The Inhibition of Subchondral Bone Lesions Significantly Reversed the Weight-Bearing Deficit and the Overexpression of CGRP in DRG Neurons, GFAP and Iba-1 in the Spinal Dorsal Horn in the Monosodium Iodoacetate Induced Model of Osteoarthritis Pain

The monosodium iodoacetate knee osteoarthritis model has been widely used for the evaluation of osteoarthritis pain, but the pathogenesis of associated chronic pain is not fully understood. The T-type calcium channel 3.2 (CaV3.2) is abundantly expressed in the primary sensory neurons, in which it regulates neuronal excitability at both the somata and peripheral terminals and facilitates spontaneous neurotransmitter release at the spinal terminals. In this study, we investigated the involvement of primary sensory neuron-CaV3.2 activation in monosodium iodoacetate osteoarthritis pain. Knee joint osteoarthritis pain was induced by intra-articular injection of monosodium iodoacetate (2 mg) in rats, and sensory behavior was evaluated for 35 days. At that time, knee joint structural histology, primary sensory neuron injury, and inflammatory gliosis in lumbar dorsal root ganglia, and spinal dorsal horn were examined. Primary sensory neuron-T-type calcium channel current by patch-clamp recording and CaV3.2 expression by immunohistochemistry and immunoblots were determined. In a subset of animals, pain relief by CaV3.2 inhibition after delivery of CaV3.2 inhibitor TTA-P2 into sciatic nerve was investigated. Knee injection of monosodium iodoacetate resulted in osteoarthritis histopathology, weight-bearing asymmetry, sensory hypersensitivity of the ipsilateral hindpaw, and inflammatory gliosis in the ipsilateral dorsal root ganglia, sciatic nerve, and spinal dorsal horn. Neuronal injury marker ATF-3 was extensively upregulated in primary sensory neurons, suggesting that neuronal damage was beyond merely knee-innervating primary sensory neurons. T-type current in dissociated primary sensory neurons from lumbar dorsal root ganglia of monosodium iodoacetate rats was significantly increased, and CaV3.2 protein levels in the dorsal root ganglia and spinal dorsal horn ipsilateral to monosodium iodoacetate by immunoblots were significantly increased, compared to controls. Perineural application of TTA-P2 into the ipsilateral sciatic nerve alleviated mechanical hypersensitivity and weight-bearing asymmetry in monosodium iodoacetate osteoarthritis rats. Overall, our findings demonstrate an elevated CaV3.2 expression and enhanced function of primary sensory neuron-T channels in the monosodium iodoacetate osteoarthritis pain. Further study is needed to delineate the importance of dysfunctional primary sensory neuron-CaV3.2 in osteoarthritis pain.

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Role of Primary Afferents in Arthritis Induced Spinal Microglial Reactivity

Frontiers in Immunology ◽

10.3389/fimmu.2021.626884 ◽

2021 ◽

Vol 12 ◽

Author(s):

Charlie H. T. Kwok ◽

Yuta Kohro ◽

Michael Mousseau ◽

Melissa S. O’Brien ◽

John R. Matyas ◽

...

Keyword(s):

Dorsal Horn ◽

Spinal Dorsal Horn ◽

Atp Release ◽

Afferent Input ◽

Female Rats ◽

Male Rats ◽

Joint Injury ◽

Joint Afferents ◽

Spinal Dorsal ◽

Monosodium Iodoacetate

Increased afferent input resulting from painful injury augments the activity of central nociceptive circuits via both neuron-neuron and neuron-glia interactions. Microglia, resident immune cells of the central nervous system (CNS), play a crucial role in the pathogenesis of chronic pain. This study provides a framework for understanding how peripheral joint injury signals the CNS to engage spinal microglial responses. During the first week of monosodium iodoacetate (MIA)-induced knee joint injury in male rats, inflammatory and neuropathic pain were characterized by increased firing of peripheral joint afferents. This increased peripheral afferent activity was accompanied by increased Iba1 immunoreactivity within the spinal dorsal horn indicating microglial activation. Pharmacological silencing of C and A afferents with co-injections of QX-314 and bupivacaine, capsaicin, or flagellin prevented the development of mechanical allodynia and spinal microglial activity after MIA injection. Elevated levels of ATP in the cerebrospinal fluid (CSF) and increased expression of the ATP transporter vesicular nucleotide transporter (VNUT) in the ipsilateral spinal dorsal horn were also observed after MIA injections. Selective silencing of primary joint afferents subsequently inhibited ATP release into the CSF. Furthermore, increased spinal microglial reactivity, and alleviation of MIA-induced arthralgia with co-administration of QX-314 with bupivacaine were recapitulated in female rats. Our results demonstrate that early peripheral joint injury activates joint nociceptors, which triggers a central spinal microglial response. Elevation of ATP in the CSF, and spinal expression of VNUT suggest ATP signaling may modulate communication between sensory neurons and spinal microglia at 2 weeks of joint degeneration.

