Increased cell-associated IL-8 in human exudative and A23187-treated peripheral blood neutrophils.

Abstract

IL-8 is a potent neutrophil chemoattractant that has been detected in high concentrations at acutely inflamed sites in vivo. Many cell types, including peripheral blood neutrophils, produce IL-8 that can be released by a variety of pro-inflammatory stimuli. However, the functional importance of neutrophil IL-8 during exudation is not yet known. We now report that neutrophils, harvested from skin lesions on the forearms of normal human volunteers (exudative neutrophils), expressed 100-fold higher levels of cell-associated IL-8 and spontaneously released up to 50-fold more IL-8 than freshly isolated peripheral blood neutrophils from the same donor. Furthermore, cell-associated IL-8 in peripheral blood neutrophils increased 20-fold during incubation at 37 degrees C in vitro and was increased over 200-fold after treatment with the Ca2+ ionophore A23187. More than 35% of the cell-associated IL-8 could be released by stimulation with either Ca2+ ionophore A23187 or phorbol myristate acetate. IL-8 was localized by sucrose gradient centrifugation to a subcellular fraction of heterogeneous, light membranous organelles. The accumulation of IL-8 within these organelles is inhibited by cycloheximide but not actinomycin D, suggesting that IL-8 accumulation is under translational, rather than transcriptional control. These studies indicate that peripheral blood neutrophils are capable of synthesis of large amounts of IL-8. Subsequent release of IL-8 during exudation may regulate neutrophil migration into sites of inflammation.