Secretory activity of equine polymorphonuclear leukocytes: stimulus specificity and priming effects of bacterial lipopolysaccharide.
Abstract: Neutrophil (PMN) contributions to the acute inflammatory process and host defense include generation of bioreactive oxygen metabolites and secretion of granule enzymes. We assessed equine PMN secretion using several PMN stimuli, singly and in combination with bacterial lipopolysaccharide (LPS). LPS avidly associated with equine PMN, as shown by strong PMN labeling with FITC-conjugated LPS. LPS alone (1 or 10 micrograms ml-1) was a weak stimulus for PMN superoxide anion (O2-) generation, but preincubation with LPS followed by phorbol ester (PMA, 10 ng ml-1) significantly augmented (P less than 0.01) secretion of O2- (19.38 nmol O2- per 2 x 10(6) PMN per 5 min) over the amount generated by PMA stimulation alone (13.75 nmol O2-). A qualitatively similar, but smaller O2(-)-generation response occurred when either opsonized zymosan or recombinant human C5a was used as the PMN stimulus. Arachidonic acid (ArA; 50-200 microM) was a potent stimulus, with secreted O2- levels similar to those from PMA-stimulated PMN. Preincubation of PMN with either the formyl peptide, fMLP, or platelet-activating factor before stimulation with ArA did not significantly increase O2- generation over levels obtained using ArA alone. Release of PMN granule enzymes was also quantitated. A small amount of lysozyme secretion resulted when PMN were exposed to LPS alone (8.20% of total cell content), and PMA stimulation caused marked release of PMN lysozyme (44.45%). Non-specific proteolytic activity in PMN supernatants, assessed by cleavage of a collagen-rich substrate, was minimal with LPS as a sole stimulus (5.08%). There was significant proteolytic activity (P less than 0.01) in supernatants from PMA-stimulated PMN (27.21%), and preincubation with LPS followed by PMA stimulation slightly enhanced (P less than 0.05) the release of PMN proteases (34.62%). The activities of beta-glucuronidase, acid phosphatase, and alkaline phosphatase were minimal in PMN supernatants when using LPS and PMA as stimuli. The activity of PMN granule enzymes was found to be sensitive to the presence of normal equine serum, and proteolytic activity was markedly reduced (80.13% reduction) in the presence of 10% pooled serum.
Publication Date: 1992-03-01 PubMed ID: 1317072DOI: 10.1016/0165-2427(92)90012-fGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- Non-P.H.S.
Summary
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This study investigates how the immune response of horses, specifically the response of neutrophils, is affected by bacterial lipopolysaccharides (LPS). The findings reveal that LPS can enhance the production of reactive oxygen species and secretion of defensive enzymes in neutrophils when combined with other specific stimuli.
Immune Response and Neutrophils
- The immune system defends the body against pathogens, with neutrophils being one of the primary cells involved in this defense. Neutrophils respond to infection by generating bioreactive oxygen metabolites, such as superoxide anion (O2-), and by secreting granule enzymes.
- For this study, the researchers measured the secretions of equine neutrophils using different stimuli, individually and together with LPS. LPS is a component of the outer membrane of Gram-negative bacteria that is recognized by the immune system.
Response to Bacterial Lipopolysaccharides
- LPS bound strongly to equine neutrophils. When used alone, LPS acted as a weak stimulus for neutrophils to produce superoxide anion, but when combined with another stimulant, phorbol ester, the secretion of superoxide anion was significantly increased.
- The investigators also report that arachidonic acid, which is involved in the regulation of cellular responses, was a potent stimulator of superoxide anion secretion at similar levels to phorbol ester-stimulated neutrophils. However, pre-treatment of neutrophils with other agents did not notably increase superoxide anion production compared with arachidonic acid alone.
Enzyme Secretion Responses
- Exposure to LPS alone only resulted in a modest release of lysozyme, an enzyme that breaks down bacterial cell walls, from neutrophils. Stimulation with phorbol ester, however, led to a significant increase in lysozyme release.
- Proteolytic activity, the breakdown of proteins, was limited when LPS was the only stimulus. There was significant proteolytic activity in the presence of phorbol ester, and this was marginally enhanced when the cells were pre-treated with LPS.
- The activities of other enzymes, including beta-glucuronidase, acid phosphatase, and alkaline phosphatase, were low in the presence of LPS and phorbol ester. The activity of these enzymes in the neutrophils was affected by the presence of normal horse serum, with proteolytic activity markedly reduced in the presence of this pooled serum.
Cite This Article
APA
Bochsler PN, Slauson DO, Neilsen NR.
(1992).
Secretory activity of equine polymorphonuclear leukocytes: stimulus specificity and priming effects of bacterial lipopolysaccharide.
Vet Immunol Immunopathol, 31(3-4), 241-253.
https://doi.org/10.1016/0165-2427(92)90012-f Publication
Researcher Affiliations
- Department of Pathobiology, College of Veterinary Medicine, University of Tennessee, Knoxville 37901-1071.
MeSH Terms
- Animals
- Cytoplasmic Granules / metabolism
- Fluorescein-5-isothiocyanate
- Horses
- Hydrolases / metabolism
- Lipopolysaccharides
- Neutrophils / metabolism
- Peptide Hydrolases / metabolism
- Superoxides / metabolism
- Tetradecanoylphorbol Acetate / pharmacology
- Zymosan / pharmacology
Citations
This article has been cited 2 times.- Benbarek H, Deby-Dupont G, Caudron I, Deby C, Lamy M, Serteyn D. Failure of lipopolysaccharides to directly trigger the chemiluminescence response of isolated equine polymorphonuclear leukocytes.. Vet Res Commun 1997 Oct;21(7):477-82.
- Jian ZJ, Yang Z, Mason GL, Slauson DO, Bochsler PN. Regulation of superoxide anion generation in bovine alveolar macrophages by bacterial lipopolysaccharide, serum proteins, and modulators of signal transduction.. Inflammation 1995 Dec;19(6):637-50.
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