Chemiluminescence of Macrophages Depends upon Their Differentiation Stage: Dissociation between Phagocytosis and Oxygen Radical Release

Abstract

The in vitro differentiation and maturation of resident and activated mouse and human macrophages (MΦ) from different anatomical sources was investigated with regard to their oxygen metabolism during zymosan phagocytosis. We found evidence that chemiluminescence (CL) of MΦ depends upon their differentiation stage: a) In the absence of any phagocytic stimulus, the human MΦ showed a lucigenin-dependent CL background that was approximately 10-fold higher than in mouse MΦ and decreased to low levels in resident MΦ (monocyte-derived human MΦ) during culture time, whereas it was persistently high in activated MΦ (peritoneal human MΦ). This background was reduced by SOD to about 50%. No relevant luminol-dependent background was observed in all mouse and human MΦ during culture time. b) Resident and activated mouse and human MΦ could be distinguished in terms of their lucigenin-dependent CL during zymosan phagocytosis, which was persistently high in activated MΦ, but decreased to comparatively low levels in resident MΦ during culture time. This zymosan-elicited CL was almost completely SOD-dependent during all culture time. c) A dissociation between phagocytosis and oxygen radical release is observed: the decrease of both minolul and lucigenin-dependent CL in resident phagocytizing MΦ during maturation did not, correspond to a decrease of their phagocytic activity. Phagocytosis occurred at a high rate also in the absence of a relevant CL-detectable generation of oxygen radicals. The oxygen radical release, as measured by SOD-inhibitable cytochrome c reduction, paralleled CL during zymosan phagocytosis and declined with maturation of monocytes into MΦ. In contrast, the zymosaninduced nitro-blue-tetrazolium reduction increased in mature resident human MΦ. Thus, it seems that different metabolic pathways are utilized during phagocytosis in young and mature MΦ.