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TRYPANOSOMA CRUZI MITOCHONDRIAL SWELLING AND MEMBRANE POTENTIAL COLLAPSE AS PRIMARY EVIDENCE OF THE MODE OF ACTION OF NAPHTHOQUINONE ANALOGUES
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Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Celular. Rio de Janeiro, RJ, Brasil.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Celular. Rio de Janeiro, RJ, Brasil.
CSIC. Instituto de Química Médica. JUan de la Cierva, Madrid, Spain.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Celular. Rio de Janeiro, RJ, Brasil.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Celular. Rio de Janeiro, RJ, Brasil.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Celular. Rio de Janeiro, RJ, Brasil.
CSIC. Instituto de Química Médica. JUan de la Cierva, Madrid, Spain.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Celular. Rio de Janeiro, RJ, Brasil.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Celular. Rio de Janeiro, RJ, Brasil.
Abstract
Background: Naphthoquinones (NQs) are privileged structures in medicinal chemistry due to the biological effects
associated with the induction of oxidative stress. The present study evaluated the activities of sixteen NQs
derivatives on Trypanosoma cruzi.
Results: Fourteen NQs displayed higher activity against bloodstream trypomastigotes of T. cruzi than benznidazole.
Further assays with NQ1, NQ8, NQ9 and NQ12 showed inhibition of the proliferation of axenic epimastigotes and
intracelulluar amastigotes interiorized in macrophages and in heart muscle cells. NQ8 was the most active NQ
against both proliferative forms of T. cruzi. In epimastigotes the four NQs induced mitochondrial swelling,
vacuolization, and flagellar blebbing. The treatment with NQs also induced the appearance of large endoplasmic
reticulum profiles surrounding different cellular structures and of myelin-like membranous contours, morphological
characteristics of an autophagic process. At IC50 concentration, NQ8 totally disrupted the ΔΨm of about 20% of the
parasites, suggesting the induction of a sub-population with metabolically inactive mitochondria. On the other
hand, NQ1, NQ9 or NQ12 led only to a discrete decrease of TMRE + labeling at IC50 values. NQ8 led also to an
increase in the percentage of parasites labeled with DHE, indicative of ROS production, possibly the cause of the
observed mitochondrial swelling. The other three NQs behaved similarly to untreated controls.
Conclusions: NQ1, NQ8, NQ9 and NQ12 induce an autophagic phenotype in T. cruzi epimastigoted, as already
observed with others NQs. The absence of oxidative stress in NQ1-, NQ9- and NQ12-treated parasites could be due
to the existence of more than one mechanism of action involved in their trypanocidal activity, leaving ROS
generation suppressed by the detoxification system of the parasite. The strong redox effect of NQ8 could be
associated to the presence of the acetyl group in its structure facilitating quinone reduction, as previously
demonstrated by electrochemical analysis. Further experiments using biochemical and molecular approaches are
needed to better characterize ROS participation in the mechanism of action of these NQs.
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