Chagas Disease Chemotherapy: What Do We Know So Far?

Chagas disease is a Neglected Tropical Disease (NTD), and although it is endemic in Latin America, it affects around 6-7 million people worldwide. The treatment of Chagas disease is based on benznidazole and nifurtimox, which are the only available drugs. However, they are not effective during the chronic phase and cause several side effects. Furthermore, BZ promotes cure in 80% of the patients in the acute phase, but the cure rate drops to 20% in adults in the chronic phase of the disease. In this review, we present several studies published in the last six years, which describe the antiparasitic potential of distinct drugs, from the synthesis of new compounds, aiming to target the parasite, as well as the repositioning and the combination of drugs. We highlight several compounds that have shown equivalency or superiority to BZ, which means that they should be further studied, either in vitro or in vivo. Furthermore, we highlight the differences in the effects of BZ on the same strain of T. cruzi, which might be related to methodological differences, such as parasite and cell ratios, host cell type, and the time of adding the drug. In addition, we discussed the wide variety of strains and also the cell types used as host cells, making it difficult to compare the trypanocidal effect of the compounds.

Basic Biology of Trypanosoma cruzi.

The present review addresses basic aspects of the biology of the pathogenic protozoa Trypanosoma cruzi and some comparative information of Trypanosoma brucei. Like eukaryotic cells, their cellular organization is similar to that of mammalian hosts. However, these parasites present structural particularities. That is why the following topics are emphasized in this paper: developmental stages of the life cycle in the vertebrate and invertebrate hosts; the cytoskeleton of the protozoa, especially the sub-pellicular microtubules; the flagellum and its attachment to the protozoan body through specialized junctions; the kinetoplast-mitochondrion complex, including its structural organization and DNA replication; glycosome and its role in the metabolism of the cell; acidocalcisome, describing its morphology, biochemistry, and functional role; cytostome and the endocytic pathway; the organization of the endoplasmic reticulum and Golgi complex; the nucleus, describing its structural organization during interphase and division; and the process of interaction of the parasite with host cells. The unique characteristics of these structures also make them interesting chemotherapeutic targets. Therefore, further understanding of cell biology aspects contributes to the development of drugs for chemotherapy.

Histone deacetylases as targets for antitrypanosomal drugs.

Parasitic protozoa comprise several species that are causative agents of important diseases. These diseases are distributed throughout the world and include leishmaniasis, Chagas disease and sleeping sickness, malaria and toxoplasmosis. Treatment is based on drugs that were developed many years ago, which have side effects and produce resistant parasites. One approach for the development of new drugs is the identification of new molecular targets. We summarize the data on histone deacetylases, a class of enzymes that act on histones, which are closely associated with DNA and its regulation. These enzymes may constitute new targets for the development of antiparasitic protozoa drugs. Although several protozoan species are mentioned, members of the Trypanosomatidae family are the main focus of this short review.

Lopinavir, an HIV-1 peptidase inhibitor, induces alteration on the lipid metabolism of Leishmania amazonensis promastigotes.

The anti-leishmania effects of HIV peptidase inhibitors (PIs) have been widely reported; however, the biochemical target and mode of action are still a matter of controversy in Leishmania parasites. Considering the possibility that HIV-PIs induce lipid accumulation in Leishmania amazonensis, we analysed the effects of lopinavir on the lipid metabolism of L. amazonensis promastigotes. To this end, parasites were treated with lopinavir at different concentrations and analysed by fluorescence microscopy and spectrofluorimetry, using a fluorescent lipophilic marker. Then, the cellular ultrastructure of treated and control parasites was analysed by transmission electron microscopy (TEM), and the lipid composition was investigated by thin-layer chromatography (TLC). Finally, the sterol content was assayed by gas chromatography-mass spectrometry (GC/MS). TEM analysis revealed an increased number of lipid inclusions in lopinavir-treated cells, which was accompanied by an increase in the lipophilic content, in a dose-dependent manner. TLC and GC-MS analysis revealed a marked increase of cholesterol-esters and cholesterol. In conclusion, lopinavir-induced lipid accumulation and affected lipid composition in L. amazonensis in a concentration-response manner. These data contribute to a better understanding of the possible mechanisms of action of this HIV-PI in L. amazonensis promastigotes. The concerted action of lopinavir on this and other cellular processes, such as the direct inhibition of an aspartyl peptidase, may be responsible for the arrested development of the parasite.

Endosymbiosis in trypanosomatid protozoa: the bacterium division is controlled during the host cell cycle.

Mutualism is defined as a beneficial relationship for the associated partners and usually assumes that the symbiont number is controlled. Some trypanosomatid protozoa co-evolve with a bacterial symbiont that divides in coordination with the host in a way that results in its equal distribution between daughter cells. The mechanism that controls this synchrony is largely unknown, and its comprehension might provide clues to understand how eukaryotic cells evolved when acquiring symbionts that later became organelles. Here, we approached this question by studying the effects of inhibitors that affect the host exclusively in two symbiont-bearing trypanosomatids, Strigomonas culicis and Angomonas deanei. We found that inhibiting host protein synthesis using cycloheximide or host DNA replication using aphidicolin did not affect the duplication of bacterial DNA. Although the bacteria had autonomy to duplicate their DNA when host protein synthesis was blocked by cycloheximide, they could not complete cytokinesis. Aphidicolin promoted the inhibition of the trypanosomatid cell cycle in the G1/S phase, leading to symbiont filamentation in S. culicis but not in A. deanei. Treatment with camptothecin blocked the host protozoa cell cycle in the G2 phase and induced the formation of filamentous symbionts in both species. Oryzalin, which affects host microtubule polymerization, blocked trypanosomatid mitosis and abrogated symbiont division. Our results indicate that host factors produced during the cell division cycle are essential for symbiont segregation and may control the bacterial cell number.

Oxyrane derivative of alpha-lapachone is potent growth inhibitor of Trypanosoma cruzi epimastigote forms.

The investigation of trypanocidal effects against Trypanosoma cruzi and cytotoxicity in VERO cell line of several oxyranes structurally related to beta-lapachone, nor-beta-lapachone, alpha-lapachone, and 4-methoxy-1,2-naphthoquinone is described. It was found that the oxyranes 10 derived from alpha-lapachone showed an approximately the same trypanocidal activity of beta-lapachone. In addition, all the oxyranes showed less cytotoxicity than the corresponding naphthoquinones.