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Preliminary Study on Pain Reduction of Monosodium Iodoacetate-Induced Knee Osteoarthritis in Rats by Carbon Dioxide Laser Moxibustion

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2014/754304 ◽

2014 ◽

Vol 2014 ◽

pp. 1-7 ◽

Cited By ~ 4

Author(s):

Fan Wu ◽

Ruixing Zhang ◽

Xueyong Shen ◽

Lixing Lao

Keyword(s):

Treatment Group ◽

Knee Osteoarthritis ◽

Dorsal Horn ◽

Carbon Dioxide Laser ◽

Spinal Dorsal Horn ◽

Pain Reduction ◽

Control Group ◽

Blank Control Group ◽

Spinal Dorsal ◽

Monosodium Iodoacetate

In order to study the effects of CO2laser moxibustion on the pain and inflammatory cytokine expression in the spinal dorsal horn of rats with monosodium iodoacetate- (MIA-) induced knee osteoarthritis (KOA), we designed an experiment by randomly assigning 8 SD rats into 3 groups, namely, a CO2laser moxibustion group, a sham treatment group, and a blank control group. The treatment group received a laser moxibustion on acupoint Dubi (ST 35; 5 min/treatment, 1 treatment/day) for 8 days, and after treatment, the rats exhibited significantly increased interhindpaw differences compared with their preinduction values. Meanwhile, cytokine microarray analysis showed that one cytokine (TIMP-1) was significantly upregulated and two cytokines (Agrin and MMP-8) were significantly downregulated in treatment group. The present study suggested that CO2laser moxibustion created certain pain reduction in the rats with MIA-induced KOA and significantly inhibited the expression of most inflammatory cytokines in the ipsilateral spinal dorsal horn.

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Convergence of peptidergic and non-peptidergic protein markers in the human dorsal root ganglion and spinal dorsal horn

10.1101/2020.10.14.339382 ◽

2020 ◽

Author(s):

Stephanie Shiers ◽

Ishwarya Sankaranarayanan ◽

Vivek Jeevakumar ◽

Anna Cervantes ◽

Jeffrey C. Reese ◽

...

Keyword(s):

Spinal Cord ◽

Dorsal Root Ganglion ◽

Dorsal Horn ◽

Dorsal Root ◽

Spinal Dorsal Horn ◽

Molecular Signature ◽

Central Projection ◽

Protein Distribution ◽

Drg Neurons ◽

Spinal Dorsal

AbstractPeripheral sensory neurons are characterized by their size, molecular profiles, and physiological responses to specific stimuli. In mouse, the peptidergic and non-peptidergic subsets of nociceptors are distinct and innervate different lamina of the spinal dorsal horn. The unique molecular signature and neuroanatomical organization of these neurons supports a labeled line theory for certain types of nociceptive stimuli. However, long standing evidence supports the polymodal nature of nociceptors in many species. We have recently shown that the peptidergic marker, CGRP, and the non-peptidergic marker, P2X3R, show largely overlapping expression at the mRNA level in human dorsal root ganglion (DRG). Herein, our aim was to assess the protein distribution of nociceptor markers, including their central projections, in the human DRG and spinal cord. Using DRGs obtained from organ donors, we observed that CGRP and P2X3R were co-expressed by approximately 33% of human DRG neurons and TrpV1 was expressed in ~60% of human DRG neurons. In the dorsal spinal cord, CGRP, P2X3R, TrpV1 and Nav1.7 protein stained the entirety of lamina II, with only P2XR3 showing a gradient of expression. This was confirmed by measuring the size of the substantia gelatinosa using Hematoxylin and Eosin staining of adjacent sections. Our findings are consistent with the known polymodal nature of most primate nociceptors and indicate that the central projection patterns of nociceptors are different between mice and humans. Elucidating how human nociceptors connect to subsets of dorsal horn neurons will be important for understanding the physiological consequences of these species differences.

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Single Intraperitoneal Injection of Low-Dose Ketamine Pretreatment Alleviates Mechanical Hyperalgesia and Downregulates the Expression of Inflammatory Cytokines in Spinal Dorsal Horn of Rats

Journal of Anesthesia and Perioperative Medicine ◽

10.24015/japm.2015.0032 ◽

2015 ◽

Vol 2 (5) ◽

pp. 236-243

Author(s):

Li Xu ◽

Yu Shen ◽

Lin Liu ◽

Yin Cui ◽

Xiao-Ping Gu ◽

...

Keyword(s):

Dorsal Horn ◽

Inflammatory Cytokines ◽

Intraperitoneal Injection ◽

Spinal Dorsal Horn ◽

Low Dose ◽

Mechanical Hyperalgesia ◽

Spinal Dorsal ◽

Single Intraperitoneal Injection

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Faculty Opinions recommendation of Spread of excitation across modality borders in spinal dorsal horn of neuropathic rats.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1105023.561186 ◽

2008 ◽

Author(s):

Nanna Finnerup

Keyword(s):

Dorsal Horn ◽

Spinal Dorsal Horn ◽

Spinal Dorsal ◽

Spread Of Excitation

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Faculty Opinions recommendation of Innocuous, not noxious, input activates PKCgamma interneurons of the spinal dorsal horn via myelinated afferent fibers.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1120062.576194 ◽

2008 ◽

Author(s):

Nanna Finnerup

Keyword(s):

Dorsal Horn ◽

Spinal Dorsal Horn ◽

Spinal Dorsal ◽

Afferent Fibers

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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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