Effect of l-leucine methyl ester on growth and ultrastructure of Trypanosoma cruzi

• Published in: Acta tropica Vol. 101; no. 1; pp. 69 - 79
• Main Authors: Adade, Camila M., Figueiredo, Regina C.B.Q., De Castro, Solange L., Soares, Maurilio J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 2007; Elsevier
• Subjects: Animals; Antiprotozoal Agents - pharmacology; Biological and medical sciences; Chagas Disease - drug therapy; Chagas Disease - parasitology; Dose-Response Relationship, Drug; Flow Cytometry; General aspects; Inhibitory Concentration 50; l-Leucine methyl ester; Leishmania amazonensis; Leucine - analogs & derivatives; Leucine - pharmacology; Lysosomes; Macrophages, Peritoneal - parasitology; Medical sciences; Mice; Microscopy, Confocal; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; Reservosomes; Trypanosoma cruzi; Trypanosoma cruzi - drug effects; Trypanosoma cruzi - growth & development; Trypanosoma cruzi - ultrastructure; Ultrastructure; Lysosomes; l-Leucine methyl ester; Ultrastructure; Reservosomes; Trypanosoma cruzi; Kinetoplastida; Protozoa; Growth; Leucine; L-Leucine methyl ester; Ester; Aminoacid; Tropical medicine; Trypanosomu cruzi
• ISSN: 0001-706X; 1873-6254
• DOI: 10.1016/j.actatropica.2006.12.006

l-Amino acid methyl esters, such as
l-leucine methyl ester (Leu-OMe), have been identified as agents targeting the lysosomal system of
Leishmania amazonensis amastigotes, by a mechanism that involves ester hydrolysis by parasite enzymes located inside megasomes. We have here analyzed the effect of Leu-OMe on all three evolutive forms of
Trypanosoma cruzi, in a search for potential targets of the compound in this protozoan. Treatment of epimastigote forms resulted in dose-dependent growth inhibition, with IC
50/1 day
=
0.55
±
0.21
mM. Incubation with 4–8
mM/1 day led to 100% cell death. Treatment of bloodstream trypomastigotes resulted in cell lysis, with an IC
50/1 day
=
1.46
±
0.16
mM. Furthermore, infected macrophages treated with 0.125–1
mM Leu-OMe showed a dose- and time-dependent decrease in the percent of amastigote infection. Morphological changes in macrophages were observed only at concentrations above 8
mM, at the third day of treatment. Analysis of treated parasites by transmission electron microscopy demonstrated severe morphological alterations in cell shape, mitochondrion and nucleus, while kinetoplast and reservosomes (pre-lysosomal compartments) appeared to be not affected. Lysis of bloodstream trypomastigotes and intracellular amastigotes indicated that lysosomes of
T. cruzi are the main target for the drug, since reservosomes occur only in epimastigote forms. The presence of lysosomes in
T. cruzi epimastigotes was demonstrated by using ultrastructural cytochemistry.