horn, but it reduced KCl-evoked acetylcholine release. Dexmedetomidine inhibited KCl-evoked acetylcholine release in synaptosomes from normal rats, but it excited KCl-evoked release in synaptosomes from SNL rats, and both effects were blocked by the alpha2-adrenoceptor antagonist idazoxan. Spinal infusion of an antibody to BDNF reduced choline acetyltransferase immunoreactivity in the spinal dorsal horn in both normal and SNL rats and abolished facilitation of KCl-evoked acetylcholine release by dexmedetomidine in SNL rats. Dexmedetomidine facilitation of acetylcholine release was also blocked by the inhibitors of Gs function. Discussion The increased reliance of spinal alpha2 adrenoceptors on cholinergic stimulation to cause analgesia after nerve injury reflects in part a shift from direct inhibition to direct excitation of spinal cholinergic neurons. The authors' results suggest that this shift relies on an interaction with Gs-proteins and BDNF.

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Calcitonin gene-related peptide regulates spinal microglial activation through the histone H3 lysine 27 trimethylation via enhancer of zeste homolog-2 in rats with neuropathic pain

Journal of Neuroinflammation ◽

10.1186/s12974-021-02168-1 ◽

2021 ◽

Vol 18 (1) ◽

Author(s):

Qi An ◽

Chenyan Sun ◽

Ruidi Li ◽

Shuhui Chen ◽

Xinpei Gu ◽

...

Keyword(s):

Neuropathic Pain ◽

Dorsal Horn ◽

Nerve Injury ◽

Spinal Dorsal Horn ◽

Microglial Activation ◽

Microglial Cells ◽

Gene Promoters ◽

Spinal Dorsal ◽

Related Peptide ◽

Calcitonin Gene

Abstract Background Calcitonin gene-related peptide (CGRP) as a mediator of microglial activation at the transcriptional level may facilitate nociceptive signaling. Trimethylation of H3 lysine 27 (H3K27me3) by enhancer of zeste homolog 2 (EZH2) is an epigenetic mark that regulates inflammatory-related gene expression after peripheral nerve injury. In this study, we explored the relationship between CGRP and H3K27me3 in microglial activation after nerve injury, and elucidated the underlying mechanisms in the pathogenesis of chronic neuropathic pain. Methods Microglial cells (BV2) were treated with CGRP and differentially enrichments of H3K27me3 on gene promoters were examined using ChIP-seq. A chronic constriction injury (CCI) rat model was used to evaluate the role of CGRP on microglial activation and EZH2/H3K27me3 signaling in CCI-induced neuropathic pain. Results Overexpressions of EZH2 and H3K27me3 were confirmed in spinal microglia of CCI rats by immunofluorescence. CGRP treatment induced the increased of H3K27me3 expression in the spinal dorsal horn and cultured microglial cells (BV2) through EZH2. ChIP-seq data indicated that CGRP significantly altered H3K27me3 enrichments on gene promoters in microglia following CGRP treatment, including 173 gaining H3K27me3 and 75 losing this mark, which mostly enriched in regulation of cell growth, phagosome, and inflammation. qRT-PCR verified expressions of representative candidate genes (TRAF3IP2, BCL2L11, ITGAM, DAB2, NLRP12, WNT3, ADAM10) and real-time cell analysis (RTCA) verified microglial proliferation. Additionally, CGRP treatment and CCI increased expressions of ITGAM, ADAM10, MCP-1, and CX3CR1, key mediators of microglial activation in spinal dorsal horn and cultured microglial cells. Such increased effects induced by CCI were suppressed by CGRP antagonist and EZH2 inhibitor, which were concurrently associated with the attenuated mechanical and thermal hyperalgesia in CCI rats. Conclusion Our findings highly indicate that CGRP is implicated in the genesis of neuropathic pain through regulating microglial activation via EZH2-mediated H3K27me3 in the spinal dorsal horn.

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Resveratrol Mediates Mechanical Allodynia Through Modulating Inflammatory Response via the TREM2-autophagy Axis in SNI Rat Model

10.21203/rs.3.rs-35728/v1 ◽

2020 ◽

Author(s):

Yaping Wang ◽

Yu Shi ◽

Yongquan Huang ◽

Wei Liu ◽

Guiyuan Cai ◽

...

Keyword(s):

Neuropathic Pain ◽

Inflammatory Response ◽

Dorsal Horn ◽

Nerve Injury ◽

Rat Model ◽

Mechanical Allodynia ◽

Spinal Dorsal Horn ◽

Intrathecal Administration ◽

Spared Nerve Injury ◽

Spinal Dorsal

Abstract Background Neuropathic pain (NeuP) is a chronic and challenging clinical problem, with little effective treatment. Resveratrol has shown neuroprotection by inhibiting inflammatory response in NeuP. Recently, the triggering receptor expressed on myeloid cells 2 (TREM2) expressed by microglia was identified as a critical factor of inflammation in nervous system diseases. In this study, we explored whether resveratrol could ameliorate neuroinflammation and produce anti-mechanical allodynia effects via regulating TREM2 in spared nerve injury rats, as well as investigated the underlying mechanisms. Methods A spared nerve injury (SNI) rat model was performed to investigate whether resveratrol could exert anti-mechanism allodynia effects via inhibiting neuroinflammation. To evaluate the role of TREM2 in anti-neuroinflammatory function of resveratrol, Lentivirus coding TREM2 was intrathecal injected into SNI rats to activate TREM2 and the pain behavior was detected by the Von Frey test. Furthermore, 3-Methyladenine (3-MA, an autophagy inhibitor) was performed to analyze the molecular mechanisms of resveratrol-mediated anti-neuroinflammation using Western blot, qPCR, immunofluorescence. Results The TREM2 expression and number of the microglial cell was significantly increased in the ipsilateral spinal dorsal horn after SNI. We found that intrathecal administration of resveratrol (300ug/day) alleviated mechanical allodynia; obviously enhanced autophagy; and markedly reduced the levels of interleukin-1β, interleukin-6, and tumor necrosis factor-α in the ipsilateral spinal dorsal horn after SNI. Moreover, the number of Iba-1+ microglial cells and TREM2 expression were downregulated after resveratrol treatment. Intrathecal administration of lentivirus coding TREM2 and/or 3-methyladenine in those rats induced deficiencies in resveratrol-mediated anti-inflammation, leading to mechanical allodynia that could be rescued via administration of Res. Furthermore, 3-MA treatment contributed to TREM2-mediated mechanical allodynia. Conclusions Taken together, these data reveal that resveratrol relieves neuropathic pain through suppressing microglia-mediated neuroinflammation via regulating the TREM2-autophagy axis in SNI rats.

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Loss of Neurons from Laminas I-III of the Spinal Dorsal Horn Is Not Required for Development of Tactile Allodynia in the Spared Nerve Injury Model of Neuropathic Pain

Journal of Neuroscience ◽

10.1523/jneurosci.1490-05.2005 ◽

2005 ◽

Vol 25 (28) ◽

pp. 6658-6666 ◽

Cited By ~ 97

Author(s):

E. Polgar

Keyword(s):

Neuropathic Pain ◽

Dorsal Horn ◽

Nerve Injury ◽

Spinal Dorsal Horn ◽

Tactile Allodynia ◽

Spared Nerve Injury ◽

Spinal Dorsal ◽

Injury Model

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Resveratrol mediates mechanical allodynia through modulating inflammatory response via the TREM2-autophagy axis in SNI rat model

Journal of Neuroinflammation ◽

10.1186/s12974-020-01991-2 ◽

2020 ◽

Vol 17 (1) ◽

Author(s):

Yaping Wang ◽

Yu Shi ◽

Yongquan Huang ◽

Wei Liu ◽

Guiyuan Cai ◽

...

Keyword(s):

Neuropathic Pain ◽

Inflammatory Response ◽

Dorsal Horn ◽

Nerve Injury ◽

Rat Model ◽

Mechanical Allodynia ◽

Spinal Dorsal Horn ◽

Intrathecal Administration ◽

Spared Nerve Injury ◽

Spinal Dorsal

Abstract Background Neuropathic pain (NeuP) is a chronic and challenging clinical problem, with little effective treatment. Resveratrol has shown neuroprotection by inhibiting inflammatory response in NeuP. Recently, the triggering receptor expressed on myeloid cells 2 (TREM2) expressed by microglia was identified as a critical factor of inflammation in nervous system diseases. In this study, we explored whether resveratrol could ameliorate neuroinflammation and produce anti-mechanical allodynia effects via regulating TREM2 in spared nerve injury rats, as well as investigated the underlying mechanisms. Methods A spared nerve injury (SNI) rat model was performed to investigate whether resveratrol could exert anti-mechanical allodynia effects via inhibiting neuroinflammation. To evaluate the role of TREM2 in anti-neuroinflammatory function of resveratrol, lentivirus coding TREM2 was intrathecally injected into SNI rats to activate TREM2, and the pain behavior was detected by the von Frey test. Furthermore, 3-methyladenine (3-MA, an autophagy inhibitor) was applied to study the molecular mechanisms of resveratrol-mediated anti-neuroinflammation using Western blot, qPCR, and immunofluorescence. Results The TREM2 expression and number of the microglial cells were significantly increased in the ipsilateral spinal dorsal horn after SNI. We found that intrathecal administration of resveratrol (300ug/day) alleviated mechanical allodynia; obviously enhanced autophagy; and markedly reduced the levels of interleukin-1β, interleukin-6, and tumor necrosis factor-α in the ipsilateral spinal dorsal horn after SNI. Moreover, the number of Iba-1+ microglial cells and TREM2 expression were downregulated after resveratrol treatment. Intrathecal administration of lentivirus coding TREM2 and/or 3-MA in those rats induced deficiencies in resveratrol-mediated anti-inflammation, leading to mechanical allodynia that could be rescued via administration of Res. Furthermore, 3-MA treatment contributed to TREM2-mediated mechanical allodynia. Conclusions Taken together, these data reveal that resveratrol relieves neuropathic pain through suppressing microglia-mediated neuroinflammation via regulating the TREM2-autophagy axis in SNI rats.

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Effects of Tetramethylpyrazine on Neuronal Apoptosis in the Superficial Dorsal Horn in a Rat Model of Neuropathic Pain

The American Journal of Chinese Medicine ◽

10.1142/s0192415x12500917 ◽

2012 ◽

Vol 40 (06) ◽

pp. 1229-1239 ◽

Cited By ~ 15

Author(s):

Yu-Fang Leng ◽

Xiang-Mei Gao ◽

Shu-Xiu Wang ◽

Yan-Hong Xing

Keyword(s):

Neuropathic Pain ◽

Dorsal Horn ◽

Spinal Dorsal Horn ◽

Neuronal Apoptosis ◽

Caspase 3 ◽

Sham Group ◽

Male Rats ◽

Spinal Dorsal ◽

Post Operation ◽

The Right

The Bennett and Xie (1988) model of chronic constriction injury (CCI) investigated the effects of tetramethylpyrazine (TMP) on neuropathic pain-associated behaviors and neuronal apoptosis in the spinal dorsal horn. Fifty-four male rats were randomly divided into sham (group S), CCI (group C) and TMP groups (group T). Each group was divided into subgroups (n = 6 in each group) according the time of sacrifice: 3 d, 7 d and 14 d. Rat sciatic nerves were unligated (group S), or the right sciatic nerve was loosely ligated (groups C and T) to produce CCI. Mechanical withdrawal thresholds (MWTs) and thermal withdrawal latencies (TWLs) were measured, and the rats were sacrificed at different time points post-operation. The L4-L6 sections of the spinal cord were removed. Apoptotic changes were evaluated using the TUNEL method. Immunohistochemistry assessed Bcl-2 and caspase-3 expression. TMP treatment increased MWT and TWL values and Bcl-2 expression, but it reduced neuronal apoptosis and caspase-3 expression in laminae I–II of the spinal dorsal horn. These results suggested that the inhibition of neuronal apoptosis via the modulation of Bcl-2 and caspase-3 proteins in the rat spinal dorsal horn contributed to TMP-induced analgesia.

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KDM6B epigenetically regulated-interleukin-6 expression in the dorsal root ganglia and spinal dorsal horn contributes to the development and maintenance of neuropathic pain following peripheral nerve injury in male rats

Brain Behavior and Immunity ◽

10.1016/j.bbi.2021.08.231 ◽

2021 ◽

Author(s):

Liren Li ◽

Liying Bai ◽

Kangli Yang ◽

Jian Zhang ◽

Yan Gao ◽

...

Keyword(s):

Neuropathic Pain ◽

Peripheral Nerve ◽

Dorsal Horn ◽

Dorsal Root Ganglia ◽

Interleukin 6 ◽

Peripheral Nerve Injury ◽

Dorsal Root ◽

Spinal Dorsal Horn ◽

Male Rats ◽

Spinal Dorsal

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Gabapentin Acts within the Locus Coeruleus to Alleviate Neuropathic Pain

Anesthesiology ◽

10.1097/aln.0b013e31818dac9c ◽

2008 ◽

Vol 109 (6) ◽

pp. 1077-1084 ◽

Cited By ~ 106

Author(s):

Ken-ichiro Hayashida ◽

Hideaki Obata ◽

Kunie Nakajima ◽

James C. Eisenach

Keyword(s):

Locus Coeruleus ◽

Dorsal Horn ◽

Nerve Injury ◽

Noradrenaline Release ◽

Spinal Dorsal Horn ◽

Local Action ◽

Male Rats ◽

Descending Inhibition ◽

Spinal Dorsal ◽

Brainstem Slices

Background Gabapentin recruits descending inhibition to produce analgesia after nerve injury, but whether this is a local action in the brainstem is unknown. The authors hypothesized that gabapentin activates noradrenergic neurons in the locus coeruleus (LC) by a local action. Methods Male rats underwent L5-L6 spinal nerve ligation (SNL) and received drugs by intra-LC or systemic routes for behavior testing, immunohistochemistry in the LC, and microdialysis in the spinal dorsal horn. In other studies, brainstem slices from normal and SNL animals were used for immunohistochemistry. Results SNL increased phosphorylated cyclic adenosine monophosphate response element binding protein (pCREB)-expressing nuclei bilaterally in the LC, and increased noradrenaline release in the spinal dorsal horn. Gabapentin, whether in isolated brainstem slices or in conscious or anesthetized animals, increased pCREB-expressing nuclei in the LC. The net increase in pCREB expression by gabapentin did not differ between normal and SNL conditions. This gabapentin-induced pCREB activation in LC neurons was abolished by an AMPA receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Intra-LC-injected gabapentin reduced hypersensitivity in SNL rats in a dose-dependent manner. Both intra-LC coadministration of CNQX and intrathecal administration of the alpha2-adrenoceptor antagonist idazoxan blocked antihypersensitivity by intra-LC gabapentin. Intravenous gabapentin induced noradrenaline release in the spinal dorsal horn. The net amount of noradrenaline release by gabapentin is larger in SNL rats compared with the normal condition, although the percentage increases from the baseline were the same. Conclusions These results suggest that gabapentin acts directly in the brainstem via a glutamate-dependent mechanism to stimulate descending inhibition to produce antihypersensitivity after peripheral nerve injury.

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