title: Naturally azole-resistant Leishmania braziliensis promastigotes are rendered susceptible in the presence of terbinafine: comparative study with azole-susceptible Leishmania mexicana promastigotes.
abstract: Leishmania braziliensis (isolate 2903) was naturally resistant to ketoconazole or the bis-triazole D0870, inhibitors of sterol C-14 demethylase, which produced only moderate effects on the proliferation of promastigotes at 10 microM. In contrast, Leishmania mexicana (isolate NR) was extremely susceptible to the azoles, as complete growth arrest and cell lysis were induced by incubation of the parasites with 0.05 microM concentrations of the drugs for 72 h. The opposite response was observed with terbinafine, an inhibitor of squalene epoxidase: L. braziliensis 2903 was three times more susceptible to the drug than L. mexicana NR (MICs of 5 and 15 microM, respectively). However, when the L. braziliensis stock was grown in the presence of 1 microM terbinafine, which by itself produced only marginal (< 10%) effects on growth, it became highly susceptible to the azoles, with an MIC of 0.03 microM. Analysis of cellular free sterols by high-resolution capillary gas chromatography coupled to mass spectrometry showed that 14-methyl sterols can support normal growth of L. braziliensis 2903 but not of L. mexicana NR. On the other hand, the higher susceptibility of the L. braziliensis isolate to terbinafine was correlated with a massive accumulation of squalene in the presence of the allylamine while no significant effects on L. mexicana sterol composition were observed at drug concentrations up to 1 microM. Thus, the > 300-fold increase in the susceptibility of L. braziliensis promastigotes to azoles in the presence of terbinafine was attributed to the combined effect of squalene and the methylated sterol precursors on the physical properties of the cell's membranes, leading to the loss of cell viability. Combination therapy with azoles and terbinafine in the treatment of human L. braziliensis infections deserves further study.
authors.affiliation: Laboratorio de Bioloía Celular de Parásitos, Facultad de Ciencias, Universidad Central de Venezuela, Caracas, Venezuela.
authors.forename: H
authors.initials: H
authors.lastname: Rangel
authors.forename: F
authors.initials: F
authors.lastname: Dagger
authors.forename: A
authors.initials: A
authors.lastname: Hernandez
authors.forename: A
authors.initials: A
authors.lastname: Liendo
authors.forename: J A
authors.initials: JA
authors.lastname: Urbina
mesh_terms: D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology*; D001393:Azoles / Q000494:pharmacology*; D065607:Cytochrome P-450 Enzyme Inhibitors; D004347:Drug Interactions; D004351:Drug Resistance; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007654:Ketoconazole / Q000494:pharmacology; D007892:Leishmania braziliensis / Q000187:drug effects* / Q000235:genetics; D007894:Leishmania mexicana / Q000187:drug effects* / Q000235:genetics; D009281:Naphthalenes / Q000494:pharmacology*; D010088:Oxidoreductases / Q000037:antagonists & inhibitors; D013185:Squalene / Q000737:chemistry; D058886:Sterol 14-Demethylase; D013261:Sterols / Q000096:biosynthesis; D000077291:Terbinafine; D014230:Triazoles / Q000494:pharmacology
chemical_list: D000935:Antifungal Agents; D001393:Azoles; C548418:CYP51A1 protein, human; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D009281:Naphthalenes; D013261:Sterols; D014230:Triazoles; C058219:ICI 195739; D013185:Squalene; D010088:Oxidoreductases; D058886:Sterol 14-Demethylase; D000077291:Terbinafine; D007654:Ketoconazole