Macrophage-mediated cytolysis of erythrocytes in the guinea pig. II. Role of oxidative burst products in macrophage cytotoxicity activated by lectins and phorbol ester derivatives

Effect of anticancer drugs on macrophage-mediated antibody-dependent cytotoxicity and secretion of reactive oxygen intermediates

The in vitro effects of methotrexate, vincristine, dexamethasone and adriamycin to modulate the antibody dependent cellular cytotoxicity (ADCC) reaction and secretion of superoxide (O2-) and hydrogen peroxide (H2O2) by phorbol myristate acetate (PMA) stimulated rat peritoneal macrophages were studied. Macrophage-mediated ADCC, as measured by the lysis of 51Cr-labeled IgG-coated sheep red blood cells in an 18 h assay, was significantly enhanced in the presence of 100 ng/ml of PMA. Treatment of macrophage monolayers for 24 h with vincristine (10(-5)-10(-7) M), dexamethasone (10(-5)-10(-9) M) and adriamycin (10(-6) M) inhibited ADCC by PMA stimulated macrophages. Vincristine, dexamethasone and adriamycin also inhibited the secretion of O2- and H2O2 by PMA stimulated macrophages at similar concentrations that reduced the ADCC reaction. Methotrexate (10(-3)-10(-7) M) did not inhibit either ADCC or O2- and H2O2 secretion by PMA stimulated macrophages. These results suggest that select anticancer drugs can inhibit macrophage mediated cytotoxicity of antibody coated target cells by suppressing the release of reactive oxygen intermediates by activated macrophages.

Monocyte-derived macrophages as helper cells in monocyte-mediated cytolysis

Human peripheral blood monocytes (M), incubated with opsonized zymosan particles (OPZ), lysed human erythrocyte (RBC) targets, as detected by a 51Cr release method. Conversely, cells derived in vitro from M (monocyte-derived macrophages, MDM) were ineffective. When added to the M-RBC system, MDM enhanced the lysis. The lysis by M and M plus MDM was prevented by catalase, azide and amino acids (alanine, taurine), consistent with the requirement for hypochlorous acid (HOCl). Moreover, MDM per se incapable of generating HOCl augmented the HOCl recovery from the M-RBC system. The results provide evidence for a previously unrecognized form of interaction between two distinct populations of mononuclear phagocytes.

Macrophage oxidative burst (OB) and related cytotoxicity--II. Differential sensitivity of erythrocytes from various animals to OB dependent lysis

Red blood cells (RBCs) from various animals, when exposed to oxidative burst (OB)-stimulated mouse macrophages, showed differences in sensitivity to OB dependent lysis. The increasing order of sensitivity was: mouse, hamster, rabbit, guinea pig, sheep and human RBCs. The degree of OB dependent hemolysis did not correlate with either the capacity of the various cells to degrade H2O2 or their osmotic fragility. The relative sensitivity of the various RBCs to OB products generated by macrophages concurred with their sensitivity to H2O2 generated by an enzymatic system. The differential sensitivity may be correlated with the sphingomyelin content of the cells.

Macrophage oxidative burst and related cytotoxicity. I. Differential activation by tumor-promoting and non-tumor-promoting phorbol esters

Mouse peritoneal macrophages elicit an oxidative burst (OB) response upon stimulation with the tumor promoter 12-O-tetradecanoyl-phorbol 13-acetate (TPA). In this study we compare the OB-stimulating capacity of phorbol ester derivatives, structurally related to TPA, which differ in their tumor-promoting activity. Non-tumor-promoting derivatives such as phorbol 13-acetate, phorbol 12-myristate, TPA-20-aldehyde and 4-O-methyl TPA were tested. These reagents stimulate macrophages to generate OB products such as O-2 and H2O2, yet the amounts required for stimulation are 1,000 times higher than the amounts of TPA required to elicit a comparable response. It has also been observed that, in the same order of magnitude, the above-mentioned derivatives are less efficient than TPA in rendering macrophages cytolytic toward erythrocytes. Another strong tumor promoter tested, teleocidin, has been found to be as potent as TPA in the activation of macrophage OB and in related activities.

