Screening of Potential anti-Trypanosoma cruzi Candidates: In Vitro and In Vivo Studies

Chagas disease (CD), caused by the intracellular protozoan Trypanosoma cruzi, is a parasitic illness endemic in Latin America. In the centennial after CD discovery by Carlos Chagas (1909), although it still represents an important public health problem in these affected areas, the existing chemotherapy, based on benznidazole and nifurtimox (both introduced more than four decades ago), is far from being considered ideal due to substantial toxicity, variable effect on different parasite stocks and well-known poor activity on the chronic phase. CD is considered one of the major “neglected” diseases of the world, as commercial incentives are very limited to guarantee investments for developing and discovering novel drugs. In this context, our group has been pursuing, over the last years, the efficacy, selectivity, toxicity, cellular targets and mechanisms of action of new potential anti-T. cruzi candidates screened from an in-house compound library of different research groups in the area of medicinal chemistry. A brief review regarding these studies will be discussed, mainly related to the effect on T. cruzi of (i) diamidines and related compounds, (ii) natural naphthoquinone derivatives, and (iii) megazol derivatives

Between Armour and Weapons — Cell Death Mechanisms in Trypanosomatid Parasites

Among the pathogenic protozoa, trypanosomatids stand out due to their medical and economic impact, especially for low-income populations in tropical countries. Together, sleeping sickness, Chagas disease and leishmaniasis affect millions of humans and animals worldwide, yet are neglected by the pharmaceutical industry. The current drugs for trypanosomatid infections are limited and unsatisfactory, with severe side effects leading to reduced quality of life and, in several instances, to the abandonment of treatment. An intense search for alternative compounds has been performed, aiming at specific parasite targets by cellular, molecular and biochemical approaches. One interesting strategy could be interference with the protozoan cell death pathways. However, these pathways are poorly understood in unicellular eukaryotes, with the controversial existence and uncertain biological relevance of programmed cell death (PCD). This chapter will discuss apoptosis-like and autophagic cell death and necrosis in Trypanosoma brucei, Trypanosoma cruzi and Leishmania sp. and the possible implications of these pathways for the parasite life cycle and infection persistence. It will also revisit the genomic and proteomic metadata of these trypanosomatids in the literature to rebuild the map of cell death proteins expressed under different conditions. The interaction of leading candidates with parasite-specific molecules, especially with enzymes that regulate key steps in the cell death process, is a rational and attractive alternative for drug development for these neglected diseases

Megazol and its bioisostere 4H-1,2,4-triazole: comparing the trypanocidal, cytotoxic and genotoxic activities and their in vitro and in silico interactions with the Trypanosoma brucei nitroreductase enzyme

Megazol (7) is a 5-nitroimidazole that is highly active against Trypanosoma cruzi and Trypanosoma brucei, as well as drug-resistant forms of trypanosomiasis. Compound 7 is not used clinically due to its mutagenic and genotoxic properties, but has been largely used as a lead compound. Here, we compared the activity of 7 with its 4H-1,2,4-triazole bioisostere (8) in bloodstream forms of T. brucei and T. cruzi and evaluated their activation by T. brucei type I nitroreductase (TbNTR) enzyme. We also analysed the cytotoxic and genotoxic effects of these compounds in whole human blood using Comet and fluorescein diacetate/ethidium bromide assays. Although the only difference between 7 and 8 is the substitution of sulphur (in the thiadiazole in 7) for nitrogen (in the triazole in 8), the results indicated that 8 had poorer antiparasitic activity than 7 and was not genotoxic, whereas 7 presented this effect. The determination of Vmax indicated that although 8 was metabolised more rapidly than 7, it bounds to the TbNTR with better affinity, resulting in equivalent kcat/KM values. Docking assays of 7 and 8 performed within the active site of a homology model of the TbNTR indicating that 8 had greater affinity than 7

The Trypanocidal Activity of Naphthoquinones: A Review

Submitted by Sandra Infurna ([email protected]) on 2019-01-03T12:17:35Z No. of bitstreams: 1 antoniopinto_solangecastro_IOC_2009.pdf: 613595 bytes, checksum: dbb943674aaf31b639ee9e639665c155 (MD5)Approved for entry into archive by Sandra Infurna ([email protected]) on 2019-01-03T12:23:48Z (GMT) No. of bitstreams: 1 antoniopinto_solangecastro_IOC_2009.pdf: 613595 bytes, checksum: dbb943674aaf31b639ee9e639665c155 (MD5)Made available in DSpace on 2019-01-03T12:23:48Z (GMT). No. of bitstreams: 1 antoniopinto_solangecastro_IOC_2009.pdf: 613595 bytes, checksum: dbb943674aaf31b639ee9e639665c155 (MD5) Previous issue date: 2009Universidade Federal do Rio de Janeiro. Centro de Ciências da Saúde. Núcleo de Pesquisas em Produtos Naturais. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Celular. Rio de Janeiro, RJ. Brasil.Naphthoquinones are compounds present in several families of higher plants. Their molecular structures confer redox properties, and they are involved in multiple biological oxidative processes. In folk medicine, especially among Indian populations, plants containing naphthoquinones have been employed for the treatment of various diseases. The biological redox cycle of quinones can be initiated by one electron reduction leading to the formation of semiquinones, unstable intermediates that react rapidly with molecular oxygen, generating free radicals. Alternatively, the reduction by two electrons, mediated by DT-diphorase, leads to the formation of hydroquinone. Lapachol, α-lapachone and β-lapachone, which are isolated from the heartwood of trees of the Bignoniaceae family, are examples of bioactive naphthoquinones. In this review, we will discuss studies investigating the activity of these natural products and their derivatives in the context of the search for alternative drugs for Chagas disease, caused by Trypanosoma cruzi, a neglected illness that is endemic in Latin America

