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Benznidazole-resistance in Trypanosoma cruzi is a readily acquired trait that can arise independently in a single population.

ABSTRACT: Benznidazole is the frontline drug used against Trypanosoma cruzi, the causative agent of Chagas disease. However, treatment failures are often reported. Here, we demonstrate that independently acquired mutations in the gene encoding a mitochondrial nitroreductase (TcNTR) can give rise to distinct drug-resistant clones within a single population. Following selection of benznidazole-resistant parasites, all clones examined had lost one of the chromosomes containing the TcNTR gene. Sequence analysis of the remaining TcNTR allele revealed 3 distinct mutant genes in different resistant clones. Expression studies showed that these mutant proteins were unable to activate benznidazole. This correlated with loss of flavin mononucleotide binding. The drug-resistant phenotype could be reversed by transfection with wild-type TcNTR. These results identify TcNTR as a central player in acquired resistance to benznidazole. They also demonstrate that T. cruzi has a propensity to undergo genetic changes that can lead to drug resistance, a finding that has implications for future therapeutic strategies.

SUBMITTER: Mejia AM

PROVIDER: S-EPMC3379838 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature

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Benznidazole-resistance in Trypanosoma cruzi is a readily acquired trait that can arise independently in a single population.

Mejia Ana Maria AM Hall Belinda S BS Taylor Martin C MC Gómez-Palacio Andrés A Wilkinson Shane R SR Triana-Chávez Omar O Kelly John M JM

The Journal of infectious diseases 20120502 2

Benznidazole is the frontline drug used against Trypanosoma cruzi, the causative agent of Chagas disease. However, treatment failures are often reported. Here, we demonstrate that independently acquired mutations in the gene encoding a mitochondrial nitroreductase (TcNTR) can give rise to distinct drug-resistant clones within a single population. Following selection of benznidazole-resistant parasites, all clones examined had lost one of the chromosomes containing the TcNTR gene. Sequence analys ...[more]

PMID: 22551809

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Project description:BackgroundDrugs currently used for the treatment of Chagas' disease, nifurtimox and benznidazole, have a limited effectiveness and toxic side effects. With the aim of finding new therapeutic approaches, in vitro and in vivo anti-Trypanosoma cruzi activity of vitamin C alone and combined with benznidazole were investigated.Methodology/principal findingsThe trypanocidal activity on epimastigote and trypomastigote forms was evaluated by counting parasites in a Neubauer chamber after treatment with the compounds. For the amastigote stage, transgenic parasites expressing β-galactosidase were used and quantified by measuring the β-galactosidase activity. The cytotoxicity of compounds was tested on Vero cells. The redox state of the parasite was evaluated by determining the reduced thiol levels (spectrophotometric assay) and the intracellular oxidative state (by flow cytometry). The in vivo trypanocidal activity was evaluated on a murine model of Chagas' disease. The trypanocidal activity of vitamin C and benznidazole was similar for the three parasite forms. When combining both drugs, vitamin C did not induce any change in the antiparasitic activity of benznidazole on trypomastigotes; however, on mammal cells, vitamin C diminished the cytotoxicity degree of benznidazole. Two mechanisms of action may be postulated for vitamin C: a lethal pro-oxidant effect on the parasite when used alone, and an antioxidant effect, when combined with benznidazole. A similar behavior was observed on infected mice; i.e., parasite counts in infected mice treated with vitamin C were lower than that of the control group. Animals treated with benznidazole presented lower parasitemia levels, as compared with those treated with vitamin C alone. Again, vitamin C did not cause any effect on the antiparasitic profile of benznidazole. Even though a combined treatment was employed, the antioxidant effect of vitamin C on the host was evidenced; a 100% survival was observed and the weight loss occurring during the acute phase of the infection was reduced.Conclusions/significanceBased on these results, the combination of vitamin C with benznidazole could be considered as an alternative treatment for Chagas' disease. These preliminary results encourage further research to improve the treatment of Chagas' disease.

Project description:Hexose transporters (HT) are membrane proteins involved in the uptake of energy-supplying glucose and other hexoses into the cell. Previous studies employing the Differential Display technique have shown that the transcription level of the HT gene from T. cruzi (TcrHT) is higher in an in vitro-induced benznidazole (BZ)-resistant population of the parasite (17 LER) than in its susceptible counterpart (17 WTS).In the present study, TcrHT has been characterized in populations and strains of T. cruzi that are resistant or susceptible to BZ. We investigated the copy number and chromosomal location of the gene, the levels of TcrHT mRNA and of TcrHT activity, and the phylogenetic relationship between TcrHT and HTs from other organisms.In silico analyses revealed that 15 sequences of the TcrHT gene are present in the T. cruzi genome, considering both CL Brener haplotypes. Southern blot analyses confirmed that the gene is present as a multicopy tandem array and indicated a nucleotide sequence polymorphism associated to T. cruzi group I or II. Karyotype analyses revealed that TcrHT is located in two chromosomal bands varying in size from 1.85 to 2.6?Mb depending on the strain of T. cruzi. The sequence of amino acids in the HT from T. cruzi is closely related to the HT sequences of Leishmania species according to phylogenetic analysis. Northern blot and quantitative real-time reverse transcriptase polymerase chain reaction analyses revealed that TcrHT transcripts are 2.6-fold higher in the resistant 17 LER population than in the susceptible 17 WTS. Interestingly, the hexose transporter activity was 40% lower in the 17 LER population than in all other T. cruzi samples analyzed. This phenotype was detected only in the in vitro-induced BZ resistant population, but not in the in vivo-selected or naturally BZ resistant T. cruzi samples. Sequencing analysis revealed that the amino acid sequences of the TcrHT from 17WTS and 17LER populations are identical. This result suggests that the difference in glucose transport between 17WTS and 17LER populations is not due to point mutations, but probably due to lower protein expression level.The BZ resistant population 17 LER presents a decrease in glucose uptake in response to drug pressure.

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Benznidazole-resistance in Trypanosoma cruzi is a readily acquired trait that can arise independently in a single population.

Publications

Benznidazole-resistance in Trypanosoma cruzi is a readily acquired trait that can arise independently in a single population.

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