Early Detection of Chronic Asymptomatic Chagas Infection.

Chagas disease, also known as American trypanosomiasis, is a chronic and systemic parasitic infection which has become a serious epidemiological problem not only in endemic regions (Latin America), but also in non-endemic ones like North America, Europe, and Oceania. Subjects with the indeterminate chagasic form (ICF), a chronic asymptomatic disease stage, are the main sources of non-vectorial dissemination through blood transfusion, organ transplantation, and congenital transmission. It has been suggested that 94% of urban infections can be explained by these subjects. Under this scenario, the availability of simple and effective screening methods for ICF detection becomes crucial for both prevention of disease propagation and detection of clinical stages. Recently, a new non-invasive method has been proposed for ICF detection. It is based on surface high-resolution ECG and it could be easily adopted and included in modern ECG devices, overcoming the limitations of serological-based tests. The proposed method shows accuracy for early ICF screening, thus improving prognosis by defining the clinical stages and allowing appropriate and effective treatment.

In vitro and in vivo drug combination for the treatment of Trypanosoma cruzi infection: A multivariate approach.

Combination therapies based on the available drugs have been proposed as promising therapeutic alternatives for many diseases. Clomipramine (CLO) has been found to modify the evolution of the experimental infection. The objective of this study was to evaluate the combined effect of benznidazole (BZ) and clomipramine (CLO) against different life-stages of Trypanosoma cruzi in vitro and their efficacy in a murine model. Life-stages of T. cruzi, BZ-partially-resistant (Y) strain, were incubated with BZ and CLO and isobolograms and combination index (CI) were obtained. Swiss mice were infected with trypomastigotes and different treatment schedules were performed, each of which consisted of 30 consecutive daily doses. Treatment efficacy was evaluated by comparing parasitemia, qPCR, survival and histological analysis. These results were analyzed using multivariate analysis to determine the combined effect of the drugs in vivo. CLO + BZ showed synergistic activity in vitro against the clinically relevant life-stages of T. cruzi. The most susceptible forms were the intracellular amastigotes (CI: 0.20), followed by trypomastigotes (CI: 0.60), with no toxicity upon mammalian cells. The combination of both drugs CLO (1.25 mg/kg) and BZ (6.25 mg/kg), in vivo, significantly diminished the parasitic load in blood and the mortality rate. CLO + BZ presented a similar inflammatory response in cardiac and skeletal muscle (amount of inflammatory cells) to BZ (6.25 mg/kg). Finally, the results from the principal component analysis reaffirmed that both drugs administered in combination presented higher activity compared with the individual administration in the acute experimental model.

Mitochondrial dysfunction in skeletal muscle during experimental Chagas disease.

