Membrane Oxidative Metabolism of Human Eosinophilic Cell Line EoL-1 in Response to Phorbol Diester and Formyl Peptide: Synergistic Augmentation by Interferon-γ Tumor Necrosis Factor

Abstract Human eosinophilic cell line EoL-1 was studied using luminol-dependent chemiluminescence (CL) for the ability to produce a respiratory burst upon stimulation with 12-O-tetradecanoylphorbol-13-acetate (TPA) and N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP). TPA, a potent activator of protein kinase C, induced a biphasic CL response in EoL-1. Treatment of EoL-1 with interferon-γ (IFN-γ) for 5 days dramatically enhanced TPA-inducible CL, and IFN-αA had a similar effect. Neither IFN-γ nor IFN-αA strongly inhibited EoL-1 cell growth. Tumor necrosis factor (TNF) also enhanced TPA-inducible CL response of EoL-1 and, furthermore, was quite inhibitory to EoL-1 cell growth. The effects of IFN-γ and TNF were synergistic, whereas those of IFN-αA and TNF were additive. Superoxide dismutase completely abrogated TPA-induced CL, but sodium azide suppressed only the late phase of CL. EoL-1 pretreated with IFN-7, IFN-αA, or TNF also became capable of producing CL response to a chemotactic peptide (fMLP). The effects of IFN-γ and TNF were again synergistic. EoL-1 cells treated with IFN-γ, IFN-αA, or TNF had abundant cytoplasm, but only TNF increased cells having distinct eosinophilic granules. IFN-γ but not IFN-αA enhanced the cytological effect of TNF. It was further demonstrated that treatment of EoL-1 with IFN-γ and TNF strongly increased the binding sites for phorbol diesters and also dramatically induced the surface expression of fMLP receptors. IFN-γ had, however, little effect on the number or the ligand-binding affinity of TNF receptors on EoL-1. Thus, EoL-1 may provide a useful experimental model for the study of differentiation and regulation of human eosinophils.