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The role of aminopeptidase N in Met-enkephalin modulated superoxide anion release
T Balog1, T Marotti, M Abramić
1Department of Molecular Medicine, Institute Ruder Bosković, Zagreb, Croatia.
Abstract:
We have previously shown that methionine-enkephalin (MENK) alters in dose-dependent fashion the capacity of human neutrophils to produce superoxide anion. The response of neutrophils from different donors was diverse and this effect could be due to variable activity of proteolytic enzymes involved in the degradation of the neuropeptide. In this study, we have demonstrated a highly individual aminopeptidase N (APN) activity of neutrophils from different donors. Preincubation of neutrophils with MENK, but not with the synthetic agonist of the mu (DAGO) or the delta (DPDPE) opioid receptor, down-regulated the APN activity. This was paralleled by a loss in cell surface expression of APN at physiological (10(-10) M) concentrations of MENK. The level of APN activity from different donors correlated with the effect of MENK on superoxide anion release. Neutrophils with low APN activity, if preincubated with MENK, released reduced amounts of superoxide anion. In contrast, neutrophils with high APN activity released increased amounts of superoxide anion after preincubation with MENK. Thus, the highly individual APN activity on the surface of neutrophils from different donors seems to be altered by MENK and to be related to the respiratory burst.
Insights
Methionine-enkephalin (MENK) affects human neutrophil superoxide anion production. Individual differences in aminopeptidase N (APN) activity on neutrophils influence MENK
Area of Science:
- Immunology
- Neuroscience
- Biochemistry
Background:
- Methionine-enkephalin (MENK) influences human neutrophil superoxide anion production.
- Neutrophil responses to MENK vary between individuals, potentially due to proteolytic enzyme activity.
- Aminopeptidase N (APN) is a key enzyme in neuropeptide degradation.
Purpose of the Study:
- To investigate the role of individual aminopeptidase N (APN) activity in human neutrophils.
- To determine how MENK affects APN activity and cell surface expression.
- To correlate APN activity with MENK-induced changes in neutrophil superoxide anion production.
Main Methods:
- Assessing aminopeptidase N (APN) activity in neutrophils from different donors.
- Preincubating neutrophils with methionine-enkephalin (MENK) and opioid receptor agonists.
- Measuring changes in APN activity and cell surface APN expression.
- Quantifying superoxide anion release from neutrophils.
Main Results:
- Neutrophil aminopeptidase N (APN) activity is highly individual across donors.
- Methionine-enkephalin (MENK), but not DAGO or DPDPE, down-regulates APN activity and cell surface expression.
- MENK reduces APN activity at physiological concentrations (10(-10) M).
- The level of APN activity correlates with MENK's effect on superoxide anion release.
Conclusions:
- Individual aminopeptidase N (APN) activity on neutrophils is modulated by methionine-enkephalin (MENK).
- This modulation of APN activity by MENK is linked to the respiratory burst response in neutrophils.
- APN activity influences the diverse responses of neutrophils to MENK.