Ionizing radiation potentiates the induction of nitric oxide synthase by IFN-gamma and/or LPS in murine macrophage cell lines: role of TNF-alpha.
Macrophages are activated to become cytotoxic by a highly coordinated set of cytokine signals. Ionizing radiation can mimic cytokine signals and lead to enhanced states of activation. We tested the ability of gamma-radiation, alone and with interferon-gamma (IFN-gamma) and/or lipopolysaccharide (LPS), to induce nitric oxide (NO) production in J774.1 and RAW264.7 murine macrophages. NO was induced weakly, moderately, or strongly by IFN-gamma alone, LPS alone, or IFN-gamma + LPS, respectively. Radiation alone (0.5-50 Gy) did not induce NO, but enhanced NO production in a dose-dependent manner (0.5-5 Gy) when cells were exposed to IFN-gamma or LPS 24 h post-irradiation. Immunoblots showed parallel induction of nitric oxide synthase (NOS2). Application of anti-tumor necrosis factor alpha (TNF-alpha) antibody before irradiation blocked induction of NO by IFN-gamma. We conclude (1) that irradiated cells produce more NO in response to either IFN-gamma or LPS and (2) that the increase is mediated by induction of TNF-alpha.
Department of Radiation Pathophysiology and Toxicology, Armed Forces Radiobiology Research Institute, Bethesda, Maryland, USA. mckinney@mx.afrri.usuhs.mil
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D000818:Animals; D000906:Antibodies; D016477:Artifacts; D002460:Cell Line; D003037:Cobalt Radioisotopes; D004307:Dose-Response Relationship, Radiation; D004790:Enzyme Induction / Q000187:drug effects / Q000528:radiation effects; D004926:Escherichia coli; D005720:Gamma Rays; D007371:Interferon-gamma / Q000494:pharmacology*; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology* / Q000528:radiation effects; D051379:Mice; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000502:physiology*
D000906:Antibodies; D003037:Cobalt Radioisotopes; D008070:Lipopolysaccharides; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase