The effect of TNF-alpha, PMA, and LPS on plasma and cell-associated IL-8 in human leukocytes.
OBJECTIVE
This study was performed to examine the proficiency of mononuclear cells (MNC) and polymorphonuclear cells (PMN) in a whole blood model to expressing interleukin-8 (IL-8) in response to various stimuli.


METHODS
Isolated cells that had been recombined with heparinized plasma were incubated with lipopolysaccharide (LPS), phorbol myristate acetate (PMA) and tumor necrosis factor (TNF)-alpha.


RESULTS
IL-8 release by MNC was most potently induced by LPS, reaching significant levels after 2-h incubation in the presence of 0.2 ng/ml LPS. In contrast, 5.0 ng/ml LPS was required for PMN to release significant amounts of the cytokine (P<0.001). When PMN and MNC were coincubated (MNC/PMN), LPS-induced IL-8 release was reduced compared to the release from MNC alone, regardless of the concentration of LPS used. IL-8 release by PMN was much more strongly induced by TNF-alpha, increasing by 1050% in the presence of 10 ng/ml TNF-alpha (P<0.005), whereas MNC or MNC/PMN subjected to this stimulus alone did not significantly enhance their IL-8 release. PMA had no effect on IL-8 release from either cell type. Since a high portion of IL-8 in blood is associated with cells, the IL-8 levels in isolated and lysed cell suspensions were also quantified. Thus, a considerably higher level of IL-8 was found in freshly isolated PMN (0.58+/-0.09 ng/ml) than in MNC (0.010+/-0.007 ng/ml). PMN remained the main source for cell-associated IL-8 after 2-h incubation in the absence of any added stimuli, harbouring a relatively high level of the cytokine (3.37+/-1.38 ng/ml), which was significantly enhanced in the presence of TNF-alpha (8.99+/-1.46 ng/ml, P<0.001).


CONCLUSIONS
This study shows that LPS is an effective inducer of IL-8 in MNC, whereas TNF-alpha is a potent agonist for IL-8 release from PMN. The main portion of cell-associated IL-8 is present in PMN when the cells are stimulated in their normal environment of plasma.
Lund
Trine
T
Department of Biochemistry, Institute of Medical Biology, University of Tromsø, 9037 Tromsø, Norway. trinel@fagmed.uit.no
Østerud
Bjarne
B
D004305:Dose-Response Relationship, Drug; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000187:drug effects* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D016209:Interleukin-8; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D013755:Tetradecanoylphorbol Acetate