[Ca2+]i changes and respiratory burst in human neutrophils and monocytes induced by NAP-1/interleukin-8, NAP-2, and gro/MGSA.

The stimulatory effects of neutrophil-activating peptide 1 (NAP-1), also termed interleukin 8 (IL-8), neutrophil-activating peptide 2 (NAP-2), and melanoma growth-stimulatory activity (gro/MGSA) on human neutrophils and monocytes were compared on the basis of two responses that can be assessed in real time, the changes in cytosolic free calcium and the respiratory burst. All three peptides induced a rapid and transient rise of cytosolic-free calcium and the respiratory burst in neutrophils. Both responses were also obtained in monocytes on stimulation with NAP-1/IL-8 and gro/MGSA, but not with NAP-2, which appeared to be more selective for neutrophils. Pretreatment with concanavalin A (ConA) enhanced several fold the rate and duration of the respiratory burst of neutrophils stimulated with all three peptides and of monocytes stimulated with NAP-1/IL-8 and gro/MGSA, but not with NAP-2. Sequential stimulation showed mutual cross desensitization by NAP-2 and gro/MGSA in neutrophils. In addition, desensitization of neutrophils toward NAP-2 and gro/MGSA, and of monocytes toward gro/MGSA, was obtained by prestimulation with NAP-1/IL-8. Prestimulation with either NAP-2 or gro/MGSA, however, did not desensitize the cells for NAP-1/IL-8. These results suggest that under conditions where multiple stimulatory agents are produced, neutrophil-activating peptides may contribute to the formation of substantial amounts of oxygen-derived radicals. In addition, the study shows that NAP-1/IL-8 and gro/MGSA, but not NAP-2, have some stimulatory effects on monocytes as well.