. Here we show that at therapeutic concentrations, amiodarone has a profound effect on the viability of Leishmania mexicana promastigotes. Additionally, its effect on the viability of the parasite was greater against intracellular amastigotes than against promastigotes, and it did not affect the host cell. Using fluorimetric and confocal microscopy techniques, we also demonstrated that the mechanism of action of amiodarone was related to the disruption of intracellular Ca 2؉ homeostasis through a direct action not only on the mitochondria but also on the acidocalcisomes. On the other hand, analysis of the free sterols in promastigotes incubated with amiodarone showed that this drug also affected the biosynthesis of 5-dehydroepisterol, which results in squalene accumulation, thus suggesting that amiodarone inhibits the squalene epoxidase activity of the parasite. Taken together, the results obtained in the present work point to a more general effect of amiodarone in trypanosomatids, opening potential therapeutic possibilities for this infectious disease.
is the causing agent of visceral leishmaniasis, a common infection that affects millions of people from the most underdeveloped countries. Miltefosine is the only oral drug to treat infections caused by Nevertheless, its mechanism of action is not well understood. While miltefosine inhibits the synthesis of phosphatidylcholine and also affects the parasite mitochondrion, inhibiting the cytochrome oxidase, it is to be expected that this potent drug also produces its effect through other targets. In this context, it has been reported that the disruption of the intracellular Ca homeostasis represents an important object for the action of drugs in trypanosomatids. Recently, we have described a plasma membrane Ca channel in , which is similar to the L-type voltage-gated Ca channel (VGCC) present in humans. Remarkably, the parasite Ca channel is activated by sphingosine, while the L-type VGCC is not affected by this sphingolipid. In the present work we demonstrated that, similarly to sphingosine, miltefosine is able to activate the plasma membrane Ca channel from Interestingly, nifedipine, the classical antagonist of the human channel, was not able to fully block the parasite plasma membrane Ca channel, indicating that the mechanism of interaction is not identical to that of sphingosine. In this work we also show that miltefosine is able to strongly affect the acidocalcisomes from , inducing the rapid alkalinization of these important organelles. In conclusion, we demonstrate two new mechanisms of action of miltefosine in, both related to disruption of parasite Ca homeostasis.
Glibenclamide reduced the rate of lesion growth in BALB/c mice infected with Leishmania (Leishmania) mexicana, the effect was dose dependent, and the highest dose proved more effective than glucantime. Crossresistance to glucantime was found in animals infected with a glibenclamide-resistant line, but combined therapy reduced lesion progression even in the glibenclamide-resistant strain.
Leishmaniasis is parasitic disease that is an important problem of public health worldwide. Intramuscularly administered glucantime and pentostam are the most common drugs used for treatment of this disease, but they have significant limitations due to toxicity and increasing resistance. A recent breakthrough has been the introduction of orally administered miltefosine for the treatment of visceral, cutaneous, and mucocutaneous leishmaniasis, but the relative high cost and concerns about teratogenicity have limited the use of this drug. Searching for alternative drugs, we previously demonstrated that the antiarrhythmic drug amiodarone is active against Leishmania mexicana promastigotes and intracellular amastigotes, acting via disruption of intracellular Ca 2؉ homeostasis (specifically at the mitochondrion and the acidocalcisomes of these parasites) and through inhibition of the parasite's de novo sterol biosynthesis (X. Serrano-Martín, Y. García-Marchan, A. Fernandez, N. Rodriguez, H. Rojas, G. Visbal, and G. Benaim, Antimicrob. Agents Chemother. 53:1403-1410, 2009). In the present work, we found that miltefosine also disrupts the parasite's intracellular Ca 2؉ homeostasis, in this case by inducing a large increase in intracellular Ca 2؉ levels, probably through the activation of a plasma membrane Ca 2؉ channel. We also investigated the in vitro and in vivo activities of amiodarone and miltefosine, used alone or in combination, on L. mexicana. It was found that the drug combination had synergistic effects on the proliferation of intracellular amastigotes growing inside macrophages and led 90% of parasitological cures in a murine model of leishmaniasis, as revealed by a PCR assay using a novel DNA sequence specific for L. mexicana.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.