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Methionine-enkephalin modulation of hydrogen peroxide (H2O2) release by rat peritoneal macrophages involves different

Stanislava Stanojević1, Vesna Vujić, Katarina Mitić

  • 1Institute of Virology, Vaccines and Sera Torlak, Immunology Research Centre Branislav Janković, Vojvode Stepe 458, 11152 Belgrade, Serbia. canac@EUnet.yu

Neuropeptides
|February 2, 2008
PubMed

Insights

Methionine-enkephalin (MET) differentially modulates hydrogen peroxide (H2O2) release in rat macrophages, with effects mediated by specific opioid receptor interactions. Individual macrophage capacity may influence these MET-induced opioid receptor responses.

Area of Science:

  • Immunology
  • Neuroscience
  • Pharmacology

Background:

  • Opioid receptors play a role in immune cell function.
  • Methionine-enkephalin (MET) is an endogenous opioid peptide.
  • Hydrogen peroxide (H2O2) is a reactive oxygen species involved in cellular signaling.

Purpose of the Study:

  • To investigate the specific opioid receptor subtypes involved in MET-induced modulation of H2O2 release by rat macrophages.
  • To determine how MET affects H2O2 release, which can be either increased or decreased.
  • To elucidate the functional interactions between opioid receptors in mediating these effects.

Main Methods:

  • Rat peritoneal macrophages were primed with phorbol myristate acetate (PMA).
  • Macrophages were treated with varying concentrations of MET.
  • H2O2 release was measured using the phenol red assay.
  • Opioid receptor antagonists were used to block specific receptor actions.

Main Results:

  • MET induced either an increase or decrease in H2O2 release in different macrophage samples.
  • Increased H2O2 release was blocked by antagonists for delta1,2 and mu, or delta1,2 and kappa opioid receptors.
  • Decreased H2O2 release was prevented by antagonists for delta1,2 or mu receptors, or combinations thereof.
  • Specific opioid receptor interactions (e.g., delta-mu, delta-kappa) mediated MET's effects.

Conclusions:

  • MET's effect on macrophage H2O2 release is dependent on specific opioid receptor subtypes and their interactions.
  • The direction of MET's effect (increase or decrease) is linked to distinct combinations of opioid receptor signaling.
  • Individual differences in macrophage H2O2 production capacity might pre-determine the expression of opioid receptors and thus the response to MET.

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