Platelet-activating factor priming of inflammatory cell activity requires cellular adherence.
BACKGROUND
Platelet-activating factor (PAF) primes tissue-fixed inflammatory cells, but has no effect on circulating cells. Adherence of inflammatory cells leads to cytoskeletal reorganization, which is essential for optimal inflammatory function. The purpose of this study was to investigate whether cellular adherence plays a role in PAF priming of inflammatory cells.


METHODS
Differentiated THP-1 cells were maintained under adherent and nonadherent conditions. Selected cells were pretreated with PAF, followed by endotoxin stimulation. Cellular and nuclear proteins were analyzed by Western blot for components of the Toll-like receptor-mediated signaling cascade. Cytokine analysis was performed by enzyme-linked immunosorbent assay.


RESULTS
Endotoxin led to activation of interleukin (IL)-1-associated kinase, extracellular signal-regulated kinase 1/2 and p38, and nuclear translocation of nuclear factor-kappaB, all of which were significantly enhanced by previous cellular adherence. PAF led to priming only under adherent conditions, demonstrated by increased IL-1-associated kinase and extracellular signal-regulated kinase 1/2 activity; nuclear factor-kappaB translocation; and IL-6, IL-8, and tumor necrosis factor-alpha production over non-PAF-treated cells. PAF had no significant effect on p38 activity or IL-10 production under any condition.


CONCLUSIONS
PAF primes mononuclear cells by increasing Toll-mediated signaling only under adherent conditions. This, therefore, would limit PAF-induced priming in vivo to foci of stimulated adherent inflammatory cells with little effect systemically on circulating cells.
Cuschieri
Joseph
J
Department of Surgery, University of Cincinnati, Ohio 45267-0558, USA.
Gourlay
David
D
Bulger
Eileen
E
Garcia
Iris
I
Jelacic
Sandra
S
Maier
Ronald V
RV
D002118:Calcium / Q000378:metabolism; D002273:Carcinogens / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects / Q000276:immunology; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology; D006801:Humans; D066298:In Vitro Techniques; D018836:Inflammation Mediators / Q000378:metabolism; D053592:Interleukin-1 Receptor-Associated Kinases; D008070:Lipopolysaccharides / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009000:Monocytes / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D010972:Platelet Activating Factor / Q000494:pharmacology*; D010980:Platelet Membrane Glycoproteins / Q000032:analysis / Q000096:biosynthesis; D011494:Protein Kinases / Q000378:metabolism; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014807:Vitamin D / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
D002273:Carcinogens; D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D016328:NF-kappa B; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; D014807:Vitamin D; D011494:Protein Kinases; D053592:Interleukin-1 Receptor-Associated Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium