Trypanosoma cruzi: the effect of variations in experimental conditions on the levels of macrophage infection in vitro

Aromatic diamidines are DNA minor groove-binding ligands that display excellent antimicrobial activity against fungi, bacteria, and protozoa. Due to the currently unsatisfactory chemotherapy for Chagas' disease and in view of our previous reports regarding the effect of diamidines and analogues against both in vitro and in vivo Trypanosoma cruzi infection, this study evaluated the effects of a diarylthiophene diamidine (DB1362) against both amastigotes and bloodstream trypomastigotes of T. cruzi, the etiological agent of Chagas' disease. The data show the potent in vitro activity of DB1362 against both parasite forms that are relevant for mammalian infection at doses which do not exhibit cytotoxicity. Ultrastructural analysis and flow cytometry studies show striking alterations in the nuclei and mitochondria of the bloodstream parasites. In vivo studies were performed at two different drug concentrations (25 and 50 mg/kg/day) using a 2-day or a 10-day regimen. The best results were obtained when acutely infected mice were treated with two doses at the lower concentration, resulting in 100% survival, compared to the infected and untreated mice. Although it did not display higher efficacy than benznidazole, DB1362 reduced both cardiac parasitism and inflammation, and in addition, it protected against the cardiac alterations (determined by measurements) common in T. cruzi infection. These results support further investigation of diamidines and related compounds as potential agents against Chagas' disease.

Section: Methodsmentioning

confidence: 99%

In Vitro and In Vivo Studies of the Trypanocidal Activity of a Diarylthiophene Diamidine against Trypanosoma cruzi

Silva

Batista

et al. 2008

“…All the cell cultures were maintained at 37°C in an atmosphere of 5% CO 2 and air. Following the treatment, the infected cultures were fixed and processed as described above for ultrastructural analysis or were fixed in Bouin's fixative and stained with Giemsa solution, as reported previously (1). The mean number of infected host cells and the mean number of parasites per infected cell were then scored.…”

Section: Methodsmentioning

confidence: 99%

Cellular Effects of Reversed Amidines on Trypanosoma cruzi

Silva

Meuser

Souza

et al. 2007

Aromatic diamidines represent a class of DNA minor groove-binding ligands that exhibit high levels of antiparasitic activity. Since the chemotherapy for Chagas' disease is still an unsolved problem and previous reports on diamidines and related analogues show that they have high levels of activity against Trypanosoma cruzi infection both in vitro and in vivo, our present aim was to evaluate the cellular effects in vitro of three reversed amidines (DB889, DB702, and DB786) and one diguanidine (DB711) against both amastigotes and bloodstream trypomastigotes of T. cruzi, the etiological agent of Chagas ' disease. Our data show that the reversed amidines have higher levels of activity than the diguanidine, with the order of trypanocidal activities being as follows: DB889 > DB702 > DB786 > DB711. Transmission electron microscopy analysis showed that the reversed amidines induced many alterations in the nuclear morphology, swelling of the endoplasmic reticulum and Golgi structures, and consistent damage in the mitochondria and kinetoplasts of the parasites. Interestingly, in trypomastigotes treated with the reversed amidine DB889, multiple axoneme structures (flagellar microtubules) were noted. Flow cytometry analysis confirmed that the treated parasites presented an important loss of the mitochondrial membrane potential, as revealed by a decrease in rhodamine 123 fluorescence. Our results show that the reversed amidines have promising activities against the relevant mammalian forms of T. cruzi and display high trypanocidal effects at very low doses. This is especially the case for DB889, which merits further in vivo evaluation.Aromatic diamidines are DNA minor groove-binding ligands (MGBLs), which present striking broad-spectrum antimicrobial effects (28). Although this class of compounds displays significant in vitro and in vivo activities against fungi, amoeba, bacteria, and especially protozoan parasites, certain structures can show toxicity toward mammalian cells (23). In addition, aromatic diamidines in general lack oral bioavailability, which limits their use (28). To overcome these limitations, prodrugs such as the methamidoxime prodrug of furamidine (DB289), which is currently undergoing phase III clinical trials for the treatment of human African trypanosomiasis, have been developed (29). Trypanosoma cruzi is the etiological agent of Chagas' disease, a zoonosis considered a major public health problem in the developing countries of Central and South America (14). The disease is widespread in areas of endemicity in Latin America, and it has been estimated that the overall prevalence of human infection is about 17 million cases and that approximately 120 million people are at risk of contracting the infection (30). However, up to now there has been neither an effective vaccine nor a satisfactory treatment for the disease. Drug therapy depends mostly upon nitrofurans and nitroimidazoles, such as nifurtimox and benznidazole (4,26,27).Our previous studies revealed that furamidine and its Nphenyl-substituted analo...

“…Animals from the T. cruzi-infected groups were inoculated by the intraperitoneal route with 10 4 trypomastigotes of T. cruzi strain Y (36) in 200 l of saline solution. The parasites were obtained from the blood of infected albino Swiss mice at the time of the peak level of parasitemia by differential centrifugation, as described previously (5).…”

Section: Methodsmentioning

confidence: 99%

Benznidazole Treatment following AcuteTrypanosoma cruziInfection Triggers CD8⁺T-Cell Expansion and Promotes Resistance to Reinfection

Olivieri

Cotta-de-Almeida

Araújo-Jorge

2002

Many studies have shed light on the mechanisms underlying both immunoprotection and immune dysregulation arising after Trypanosoma cruzi infection. However, little is known about the impact of benznidazole (N-benzyl-2-nitroimidazole acetamide), the drug available for clinical treatment of the infection, on the immune system in the infected host. In the present study we investigated the effect of benznidazole therapy on the lymphoid compartment during the course of experimental T. cruzi infection. Although amelioration of a variety of clinical and parasitological signs was observed in treated mice, amelioration of splenocyte expansion was not detected. Interestingly, this sustained splenomegaly observed in benznidazole-treated mice showed a preferential expansion of CD8 ؉ T lymphocytes. Moreover, although benznidazole treatment blocked the expansion of recently activated CD4؉ and CD8 ؉ T cells seen in infected hosts, benznidazole treatment led to a selective expansion of effector and memory CD8 ؉ T lymphocytes in association with a lower rate of apoptosis. In addition, the surviving treated animals were protected from reinfection. Together, these data suggest that, in addition to its well-known direct role in blocking parasite replication in vivo, benznidazole appears to directly affect immune regulation in T. cruzi-infected hosts.Chagas' disease, caused by the intracellular protozoan parasite Trypanosoma cruzi, is a human parasitosis affecting 16 million to 18 million people in Latin America (42). This disease is characterized by an acute phase with detectable parasitemia and acute myocarditis in 8% of cases (20) and a longlasting chronic phase in which most infected people remain asymptomatic. However, approximately 36% of chronically infected individuals develop digestive problems and/or cardiomyopathy (42) in association with parasitemia and some parasitism in tissues.