Priming interleukin 8 production: role of platelet-activating factor and p38.
OBJECTIVE
Platelet-activating factor (PAF) activates p38, an important intracellular signal transduction kinase, and primes human mononuclear cells for the production of interleukin 8 (IL-8), a potent chemoattractant and activator of neutrophils.


METHODS
Human mononuclear cells were isolated from healthy adults by Ficoll-paque density-gradient centrifugation. Interleukin-8 in the supernatant was measured by enzyme-linked immunosorbent assay. Dual phospho-specific p38 antibody was used to detect activated p38 by Western blotting.


RESULTS
Lipopolysaccharide (LPS) and PAF activated p38. There was a shorter latency to peak p38 activation with PAF vs LPS stimulation, 5 vs 30 minutes. Platelet-activating factor-induced p38 activation was calcium dependent because it was inhibited by ethyleneglycoltetracetic acid. Lipopolysaccharide, 0.01 to 1.00 ng/mL, induced significant IL-8 production. Although PAF did not induce significant IL-8 production, it potentiated LPS-induced IL-8 production. Production of IL-8, in response to LPS alone or in combination with PAF, was inhibited by SB202190, a specific p38 inhibitor.


CONCLUSIONS
Although LPS and PAF activated p38, only LPS induced IL-8 production; PAF acted as a priming agent. It seems that p38 activation is necessary but not sufficient for IL-8 production by human mononuclear cells. Identifying and evaluating the activation state of inflammatory signal transduction pathways might lead to methods for controlling and preventing neutrophil-induced tissue injury without interfering with the normal host immune response.
Arbabi
S
S
Department of Surgery, University of Washington, Seattle 98195, USA. sarbabi@u.washington.edu
Rosengart
M R
MR
Garcia
I
I
Jelacic
S
S
Maier
R V
RV
D000328:Adult; D002118:Calcium / Q000502:physiology; D004789:Enzyme Activation; D006801:Humans; D016209:Interleukin-8 / Q000097:blood*; D008070:Lipopolysaccharides / Q000276:immunology; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D010972:Platelet Activating Factor / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases
D016209:Interleukin-8; D008070:Lipopolysaccharides; D010972:Platelet Activating Factor; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D002118:Calcium