Trypanosoma cruzi: Alteration in the lymphoid compartments following interruption of infection by early acute benznidazole therapy in mice

Schistosoma mansoni co-infection modulates Chagas disease development but does not impair the effect of benznidazole-based chemotherapy

The adequate management of parasite co-infections represents a challenge that has not yet been overcome, especially considering that the pathological outcomes and responses to treatment are poorly understood. Thus, this study aimed to evaluate the impact of Schistosoma mansoni infection on the efficacy of benznidazole (BZN)-based chemotherapy in Trypanosoma cruzi co-infected mice. BALB/c mice were maintained uninfected or co-infected with S. mansoni and T. cruzi, and were untreated or treated with BZN. Body weight, mortality, parasitemia, cardiac parasitism, circulating cytokines (Th1/Th2/Th17); as well as heart, liver and intestine microstructure were analyzed. The parasitemia peak was five times higher and myocarditis was more severe in co-infected than T. cruzi-infected mice. After reaching peak, parasitemia was effectively controlled in co-infected animals. BZN successfully controlled parasitemia in both co-infected and T. cruzi-infected mice and improved body mass, cardiac parasitism, myocarditis and survival in co-infected mice. Co-infection dampened the typical cytokine response to either parasite, and BZN reduced anti-inflammatory cytokines in co-infected mice. Despite BZN normalizing splenomegaly and liver cellular infiltration, it exacerbated hepatomegaly in co-infected mice. Co-infection or BZN exerted no effect on hepatic granulomas, but increased pulmonary and intestinal granulomas. Marked granulomatous inflammation was identified in the small intestine of all schistosomiasis groups. Taken together, our findings indicate that BZN retains its therapeutic efficacy against T. cruzi infection even in the presence of S. mansoni co-infection, but with organ-specific repercussions, especially in the liver.

Oxidative stress, cardiomyocytes senescence and contractile dysfunction in in vitro and in vivo experimental models of Chagas disease

AIMS

The relationship between redox imbalance and cardiovascular senescence in infectious myocarditis is unknown. Thus, the aim of this study was to investigate whether cardiomyocytes parasitism, oxidative stress and contractile dysfunction can be correlated to senescence-associated β-galactosidase (SA-β-Gal) activity in Trypanosoma cruzi-infection in vitro and in vivo.

METHODS

Uninfected, T. cruzi-infected untreated and benznidazole (BZN)-treated H9c2 cardiomyocytes and rats were investigated. Parasitological, prooxidant, antioxidant, microstructural, and senescence-associated markers were quantified in vitro and in vivo.

RESULTS

T. cruzi infection triggered intense cardiomyocytes parasitism in vitro and in vivo, which was accompanied by reactive oxygen species (ROS) upregulation, lipids, proteins and DNA oxidation in cardiomyocytes and cardiac tissue. Oxidative stress was parallel to microstructural cell damage (e.g., increased cardiac toponin I levels) and contractile dysfunction in cardiomyocytes in vitro and in vivo, whose severity accompanied a premature cellular senescence-like phenotype revealed by increased senescence-associated β-galactosidase (SA-β-Gal) activity and DNA oxidation (8-OHdG). Cellular parasitism (e.g., infection rate and parasite load), myocarditis and T. cruzi-induced prooxidant responses were attenuated by early BZN administration to interrupt the progression of T. cruzi infection, protecting against SA-β-gal-based premature cellular senescence, microstructural damage and contractile deterioration in cardiomyocytes from T. cruzi-infected animals.

CONCLUSION

Our findings indicated that cell parasitism, redox imbalance and contractile dysfunction were correlated to SA-β-Gal-based cardiomyocytes premature senescence in acute T. cruzi infection. Therefore, in addition to controlling parasitism, inflammation and oxidative stress; inhibiting cardiomyocytes premature senescence should be further investigated as an additional target of specific Chagas disease therapeutics.

Effect of benznidazole on cerebral microcirculation during acute Trypanosoma cruzi infection in mice

Central nervous system alterations was described in Chagas disease in both human and experimental models, leading to meningoencephalitis, stroke and cognitive impairment. Recently, our group demonstrated that acute infection by Trypanossoma cruzi leads to cerebral microvasculophaty in mice with endothelial dysfunction, capillary rarefaction, increased rolling and leukocyte adhesion. Only benznidazole and nifurtimox are available for clinical treatment, they have an efficiency of 80% in the acute phase and less than 20% in chronic phase. However, the effect of these drugs on brain microcirculation has not yet been evaluated. We hypothesized that early treatment with benznidazole could protect brain microcirculation during acute experimental Chagas disease. Swiss Webster mice were inoculated with 10⁴ trypomastigotes forms of T. cruzi, and after 24 h they were treated with 50 or 100 mg/kg/day of benznidazole for 14 consecutive days. In untreated infected mice, we observed cerebral microvascular rarefaction, increase in leukocyte rolling and adhesion, reduced cerebral blood flow, and increased CD3+ and F4-80+ cells in brain tissue. Early treatment with benznidazole at 100 mg/kg/day and 50 mg/kg/day prevented the occurrence of the alterations mentioned. Here, we show that BZ is able to protect the microcirculation and reduced brain inflammation in acute experimental Chagas disease.