Trypanosoma cruzi invasion and replication in cardiomyocytes and other tissues induce cellular injuries and cytotoxic reactions, with the production of inflammatory cytokines and nitric oxide, both sources of reactive oxygen species. The myocyte response to oxidative stress involves the progression of cellular changes primarily targeting mitochondria. Similar alterations could be taking place in mitochondria from the skeletal muscle; if that is the case, a simple skeletal muscle biopsy would give information about the cardiac energetic production that could be used as a predictor of the chagasic cardiopathy evolution. Therefore, in the present paper we studied skeletal muscle mitochondrial structure and the enzymatic activity of citrate synthase and respiratory chain complexes I to IV (CI-CIV), in Albino Swiss mice infected with T. cruzi, Tulahuen strain and SGO Z12 and Lucky isolates, along the infection. Changes in the mitochondrial structure were detected in 100% of the mitochondria analyzed from the infected groups: they all presented at least 1 significant abnormality such as increase in their matrix or disorganization of their cristae, which are probably related to the enzymatic dysfunction. When we studied the Krebs cycle functionality through the measurement of the specific citrate synthase activity, we found it to be significantly diminished during the acute phase of the infection in Tulahuen and SGO Z12 infected groups with respect to the control one; citrate synthase activity from the Lucky group was significantly increased (p<0.05). The activity of this enzyme was reduced in all the infected groups during the chronic asymptomatic phase (p<0.001) and return to normal values (Tulahuen and SGO Z12) or increased its activity (Lucky) by day 365 post-infection (p.i.). When the mitochondrial respiratory chain was analyzed from the acute to the chronic phase of the infection through the measurement of the activity of complexes I to IV, the activity of CI remained similar to control in Tulahuen and Lucky groups, but was significantly augmented in the SGO Z12 one in the acute and chronic phases (p<0.05). CII increased its activity in Tulahuen and Lucky groups by day 75 p.i. and in SGO Z12 by day 365 p.i. (p<0.05). CIII showed a similar behavior in the 3 infected groups, remaining similar to control values in the first two stages of the infection and significantly increasing later on (p<0.0001). CIV showed an increase in its activity in Lucky throughout all stages of infection (p<0.0001) and an increase in Tulahuen by day 365days p.i. (p<0.0001); SGO Z12 on the other hand, showed a decreased CIV activity at the same time. The structural changes in skeletal muscle mitochondria and their altered enzyme activity began in the acute phase of infection, probably modifying the ability of mitochondria to generate energy; these changes were not compensated in the rest of the phases of the infection. Chagas is a systemic disease, which produces not only heart damage but also permanent skeletal muscle alterations.

Chronic indeterminate phase of Chagas' disease: mitochondrial involvement in infection with two strains.

Chagasic cardiopathy has become one of the most frequent causes of heart failure and sudden death, as well as one of the most common causes of cardio-embolic stroke in Latin America. The myocyte response to oxidative stress involves the progression of cellular changes, primarily targeting the mitochondria and modifying therefore the energy supply. In this paper we analysed the effect of the infection of mice with 2 different strains of Trypanosoma cruzi (Tulahuen and SGO Z12) in the chronic indeterminate stage (75 days post-infection), upon the structure and function of cardiac mitochondria. The structural results showed that 83% of the mitochondria from the Tulahuen-infected mice presented an increase in their matrix and 91% of the mitochondria from the SGO Z12-infected group showed a reduction in their diameter (P < 0.05). When the Krebs cycle and mitochondrial respiratory chain functionality was analysed through the measurement of the citrate synthase and complexes I to IV activity, it showed that their activity was altered in all cases in a similar manner in both infected groups. In this paper we have demonstrated that the chronic indeterminate phase is not 'silent' and that cardiac mitochondria are clearly involved in the genesis and progression to the chronic chagasic cardiopathy when different factors alter the host-parasite equilibrium.

Use of clomipramine as chemotherapy of the chronic phase of Chagas disease.

Chagas infection is a major endemic disease affecting Latin American countries. The persistence of Trypanosoma cruzi generates a chronic inflammatory reactivity that induces an immune response directed to the host's tissues. The effectiveness of the treatment in the chronic phase is still unsatisfactory due, amongst other reasons, to the collateral effects of the drugs used. We investigated the effect of clomipramine, a tricyclic antidepressant that, when used as a treatment of T. cruzi-chronically infected mice, inhibits trypanothione reductase, an exclusive and vital enzyme of T. cruzi. Clomipramine improved survival (P<0.05) by diminishing the parasite intensity as demonstrated by PCR studies in the heart and skeletal muscle, and significantly prevented the evolution to fibrosis of the inflammatory infiltrates. Clomipramine could be a good candidate for the treatment of chronic Chagas disease.

Association of clomipramine and allopurinol for the treatment of the experimental infection with Trypanosoma cruzi.

