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Indole alkaloids possess a large spectrum of biological activities including anti-protozoal action. Here we report for the first time that voacamine, isolated from the plant Tabernaemontana coronaria, is an antiprotozoal agent effective against a large array of trypanosomatid parasites including Indian strain of Leishmania donovani and Brazilian strains of Leishmania amazonensis and Trypanosoma cruzi. It inhibits the relaxation activity of topoisomerase IB of L. donovani (LdTop1B) and stabilizes the cleavable complex. Voacamine is probably the first LdTop1B-specific poison to act uncompetitively. It has no impact on human topoisomerase I and II up to 200μM concentrations. The study also provides a thorough insight into ultrastructural alterations induced in three kinetoplastid parasites by a specific inhibitor of LdTop1B. Voacamine is also effective against intracellular amastigotes of different drug unresponsive field isolates of Leishmania donovani obtained from endemic zones of India severely affected with visceral leishmaniasis. Most importantly, this is the first report demonstrating the efficacy of a compound to reduce the burden of drug resistant parasites, unresponsive to SAG, amphotericin B and miltefosine, in experimental BALB/c mice model of visceral leishmaniasis. The findings cumulatively provide a strong evidence that voacamine can be a promising drug candidate against trypanosomatid infections., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: Trypanosoma cruzi is the etiological agent of Chagas' disease that is an endemic disease in Latin America and affects about 8 million people. This parasite belongs to the Trypanosomatidae family which contains a single mitochondrion with an enlarged region, named kinetoplast that harbors the mitochondrial DNA (kDNA). The kinetoplast and the nucleus present a great variety of essential enzymes involved in DNA replication and topology, including DNA topoisomerases. Such enzymes are considered to be promising molecular targets for cancer treatment and for antiparasitic chemotherapy. In this work, the proliferation and ultrastructure of T. cruzi epimastigotes were evaluated after treatment with eukaryotic topoisomerase I inhibitors, such as topotecan and irinotecan, as well as with dual inhibitors (compounds that block eukaryotic topoisomerase I and topoisomerase II activities), such as baicalein, luteolin and evodiamine. Previous studies have shown that such inhibitors were able to block the growth of tumor cells, however most of them have never been tested on trypanosomatids., Results: Considering the effects of topoisomerase I inhibitors, our results showed that topotecan decreased cell proliferation and caused unpacking of nuclear heterochromatin, however none of these alterations were observed after treatment with irinotecan. The dual inhibitors baicalein and evodiamine decreased cell growth; however the nuclear and kinetoplast ultrastructures were not affected., Conclusions: Taken together, our data showed that camptothecin is more efficient than its derivatives in decreasing T. cruzi proliferation. Furthermore, we conclude that drugs pertaining to a certain class of topoisomerase inhibitors may present different efficiencies as chemotherapeutical agents.

The protozoan Trypanosoma cruzi is the etiological agent of Chagas disease, which affects approximately 8 million people in Latin America. This parasite contains a single nucleus and a kinetoplast, which harbors the mitochondrial DNA (kDNA). DNA topoisomerases act during replication, transcription and repair and modulate DNA topology by reverting supercoiling in the DNA double-strand. In this work, we evaluated the effects promoted by camptothecin, a topoisomerase I inhibitor that promotes protozoan proliferation impairment, cell cycle arrest, ultrastructure alterations and DNA lesions in epimastigotes of T. cruzi. The results showed that inhibition of cell proliferation was reversible only at the lowest drug concentration (1μM) used. The unpacking of nuclear heterochromatin and mitochondrion swelling were the main ultrastructural modifications observed. Inhibition of parasite proliferation also led to cell cycle arrest, which was most likely caused by nuclear DNA lesions. Following camptothecin treatment, some of the cells restored their DNA, whereas others entered early apoptosis but did not progress to late apoptosis, indicating that the protozoa stay alive in a "senescence-like" state. This programmed cell death may be associated with a decrease in mitochondrial membrane potential and an increase in the production of reactive oxygen species. Taken together, these results indicate that the inhibition of T. cruzi proliferation is related to events capable of affecting cell cycle, DNA organization and mitochondrial activity., (Copyright © 2014. Published by Elsevier B.V.)