Activated neutrophils secrete stored alpha 1-antitrypsin.
Neutrophil elastase (NE), a potent serine protease, is stored in primary granules of neutrophils and released following neutrophil activation. Alpha-1-antitrypsin (alpha 1-AT), the major inhibitor of NE, is synthesized by mature neutrophils. In the context of the maintenance of tissue homeostasis, we hypothesized that neutrophils may be able to store alpha 1-AT, thus having it available for release concordantly with NE. Immunofluorescence and quantitative flow-cytometric studies of neutrophils and monocytes labeled with fluorescein-conjugated alpha 1-AT-antibody demonstrated larger amounts of cytoplasmic alpha 1-AT in neutrophils than in monocytes. [35S]methionine-labeling and anti-alpha 1-AT immunoprecipitation analysis showed that although both neutrophils and monocytes synthesize alpha 1-AT, the proportion of newly synthesized intracellular alpha 1-AT was much higher in neutrophils than in monocytes. Flow-cytometric analysis showed that in the presence of surface stimulation with cytochalasin B followed by formyl-methionyleucylphenylalanine (fMLP), mean intracellular alpha 1-AT was decreased in stimulated neutrophils compared with that in resting cells, suggesting that the stored alpha 1-AT was rapidly released following surface triggering. Evaluation of surface-stimulated neutrophils by [35S]methionine labeling and anti-alpha 1-AT immunoprecipitation demonstrated increased secretion of alpha 1-AT compared with that of resting neutrophils, with some of the secreted alpha 1-AT capable of forming complexes with NE. Thus, neutrophils respond to surface stimulation not only by secreting NE but also by secreting its inhibitor, alpha 1-AT, suggesting that these cells have an inherent mechanism for damping the local effects of NE, their most powerful proteolytic enzyme.
Pääkkö
P
P
Department of Pathology, University of Oulu, Finland.
Kirby
M
M
du Bois
R M
RM
Gillissen
A
A
Ferrans
V J
VJ
Crystal
R G
RG
D003571:Cytochalasin B / Q000494:pharmacology; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D019272:Leukocyte Elastase / Q000096:biosynthesis; D009000:Monocytes / Q000378:metabolism; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D018375:Neutrophil Activation; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D000515:alpha 1-Antitrypsin / Q000096:biosynthesis / Q000378:metabolism*
D000515:alpha 1-Antitrypsin; D003571:Cytochalasin B; D009240:N-Formylmethionine Leucyl-Phenylalanine; D019272:Leukocyte Elastase