Chemogenetic manipulation of microglia inhibits neuroinflammation and neuropathic pain in mice

AbstractMicroglia play an important role in the central sensitization and chronic pain. However, a direct connection between microglial function and the development of neuropathic pain in vivo remains incompletely understood. To address this issue, we applied chemogenetic approach by using CX3CR1creER/+:R26LSL-hM4Di/+ transgenic mice to enable expression of inhibitory Designer Receptors Exclusively Activated by Designer Drugs (Gi DREADD) exclusively in microglia. We found that microglial Gi DREADD activation inhibited spinal nerve transection (SNT)-induced microglial reactivity as well as chronic pain initiation and maintenance. Gi DREADD activation downregulated the transcription factor interferon regulatory factor 8 (IRF8) and its downstream target pro-inflammatory cytokine interleukin 1 beta (IL-1β). Using in vivo spinal cord recording, we found that activation of microglial Gi DREADD attenuated synaptic transmission following SNT. Our results demonstrate that microglial Gi DREADD reduces neuroinflammation, synaptic function and neuropathic pain after peripheral nerve injury. Thus, chemogenetic approaches provide a potential opportunity for interrogating microglial function and neuropathic pain treatment.

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Morphine paradoxically prolongs neuropathic pain in rats by amplifying spinal NLRP3 inflammasome activation

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1602070113 ◽

2016 ◽

Vol 113 (24) ◽

pp. E3441-E3450 ◽

Cited By ~ 150

Author(s):

Peter M. Grace ◽

Keith A. Strand ◽

Erika L. Galer ◽

Daniel J. Urban ◽

Xiaohui Wang ◽

...

Keyword(s):

Chronic Pain ◽

Neuropathic Pain ◽

Strong Support ◽

Designer Drugs ◽

Male Rats ◽

Receptor Protein ◽

Inflammasome Activation ◽

Opioid Use ◽

Nlrp3 Inflammasomes

Opioid use for pain management has dramatically increased, with little assessment of potential pathophysiological consequences for the primary pain condition. Here, a short course of morphine, starting 10 d after injury in male rats, paradoxically and remarkably doubled the duration of chronic constriction injury (CCI)-allodynia, months after morphine ceased. No such effect of opioids on neuropathic pain has previously been reported. Using pharmacologic and genetic approaches, we discovered that the initiation and maintenance of this multimonth prolongation of neuropathic pain was mediated by a previously unidentified mechanism for spinal cord and pain—namely, morphine-induced spinal NOD-like receptor protein 3 (NLRP3) inflammasomes and associated release of interleukin-1β (IL-1β). As spinal dorsal horn microglia expressed this signaling platform, these cells were selectively inhibited in vivo after transfection with a novel Designer Receptor Exclusively Activated by Designer Drugs (DREADD). Multiday treatment with the DREADD-specific ligand clozapine-N-oxide prevented and enduringly reversed morphine-induced persistent sensitization for weeks to months after cessation of clozapine-N-oxide. These data demonstrate both the critical importance of microglia and that maintenance of chronic pain created by early exposure to opioids can be disrupted, resetting pain to normal. These data also provide strong support for the recent “two-hit hypothesis” of microglial priming, leading to exaggerated reactivity after the second challenge, documented here in the context of nerve injury followed by morphine. This study predicts that prolonged pain is an unrealized and clinically concerning consequence of the abundant use of opioids in chronic pain.

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A Combination of Gabapentin and Morphine Mediates Enhanced Inhibitory Effects on Dorsal Horn Neuronal Responses in a Rat Model of Neuropathy

Anesthesiology ◽

10.1097/00000542-200203000-00020 ◽

2002 ◽

Vol 96 (3) ◽

pp. 633-640 ◽

Cited By ~ 91

Author(s):

Elizabeth A. Matthews ◽

Anthony H. Dickenson

Keyword(s):

