Zymosan-induced IL-8 release from human neutrophils involves activation via the CD11b/CD18 receptor and endogenous platelet-activating factor as an autocrine modulator.
We have investigated mechanisms that regulate the generation of IL-8 by human neutrophils on contact with zymosan particles in vitro. Zymosan stimulated IL-8 production, which increased with increasing particle numbers and was abolished by the protein synthesis inhibitor cycloheximide. IL-8 was detectable in culture supernatant at 8 h reaching a maximum at 24 h. In all further experiments IL-8 was measured at 24 h. mAbs to neutrophil CD18 (60.3 and 6.5E) caused a marked suppression of IL-8 generation, but only if added up to 2 h after zymosan stimulation. An anti-CD11b mAb (KIM 225) substantially inhibited zymosan-induced IL-8 release. We investigated whether other mediators generated during phagocytosis modulate IL-8 production. Two selective platelet-activating factor (PAF) receptor antagonists, WEB 2086 and UK 74505, produced a profound suppression of IL-8 generation, when added within 30 min to 1 h of zymosan stimulation. An IL-1R antagonist, a leukotriene B4 antagonist, and an anti-TNF-alpha Ab had no effect on IL-8 generation. FMLP, PAF, and a stable PAF agonist did not stimulate significant IL-8 production, however, a calcium ionophore (A23187) did induce IL-8 release and this was suppressed by UK 74505. We conclude that zymosan-induced IL-8 generation involves stimulation of the neutrophil via a CD11b/CD18 receptor resulting in beta 2-integrin mediated activation of signal transduction mechanisms that leads to cytokine synthesis. Furthermore, endogenously generated PAF, or a PAF, or a PAF-like molecule, appears to have an autocrine function in regulating this pathway of IL-8 production at an early stage after the interaction between the neutrophil and the particles.
Au
B T
BT
Department of Applied Pharmacology, National Heart & Lung Institute, London, United Kingdom.
Williams
T J
TJ
Collins
P D
PD
D000911:Antibodies, Monoclonal / Q000276:immunology; D018821:CD18 Antigens; D000001:Calcimycin / Q000494:pharmacology; D006801:Humans; D016023:Integrins / Q000502:physiology; D053590:Interleukin 1 Receptor Antagonist Protein; D016209:Interleukin-8 / Q000378:metabolism*; D016177:Macrophage-1 Antigen / Q000502:physiology*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000502:physiology*; D012795:Sialoglycoproteins / Q000494:pharmacology; D013777:Tetrazoles / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D015054:Zymosan / Q000494:pharmacology*
D000911:Antibodies, Monoclonal; D018821:CD18 Antigens; C507763:IL1RN protein, human; D016023:Integrins; D053590:Interleukin 1 Receptor Antagonist Protein; D016209:Interleukin-8; D016177:Macrophage-1 Antigen; D010972:Platelet Activating Factor; D012795:Sialoglycoproteins; D013777:Tetrazoles; D014409:Tumor Necrosis Factor-alpha; D000001:Calcimycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D015054:Zymosan; C063823:LY 255283