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Intra- and extracellular events in luminol-dependent chemiluminescence of polymorphonuclear leukocytes
Abstract:
When polymorphonuclear leukocytes (PMNL) and soluble or particulate matter interact, the cells produce chemiluminescence. Luminol-dependent light emission from PMNL is linked to the myeloperoxidase (MPO)-H2O2 system. Light emission from a cell-free MPO-H2O2 system was found to be totally inhibited by human serum albumin (HSA), and since HSA is a large molecular protein that does not readily gain access to intracellular sites of PMNL, it could be used to determine the importance of extra- and intracellular events in PMNL chemiluminescence. In studies with cells from an MPO-deficient patient, we found that HSA inhibited more than 90% of extracellularly produced chemiluminescence. The chemotactic peptide formylmethionyl-leucyl-phenylalanine induced a two-peak chemiluminescence response in normal PMNL, and addition of HSA reduced the first peak, whereas the second peak was unaffected. This result indicated that the first peak was a result of extracellular reactions and the second peak was a result of intracellular reactions of the MPO-H2O2 system. Most of the phorbol myristate acetate-induced response in normal PMNL was due to intracellular events. Furthermore, chemiluminescence of intracellular origin seems to be limited not by generation of oxidative metabolites but by diffusion of luminol into the cells.
Insights
Human serum albumin (HSA) distinguishes extracellular and intracellular chemiluminescence in polymorphonuclear leukocytes (PMNL). HSA inhibited extracellular light emission, revealing insights into myeloperoxidase (MPO)-H2O2 system activity.
Area of Science:
- Immunology
- Cellular Biology
- Biochemistry
Background:
- Polymorphonuclear leukocytes (PMNL) produce chemiluminescence upon interaction with stimuli.
- Luminol-dependent light emission is primarily mediated by the myeloperoxidase (MPO)-hydrogen peroxide (H2O2) system within PMNL.
Purpose of the Study:
- To differentiate between extracellular and intracellular contributions to PMNL chemiluminescence.
- To investigate the role of the MPO-H2O2 system in PMNL light emission using human serum albumin (HSA) as a probe.
Main Methods:
- Utilized a cell-free MPO-H2O2 system and PMNL from an MPO-deficient patient.
- Applied HSA to inhibit extracellular reactions and analyzed chemiluminescence responses to formylmethionyl-leucyl-phenylalanine and phorbol myristate acetate.
Main Results:
- HSA completely inhibited cell-free MPO-H2O2 system light emission.
- HSA significantly inhibited extracellular chemiluminescence (>90%) in PMNL from normal donors.
- The first peak of the formylmethionyl-leucyl-phenylalanine-induced response was inhibited by HSA (extracellular), while the second peak was unaffected (intracellular).
- Phorbol myristate acetate-induced chemiluminescence was predominantly intracellular.
Conclusions:
- HSA effectively distinguishes extracellular MPO-H2O2 reactions from intracellular ones.
- Intracellular chemiluminescence is likely limited by luminol diffusion rather than oxidative metabolite generation.