Improved efficacy and safety of low doses of benznidazole-loaded multiparticulate delivery systems in experimental Chagas disease therapy

Benznidazole (BZ) is a first-line drug for the treatment of Chagas disease; however, it presents several disadvantages that could hamper its therapeutic success. Multiparticulate drug delivery systems (MDDS) are promising carriers to improve the performance of drugs. We developed BZ-loaded MDDS intended for improving Chagas disease therapy. To assess their efficacy and safety, Trypanosoma (T) cruzi infected BALB/c mice were orally treated with free BZ or BZ-MDDS at different regimens (doses of 50 and 100 mg/kg/day, administered daily or at 2- or 5-days intervals) and compared with infected non-treated (INT) mice. At 100 mg/kg/day, independent of the administration regimen, both treatments were able to override the parasitemia, and at 50 mg/kg/day significantly reduced it compared to INT mice. BZ-MDDS at a dose of 100 mg/kg/day administered every 5 days (BZ-MDDS 100-13d) induced the lowest cardiac parasite load, indicating an improved efficacy with lower total dose of BZ when loaded to the MDDS. Reactive oxygen species produced by leukocytes were higher in INT and mice treated with BZ at 50 mg/kg/day compared to 100 mg/kg/day, likely because of persistent infection. BZ-MDDS treatments markedly reduced heart and liver injury markers compared to INT mice and those receiving the standard treatment. Therefore, BZ-MDDS exhibited enhanced activity against T. cruzi infection even at lower doses and reduced administration frequency compared to free BZ while increasing the treatment safety. They likely avoid undesired side effects of BZ by keeping a sustained concentration, avoiding plasmatic drug peaks. BZ-MDDS evidenced significant improvements in experimental Chagas disease treatment and can be considered as a potential improved therapeutic alternative against this illness.

Pharmacokinetics and Tissue Distribution of Benznidazole after Oral Administration in Mice

Specific chemotherapy using benznidazole (BNZ) for Chagas disease during the chronic stage is controversial due to its limited efficacy and toxic effects. Although BNZ has been used to treat Chagas disease since the 1970s, few studies about the biodistribution of this drug exist. In this study, BNZ tissue biodistribution in a murine model and its pharmacokinetic profile in plasma were monitored. A bioanalytical high-performance liquid chromatography method with a UV detector (HPLC-UV) was developed and validated according to the European Medicines Agency for quantification of BNZ in organs and plasma samples prepared by liquid-liquid extraction using ethyl acetate. The developed method was linear in the BNZ concentration, which ranged from 0.1 to 100.0 μg/ml for plasma, spleen, brain, colon, heart, lung, and kidney and from 0.2 to 100.0 μg/ml for liver. Validation assays demonstrated good stability for BNZ under all conditions evaluated. Pharmacokinetic parameters confirmed rapid, but low, absorption of BNZ after oral administration. Biodistribution assays demonstrated different maximum concentrations in organs and similar times to maximum concentration and mean residence times, with means of 40 min and 2.5 h, respectively. Therefore, the biodistribution of BNZ is extensive, reaching organs such as the heart and colon, which are the most relevant organs affected by Trypanosoma cruzi infection, and also the spleen, brain, liver, lungs, and kidneys. Simultaneous analyses of tissues and plasma indicated high BNZ metabolism in the liver. Our results suggest that low bioavailability, instead of inadequate biodistribution, could be responsible for therapeutic failure during the chronic phase of Chagas disease.

Canova medication changes TNF-α and IL-10 serum levels in mice infected with Trypanosoma cruzi Y strain

OBJECTIVE

To identify whether Canova medication changes TNF-α and IL-10 serum levels in mice infected with Trypanosoma cruzi Y strain.

