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Spermine down-regulates superoxide generation induced by fMet-Leu-Phe in electropermeabilized human neutrophils
K Ogata1, M Tamura, M Takeshita
1Department of Biochemistry, Medical College of Oita, Japan.
Abstract:
Effect of spermine, a naturally occurring polyamine, was investigated on superoxide generation in intact and electropermeabilized human neutrophils. Spermine suppressed N-formyl-methionyl leucyl phenylalanine (fMLP)-induced superoxide generation in permeabilized cells by reducing the rate and shortening the duration time. The inhibition was specific for spermine comparing with its precursor amines, spermidine and putrescine. The inhibition was not observed when cells were preincubated with spermine without permeabilization. Concanavalin A-induced superoxide generation was also down-regulated by spermine in permeabilized cells, but the activation induced by non receptor-mediated agonist (dioctanoylglycerol, phorbol myristate acetate, and arachidonate) was not affected by spermine. On the other hand, GTP-gamma-S-induced activation of superoxide generation was substantially suppressed by spermine. These results indicate that spermine inhibition occurs at a step prior to protein kinase C in signal transduction or in a pathway which is independent of the kinase.
Insights
Spermine, a polyamine, inhibits superoxide generation in human neutrophils by affecting signaling pathways before protein kinase C activation. This effect was observed in permeabilized cells, highlighting spermine's specific role in neutrophil function.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Neutrophils play a critical role in the innate immune system.
- Superoxide generation is a key function of neutrophils in fighting pathogens.
- Polyamines, like spermine, are involved in various cellular processes.
Purpose of the Study:
- To investigate the effect of spermine on superoxide generation in human neutrophils.
- To determine the specific signaling pathways modulated by spermine during neutrophil activation.
Main Methods:
- Human neutrophils were used, both intact and electropermeabilized.
- Superoxide generation was measured following stimulation with various agonists, including N-formyl-methionyl leucyl phenylalanine (fMLP), Concanavalin A, dioctanoylglycerol, phorbol myristate acetate, arachidonate, and GTP-gamma-S.
- The effect of spermine and its precursor amines (spermidine, putrescine) was assessed.
Main Results:
- Spermine significantly suppressed fMLP-induced superoxide generation in permeabilized neutrophils by reducing the rate and duration.
- This inhibitory effect was specific to spermine and not observed with spermidine or putrescine.
- Spermine also down-regulated Concanavalin A-induced superoxide generation in permeabilized cells.
- Activation of superoxide generation by non-receptor-mediated agonists was unaffected by spermine.
- GTP-gamma-S-induced activation was substantially suppressed by spermine.
Conclusions:
- Spermine inhibits neutrophil superoxide generation at a signaling step prior to protein kinase C activation.
- The mechanism of inhibition appears to involve pathways independent of protein kinase C.
- Spermine's specific modulatory role in neutrophil signaling warrants further investigation.