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Platelet-activating factor-induced polymorphonuclear neutrophil priming independent of CD11b adhesion
R A Read1, E E Moore, F A Moore
1Department of Surgery, Denver General Hospital, University of Colorado Health Sciences Center 80204-4507.
Background:
Our previous studies have implicated phospholipase A2-dependent platelet-activating factor (PAF) production in the genesis of polymorphonuclear neutrophil (PMN)-mediated tissue injury after gut ischemia-reperfusion. Further, these studies have suggested a discordance of PMN sequestration and tissue injury. CD11B-dependent PMN-endothelial cell adhesion has been purported to play a dominant role in PMN-mediated tissue injury. We therefore undertook this study with the hypothesis that PAF-induced PMN superoxide production requires CD11B-mediated PMN-endothelial cell adherence.
Methods:
Human PMNs, isolated by Percoll gradient centrifugation, were exposed to PAF (10 ng/ml). At fixed times of exposure during 120 minutes, (1) superoxide production, (2) CD11B receptor expression, and (3) PMN adhesion to unstimulated human umbilical vein endothelial cell cultures were assayed.
Results:
PAF induced prompt changes in PMN priming (increased superoxide production after N-formyl-methyl-leucyl-phenylalanine activation), adhesion to unstimulated endothelial cells, and CD11B receptor expression. Priming was temporally concordant with the rise and fall of CD11B expression but appeared to precede adhesion. CD11B blockade (F(Ab') 2 anti-CD11B [60.1] antibodies), before or at maximal PAF priming, reduced PMN adhesion but had no effect on superoxide production.
Conclusions:
In summary, PAF-induced PMN priming occurs in temporal concordance with the expression of CD11B and subsequent endothelial cell adherence, but CD11B-mediated adherence is not essential for this process.
Insights
Platelet-activating factor (PAF) primes neutrophils, increasing their superoxide production. However, CD11B-mediated adherence to endothelial cells is not essential for this PAF-induced priming process.
Area of Science:
- Immunology
- Cellular Biology
- Inflammation Research
Background:
- Previous studies link phospholipase A2-dependent platelet-activating factor (PAF) to neutrophil-mediated tissue injury following gut ischemia-reperfusion.
- A discordance between neutrophil sequestration and tissue injury has been observed.
- CD11B-dependent neutrophil-endothelial cell adhesion is thought to be crucial for neutrophil-mediated tissue injury.
Purpose of the Study:
- To investigate the hypothesis that PAF-induced neutrophil superoxide production necessitates CD11B-mediated neutrophil-endothelial cell adherence.
Main Methods:
- Human neutrophils were isolated and exposed to PAF (10 ng/ml) for up to 120 minutes.
- Assays were performed to measure superoxide production, CD11B receptor expression, and neutrophil adhesion to endothelial cells.
Main Results:
- PAF induced rapid changes in neutrophil priming, including increased superoxide production, CD11B receptor expression, and adhesion to endothelial cells.
- Neutrophil priming correlated temporally with CD11B expression but preceded adhesion.
- Blocking CD11B reduced neutrophil adhesion but did not affect superoxide production.
Conclusions:
- PAF-induced neutrophil priming occurs concurrently with CD11B expression and subsequent endothelial cell adherence.
- CD11B-mediated adherence is not essential for PAF-induced neutrophil priming.