Uso da associação de Benznidazol e espironolactona em camundongos na fase aguda da infecção pelo Trypanosoma cruzi / The impact of the benznidazole and spironolactone combination in the evolution of the acute phase of Trypanosoma cruzi-infected mice

A doença de Chagas, causada pelo protozoário Trypanosoma cruzi, foi responsável por 4.916 óbitos no Brasil no ano de 2005, o que ressalta a importância de que se busquem novas formas de tratamento para esses pacientes. Estudos anteriores revelaram uma marcante lesão renal em camundongos infectados pelo T. cruzi nos estágios iniciais da infecção. Além disso, foi constatado que o bloqueiodas vias cardiovascular e renal (como o sistema renina angiotensina-aldosterona) diminuiu a mortalidade dos animais em 40por cento. Recentemente foi observado que o bloqueio de aldosterona minimiza a perda de potássio e os efeitos cardiovasculares da infecção pelo T. cruzi. O objetivodeste trabalho foi avaliar a eficiência da associação entre o benznidazol (Bz) e a espironolactona (Sp) na condição física dos camundongos infectados. Comparando os camundongos infectados e os tratados com Bz/Sp, observamos que a associação promove uma sobrevida de 100por cento, com ganho de peso, manutenção do consumo de alimentos e da atividade física dos animais. Em comparação com o tratamento somente com Bz, a combinação mantém níveis superiores das atividades motora e exploratória, principalmente no décimo quinto dia pós-infecção. Os dados sugerem, portanto, que a associação entre Bz e Sp apresenta uma benéfica influência na condição física dos camundongos durante a fase aguda experimental.

Acute experimental Trypanosoma cruzi infection: establishing a murine model that utilises non-invasive measurements of disease parameters.

Trypanosoma cruzi infection has a large public health impact in Latin American countries. Although the transmission rates via blood transfusions and insect vectors have declined sharply in the past 20 years due to policies of the Southern Cone countries, a large number of people are still at risk for infection. Currently, no accepted experimental model or descriptions of the clinical signs that occur during the course of acute murine infection are available. The aim of this work was to use non-invasive methods to evaluate the clinical signs of Balb/c mice infected with the Y strain of T. cruzi. The infected mice displayed evident clinical changes beginning in the third week of infection. The mice were evaluated based on physical characteristics, spontaneous activity, exploratory behaviour and physiological alterations. We hope that the results presented in this report provide parameters that complement the effective monitoring of trypanocidal treatment and other interventions used to treat experimental Chagas disease.

Acute experimental Trypanosoma cruzi infection: establishing a murine model that utilises non-invasive measurements of disease parameters

Trypanosoma cruzi infection has a large public health impact in Latin American countries. Although the transmission rates via blood transfusions and insect vectors have declined sharply in the past 20 years due to policies of the Southern Cone countries, a large number of people are still at risk for infection. Currently, no accepted experimental model or descriptions of the clinical signs that occur during the course of acute murine infection are available. The aim of this work was to use non-invasive methods to evaluate the clinical signs of Balb/c mice infected with the Y strain of T. cruzi. The infected mice displayed evident clinical changes beginning in the third week of infection. The mice were evaluated based on physical characteristics, spontaneous activity, exploratory behaviour and physiological alterations. We hope that the results presented in this report provide parameters that complement the effective monitoring of trypanocidal treatment and other interventions used to treat experimental Chagas disease.

Experimental Chemotherapy for Chagas Disease: A Morphological, Biochemical, and Proteomic Overview of Potential Trypanosoma cruzi Targets of Amidines Derivatives and Naphthoquinones.

Chagas disease (CD), caused by Trypanosoma cruzi, affects approximately eight million individuals in Latin America and is emerging in nonendemic areas due to the globalisation of immigration and nonvectorial transmission routes. Although CD represents an important public health problem, resulting in high morbidity and considerable mortality rates, few investments have been allocated towards developing novel anti-T. cruzi agents. The available therapy for CD is based on two nitro derivatives (benznidazole (Bz) and nifurtimox (Nf)) developed more than four decades ago. Both are far from ideal due to substantial secondary side effects, limited efficacy against different parasite isolates, long-term therapy, and their well-known poor activity in the late chronic phase. These drawbacks justify the urgent need to identify better drugs to treat chagasic patients. Although several classes of natural and synthetic compounds have been reported to act in vitro and in vivo on T. cruzi, since the introduction of Bz and Nf, only a few drugs, such as allopurinol and a few sterol inhibitors, have moved to clinical trials. This reflects, at least in part, the absence of well-established universal protocols to screen and compare drug activity. In addition, a large number of in vitro studies have been conducted using only epimastigotes and trypomastigotes instead of evaluating compounds' activities against intracellular amastigotes, which are the reproductive forms in the vertebrate host and are thus an important determinant in the selection and identification of effective compounds for further in vivo analysis. In addition, due to pharmacokinetics and absorption, distribution, metabolism, and excretion characteristics, several compounds that were promising in vitro have not been as effective as Nf or Bz in animal models of T. cruzi infection. In the last two decades, our team has collaborated with different medicinal chemistry groups to develop preclinical studies for CD and investigate the in vitro and in vivo efficacy, toxicity, selectivity, and parasite targets of different classes of natural and synthetic compounds. Some of these results will be briefly presented, focusing primarily on diamidines and related compounds and naphthoquinone derivatives that showed the most promising efficacy against T. cruzi.

Trypanosoma cruzi infection: do distinct populations cause intestinal motility alteration?

Chagas disease, caused by Trypanosoma cruzi, is an important public health problem in Latin America. Disturbances in gastrointestinal motility are observed in 15-20% of patients at the chronic phase. We previously observed a decrease in intestinal motility in mice infected with Y strain from T. cruzi. Thus, we decided to test if infection with other T. cruzi strains also caused the intestinal disturbance. Male adult Swiss mice were infected intraperitoneally with CL-Brener clone (CL-B), Brazil strain (Br), or Dm28 clone (Dm) of T. cruzi. All infected mice presented a low cumulative mortality (CL-B, 17%; Br, 8%; Dm, 25%) at 35 days post infection (dpi) and their typical parasitemia curves. Br and Dm groups exhibited a maximal reduction of intestinal motility at 35 dpi (176.8 +/- 51.3 and 198.3 +/- 52.6 min, respectively), when compared with non-infected mice (90.2 +/- 19.5 min). However, CL mice presented the peak of delayed intestinal transit at 12 dpi (191.0 +/- 33.3 min), when compared with non-infected mice (105.6 +/- 26.4 min), very close to the 15 dpi for the intense alteration (310.2 +/- 67.4 min) observed with the Y strain. We clearly demonstrate a reduction in intestinal motility in mice infected with different groups of T. cruzi during the acute phase of the infection. Since Br, Dm, and CL strains presented low mortality rates in adult Swiss mice, a prospective study concerning the chronic intestinal alteration is encouraged, particularly for studies of alternative therapies.

Acute Trypanosoma cruzi experimental infection induced renal ischemic/reperfusion lesion in mice.

Experimental acute infection with Trypanosoma cruzi in mice promotes an intense myocarditis and other systemic changes. However, the network of pathophysiological disorders and renal injury caused by the infection has not been elucidated. Our previous results with a murine model observed a discrete acute myocarditis and high mortality with significant inflammatory kidney injury with T. cruzi infection. The aim of this study was to investigate the mechanisms of kidney injury caused by the parasite in mice during the experimental acute phase. Results employing BALB/c mice infected with T. cruzi of Y strain showed renal injury on the 6th day postinfection (dpi) caused by a transitory decrease of renal blood flow. Acute kidney injury (AKI) was also observed similar to the model of ischemia/reperfusion lesion in these infected mice. The injury was not related to the presence (or multiplication) of parasites. Only rare nests were microscopically detected, and the presence of scattered parasites in renal parenchyma was seen on the 15th dpi. Thus, it was observed that during the acute phase of the disease, AKI in infected mice is linked to early cardiovascular effects, including heart failure, caused by striking inflammatory lesions in the myocardium, which lead to the high mortality rate of animals.

Applicability of the use of charcoal for the evaluation of intestinal motility in a murine model of Trypanosoma cruzi infection.

Chagas disease, caused by the protozoan Trypanosoma cruzi, remains a serious public health problem in Latin America. In relation to digestive problems, 4.5% of patients show mega syndromes (megacolon) in the chronic phase. In this article, we evaluated intestinal motility at the acute phase of T. cruzi infection through charcoal ingestion in adult mice. After infection, Swiss mice were administered an aqueous suspension of charcoal in water by gavage. Decrease in intestinal motility was determined by increased time of appearance of charcoal in the feces. The uninfected group showed a mean time of charcoal elimination of 109.0 +/- 14.6 min throughout the assay. On the other hand, infected mice presented a significant increase in charcoal defecation time during infection. At 15 days postinfection, infected mice showed a significant increase in charcoal defecation time, 310.2 +/- 67.4 min when compared to the uninfected group, which presented 97.8 +/- 31.8 min, indicating that the T. cruzi infection interferes with intestinal motility. Our results demonstrate that the use of charcoal is an ethical and efficient procedure to evaluate the intestinal motility in the murine model of T. cruzi infection.

Fas ligand-dependent inflammatory regulation in acute myocarditis induced by Trypanosoma cruzi infection.

Fas/Fas ligand (Fas-L) engagement, a potent inducer of apoptosis, is also important for cellular activation, regulation of effector and chemotactic activity, and secretion of chemokines and cytokines. We evaluated the relevance of Fas/Fas-L in the regulation of myocarditis induced by Trypanosoma cruzi infection and observed that in Fas-L(-/-) mice (gld/gld), cardiac infiltration was significantly reduced, accordingly showing less cardiomyocyte destruction. Fluorescence-activated cell sorting analysis of cardiac inflammatory cells showed higher numbers of CD8(+) T cells in BALB/c compared with gld/gld mice but similar levels of lymphocyte function-associated antigen-1, intercellular adhesion molecule, CD2, and CD69 expression; MAC-1(+) myeloid cells and mast cells were increased in BALB/c mice, whereas gld/gld mice exhibited an enrichment of CD4(+/low) T cells. Intracellular labeling of cytokines revealed no clear cardiac skewing of Th1 or Th2 responses, but we found a higher number of interleukin-10(+) cells in gld/gld mice and a deficient expression of vascular cell adhesion molecule-1 on cardiac endothelial cells in gld/gld mice. Finally, we found a population of CD3(+) but CD4/CD8 double negative cardiac T cells in both groups of infected mice, but down-regulation of some adhesion molecules and surface receptors was only observed in gld/gld mice, indicating a targeted T-cell population mostly affected by the lack of Fas-L engagement. These results point to a role for myocarditis regulation by Fas/Fas-L beyond its possible direct relevance in cellular death.