Neuropathic Pain ◽

Dorsal Horn ◽

Low Dose ◽

Pain Treatment ◽

Clinical Problem ◽

Spinal Nerve ◽

Neuronal Responses ◽

Inhibitory Effects ◽

Combinational Treatment

Background Peripheral nerve damage can result in severe, long-lasting pain accompanied by sensory deficits. This neuropathic pain remains a clinical problem, and effective morphine analgesia is often limited by intolerable side effects. The antiepileptic gabapentin has recently emerged as an alternative chronic pain treatment. Improved management of the diverse symptoms and mechanisms of neuropathic pain may arise from combination therapy, based on multiple pharmacologic targets and low drug doses. Methods The authors used the Kim and Chung rodent model of neuropathy to induce mechanical and cold allodynia in the ipsilateral hind paw. In vivo electrophysiologic techniques were subsequently used to record evoked dorsal horn neuronal responses in which the effects of systemic morphine and gabapentin were investigated, both individually and in combination. Results Morphine (1 and 4 mg/kg) inhibited neuronal responses of control rats but not after neuropathy. Gabapentin (10 and 20 mg/kg) inhibited neuronal responses in nerve injured rats and to a lesser extent in sham rats but not in naive rats. In the presence of gabapentin (ineffective low dose of 10 mg/kg), morphine (1 and 3 mg/kg) mediated significant inhibitory effects in all experimental groups, with the greatest inhibitions observed in spinal nerve-ligated and sham-operated rats. After neuropathy, inhibitions mediated by morphine were significantly increased in the presence of gabapentin compared with morphine alone. Conclusions After spinal nerve ligation, the inhibitory effects of systemic morphine on evoked dorsal horn neuronal responses are reduced compared with control, whereas the effectiveness of systemic gabapentin is enhanced. In combination with low-dose gabapentin, significant improvement in the effectiveness of morphine is observed, which demonstrates a clinical potential for the use of morphine and gabapentin combinational treatment for neuropathic pain.

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The Potential Role of IL1RAP on Tumor Microenvironment-Related Inflammatory Factors in Stomach Adenocarcinoma

Technology in Cancer Research & Treatment ◽

10.1177/1533033821995282 ◽

2021 ◽

Vol 20 ◽

pp. 153303382199528

Author(s):

Qing Lv ◽

Qinghua Xia ◽

Anshu Li ◽

Zhiyong Wang

Keyword(s):

Tumor Microenvironment ◽

Interleukin 1 ◽

Mrna Level ◽

Inflammatory Factors ◽

Stomach Carcinoma ◽

Downstream Target ◽

Volume Weight

This study was performed to investigate the role of interleukin-1 receptor accessory protein (IL1RAP) in stomach carcinoma in vitro and in vivo, determine whether IL1RAP knockdown could regulate the development of stomach carcinoma, and elucidate the relationship between IL1RAP knockdown and inflammation by tumor microenvironment-related inflammatory factors in stomach carcinoma. We first used TCGA and GEPIA systems to predict the potential function of IL1RAP. Second, western blot and RT-PCR were used to analyze the expression, or mRNA level, of IL1RAP at different tissue or cell lines. Third, the occurrence and development of stomach carcinoma in vitro and in vivo were observed by using IL1RAP knockdown lentivirus. Finally, the inflammation of stomach carcinoma in vitro and in vivo was observed. Results show that in GEPIA and TCGA systems, IL1RAP expression in STAD tumor tissue was higher than normal, and high expression of IL1RAP in STAD patients had a worse prognostic outcome. Besides, GSEA shown IL1RAP was negative correlation of apopopsis, TLR4 and NF-κB signaling pathway. We also predicted that IL1RAP may related to IL-1 s, IL-33, and IL-36 s in STAD. The IL1RAP expression and mRNA level in tumor, or MGC803, cells were increased. Furthermore, IL1RAP knockdown by lentivirus could inhibit stomach carcinoma development in vitro and in vivo through weakening tumor cell proliferation, migration, invasion, therefore reducing tumor volume, weight, and biomarker levels, and increasing apoptotic level. Finally, we found IL1RAP knockdown could increase inflammation of tumor microenvironment-related inflammatory factors of stomach carcinoma, in vitro and in vivo. Our study demonstrates that IL1RAP is possibly able to regulate inflammation and apoptosis in stomach carcinoma. Furthermore, TLR4, NF-κB, IL-1 s, IL-33, and IL-36 s maybe the downstream target factor of IL1RAP in inflammation. These results may provide a new strategy for stomach carcinoma development by regulating inflammation.

