title: Regulation of the expression of nitric oxide synthase by Leishmania mexicana amastigotes in murine dendritic cells.
abstract: In mammalian hosts, Leishmania parasites are obligatory intracellular organisms that invade macrophages (M phi) and dendritic cells (DC). In M phi, the production of nitric oxide (NO) catalyzed by the inducible nitric oxide synthase (iNOS) has been implicated as a major defense against Leishmania infection. The modulation of this microbicidal mechanism by different species of Leishmania has been well studied in M phi. Although DC are permissive for infection with Leishmania both in vivo and in vitro, the effect of this parasite in the expression of iNOS and NO production in these cells has not been established. To address this issue, we analyzed the regulation of iNOS by Leishmania mexicana amastigotes in murine bone marrow-derived dendritic cells (BMDC) stimulated with LPS and IFN-gamma. We show that the infection of BMDC with amastigotes down regulated NO production and diminished iNOS protein levels in cells stimulated with LPS alone or in combination with IFN-gamma. The reduction in iNOS protein levels and NO production did not correlate with a decrease in iNOS mRNA expression, suggesting that the parasite affects post-transcriptional events of NO synthesis. Although amastigotes were able to reduce NO production in BMDC, the interference with this cytotoxic mechanism was not sufficient to permit the survival of L. mexicana. At 48 h post-infection, BMDC stimulated with LPS+IFN-gamma were able to eliminate the parasites. These results are the first to identify the regulation of iNOS by L. mexicana amastigotes in DC.
authors.affiliation: Departamento de Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México, Dr. Balmis 148, Col. Doctores, México 06726, D.F., Mexico.
authors.forename: Arturo A
authors.initials: AA
authors.lastname: Wilkins-Rodríguez
authors.forename: Alma Reyna
authors.initials: AR
authors.lastname: Escalona-Montaño
authors.forename: Magdalena
authors.initials: M
authors.lastname: Aguirre-García
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Becker
authors.forename: Laila
authors.initials: L
authors.lastname: Gutiérrez-Kobeh
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000469:parasitology*; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000469:parasitology*; D015536:Down-Regulation; D005260:Female; D005434:Flow Cytometry; D015971:Gene Expression Regulation, Enzymologic; D016130:Immunophenotyping; D007894:Leishmania mexicana / Q000201:enzymology* / Q000254:growth & development; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D012333:RNA, Messenger; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase