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Toll-like Receptor 4 Mediates Morphine-Induced Neuroinflammation and Tolerance via Soluble Tumor Necrosis Factor Signaling.

ABSTRACT: Opioid tolerance and the potential for addiction is a significant burden associated with pain management, yet its precise underlying mechanism and prevention remain elusive. Immune signaling contributes to the decreased efficacy of opioids, and we recently demonstrated that Toll-like receptor 4 (TLR4)-mediated neuroinflammation in the periaqueductal gray (PAG) drives tolerance. Tumor necrosis factor (TNF), a product of TLR4 signaling, promotes inflammation and facilitates glutamatergic signaling, key components of opioid tolerance. Therefore, we hypothesize that TLR4-mediated opioid tolerance requires TNF signaling. By expression of a dominant-negative TNF peptide via lentiviral vector injection in rat PAG to sequester soluble TNF (solTNF), we demonstrate that solTNF mediates morphine tolerance induced by TLR4 signaling, stimulates neuroinflammation (increased IL-1? and TLR4 mRNA), and disrupts glutamate reuptake (decreased GLT-1 and GLAST mRNA). We further demonstrate the efficacy of the brain-permeant PEGylated version of the anti-solTNF peptide, XPro1595, injected systemically, to normalize morphine-induced CNS neuroinflammation and morphine- and endotoxin-induced changes in glutamate transport, effectively preserving the efficacy of morphine analgesia and eliminating tolerance. Our findings provide a novel pharmacological target for the prevention of opioid-induced immune signaling, tolerance, and addiction.

SUBMITTER: Eidson LN

PROVIDER: S-EPMC5240168 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Toll-like Receptor 4 Mediates Morphine-Induced Neuroinflammation and Tolerance via Soluble Tumor Necrosis Factor Signaling.

Eidson Lori N LN Inoue Kiyoshi K Young Larry J LJ Tansey Malu G MG Murphy Anne Z AZ

Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology 20160727 3

Opioid tolerance and the potential for addiction is a significant burden associated with pain management, yet its precise underlying mechanism and prevention remain elusive. Immune signaling contributes to the decreased efficacy of opioids, and we recently demonstrated that Toll-like receptor 4 (TLR4)-mediated neuroinflammation in the periaqueductal gray (PAG) drives tolerance. Tumor necrosis factor (TNF), a product of TLR4 signaling, promotes inflammation and facilitates glutamatergic signaling ...[more]

PMID: 27461080

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Project description:Biochemical irritation of the dorsal root ganglion (DRG) after intervertebral disc herniation contributes to radiculopathy through tumor necrosis factor-alpha (TNFalpha)-mediated inflammation. Soluble TNF receptor Type II (sTNFRII) sequesters this cytokine, providing clinical benefit. Previous work involving conjugation of sTNFRII with thermally responsive elastin-like polypeptide (ELP) yielded a chimeric protein (ELP-sTNFRII) with in vitro anti-TNFalpha bioactivity. Furthermore, temperature-triggered ELP aggregation into a "depot" prolongs protein residence time following perineural injection. In this study the authors evaluated the inflammatory phenotype of DRG explants after TNFalpha stimulation, and assessed the abilities of sTNFRII or ELP-sTNFRII to attenuate these neuro-inflammatory changes.Rat lumbar DRGs (35 animals) were treated in 6 groups, as follows: control; TNFalpha (25 ng/ml); TNFalpha with low-(0.2 microg/ml) or high-dose (1 microg/ml) sTNFRII; and TNFalpha with low-(52.5 microg/ml) or high-dose (262.5 microg/ml) ELP-sTNFRII. After 24 hours, supernatant was evaluated for inflammatory cytokines (interleukin [IL]-1, IL-6, and IL-10); prostaglandin E2; and metabolites (glutamate, lactate, and pyruvate). Single-factor analysis of variance with post hoc Dunn analysis (alpha = 0.05) was used to assess treatment differences.Incubation of explants with TNFalpha caused metabolic stress reflected by an increased lactate/pyruvate ratio (1.8 +/- 0.5-fold) and extracellular glutamate (79 +/- 8% increase). Inflammatory activation was observed with heightened IL-6 release (5.2 +/- 1.4-fold) and prostaglandin E2 production (14 +/- 3-fold). An autoregulatory response occurred with an 11.8 +/- 0.6-fold increase in sTNFRI shedding. Treatment with high doses of sTNFRII or ELP-sTNFRII reversed all changes. Values are expressed as the mean +/- standard deviation.These results demonstrate that TNFalpha stimulation of DRG explants yields a phenotype of neurotoxic metabolite release and inflammatory mediator expression. Coincubation with either sTNFRII or ELP-sTNFRII antagonizes TNFalpha activity to abrogate these changes, suggesting potential for therapeutic intervention to treat peripheral nerve inflammatory disease.

Project description:Tumor necrosis factor (TNF) is elevated in human abdominal aortic aneurysms (AAA). Non-selective TNF inhibition has been linked to several severe side effects. Compounds that target the proinflammatory soluble TNF (solTNF) while preserving the immunomodulatory capabilities of transmembrane TNF (tmTNF) may prevent such side effects. We hypothesize that inhibition of solTNF signaling by XPro1595 is just as effective as non-selective TNF inhibition by etanercept (ETN) in preventing AAA expansion. The effect of XPro1595 and ETN was examined in porcine pancreatic elastase (PPE) induced AAA mice and findings of XPro1595 was confirmed in Angiotensin II (AngII) induced AAA in hyperlipidemic apolipoprotein E (Apoe) -/- mice. XPro1595 treatment significantly reduced AAA expansion in both models, while a similar trend (p=0.06) was observed in ETN-treated mice using the PPE model. In the PPE aneurysm wall, elastin integrity scores were significantly improved in the XPro1595 group. In the aneurysms, mean TNFR1wasreduced no-significantly (p=0.07) by 50% non-significant after TNF inhibition, but the cellular location in murine AAAs were unaffected and like the localization in human AAAs. Systemic TNF levels were elevated in XPro1595-treated mice, while systemic IL-10 levels were significantly increased after ETN-treatment, while in AngII induced AAA mice systemic TNF and IL5 levels were elevated after XPro1595 treatment. In early AAA development, proteomic analyses revealed that components of the fibrinogen complex were elevated while prostaglandin E2 synthase was down regulated by Xpro1595 (unadjusted p-values). David’s ontology analyses revealed that several pathways including cell matrix adhesion, extracellular space, fibrinogen complex, blood microparticles and glycoproteins were elevated by XPro1595 treatment. In conclusion, selective inhibition of solTNF reduces aneurysm expansion. This supports targeting solTNF as an attractive treatment option for AAA patients.

Dataset Information

Toll-like Receptor 4 Mediates Morphine-Induced Neuroinflammation and Tolerance via Soluble Tumor Necrosis Factor Signaling.

Publications

Toll-like Receptor 4 Mediates Morphine-Induced Neuroinflammation and Tolerance via Soluble Tumor Necrosis Factor Signaling.

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