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Locating the Site of Neuropathic Pain In Vivo Using MMP-12-Targeted Magnetic Nanoparticles

Pain Research and Management ◽

10.1155/2019/9394715 ◽

2019 ◽

Vol 2019 ◽

pp. 1-11 ◽

Cited By ~ 3

Author(s):

Syeda Fabeha Husain ◽

Raymond W. M. Lam ◽

Tao Hu ◽

Michael W. F. Ng ◽

Z. Q. G. Liau ◽

...

Keyword(s):

Neuropathic Pain ◽

Magnetic Resonance ◽

Intrathecal Injection ◽

Thermal Hyperalgesia ◽

Spinal Nerve ◽

Iron Oxide Nanoparticle ◽

Anatomical Location ◽

Spinal Nerves ◽

Potential Biomarker

Neuropathic pain remains underrecognised and ineffectively treated in chronic pain sufferers. Consequently, their quality of life is considerably reduced, and substantial healthcare costs are incurred. The anatomical location of pain must be identified for definitive diagnosis, but current neuropsychological tools cannot do so. Matrix metalloproteinases (MMP) are thought to maintain peripheral neuroinflammation, and MMP-12 is elevated particularly in such pathological conditions. Magnetic resonance imaging (MRI) of the peripheral nervous system has made headway, owing to its high-contrast resolution and multiplanar features. We sought to improve MRI specificity of neural lesions, by constructing an MMP-12-targeted magnetic iron oxide nanoparticle (IONP). Its in vivo efficiency was evaluated in a rodent model of neuropathic pain, where the left lumbar 5 (L5) spinal nerve was tightly ligated. Spinal nerve ligation (SNL) successfully induced mechanical allodynia, and thermal hyperalgesia, in the left hind paw throughout the study duration. These neuropathy characteristics were absent in animals that underwent sham surgery. MMP-12 upregulation with concomitant macrophage infiltration, demyelination, and elastin fibre loss was observed at the site of ligation. This was not observed in spinal nerves contralateral and ipsilateral to the ligated spinal nerve or uninjured left L5 spinal nerves. The synthesised MMP-12-targeted magnetic IONP was stable and nontoxic in vitro. It was administered onto the left L5 spinal nerve by intrathecal injection, and decreased magnetic resonance (MR) signal was observed at the site of ligation. Histology analysis confirmed the presence of iron in ligated spinal nerves, whereas iron was not detected in uninjured left L5 spinal nerves. Therefore, MMP-12 is a potential biomarker of neuropathic pain. Its detection in vivo, using IONP-enhanced MRI, may be further developed as a tool for neuropathic pain diagnosis and management.

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Usefulness of Olanzapine as an Adjunct to Opioid Treatment and for the Treatment of Neuropathic Pain

Anesthesiology ◽

10.1097/aln.0b013e31823c7e56 ◽

2012 ◽

Vol 116 (1) ◽

pp. 159-169 ◽

Cited By ~ 27

Author(s):

Kazuhiro Torigoe ◽

Kae Nakahara ◽

Mahardian Rahmadi ◽

Kazumi Yoshizawa ◽

Hiroshi Horiuchi ◽

...

Keyword(s):

Chronic Pain ◽

Neuropathic Pain ◽

Sleep Disturbance ◽

Brain Tissue ◽

Gastrointestinal Transit ◽

Thermal Hyperalgesia ◽

Nausea And Vomiting ◽

Dependent Manner ◽

Antiemetic Effect

Background The use of opioids for pain management is often associated with nausea and vomiting. Although conventional antipsychotics are often used to counter emesis, they can be associated with extrapyramidal symptoms. However, chronic pain can induce sleep disturbance. The authors investigated the effects of the atypical antipsychotic olanzapine on morphine-induced emesis and the sleep dysregulation associated with chronic pain. Methods A receptor binding assay was performed using mouse whole brain tissue. The emetic response in ferrets was evaluated by counting retching and vomiting behaviors. Catalepsy in mice was evaluated by placing both of their forepaws over a horizontal bar. Released dopamine was measured by an in vivo microdialysis study. Sleep disturbance in mice in a neuropathic pain-like state was assayed by electroencephalogram and electromyogram recordings. Results Olanzapine showed high affinity for muscarinic M1 receptor in brain tissue. Olanzapine decreased morphine-induced nausea and vomiting in a dose-dependent manner. However, olanzapine at a dose that had an antiemetic effect (0.03 mg/kg) did not induce catalepsy or hyperglycemia. In addition, olanzapine at this dose had no effect on the morphine-induced release of dopamine or inhibition of gastrointestinal transit. Finally, olanzapine inhibited thermal hyperalgesia and completely alleviated the sleep disturbance induced by sciatic nerve ligation. Conclusion These findings suggest that olanzapine may be useful for the treatment of morphine-induced emesis and as an adjunct for the treatment of neuropathic pain associated with sleep disturbance.

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Dorsal Root Ganglion (DRG) and Chronic Pain

Anesthesiology and Pain Medicine ◽

10.5812/aapm.113020 ◽

2021 ◽

Vol In Press (In Press) ◽

Author(s):

Amnon A. Berger ◽

Yao Liu ◽

HarLee Possoit ◽

Anna C. Rogers ◽

Warner Moore ◽

...

Keyword(s):

Quality Of Life ◽

Chronic Pain ◽

Neuropathic Pain ◽

Dorsal Root ◽

Randomized Trials ◽

Pain Treatment ◽

Common Condition ◽

Significant Morbidity ◽

Chronic Neuropathic Pain

Context: Chronic neuropathic pain is a common condition, and up to 11.9% of the population have been reported to suffer from uncontrolled neuropathic pain. Chronic pain leads to significant morbidity, lowered quality of life, and loss of workdays, and thus carries a significant price tag in healthcare costs and lost productivity. dorsal root ganglia (DRG) stimulation has been recently increasingly reported and shows promising results in the alleviation of chronic pain. This paper reviews the background of DRG stimulation, anatomical, and clinical consideration and reviews the clinical evidence to support its use. Evidence Acquisition: The DRG span the length of the spinal cord and house the neurons responsible for sensation from the periphery. They may become irritated by direct compression or local inflammation. Glial cells in the DRG respond to nerve injury, producing inflammatory markers and contribute to the development of chronic pain, even after the resolution of the original insult. While the underlying mechanism is still being explored, recent studies explored the efficacy of DRG stimulation and neuromodulation for chronic pain treatment. Results: Several reported cases and a small number of randomized trials were published in recent years, describing different methods of DRG stimulation and neuromodulation with promising results. Though evidence quality is mostly low, these results provide evidence to support the utilization of this technique. Conclusions: Chronic neuropathic pain is a common condition and carries significant morbidity and impact on the quality of life. Recent evidence supports the use of DRG neuromodulation as an effective technique to control chronic pain. Though studies are still emerging, the evidence appears to support this technique. Further studies, including large randomized trials evaluating DRG modulation versus other interventional and non-interventional techniques, are needed to further elucidate the efficacy of this method. These studies are also likely to inform the patient selection and the course of treatment.

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Systemic Antiinflammatory Corticosteroid Reduces Mechanical Pain Behavior, Sympathetic Sprouting, and Elevation of Proinflammatory Cytokines in a Rat Model of Neuropathic Pain

Anesthesiology ◽

10.1097/01.anes.0000278907.37774.8d ◽

2007 ◽

Vol 107 (3) ◽

pp. 469-477 ◽

Cited By ~ 64

Author(s):

Huiqing Li ◽

Wenrui Xie ◽

Judith A. Strong ◽

Jun-Ming Zhang

Keyword(s):