We have previously shown that clomipramine and allopurinol used separately are effective in preventing chronic chagasic cardiomyopathy. The aim of the present study was to evaluate the effect of the association of clomipramine (Clo--5 mg/kg/day/90 days) and allopurinol (Allo--5, 10, or 15 mg/kg/day/90 days) for the treatment of experimental Chagas disease in the acute stage. Treatment effectiveness was evaluated through parasitemia, survival, electrocardiography, serology, and cardiac histopathology. Groups treated showed no electrocardiographic abnormalities, in contrast to those untreated which presented 25% of mice with conduction alterations. The myocardium of treated mice (Clo, Allo10+Clo, and Allo15+Clo) presented no structural alterations. Cardiac b-receptor affinity was preserved in mice treated with Clo or Clo+Allo at the different doses; receptor density of the Clo and Allo15+Clo groups did not differ from the non-infected group. Anti-cruzipain antibody levels were similar in treated and untreated groups. Survival was significantly increased in the treated groups (p < 0.05), with Clo and all the Clo+Allo groups presenting the highest rates. These results show that the association of clomipramine + allopurinol is effective for Chagas disease treatment and has the same effect as clomipramine alone.

[Role of mitochondria and reactive oxygen species in the progression of heart failure]. / Rol de las mitocondrias y de las especie reactivas de oxigeno en la pro-gresion de la insuficiencia cardiaca.

Congestive heart failure (CHF) would be associated with mitochondrial abnormalities and increased of reactive species of oxygen (ROS). To clarify these issues we studied the structure, function of the mitochondrial enzyme nitro oxide synthase inducible (iNOS) and lipoperoxidation of membranes, one of their products through the peroxide nitrite ion (ONOO-), in the heart muscle of patients with heart failure congestive (ICC) grade III and IV (according to New York Heart Association). We included 25 patients who underwent cardiovascular surgery to biopsies of the heart muscle. They were stratified into a group with CHF (n = 18) and control group (n = 7). In di-chas biopsies analyzed the enzymatic activity of mitochondrial complex III spectrophotometrically, which was measured in mM.ubiquinona-1.mg prot, while the mitochondrial morphology was analyzed by the Zeiss electron microscope, the areas were quantified with program Axionvision 4.6. Lipoperoxidation of membranes was measured by the presence of ONOO-by immunohistochemistry against primary antibody against 3-nitrotyrosine was used lab kit system biogenic steptobidin biotin peroxidase (SBA) and coloring triamiobencidina (TAB), it is made with semicuantificacion intensity SCORE test. The statistical test used was ANOVA. The heart muscle of patients with CHF showed that the mitochondrial area was reduced by 78% compared with the control (160.37 µm2 ± 9.87) (936.81 µm2 ± 78.48) p 0.0001. There was also a 70% reduction in complex III activity compared to control (1.9 10-2 mM ubiq.mim-prot 1.mg ± 12.6) (5.79 10-2mM ubiq.mim prot-1.mg ± 36.6) p . The presence of ONOO-was significantly increased in patients with CHF. Alterations ultraestructutural and functional mitochondria found in patients with CHF and increased ROS are involved in the measures of physiopathology CCI and whites should be taken into account for future therapies of this condition.

[Importance of host sex in the development of trypanosoma cruzi infection]. / Importancia del sexo del huésped en el desarrollo de la infección por Trypanosoma Cruzi.

Multiple factors, both dependent on the host and the parasite are involved in determining resistance or susceptibility to infection with T. cruzi, but the influence of the sex of the host is a factor that has not been clearly established. In this paper we analyzed the influence of this factor upon the infected individuals. We used Swiss albino mice infected with 50 trypomastigotes / mouse of T. cruzi, strain Tulahuen: males (n = 73) and females (n = 64). The highest parasitemia was detected on day 21 post-infection (pi) in both males and females and became negative on day 56 pi, and males exhibited significantly higher levels of parasitemia. The highest mortality occurred between day 21 and day 28 pi; by day 270 pi (chronic stage) one male (3%) survived every 7.6 females (23%). In skeletal muscle of male and female mice on days 90, 180 and 270 pi, lympho-monocitary infiltrates were found nests of amastigotes, whereas the myocardium of these animals showed inflammatory infiltrates only. We conclude that males showed greater susceptibility to infection and higher mortality than females in this mouse model infected with T. cruzi, Tulahuen strain, but the characteristics of the infection and cardiomyopathy development are similar in nature.

