Interactions between inflammatory mediators in expression of antitumor cytostatic activity of macrophages

Abstract Antitumor properties and participation in inflammatory events are important characteristics of activated macrophages. We show here that both antitumor cytostatic function of macrophages and participation of these cells at inflammatory sites are controlled by two main groups of mediators: cytokines (IL-1, TNFα) and eicosanoids (prostanoids and leukotrienes). These two groups of mediators represent a complex system of mutual interactions in regulation of their production and activities. Multiple sets of experiments with murine macrophages are discussed in favor of the views that PGE2 and lipoxygenase products oppose each other's actions, and that the regulating role of PGE2 in the secretions of cytokines are of pivotal importance in antitumor cytostasis of macrophages in vitro. Such observations can be extended to a situation ex vivo, showing that human macrophages harvested from inflammatory sites have markedly augmented cytostatic expression. It thus appears that the antitumor cytostatic function of macrophages is related to the production of inflammatory mediators by these cells. Accordingly, it might be that occurrence of inflammation in tumor-bearing individuals plays a role in the promotion of antitumor activity of macrophages

THE ROLE OF COMPLEMENT IN THE PASSIVE CUTANEOUS REACTION OF MICE

Intradermal injection of mice with ribonuclease antibody, followed by intravenous injection with ribonuclease, resulted in permeability increase, demonstrable by "blueing." The size of the blued area depends on the quantity of antibody injected and on the interval between the two injections. If antigen was injected first and antibody was injected subsequently, a similar increase in permeability was observed in animals having a complete complement system (MuB1-positive) and in animals which have a deficient complement system (MuB1-negative). Marked differences in response were observed between these two types of mice if antigen was injected some hours after the antibody. In MuB1-negative mice, a blueing reaction was not observed at intervals between injections (2½ hours if 3 µg N antibody and 15 hours if 25 µg N antibody were injected intradermally) at which MuB1-positive animals showed a marked permeability increase. At these intervals, blueing did occur in MuB1-negative animals if they were injected with the serum of MuB1-positive mice or with fresh guinea pig serum. Blueing was not induced if the serum of MuB1-negative mice or heated guinea pig serum was injected. The occurrence of two distinct phases of the cutaneous reaction, of which only one involves the complete hemolytic complement system, was deduced from these observations

Macrophage cytokines render WEHI-3B tumor cells susceptible to cytostasis by prostaglandins

Abstract The growth of the murine myelomonocytic leukemia tumor, WEHI-3B, has been shown to be inhibited by a two-step treatment: first, incubation for one hour with either interleukin-1 (human recombinant IL-1α or tumor necrosis factor (human recombinant TNF-α); second, subsequent exposure to prostaglandins. Preincubation with IL-1 rendered the tumor cells more susceptible to subsequent treatment with either prostaglandin E2 or to the stable synthetic analogue of prostacyclin DC-PGI2. Preincubation with TNF-α rendered the tumor cells more susceptible to further treatment with PGE2 but not with DC-PGI2. Preconditioning of the tumour cells with either IL-1α or TNFα did not affect cytostasis by subsequent culture of tumor cells in presence of either one of the cytokines. It is concluded that the interactions between macrophage cytokines and prostaglandins in enhancement of antitumor activity might imply first binding or induction of certain modifications in the tumor cells by the cytokines which render the cells more susceptible to exposure to prostaglandins

Release of tumor necrosis factor-alpha and prostanoids in whole blood cultures after in vivo exposure to low-dose aspirin.

BACKGROUND: The preventive effect of low-dose aspirin in cardiovascular disease is generally attributed to its antiplatelet action caused by differential inhibition of platelet cyclooxygenase-1. However, there is evidence that aspirin also affects release of inflammatory cytokines, including tumor necrosis factor-alpha (TNF-alpha). It is not known whether this is caused by direct action on the cytokine pathway or indirectly through cyclooxygenase inhibition and altered prostanoid synthesis, or both. METHODS: We assessed the capacity of lipopolysaccharide-activated leukocytes in whole blood cultures of eight healthy subjects following a single oral dose of 80 mg aspirin to release TNF-alpha, prostanoid E2 (PGE2) and prostanoid I2 (PGI2), and thromboxane A2 (TXA2). TNF-alpha and prostanoids were determined by enzyme-linked immunoassays. RESULTS: In seven subjects, TNF-alpha release in blood cultures decreased 24h after intake of aspirin. The effect of aspirin on prostanoid release was assessed in three individuals: PGE2 increased in all subjects, PGI2 increased in two and remained unchanged in one, and TXA2 was reduced in two and unchanged in one individual The presence of DFU, a specific inhibitor of cyclooxygenase 2, did not affect the reduction of TNF-alpha release by aspirin, but abolished prostanoid production in all three individuals. Conclusion: The capacity of activated leukocytes to release TNF-alpha is reduced by ingestion of low-dose aspirin, independent of changes in prostanoid biosynthesis

Interleukin-6 and interleukin-6 receptor secretion by chronic lymphatic leukaemia and normal B lymphocytes: effect of PMA and PWM

Interleukin-6 (IL-6) and soluble interleukin-6 receptor (sIL-6R) were detected in supernatants of cultures of B chronic lymphatic leukaemia (CLL) lymphocytes. Phorbol-12-myristate 13 acetate (PMA) caused a decrease in the levels of IL-6 in 14 out of 16 cultures and an increase in levels of sIL6R in all 15 cases. The effect of pokeweed mitogen (PWM) was variable and not significant. The levels of IL-6 were below the detection limit (60 pg/ml) in sera of 13 CLL patients whereas sIL-6R was detected (13 ng/ml to 97 ng/ml) in the 13 sera. IL6 was not detected in cultures of unstimulated or stimulated with PMA or PWM normal human B cells. Levels of sIL-6R were minimal in cultures of normal B lymphocytes and were increased in PMA stimulated cultures. The results are consistent with the view that B-CLL cells produce spontaneously IL-6 which could act in an autocrine fashion to cause shedding of surface IL-6R and account for the correlation found between serum levels of sIL-6R and B-CLL lymphocyte numbers. The fall in levels of IL-6 in PMA stimulated CLL cultures might express masking or degradation of IL-6 after combination with the receptor

Serum levels of tumor necrosis factor determine the fatal or non-fatal course of endotoxic shock

Abstract The role of tumor necrosis factor alpha (TNFα) in endotoxin-induced shock was investigated in pigs receiving 5 μg kg− of Escherichia coli endotoxin (LPS) during 60 min of continuous infusion into the superior mesenteric artery. LPS concentration in aortic plasma, as determined by a chromogenic Limulus amoebocyte lysate (LAL) test, reached a peak of approximately 1000 ng 1−1 during LPS infusion, and declined rapidly after discontinuation of the infusion. Serum TNF levels were determined by a bioassay using the L929 murine transformed fibroblast line. Eight of the 17 animals infused with LPS died within 30 min after beginning LPS administration, while the other 9 pigs survived beyond the experimental observation period of 3 h, although they were in a state of shock. No difference in LPS concentration was found between the survivors and the non-survivors. However, the serum TNF levels in non-survivors were significantly higher than in survivors when measured at 30 min after beginning LPS administration. In survivors, the peak increase in serum TNF levels was measured at 60 min after the beginning of LPS injection and returned rapidly to the baseline values. Although the role of TNF inducing rapid death seems to be dominant, the hemodynamic, hematology and blood chemistry disturbances seen during shock continued in survivors long after the return of TNF to baseline levels. These findings indicate that besides TNF other mediators are also involved in the LPS infusion-induced shock