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Cellular and extracellular myeloperoxidase in pyogenic inflammation
Abstract:
We explored the effect of in vitro phagocytosis and in vivo inflammation on the MPO content of functioning neutrophils and on the ability of these cells to export active MPO into the extracellular environment. After ingestion of staphylococci, neutrophils retained 52% of their MPO and released 8% into the medium in active form; the remaining 40% of their MPO could no longer be detected. During bacterial infection induced by intradermally injecting staphylococci, neutrophils harvested from minced infected lesions contained 52% of the MPO of circulating neutrophils that had not reached the lesions. Extracellular fluid from the lesions contained active MPO secreted by the neutrophils, and concentrations of 10-45 U/ml were detected. These data demonstrate that functioning neutrophils can lose approximately half of their MPO. In vitro, 4%-8% of neutrophilic MPO appears in the extracellular space and 40% is inactivated. In vivo, the MPO content of inflammatory neutrophils also decreases, and MPO appears in the extracellular fluid in active form where it is available to participate in a variety of physiologic processes.
Insights
Neutrophils lose about half their myeloperoxidase (MPO) during bacterial infections. This active MPO is released extracellularly, contributing to inflammation and physiological processes.
Area of Science:
- Immunology
- Cell Biology
Background:
- Neutrophils play a crucial role in innate immunity.
- Myeloperoxidase (MPO) is a key enzyme in neutrophil antimicrobial activity.
Purpose of the Study:
- To investigate the impact of phagocytosis and inflammation on neutrophil MPO content.
- To determine the extracellular release of active MPO by neutrophils.
Main Methods:
- In vitro phagocytosis assays with staphylococci.
- Induction of bacterial infection in vivo.
- Quantification of MPO in neutrophils and extracellular fluid.
Main Results:
- Neutrophils retained 52% of MPO after in vitro phagocytosis, releasing 8% actively.
- Inflammatory neutrophils contained 52% of MPO compared to circulating neutrophils.
- Active MPO was detected extracellularly in infected lesions at concentrations of 10-45 U/ml.
Conclusions:
- Functioning neutrophils can lose approximately 50% of their MPO content.
- Neutrophils release active MPO extracellularly during inflammation.
- Extracellular MPO is available for various physiological processes.