Chemiluminescence of macrophages depends upon their differentiation stage: dissociation between phagocytosis and oxygen radical release

The in vitro differentiation and maturation of resident and activated mouse and human macrophages (M phi) from different anatomical sources was investigated with regard to their oxygen metabolism during zymosan phagocytosis. We found evidence that chemiluminescence (CL) of M phi depends upon their differentiation stage: a) In the absence of any phagocytic stimulus, the human M phi showed a lucigenin-dependent CL background that was approximately 10-fold higher than in mouse M phi and decreased to low levels in resident M phi (monocyte-derived human M phi). This background was reduced by SOD to about 50%. No relevant luminol-dependent background was observed in all mouse and human M phi during culture time. b) Resident and activated mouse and human M phi could be distinguished in terms of their lucigenin-dependent CL during zymosan phagocytosis, which was persistently high in activated M phi, but decreased to comparatively low levels in resident M phi 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 M phi 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 M phi. In contrast, the zymosan-induced nitro-blue-tetrazolium reduction increased in mature resident human M phi. Thus, it seems that different metabolic pathways are utilized during phagocytosis in young and mature M phi.

The oxidative burst and related phenomena in mouse macrophages elicited by different sterile inflammatory stimuli

Mouse peritoneal macrophages (MPM) elicited by paraffin oil (PO) or thioglycollate (TG) were compared in their capacity to generate oxidative burst (OB) products such as superoxide ion (O2-) and hydrogen peroxide (H2O2) and lyse target erythrocytes. Strong OB stimulants such as 12-O-tetradecanoyl-phorbol-13-acetate (TPA), opsonized zymosan; and wheat-germ agglutinin (WGA) were found to stimulate O2 and H2O2 production by both PO- and TG-elicited MPM. PO-elicited MPM exhibited a vigorous OB response compared to TG-elicited MPM and showed a higher degree of self iodination in the presence of 125I. Macrophage-mediated cytolysis of 51Cr-labeled red blood cells, following OB stimulation, was revealed by PO-elicited MPM triggered by TPA, opsonized zymosan, WGA, and Concanavalin A. TG-elicited MPM failed to respond to TPA and opsonized zymosan. In the presence of horseradish peroxidase, both PO- and TG-elicited MPM exhibited augmented cytocidal activities upon stimulation with TPA, whereas catalase abrogated the capacity of TPA-stimulated MPM to lyse red blood cells, which may suggest the involvement of H2O2 in the lytic process.

Implications of an elevated sister-chromatid exchange frequency in rat lymphocytes cultured in the absence of erythrocytes

One important variable in complex culture systems such as whole blood is the interaction of the cell types present. To investigate the effects of erythrocytes (RBCs) and monocytes on the sister-chromatid exchange (SCE) frequency, Ficoll-Hypaque-separated Fischer-344 rat leukocytes were added to 1.9 ml of culture medium containing either 4 micrograms phytohemagglutinin or 4-8 micrograms concanavalin A/ml. Bromodeoxyuridine (BrdU;2 microM) was added at 24 h, and the cultures were harvested at 54 or 72 h. SCE frequencies in the mononuclear leukocyte cultures were consistently about 1.5- to 2-fold higher than in the whole-blood cultures. The titration of rat or human RBCs (0.05-2.5 X 10(9)) into purified rat leukocyte cultures reduced the SCE frequency to that of whole-blood cultures. Monocyte depletion decreased the elevated SCE frequency by approximately 50%. Scintillation counting of [14C]BrdU uptake in isolated RBCs revealed that less than 8% of the total amount of BrdU was sequestered. Also, BrdU induced a concentration-dependent increase in SCE in purified leukocytes, but the absolute increase was no greater than in whole-blood lymphocytes. Thus, BrdU had a minor role in the elevated SCE frequency in purified lymphocytes. Neither anti-oxidant enzymes such as catalase and superoxide dismutase nor the hydroxyl radical scavenger, dimethyl sulfoxide, decreased the SCE frequency. Although purified human lymphocytes had a small, but significant increase in SCE compared to whole blood, the magnitude of the dichotomous response between man and rat may represent a fundamental species difference.