title: Leishmania infantum amastigotes resistant to nitric oxide cytotoxicity: Impact on in vitro parasite developmental cycle and metabolic enzyme activities.
abstract: Nitric oxide (NO) has been demonstrated to be the principal effector molecule mediating intracellular killing of Leishmania. The free radical characteristic of NO prevented direct induction of resistance in Leishmania wild-type parasites. Starting from the previous observation that antimony-resistant amastigotes of Leishmania infantum were not affected by NO-induced apoptotic death, we used a continuous NO pressure protocol and succeeded in inducing NO resistance in amastigote forms of L. infantum. Two clones resistant to 50 microM (LiNOR50) and 100 microM (LiNOR100) of the NO donor DETA/NONOate, derived from parental clone weakly resistant to trivalent antimony (LiSbIIIR4), were selected and analysed. Both clones were also resistant to other NO donors, particularly SNAP. In the absence of potassium antimonyl tartrate, all clones (LiSbIIIR4, LiNOR50 and LiNOR100) lost their antimony resistance almost totally. Interestingly, the parasitic developmental life cycle of NO-resistant mutants was dramatically disturbed. NO-resistant amastigotes differentiated more rapidly into promastigotes than the wild-type ones. Nevertheless, NO-resistant amastigotes produce a maximal number of parasites 1.5-2 times lower than the wild-type whereas, after differentiation, NO-resistant promastigotes produced more cells than the wild-type. We showed that this last phenomenon could be a consequence of the overexpression of parasitic enzymes involved in both glycolysis and respiration processes. NO-resistant amastigotes overexpressed three enzymes: cis-aconitase, glyceraldehyde-3-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. The two first enzymes are NO molecular targets which could be directly involved in NO resistance and the third one could interfere in modifying Leishmania metabolism.
authors.affiliation: UR 008 Pathogénie des Trypanosomatidés, IRD (Institut de Recherche pour le Développement), B.P. 64501, 911 avenue Agropolis, 34394 Montpellier cedex 5, France. holzmull@mpl.ird.fr
authors.forename: Philippe
authors.initials: P
authors.lastname: Holzmuller
authors.forename: Mallorie
authors.initials: M
authors.lastname: Hide
authors.forename: Denis
authors.initials: D
authors.lastname: Sereno
authors.forename: Jean-Loup
authors.initials: JL
authors.lastname: Lemesre
mesh_terms: D000154:Aconitate Hydratase / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D004351:Drug Resistance; D005260:Female; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating) / Q000378:metabolism*; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000494:pharmacology; D018314:Leishmania infantum / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D008018:Life Cycle Stages / Q000187:drug effects*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation / Q000187:drug effects; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000469:parasitology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009154:Mutation; D009569:Nitric Oxide / Q000633:toxicity*; D009573:Nitrites / Q000032:analysis; D010734:Phosphogluconate Dehydrogenase / Q000378:metabolism*; D012641:Selection, Genetic
chemical_list: D008070:Lipopolysaccharides; D009573:Nitrites; D009569:Nitric Oxide; D007371:Interferon-gamma; D010734:Phosphogluconate Dehydrogenase; D024581:Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating); D000154:Aconitate Hydratase