Chronic Pain ◽

Neuropathic Pain ◽

Nerve Injury ◽

Protein Profile ◽

Spinal Nerve ◽

Interleukin 4 ◽

Sensory Ganglia ◽

Monocyte Chemoattractant Protein 1 ◽

Inflammatory Processes ◽

Sympathetic Sprouting

Background Chronic pain models are commonly defined as either nerve-injury or inflammation models, but recent work suggests inflammatory processes are important in nerve injury-induced pain. Methods In the rat spinal nerve ligation model, the authors examined effects of systemic corticosteroid triamcinolone acetonide (TA) on the cytokine protein profile and sympathetic sprouting in the axotomized sensory ganglia, excitability of sensory neurons, and mechanical sensitivity. Results By postoperative day 3, marked increases (5- to 16-fold) in monocyte chemoattractant protein-1, growth-related oncogene (GRO/KC or CXCL1), and interleukin (IL)-6 were observed, whereas IL-4 and IL-2 levels fell more than fourfold. The increased cytokines and number of sympathetic basket formations in the sensory ganglia were reduced toward normal values by TA given starting at the time of injury. Interleukin-4 and IL-2 levels were not restored by TA. Systemic TA also reduced the firing rate and incidence of bursting activity, but not the overall incidence of spontaneous activity, in large- and medium-sized neurons. Mechanical hypersensitivity on postoperative day 3 was reduced by TA, and some effect could still be observed 4 days after cessation of TA. However, starting TA at day 7 was ineffective. Conclusions Several components of the spinal nerve injury model are responsive to corticosteroid, suggesting inflammatory processes are important in the development of neuropathic pain. The observation that TA was effective when given starting at the time of injury suggests that steroid treatment might alter the development of chronic pain after surgical procedures that involve nerve injury, such as amputation or hernia repair.

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Targeting the CaVα-β interaction yields a selective antagonist of the N-type CaV2.2 channel with broad antinociceptive efficacy

10.1101/492181 ◽

2018 ◽

Author(s):

Aude Chefdeville ◽

Jie Yu ◽

Xiaofang Yang ◽

Aubin Moutal ◽

Vijay Gokhale ◽

...

Keyword(s):

Chronic Pain ◽

Small Molecule ◽

Neurological Diseases ◽

Motor Impairment ◽

Common Adverse Effect ◽

Spinal Nerve ◽

Subunit Structure ◽

Α Subunit ◽

Voltage Gated

AbstractInhibition of voltage-gated calcium (CaV) channels is a potential therapy for many neurological diseases including chronic pain. Neuronal CaV1/CaV2 channels are composed of α, β and α2δ subunits. The β-subunits of CaV channels are cytoplasmic proteins that increase the surface expression of the pore-forming α subunit of CaV. We targeted the high-affinity protein-protein interface of CaVβ’s pocket within the CaVα-subunit. Structure-based virtual screening of 50,000 small molecule library docked to the β-subunit led to the identification of 2-(3,5-dimethylisoxazol-4-yl)-N-((4-((3-phenylpropyl)amino)quinazolin-2-yl)methyl)acetamide (compound 45). This small molecule bound to CaVβ and inhibited its coupling with N-type voltage-gated calcium (CaV2.2) channels, leading to a reduction in CaV2.2 currents in rat dorsal root ganglion (DRG) sensory neurons, decreased pre-synaptic localization of CaV2.2 in vivo, decreased frequency of spontaneous excitatory post-synaptic potentials (sEPSC), and inhibited release of the nociceptive neurotransmitter calcitonin gene related peptide (CGRP) from spinal cord. 45 was antinociceptive in naïve animals and reversed allodynia and hyperalgesia in models of acute (post-surgical) and neuropathic (spinal nerve ligation, chemotherapy- and gp120-induced peripheral neuropathy, and genome-edited neuropathy) pain. 45 did not cause akinesia or motor impairment, a common adverse effect of CaV2.2 targeting drugs, when injected into the brain. 45, a quinazoline analog, represents a novel class of CaV2.2-targeting compounds that may serve as probes to interrogate CaVα-β function and ultimately be developed as a non-opioid therapeutic for chronic pain.

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Opioid Facilitation of Rewarding Electrical Brain Stimulation Is Suppressed in Rats with Neuropathic Pain

Anesthesiology ◽

10.1097/aln.0b013e31820a4edb ◽

2011 ◽

Vol 114 (3) ◽

pp. 624-632 ◽

Cited By ~ 29

Author(s):

Eric E. Ewan ◽

Thomas J. Martin

Keyword(s):

Chronic Pain ◽

Neuropathic Pain ◽

Electrical Stimulation ◽

Ventral Tegmental Area ◽

Drugs Of Abuse ◽

Spinal Nerve ◽

Abuse Liability ◽

Prescription Opioid ◽

Ventral Tegmental ◽

Stimulation Of

Introduction Opioids are powerful analgesics, but are also common drugs of abuse. Few studies have examined how neuropathic pain alters the pharmacology of opioids in modulating limbic pathways that underlie abuse liability. Methods Rats with or without spinal nerve ligation (SNL) were implanted with electrodes into the left ventral tegmental area and trained to lever press for electrical stimulation. The effects of morphine, heroin, and cocaine on facilitating electrical stimulation of the ventral tegmental area and mechanical allodynia were assessed in SNL and control subjects. Results Responding for electrical stimulation of the ventral tegmental area was similar in control and SNL rats. The frequency at which rats emitted 50% of maximal responding was 98.2 ± 5.1 (mean ± SEM) and 93.7 ± 2.8 Hz in control and SNL rats, respectively. Morphine reduced the frequency at which rats emitted 50% of maximal responding in control (maximal shift of 14.8 ± 3.1 Hz), but not SNL (2.3 ± 2.2 Hz) rats. Heroin was less potent in SNL rats, whereas cocaine produced similar shifts in control (42.3 ± 2.0 Hz) and SNL (37.5 ± 4.2 Hz) rats. Conclusions Nerve injury suppressed potentiation of electrical stimulation of the ventral tegmental area by opioids, suggesting that the positive reinforcing effects are diminished by chronic pain. Given concerns regarding prescription opioid abuse, developing strategies that assess both analgesia and abuse liability within the context of chronic pain may aid in determining which opioids are most suitable for treating chronic pain when abuse is a concern.

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Cannabinoids suppress inflammatory and neuropathic pain by targeting α3 glycine receptors

Journal of Experimental Medicine ◽

10.1084/jem.20120242 ◽

2012 ◽

Vol 209 (6) ◽

pp. 1121-1134 ◽

Cited By ~ 129

Author(s):

Wei Xiong ◽

Tanxing Cui ◽

Kejun Cheng ◽

Fei Yang ◽

Shao-Rui Chen ◽

...

Keyword(s):

Chronic Pain ◽

Neuropathic Pain ◽

Transmembrane Domain ◽

Pain Treatment ◽

Direct Interaction ◽

Intrathecal Administration ◽

Glycine Receptors ◽

Analgesic Tolerance ◽

Dorsal Horn Neurons ◽

Chronic Pain Treatment

Certain types of nonpsychoactive cannabinoids can potentiate glycine receptors (GlyRs), an important target for nociceptive regulation at the spinal level. However, little is known about the potential and mechanism of glycinergic cannabinoids for chronic pain treatment. We report that systemic and intrathecal administration of cannabidiol (CBD), a major nonpsychoactive component of marijuana, and its modified derivatives significantly suppress chronic inflammatory and neuropathic pain without causing apparent analgesic tolerance in rodents. The cannabinoids significantly potentiate glycine currents in dorsal horn neurons in rat spinal cord slices. The analgesic potency of 11 structurally similar cannabinoids is positively correlated with cannabinoid potentiation of the α3 GlyRs. In contrast, the cannabinoid analgesia is neither correlated with their binding affinity for CB1 and CB2 receptors nor with their psychoactive side effects. NMR analysis reveals a direct interaction between CBD and S296 in the third transmembrane domain of purified α3 GlyR. The cannabinoid-induced analgesic effect is absent in mice lacking the α3 GlyRs. Our findings suggest that the α3 GlyRs mediate glycinergic cannabinoid-induced suppression of chronic pain. These cannabinoids may represent a novel class of therapeutic agents for the treatment of chronic pain and other diseases involving GlyR dysfunction.

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