Inhibition of tumor cell mitochondrial respiration by macrophage cytotoxic mediators distinct from interferon-γ

Abstract

Macrophage-mediated inhibition of mitochondrial respiration in EMT-6 murine mammary adenocarcinoma cells can be mimicked in vitro by treatment of the cells with interferon-gamma (IFN-gamma) in combination with tumor necrosis factor, interleukin-1, or lipopolysaccharide. Conditioned supernatants obtained from activated macrophages appear to contain interferon-gamma, suggesting that inhibition of mitochondrial respiration in tumor cells was caused by synergy of IFN-gamma with other cytokines. To further characterize monokines that cause inhibition of mitochondrial respiration in tumor cells, EA13.5 macrophage-like cells were isolated and selected for inhibition of mitochondrial respiration in EMT-6 tumor cells. After stimulation with IFN-gamma and lipopolysaccharide, the EA13.5 cells released into conditioned supernatants a cytotoxic mediator that induced nitric oxide synthesis and caused lesions in the electron transport chain of EMT-6 cells similar to the lesions caused by activated peritoneal macrophages. Enzyme-linked immunosorbent assay demonstrated that the conditioned supernatants produced by EA13.5 macrophage cells did not contain IFN-gamma. Treatment of the EA13.5 cell-conditioned supernatants with neutralizing antibody against IFN-gamma did not abrogate the inhibition of mitochondrial respiration in EMT-6 cells caused by these conditioned supernatants. This study demonstrated that unidentified macrophage cytotoxic mediators distinct from IFN-gamma are involved in the induction of nitric oxide synthesis and inhibition of mitochondrial respiration in tumor cells.

Effect of recombinant human tumor necrosis factor-alpha on cerebral oxygen uptake, cerebrospinal fluid lactate, and cerebral blood flow in the rabbit: role of nitric oxide.

“…In vivo evidence for this was provided by Kilboum et al who demonstrated that intravenous TNF-a-induced hypotension in dogs was completely reversed by treatment with N-G-methyl-L-arginine, an inhibitor of NOS (25). In vitro studies of the effect of nitric oxide on isolated mitochondria have demonstrated inhibition of mitochondrial respiration from a number of tissues, including skeletal muscle (26), tumor cells (27), vascular smooth muscle cells (28), and hepatocytes (29). The effects on mitochondrial metabolism are thought to occur by inhibition of the Krebs cycle enzyme, aconitase (29,30) and complexes I and II of the mitochondrial respiratory chain (28,29).…”

Nitric oxide inhibits enterocyte mitochondrial phospholipase D

“…Supporting data are available in the literature for both a protective and a cytotoxic role for NO in biological systems. Nitric oxide has been shown to inhibit mitochondrial function of activated macrophages [29, 30]. Mitochondria respiration was inhibited by NO resulting in reduced ATP synthesis in a concentration dependent manner without affecting the activity of energy transducing enzymes and the inhibition was significantly stronger at physiologically low intracellular oxygen tension [31].…”

Antiproliferative Properties of Human Alveolar Macrophages

“…Lung macrophages may inhibit tumoral growth in several ways, including direct cytotoxicity by cell-to-cell contact or indirectly through a large variety of mediators or recruitment of other cells with immune functions [4][5][6][7]. On the other hand, lung macrophages may promote tumoral growth by enhancing stroma formation and metastasis [8,9].…”