Abstract
Interleukin 8 (IL-8) stimulated an increase in cytoplasmic free Ca2+ ( [Ca2+] i) and intracellular pH (pHi) in parallel at low concentrations (0.5-5 ng/ml), and stimulated O-2 release and membrane depolarization in parallel at high concentrations (50-5, 000 ng/ml) . IL-8-induced O-2 release was potentiated by tumornecrosis factor (TNF), granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) in a dose-dependent manner. These characteristics and the time-courses of the responses stimulated by IL-8 were similar to those stimulated by N-formyl-methionyl-leucyl-phenylalanine (FMLP), except that the cells stimulated by IL-8 showed shorter duration and less magnitude in some responses. In addition, IL-8 was found to be a potent priming agent and to enhance O-2 release stimulated by FMLP. Priming effect of IL-8 was very rapid and was maximal within 5 min of preincubation. The dose-response curves for priming was identical to those for triggering of an increase in [Ca2+] i and pHi. These findings suggest that IL-8 stimulates or primes human neutrophils according to its concentrations and cross-talks with TNF, GM-CSF, G-CSF or FMLP at the inflammatory sites.