Electron microscopy in antiparasitic chemotherapy: a (close) view to a kill

Submitted by Martha Martínez Silveira ([email protected]) on 2015-03-31T18:51:00Z No. of bitstreams: 1 Santos MAV Electron microscopy in antiparasitic chemotherapy.pdf: 989293 bytes, checksum: f3d2b41cdec7c503da0b5479c81f990f (MD5)Approved for entry into archive by Martha Martínez Silveira ([email protected]) on 2015-03-31T19:03:45Z (GMT) No. of bitstreams: 1 Santos MAV Electron microscopy in antiparasitic chemotherapy.pdf: 989293 bytes, checksum: f3d2b41cdec7c503da0b5479c81f990f (MD5)Made available in DSpace on 2015-03-31T19:03:45Z (GMT). No. of bitstreams: 1 Santos MAV Electron microscopy in antiparasitic chemotherapy.pdf: 989293 bytes, checksum: f3d2b41cdec7c503da0b5479c81f990f (MD5) Previous issue date: 2009Fundação Oswaldo Cruz. Centro de Pesquisa Gonçalo Moniz. Laboratório de Biomorfologia Parasitária. Salvador, BA, BrasilFundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Celular. Rio de Janeiro, RJ, BrasilElectron microscopy may be useful in chemotherapy studies at distinct levels, such as the identification of subcellular targets in the parasites and the elucidation of the ultimate drug mechanism of action, inferred by the alterations induced by antiparasitic compounds. In this review we present data obtained by electron microscopy approaches of different parasitic protozoa, such as Trypanosoma cruzi, Leishmania spp., Giardia lamblia and trichomonads, under the action of drugs, demonstrating that the cell architecture organization is only determined in detail at the ultrastructural level. The transmission electron microscopy may shed light (i.e. electrons) not only on the affected compartment, but also on the manner it is altered, which may indicate presumable target metabolic pathways as well as the actual toxic or lethal effects of a drug. Cytochemical and analytical techniques can provide valuable information on the composition of the altered cell compartment, permitting the bona fide identification of the drug target and a detailed understanding of the mechanism underneath its effect. Scanning electron microscopy permits the recognition of the drug-induced alterations on parasite surface and topography. Such observations may reveal cytokinetic dysfunctions or membrane lesions not detected by other approaches. In this context, electron microscopy techniques comprise valuable tools in chemotherapy studie

Doença de chagas: manual para experimentação animal

Edição comemorativa aos noventa anos da descoberta da doença de Chagas, esta obra propicia a estudantes e pesquisadores brasileiros e latino-americanos uma visão global de questões obscuras da relação Trypanosoma cruzi-hospedeiro - para as quais cientistas de todo o mundo ainda buscam respostas, junto com as ferramentas para a investigação da moléstia - em forma de manual para experimentação animal. O objetivo é municiar a nova geração de cientistas com que o Brasil contará neste início de século e milênio. Eles ainda encontrarão cinco milhões de indíviduos chagásicos, sob o risco de morte por cardiopatia, a desafiar sua capacidade de explicar por que alguns desenvolvem a doença enquanto outros equilibram muito bem o convívio na relação parasita-hospedeiro

Activity of Brazilian and Bulgarian propolis against different species of Leishmania

Extracts of propolis samples collected in Brazil and Bulgaria were assayed against four Leishmania species _ Leishmania amazonensis, L. braziliensis, L. chagasi from the New World, and L. majori from the Old World _ associated to different clinical forms of Leishmaniasis. The composition of the extracts has been previously characterized by high temperature high resolution gas chromatography coupled to mass spectrometry. Considering the chemical differences among the extracts and the behavior of the parasites, it was observed significant differences in the leishmanicidal activities with IC50/1 day values in the range of 2.8 to 229.3 µg/ml. An overall analysis showed that for all the species evaluated, Bulgarian extracts were more active than the ethanol Brazilian extract. As the assayed propolis extracts have their chemical composition determined it merits further investigation the effect of individual components or their combinations on each Leishmania species

The effect of Bulgarian propolis against Trypanosoma cruzi and during its interaction with host cells

Propolis has shown activity against pathogenic microorganisms that cause diseases in humans and animals. The ethanol (Et-Blg) and acetone (Ket-Blg) extracts from a Bulgarian propolis, with known chemical compositions, presented similar activity against tissue culture-derived amastigotes. The treatment of Trypanosoma cruzi-infected skeletal muscle cells with Et-Blg led to a decrease of infection and of the intracellular proliferation of amastigotes, while damage to the host cell was observed only at concentration 12.5 times higher than those affecting the parasite. Ultrastructural analysis of the effect of both extracts in epimastigotes revealed that the main targets were the mitochondrion and reservosomes. Et-Blg also affected the mitochondrion-kinetoplast complex in trypomastigotes, offering a potential target for chemotherapeutic agents