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Modulation of superoxide anion release from human polymorphonuclear cells by Met- and Leu-enkephalin
1Department of Experimental Biology and Medicine, Rudjer Bosković Institute, Zagreb, Yugoslavia.
Abstract:
The present work describes the ability of Met- and Leu-enkephalin to modulate the superoxide anion (O2-) release from unstimulated human polymorphonuclear cells (PMN) and from PMN stimulated with phorbol myristate acetate (PMA). The direction (stimulation or suppression) and the magnitude of change were dependent upon the baseline reactivity of the donor's PMN. Both opioid peptides stimulated O2- release by PMN from donors with low baseline reactivity in a concentration-dependent manner. PMNs collected from donors with medium baseline reactivity incubated with Leu-enkephalin regardless of concentration released less O2- than control, nontreated PMNs. Met-enkephalin stimulated O2- release but only at 2 X 10(-15) M concentration. Superoxide anion release from PMNs of individuals with high baseline reactivity was concentration dependent and suppressed by Met- and Leu-enkephalin. Leu-enkephalin induced baseline reactivity was dependent upon progressive increase in the magnitude of change on O2- release (i.e., the higher the baseline the higher the magnitude of change in O2- generation). Met-enkephalin data show this also, but to a lesser extent. In cells stimulated with PMA, Met-enkephalin caused additional O2- release, while Leu-enkephalin was ineffective in triggering already stimulated cells. The modulating effect of both opioid peptides on superoxide anion release by human PMN is a short phenomenon that lasts up to 10 min after the addition of the peptide.
Insights
Met- and Leu-enkephalin modulate superoxide anion release from human polymorphonuclear cells (PMN). Effects vary based on PMN baseline reactivity and peptide concentration, with generally stimulatory effects in low reactivity donors and suppressive effects in high reactivity donors.
Area of Science:
- Immunology
- Neuroscience
- Biochemistry
Background:
- Polymorphonuclear cells (PMN) are crucial immune cells involved in host defense.
- Superoxide anion (O2-) release by PMN is a key indicator of oxidative burst and immune response.
- Opioid peptides, such as Met- and Leu-enkephalin, are known to have immunomodulatory effects.
Purpose of the Study:
- To investigate the modulatory effects of Met- and Leu-enkephalin on superoxide anion release from human PMN.
- To determine if these effects are dependent on the baseline reactivity of PMN.
- To assess the impact of these opioid peptides on both unstimulated and stimulated PMN.
Main Methods:
- Human peripheral blood polymorphonuclear cells (PMN) were isolated.
- Superoxide anion (O2-) release was measured from unstimulated and phorbol myristate acetate (PMA)-stimulated PMN.
- Cells were incubated with varying concentrations of Met- and Leu-enkephalin.
Main Results:
- Both Met- and Leu-enkephalin modulated O2- release in a manner dependent on PMN baseline reactivity.
- Opioid peptides stimulated O2- release in PMN from low reactivity donors and suppressed it in PMN from high reactivity donors.
- Met-enkephalin further stimulated O2- release in PMA-activated PMN, while Leu-enkephalin did not.
Conclusions:
- Met- and Leu-enkephalin exhibit differential immunomodulatory effects on human PMN superoxide anion release.
- The observed effects are highly dependent on the donor's baseline PMN reactivity.
- These modulatory effects are transient, lasting up to 10 minutes post-peptide addition.