title: [Effect of lipophilic ortho-naphthoquinones on the growth of and production of peroxides by Leptomonas seymouri and Crithidia fasciculata].
abstract: The lipophilic o-naphthoquinones CG 8-935, CG 9-442, CG 10-248 and mansonones A, C, E and F inhibit growth of the trypanosomatids Leptomonas seymouri (LS) and Crithidia fasciculata (CF). The most active mansonones were E and F (I50, 0.1-0.4 microM with LS; 0.3-1.2 microM with CF) with cytotoxic activities equal to or higher than quinones CG, as reported previously. Incubation of LS or CF with the CG-quinones and mansonones E and F caused the release of H2O2 and O2-. from the whole cells to the suspending medium, as detected by the microperoxidase and adrenochrome assays, respectively. Lower O2-. and H2O2 production values were obtained with perezone and primine, two p-benzoquinones used as controls. Quinones effect on O2-. and H2O2 production was closely related to their concentration and with mansonones E and F, O2-. production was 4-5-fold higher than H2O2 production. Smaller differences were observed with the CG-quinones. Peroxide production in the assayed organisms was the result of quinone redox-cycling, which involved an anaerobic, reductive phase producing quinols, and an aerobic phase (II), in which quinol oxidation and peroxide production (O2-., H2O2) occurred. With mansonones E and F, and quinone CG, phase II rate was faster than or similar to phase I rate, but with mansonones A and C, the quinols oxidation rate was 8-10-fold slower than the quinones reduction rate. These differences fit in well with a) the quinol oxidation rates, measured in vitro; b) O2-. production by quinols oxidation and c) quinols capability for producing lucigenin chemiluminescence. These results support the assumption that oxyradicals play a relevant role in o-naphthoquinones cytotoxic action, despite the presence of catalase and other protective enzymes in CF and LS. Other effects are not, however, ruled out. CF and LS sensitivity towards the assayed o-quinones was similar or higher than that of Trypanosoma cruzi, thus allowing the use of those organisms for preliminary screening of antichagasic drugs.
authors.affiliation: Centro de Investigaciones Bioenergéticas, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
authors.forename: M P
authors.initials: MP
authors.lastname: Molina Portela
authors.forename: E M
authors.initials: EM
authors.lastname: de Pahn
authors.forename: C
authors.initials: C
authors.lastname: Galeffi
authors.forename: A O
authors.initials: AO
authors.lastname: Stoppani
mesh_terms: D000818:Animals; D016831:Crithidia fasciculata / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D009285:Naphthoquinones / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010545:Peroxides / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D014349:Trypanosoma cruzi / Q000187:drug effects / Q000254:growth & development; D014351:Trypanosomatina / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism
chemical_list: D009285:Naphthoquinones; D010545:Peroxides; D013481:Superoxides; D006861:Hydrogen Peroxide
vernacular_title: Efecto de orto-naftoquinonas lipofilicas sobre el crecimiento y la producción de peróxidos por Leptomonas seymouri y Crithidia fasciculata.