title: Toxoplasma gondii partially inhibits nitric oxide production of activated murine macrophages.
abstract: Activated macrophages produce nitric oxide (NO) and as such are able to control the multiplication of Toxoplasma gondii. Until now, no reports have described a possible modulation of NO production of macrophages after T. gondii infection. To investigate this possibility, murine blood monocyte-derived and peritoneal macrophages were activated in vitro with interferon-gamma and lipopolysaccharide and infected with T. gondii and Trypanosoma cruzi, and NO production was evaluated. NO was produced by monocyte-derived macrophages only if cultured in the presence of macrophage-colony-stimulating factor. Monocyte-derived or peritoneal macrophages infected with T. gondii presented a significant reduction in NO production. NO production inhibition was not detected after T. cruzi infection. Macrophages infected with higher T. gondii/macrophage ratios presented lower NO production. Furthermore, only viable T. gondii could cause partial inhibition of NO production. In macrophages activated 24 h before the interaction, partial inhibition was detected after 3 h of infection and continued for 48 h. In macrophages activated immediately after the interaction, partial inhibition was not detected at 12 h, but was observed at 24 h. T. gondii-infected macrophages present lower inducible nitric oxide synthase expression as assayed by immunofluorescence. T. gondii did not develop in monocyte-derived macrophages producing NO, but were not totally eliminated. These results demonstrate that T. gondii infection partially inhibits NO production by murine macrophages, suggesting that a deactivating macrophage mechanism may be used for better survival into phagocytic cells.
authors.affiliation: Laboratório de Biologia Celular e Tecidual, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, Avenida Alberto Lamego 2000, 28015-620 Campos dos Goytacazes, RJ, Brazil.
authors.forename: Sergio H
authors.initials: SH
authors.lastname: Seabra
authors.forename: Wanderley
authors.initials: W
authors.lastname: de Souza
authors.forename: Renato A
authors.initials: RA
authors.lastname: DaMatta
mesh_terms: D000818:Animals; D007372:Interferons / Q000494:pharmacology; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism / Q000469:parasitology*; D008297:Male; D051379:Mice; D009000:Monocytes / Q000166:cytology; D009569:Nitric Oxide / Q000096:biosynthesis*; D014122:Toxoplasma / Q000502:physiology*
chemical_list: D008070:Lipopolysaccharides; D009569:Nitric Oxide; D007372:Interferons