METHODS

Animals were divided into five groups: non-treated infected animals (I); benznidazole-treated infected animals (Bz; 100 mg/kg body weight, single daily dose by gavage); Canova medication (CM) treated infected animals (CM; 0.2 mL/animal, single daily dose by gavage); benznidazole- and Canova medication-treated infected animals with the above-mentioned dose (Bz+CM); and non-infected animals (C). TNF-α and IL-10 levels were determined in serum aliquots after 4, 7, 10, 13, and 29 days of infection. An ELISA technique was employed with R&D System Inc. antibody pairs.

RESULTS

A high increase in TNF-α and IL-10 levels occurred in the infected and CM-treated groups within the treatment employed on the 10th day after infection, coupled with a IL-10 decrease on the 13th day after infection when compared with the other experimental groups.

CONCLUSIONS

CM may change the balance between plasma cytokine levels (TNF-α and IL-10) in mice infected with Y strain T. cruzi, with important consequences leading towards a more severe infection.

Modulation of Trypanosoma cruzi-specific T-cell responses after chemotherapy for chronic Chagas disease

The aim of this review is to describe the contributions of the knowledge of T-cell responses to the understanding of the physiopathology and the responsiveness to etiological treatment during the chronic phase of Chagas disease. T-helper (Th)1 and interleukin (IL)-10 Trypanosoma cruzi-specific T-cells have been linked to the asymptomatic phase or to severe clinical forms of the disease, respectively or vice versa, depending on the T. cruzi antigen source, the patient's location and the performed immunological assays. Parasite-specific T-cell responses are modulated after benznidazole (BZ) treatment in chronically T. cruzi-infected subjects in association with a significant decrease in T. cruzi-specific antibodies. Accumulating evidence has indicated that treatment efficacy during experimental infection with T. cruzi results from the combined action of BZ and the activation of appropriate immune responses in the host. However, strong support of this interaction in T. cruzi-infected humans remains lacking. Overall, the quality of T-cell responses might be a key factor in not only disease evolution, but also chemotherapy responsiveness. Immunological parameters are potential indicators of treatment response regardless of achievement of cure. Providing tools to monitor and provide early predictions of treatment success will allow the development of new therapeutic options.

Oral administration of GW788388, an inhibitor of transforming growth factor beta signaling, prevents heart fibrosis in Chagas disease

BACKGROUND

Chagas disease induced by Trypanosoma cruzi (T. cruzi) infection is a major cause of mortality and morbidity affecting the cardiovascular system for which presently available therapies are largely inadequate. Transforming Growth Factor beta (TGFß) has been involved in several regulatory steps of T. cruzi invasion and in host tissue fibrosis. GW788388 is a new TGFß type I and type II receptor kinase inhibitor that can be orally administered. In the present work, we studied its effects in vivo during the acute phase of experimental Chagas disease.

METHODOLOGY/PRINCIPAL FINDINGS

Male Swiss mice were infected intraperitoneally with 10(4) trypomastigotes of T. cruzi (Y strain) and evaluated clinically. We found that this compound given once 3 days post infection (dpi) significantly decreased parasitemia, increased survival, improved cardiac electrical conduction as measured by PR interval in electrocardiography, and restored connexin43 expression. We could further show that cardiac fibrosis development, evaluated by collagen type I and fibronectin expression, could be inhibited by this compound. Interestingly, we further demonstrated that administration of GW788388 at the end of the acute phase (20 dpi) still significantly increased survival and decreased cardiac fibrosis (evaluated by Masson's trichrome staining and collagen type I expression), in a stage when parasite growth is no more central to this event.

CONCLUSION/SIGNIFICANCE

This work confirms that inhibition of TGFß signaling pathway can be considered as a potential alternative strategy for the treatment of the symptomatic cardiomyopathy found in the acute and chronic phases of Chagas disease.

Dynamics of Lymphocyte Populations during Trypanosoma cruzi Infection: From Thymocyte Depletion to Differential Cell Expansion/Contraction in Peripheral Lymphoid Organs

The comprehension of the immune responses in infectious diseases is crucial for developing novel therapeutic strategies. Here, we review current findings on the dynamics of lymphocyte subpopulations following experimental acute infection by Trypanosoma cruzi, the causative agent of Chagas disease. In the thymus, although the negative selection process of the T-cell repertoire remains operational, there is a massive thymocyte depletion and abnormal release of immature CD4⁺CD8⁺ cells to peripheral lymphoid organs, where they acquire an activated phenotype similar to activated effector or memory T cells. These cells apparently bypassed the negative selection process, and some of them are potentially autoimmune. In infected animals, an atrophy of mesenteric lymph nodes is also observed, in contrast with the lymphocyte expansion in spleen and subcutaneous lymph nodes, illustrating a complex and organ specific dynamics of lymphocyte subpopulations. Accordingly, T- and B-cell activation is seen in subcutaneous lymph nodes and spleen, but not in mesenteric lymph nodes. Lastly, although the function of peripheral CD4⁺CD8⁺ T-cell population remains to be defined in vivo, their presence may contribute to the immunopathological events found in both murine and human Chagas disease.

