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Methionine-enkephalin primes human neutrophils for enhanced superoxide anion production
1Department of Experimental Biology and Medicine, Laboratory for Biological Response Modifiers, Zagreb, Croatia.
Abstract:
Methionine-enkephalin (MENK) is not an effective stimulus for inducing the superoxide (O2-) generation of human neutrophils, but it enhanced the O2- generation stimulated by the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) or human recombinant interferon gamma (hrIFN gamma) when the cells had been preincubated with MENK for 30 min at 37 degrees C. The priming effect of MENK was not observed with stimulus such as lipopolysaccharide (LPS) or phorbol-12-myristate-13-acetate (PMA). The enhancing effect of MENK was abrogated if cells were treated with protein kinase C (PKC) inhibitor H7 (1-(5-isoquinolinylsulfonyl)-2-methylpiperazine) before fMLP or IFN gamma. This finding indicates that MENK is a potent modulator of human neutrophils and can contribute to inflammatory process.
Insights
Methionine-enkephalin (MENK) primes human neutrophils, enhancing superoxide generation stimulated by specific peptides and interferons. This priming effect, mediated by protein kinase C, suggests MENK
Area of Science:
- Immunology
- Cellular Biology
- Pharmacology
Background:
- Neutrophils are key immune cells involved in inflammatory responses.
- Superoxide generation is a critical function of neutrophils in combating pathogens.
- Methionine-enkephalin (MENK) is an endogenous opioid peptide with immunomodulatory potential.
Purpose of the Study:
- To investigate the effect of Methionine-enkephalin (MENK) on human neutrophil superoxide (O2-) generation.
- To determine if MENK acts as a priming agent for neutrophils.
- To elucidate the signaling pathways involved in MENK-mediated neutrophil activation.
Main Methods:
- Human neutrophils were preincubated with MENK.
- Superoxide generation was measured following stimulation with N-formyl-methionyl-leucyl-phenylalanine (fMLP), human recombinant interferon gamma (hrIFN gamma), lipopolysaccharide (LPS), or phorbol-12-myristate-13-acetate (PMA).
- The role of protein kinase C (PKC) was assessed using the inhibitor H7.
Main Results:
- MENK alone did not induce significant superoxide generation.
- MENK preincubation enhanced fMLP- and hrIFN gamma-stimulated superoxide generation.
- MENK's priming effect was not observed with LPS or PMA stimulation.
- The enhancing effect of MENK was blocked by the PKC inhibitor H7.
Conclusions:
- MENK acts as a potent priming agent for human neutrophils, enhancing their response to specific stimuli.
- The priming effect of MENK on superoxide generation is dependent on protein kinase C signaling.
- MENK may play a significant role in modulating inflammatory processes involving neutrophils.