Pharmacological characterization of LPS and opioid interactions at the toll-like receptor 4

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Abstract

Background and Purpose Previous work in our laboratory showed opioid agents inhibit cytokine expression in astrocytes. Recently, Watkins and colleagues hypothesized that opioid agonists activate toll-like receptor 4 (TLR4) signalling, which leads to neuroinflammation. To test this hypothesis, we characterized LPS and opioid effects on TLR4 signalling in reporter cells. Experimental Approach NF-κB reporter cells expressing high levels of TLR4 were used to compare LPS and opioid effects on NF-κB activation, a pathway activated by TLR4 stimulation. Key Results LPS increased TLR4 signalling in a concentration-dependent manner and was antagonized by LPS antagonist (LPS-RS, from Rhodobacter sphaeroides). A concentration ratio analysis showed that LPS-RS was a competitive antagonist. The opioid agonists, morphine and fentanyl, produced minor activation of TLR4 signalling when given alone. When tested following LPS stimulation, opioid agonists inhibited NF-κB activation but this inhibition was not blocked by the general opioid antagonist, naloxone, nor by the selective μ opioid receptor antagonist, β-FNA. Indeed, both naloxone and β-FNA also inhibited NF-κB activation in reporter cells. Further examination of fentanyl and β-FNA effects revealed that both opioid agents inhibited LPS signalling in a non-competitive fashion. Conclusions and Implications These results show that LPS-RS is a competitive antagonist at the TLR4 complex, and that both opioid agonists and antagonists inhibit LPS signalling in a non-competitive fashion through a non-GPCR, opioid site(s) in the TLR4 signalling pathway. If confirmed, existing opioid agents or other drug molecules more selective at this novel site may provide a new therapeutic approach to the treatment of neuroinflammation.

Original languageEnglish
Pages (from-to)1421-1429
Number of pages9
JournalBritish Journal of Pharmacology
Volume168
Issue number6
DOIs
StatePublished - 1 Mar 2013

Fingerprint

Toll-Like Receptor 4
Opioid Analgesics
Pharmacology
Narcotic Antagonists
Fentanyl
Naloxone
Rhodobacter sphaeroides
Astrocytes
Morphine
Cytokines

Keywords

  • FNA
  • fentanyl
  • lipopolysaccharide (LPS)
  • morphine
  • naltrexone
  • opioid-immune crosstalk
  • opioids
  • toll-like receptor 4 (TLR4)

Cite this

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title = "Pharmacological characterization of LPS and opioid interactions at the toll-like receptor 4",
abstract = "Background and Purpose Previous work in our laboratory showed opioid agents inhibit cytokine expression in astrocytes. Recently, Watkins and colleagues hypothesized that opioid agonists activate toll-like receptor 4 (TLR4) signalling, which leads to neuroinflammation. To test this hypothesis, we characterized LPS and opioid effects on TLR4 signalling in reporter cells. Experimental Approach NF-κB reporter cells expressing high levels of TLR4 were used to compare LPS and opioid effects on NF-κB activation, a pathway activated by TLR4 stimulation. Key Results LPS increased TLR4 signalling in a concentration-dependent manner and was antagonized by LPS antagonist (LPS-RS, from Rhodobacter sphaeroides). A concentration ratio analysis showed that LPS-RS was a competitive antagonist. The opioid agonists, morphine and fentanyl, produced minor activation of TLR4 signalling when given alone. When tested following LPS stimulation, opioid agonists inhibited NF-κB activation but this inhibition was not blocked by the general opioid antagonist, naloxone, nor by the selective μ opioid receptor antagonist, β-FNA. Indeed, both naloxone and β-FNA also inhibited NF-κB activation in reporter cells. Further examination of fentanyl and β-FNA effects revealed that both opioid agents inhibited LPS signalling in a non-competitive fashion. Conclusions and Implications These results show that LPS-RS is a competitive antagonist at the TLR4 complex, and that both opioid agonists and antagonists inhibit LPS signalling in a non-competitive fashion through a non-GPCR, opioid site(s) in the TLR4 signalling pathway. If confirmed, existing opioid agents or other drug molecules more selective at this novel site may provide a new therapeutic approach to the treatment of neuroinflammation.",
keywords = "FNA, fentanyl, lipopolysaccharide (LPS), morphine, naltrexone, opioid-immune crosstalk, opioids, toll-like receptor 4 (TLR4)",
author = "Craig Stevens and S. Aravind and Subhas Das and Randall Davis",
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Pharmacological characterization of LPS and opioid interactions at the toll-like receptor 4. / Stevens, Craig; Aravind, S.; Das, Subhas; Davis, Randall.

In: British Journal of Pharmacology, Vol. 168, No. 6, 01.03.2013, p. 1421-1429.

Research output: Contribution to journalArticle

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T1 - Pharmacological characterization of LPS and opioid interactions at the toll-like receptor 4

AU - Stevens, Craig

AU - Aravind, S.

AU - Das, Subhas

AU - Davis, Randall

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AB - Background and Purpose Previous work in our laboratory showed opioid agents inhibit cytokine expression in astrocytes. Recently, Watkins and colleagues hypothesized that opioid agonists activate toll-like receptor 4 (TLR4) signalling, which leads to neuroinflammation. To test this hypothesis, we characterized LPS and opioid effects on TLR4 signalling in reporter cells. Experimental Approach NF-κB reporter cells expressing high levels of TLR4 were used to compare LPS and opioid effects on NF-κB activation, a pathway activated by TLR4 stimulation. Key Results LPS increased TLR4 signalling in a concentration-dependent manner and was antagonized by LPS antagonist (LPS-RS, from Rhodobacter sphaeroides). A concentration ratio analysis showed that LPS-RS was a competitive antagonist. The opioid agonists, morphine and fentanyl, produced minor activation of TLR4 signalling when given alone. When tested following LPS stimulation, opioid agonists inhibited NF-κB activation but this inhibition was not blocked by the general opioid antagonist, naloxone, nor by the selective μ opioid receptor antagonist, β-FNA. Indeed, both naloxone and β-FNA also inhibited NF-κB activation in reporter cells. Further examination of fentanyl and β-FNA effects revealed that both opioid agents inhibited LPS signalling in a non-competitive fashion. Conclusions and Implications These results show that LPS-RS is a competitive antagonist at the TLR4 complex, and that both opioid agonists and antagonists inhibit LPS signalling in a non-competitive fashion through a non-GPCR, opioid site(s) in the TLR4 signalling pathway. If confirmed, existing opioid agents or other drug molecules more selective at this novel site may provide a new therapeutic approach to the treatment of neuroinflammation.

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KW - naltrexone

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