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The role of cytokines in MET-enkephalin-modulated nitric oxide release

T Marotti1, T Balog, R Mazuran

  • 1Department of Biology and Medicine, Ruder Bosković Institute, Zagreb, Croatia.

Neuropeptides
|May 8, 1998
PubMed

Insights

Met-enkephalin (MENK) affects nitric oxide (NO) release from macrophages differently in vitro and in vivo. In vivo, MENK bimodally modulated NO release, with stimulatory effects mediated by opioid receptors and cytokines.

Area of Science:

  • Immunology
  • Neuroscience
  • Pharmacology

Background:

  • Nitric oxide (NO) plays a crucial role in immune responses.
  • Opioid peptides, like Met-enkephalin (MENK), can modulate immune cell function.
  • The interaction between opioid signaling and NO production in macrophages is not fully understood.

Purpose of the Study:

  • To investigate the in vitro and in vivo effects of Met-enkephalin (MENK) on nitric oxide (NO) release by mouse peritoneal macrophages.
  • To determine the involvement of opioid receptors and cytokines in MENK-induced NO modulation.

Main Methods:

  • In vitro and in vivo experiments using mouse peritoneal macrophages.
  • Administration of varying doses of MENK (2.5, 5, 10 mg/kg bw).
  • Assessment of NO release, with and without naloxone (opioid receptor antagonist) and specific cytokine antibodies (anti-IL, anti-IFN gamma).

Main Results:

  • In vitro, MENK alone did not affect NO release, but enhanced it when combined with suboptimal interferon gamma (IFN gamma).
  • In vivo, MENK exhibited bimodal modulation of NO release: stimulatory at 2.5 and 10 mg/kg, and suppressive at 5 mg/kg.
  • The stimulatory effects were opioid receptor-mediated (blocked by naloxone) and associated with interleukin (IL) and IFN gamma production (blocked by specific antibodies).
  • The suppressive dose did not involve opioid receptors.

Conclusions:

  • Met-enkephalin modulates nitric oxide release from macrophages in a dose-dependent and context-specific manner.
  • In vivo, MENK's stimulatory effect on NO release is mediated through opioid receptors and involves the induction of cytokines like IL and IFN gamma.
  • These findings suggest that opioid-mediated immune responses can be significantly influenced by cytokine release.

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