The data are representative of at least three independent experiments. Scale bars = 5 μm. Flow cytometric measurement of amastigote culture Live L. amazonensis cells were incubated with propidium RO4929097 chemical structure iodide and rhodamine 123, and fluorescence was measured by flow cytometry. The gated percentage of propidium iodide-stained amastigotes after

treatment with amphotericin B (positive control) was 71.4%, much higher than untreated parasites (negative control) that presented 6.0% (Figure 5A). When the cells were treated with 20 and 40 μM parthenolide, the percentages of labeled amastigotes were 34.2% and 56.2%, respectively (Figure 5B), possibly indicating a considerable increase in plasma membrane permeability. To prove that Leishmania cells functionally respond to the pharmacological alteration of ΔΨm, amastigotes C188-9 mw were treated with the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP), which has been shown to interfere with mitochondrial membrane potential in various cell types [12]. The results showed that 82.5% of the amastigotes without treatment (negative control) presented a maximal increase in fluorescence, and with 200 μM CCCP, 46.7% showed fluorescence, indicating a loss of ΔΨm (Figure 5C). We next observed ΔΨm reductions of 68.4% and 56.1% when the amastigotes were

treated with 20 and 40 μM parthenolide, respectively, suggesting that this compound interferes with the mitochondrial membrane potential leading to alteration of ATP generation and in consequence cell damage takes place. Figure 5 Flow cytometry analysis of propidium iodide- (A, B) and rhodamine 123- (C, D) labeled axenic amastigotes of L. amazonensis . (A) Untreated cells: negative control (C-) and amphotericin B as positive control (C+). (B) Amastigotes Adenosine treated with 20 or 40 μM parthenolide (Pt 20 or Pt 40). (C) Untreated cells: negative control and carbonyl cyanide m-chlorophenylhydrazone as a positive control. (D) Amastigotes treated with 20 or 40 μM parthenolide (Pt 20 or Pt 40). The data are representative of at least two independent experiments. EPR spectra of spin-labeled Leishmania The experimental and best-fit EPR spectra

of spin-label 5-DSA structured in the plasma membrane of Leishmania are shown in Figure 6. These EPR spectra are typical for cellular membranes that contain an appreciable amount of integral proteins. Treatment with parthenolide increased two EPR parameters, the outer hyperfine splitting, 2A//, and rotational correlation time, τ C , indicating a significant reduction of membrane lipid dynamics. 2A//is a practice check details parameter measured directly in EPR spectra that has been widely used to monitor membrane fluidity, although in principle it is a static parameter associated with the orientation distribution of the spin labels in the membrane. The theoretical EPR spectrum of spin-label 5-DSA in the plasma membrane of Leishmania was best fitted using a model of two spectral components.