Pharmacological inhibition of transforming growth factor beta signaling decreases infection and prevents heart damage in acute Chagas' disease

Chagas' disease induced by Trypanosoma cruzi infection is an important cause of mortality and morbidity affecting the cardiovascular system for which presently available therapies are largely inadequate. We previously reported that transforming growth factor beta (TGF-beta) is implicated in several regulatory aspects of T. cruzi invasion and growth and in host tissue fibrosis. This prompted us to evaluate the therapeutic action of an inhibitor of TGF-beta signaling (SB-431542) administered during the acute phase of experimental Chagas' disease. Male Swiss mice were infected intraperitoneally with 10(4) trypomastigotes of T. cruzi (Y strain) and evaluated clinically for the following 30 days. SB-431542 treatment significantly reduced mortality and decreased parasitemia. Electrocardiography showed that SB-431542 treatment was effective in protecting the cardiac conduction system. By 14 day postinfection, enzymatic biomarkers of tissue damage indicated that muscle injury was decreased by SB-431542 treatment, with significantly lower blood levels of aspartate aminotransferase and creatine kinase. In conclusion, inhibition of TGF-beta signaling in vivo appears to potently decrease T. cruzi infection and to prevent heart damage in a preclinical mouse model. This suggests that this class of molecules may represent a new therapeutic agent for acute and chronic Chagas' disease that warrants further clinical exploration.

Absence of CD4+ T lymphocytes, CD8+ T lymphocytes, or B lymphocytes has different effects on the efficacy of posaconazole and benznidazole in treatment of experimental acute Trypanosoma cruzi infection

We investigated the influence of CD4(+) T lymphocytes, CD8(+) T lymphocytes, and B lymphocytes on the efficacy of posaconazole (POS) and the reference drug benznidazole (BZ) during treatment of acute Trypanosoma cruzi infection in a murine model. Wild-type mice infected with T. cruzi and treated with POS or BZ presented no parasitemia, 100% survival, and 86 to 89% cure rates, defined as the percentages of animals with negative hemocultures at the end of the observation period. CD4(+)-T-lymphocyte-knockout (KO) mice infected with T. cruzi and treated with BZ or POS controlled parasitemia during treatment, although circulating parasites reappeared after drug pressure cessation, leading to only a 6% survival rate and no cure. CD8(+)-T-lymphocyte-KO mice infected with T. cruzi and treated with POS or BZ had intermediate results, displaying discrete parasitemia after the treatment was ended, 81 and 86% survival, and cure rates of 31 and 66%, respectively. B-lymphocyte-KO mice infected with T. cruzi and treated with BZ relapsed with parasitemia 1 week after the end of treatment and had a 67% survival rate and only a 22% cure rate. In contrast, the activity of POS was much less affected in these animals, with permanent suppression of parasitemia, 100% survival, and a 71% cure rate. Our results demonstrate that abrogation of different lymphocytes' activities has distinct effects on the efficacy of POS and BZ in this experimental model, probably reflecting different parasite stages preferentially targeted by the two drugs and distinct cooperation patterns with the host immune system.

Trypanosoma cruzi: effect of benznidazole therapy combined with the iron chelator desferrioxamine in infected mice

Iron chelators have been employed in various studies aimed at evaluating the relationship between the iron status of the host and the development of infection. In the present study, the effects of benznidazole (BZ) therapy in combination with the iron chelator desferrioxamine (DFO) on the development of infection in mice inoculated with Trypanosoma cruzi Y strain have been investigated. Infected mice treated with DFO presented lower levels of parasitemia compared with infected untreated animals. Therapy with BZ for 21 days, with or without DFO, led to decreased parasitemia and reduced mortality, but BZ in combination with DFO treatment for 35 days (BZ/DFO-35) gave 0% mortality. All infected groups presented lower levels of iron in the liver, but serum iron concentrations were greater in DFO-35 and BZ/DFO-35, whereas hemoglobin levels were higher in BZ/DFO-35 and lower in DFO-35 compared with other treated groups. The percentage cure, determined from negative hemoculture and PCR results in animals that had survived for 60 days post-infection, was 18% for BZ and BZ/DFO-35, 42% for BZ combined with DFO for 21 days, and 67% for DFO-35. The results demonstrate that modification in iron stores increases BZ efficacy.

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.