Generation of EPR-detectable nitrosyl-iron complexes in tumor target cells cocultured with activated macrophages.
After immunostimulation, murine macrophages oxidize L-arginine into nitric oxide (NO) which acts as an effector molecule. In this study, we attempted to establish whether activated macrophage-derived NO forms paramagnetic complexes in tumor target cells which do not express by themselves the L-arginine:NO pathway. Accordingly, murine L1210 leukemia cells were cocultivated with activated peritoneal macrophages from Bacillus-Calmette-Guérin-infected mice, or activated in vitro with interferon-gamma. In control experiments, macrophages were prevented from producing nitrogen oxides by incubation with NG-monomethyl-L-arginine, a specific inhibitor of the L-arginine:NO pathway. After coculture, L1210 cells were removed from adherent macrophage monolayers and analyzed by electron paramagnetic resonance at 77 K. In the L1210 cells cultured with activated macrophages, we detected a signal typical of nitrosyl-iron-sulfur complexes, with g values of 2.041 and 2.015. This signal was not present when L1210 cells were either cultured alone or cocultured with activated macrophages in the presence of NG-monomethyl-L-arginine. Mitochondria from activated macrophage-injured L1210 cells also exhibited the signal with g values of 2.041 and 2.015. These results show that when tumor target cells undergo cell-to-cell contact with activated macrophages during culture, the macrophages promote target cell nitrosylation in compartments like mitochondria.
Drapier
J C
JC
Unité 196 Institut National de la Santé et de la Recherche Médicale, Institut Curie, Paris, France.
Pellat
C
C
Henry
Y
Y
D000818:Animals; D001500:BCG Vaccine / Q000276:immunology; D004578:Electron Spin Resonance Spectroscopy; D007502:Iron Chelating Agents / Q000737:chemistry*; D007939:Leukemia L1210 / Q000378:metabolism*; D008264:Macrophages / Q000737:chemistry* / Q000276:immunology; D051379:Mice; D008928:Mitochondria / Q000737:chemistry; D009569:Nitric Oxide / Q000737:chemistry*; D010084:Oxidation-Reduction; D014407:Tumor Cells, Cultured / Q000737:chemistry
D001500:BCG Vaccine; D007502:Iron Chelating Agents; D009569:Nitric Oxide