Macrophages cultured in vitro release leukotriene B₄ and neutrophil attractant/activation protein (interleukin 8) sequentially in response to stimulation with lipopolysaccharide and zymosan

The capacity of lipopolysaccharide (LPS), zymosan, arid calcium ionophore A23187 to induce neutrophil chemotactic activity (NCA), leukotriene B₄ (LTB₄), and neutrophil attractant/activation protein (NAP-1) release from human alveolar macrophages (AM) retrieved from normal nonsmokers was evaluated. LPS induced a dose-dependent release Of LTB₄ that began by 1 h, 4.0±3.2 ng/10⁶ viable AM; peaked at 3 h, 24.7±13.5 ng/10⁶ viable AM; and decreased by 24 h, 1.2±1.0 ng/10⁶ viable AM (n = 8). Quantities of LTB₄ in cell-free supernatants of AM stimulated with LPS were determined by reverse-phase high-performance liquid chromatography and corresponded well with results obtained by radioimmunoassay. By contrast, NAP-1 release began ∼ 3-5 h after stimulation of AM with LPS, 197±192 ng/ml, and peaked at 24 h, 790±124 ng/ml. Release of NAP-1 was stimulus specific because A23187 evoked the release of LTB₄ but not NAP-1, whereas LPS and zymosan induced the release of both LTB₄ and NAP-1. The appearance of neutrophil chemotactic activity in supernatants of AM challenged with LPS for 3 h could be explained completely by the quantities of LTB₄ present. After stimulation with LPS or zymosan for 24 h, AM had metabolized almost all generated LTB₄. Preincubation of AM with nordihydroguiaretic acid (10^-4 M) completely abolished the appearance of NCA, LTB₄, and NAP-1 in supernatants of AM challenged with LPS. Therefore, LPS and zymosan particles were potent stimuli of the sequential release of LTB₄ and NAP-I from AM.