Analysis of mitochondrial enzymatic activity in blood lymphomonocyte fractions during infection with different Trypanosoma cruzi strains.

Proinflammatory and inflammatory mediators induced by Trypanosoma cruzi infection increase the oxidative stress, generating toxicity for cells targeting mitochondria of different tissues. We studied the activity of citrate synthase and complexes I-IV of respiratory chain in mitochondria of blood lymphomonocyte fraction, from albino Swiss mice infected with different isolates of T. cruzi , during Chagas disease evolution. Complexes I-IV were modified in infected groups (p<0.05) in all the stages, and an inflammatory process of different magnitudes was detected in the heart and skeletal muscle according to the isolate. The citrate synthase activity presented modifications in the SGO Z12 and the Tulahuen group (p<0.05). Hearts showed fiber fragmentation and fibrosis; skeletal muscle presented inflammatory infiltrates and in the Tulahuen infected group, there were also amastigote nests. The inflammatory processes produced an oxidative stress that induced different alterations of mitochondrial enzymes activities in the lymphomonocyte fraction that can be detected by a simple blood extraction, suggesting that they could be used as disease markers, especially in the indeterminate phase of Chagas disease.

Nitric oxide synthase and oxidative-nitrosative stress play a key role in placental infection by Trypanosoma cruzi.

PROBLEM: The innate immune response of the placenta may participate in the congenital transmission of Chagas disease through releasing reactive oxygen and nitrogen intermediates. METHOD OF STUDY: Placental explants were cultured with 1 × 106 and 1 × 105 trypomastigotes of Tulahuen and Lucky strains and controls without parasites, and with the addition of nitric oxide synthase inhibitor Nω-Nitro-l-arginine methyl ester (l-NAME) and N-acetyl cysteine (NAC) as the reactive oxygen species (ROS) scavenger. Detachment of the syncytiotrophoblast (STB) was examined by histological analysis, and the nitric oxide synthase, endothelial (eNOS), and nitrotyrosine expressions were analyzed by immunohistochemistry, as well as the human chorionic gonadotrophin (hCG) levels in the culture supernatant through ELISA assays. Parasite load with qPCR using Taqman primers was quantified. RESULTS: The higher number of T. cruzi (106 ) increased placental infection, eNOS expression, nitrosative stress, and STB detachment, with the placental barrier being injured by oxidative stress. CONCLUSION: The higher number of parasites caused deleterious consequences to the placental barrier, and the inhibitors (l-NAME and NAC) prevented the damage caused by trypomastigotes in placental villi but not that of the infection. Moreover, trophoblast eNOS played a key role in placental infection with the highest inoculum of Lucky, demonstrating the importance of the enzyme and nitrosative-oxidative stress in Chagas congenital transmission.

Differential tissue distribution of Trypanosoma cruzi during acute experimental infection: Further evidence using natural isolates.

In the present work, we evaluated the effect of mixed Trypanosoma cruzi infections, studying the biological distribution of the different parasites in blood, heart and skeletal muscle during the acute phase. Albino Swiss mice were infected with different parasite strain/isolates or with a combination of them. The parasites in the different tissues were typified through specific PCR, population variability was analyzed through RFLP studies and parasitological and histopathological parameters were evaluated. We found a predominance of TcII and TcVI in all tissues samples respect to TcV and different parasite populations were found in circulation and in the tissues from the same host. These results verify the distribution of parasites in host tissues from early stages of infection and show biological interactions among different genotypes and populations of T. cruzi.

Treatment with benznidazole or thioridazine in the chronic phase of experimental Chagas disease improves cardiopathy.

Mice infected with Trypanosoma cruzi Tulahuen strain or SGO-Z12 isolate were treated at 180 days post infection (p.i.) (i.e. chronic phase) with benznidazole (for 30 days) or thioridazine (for 12 days). Both drugs produced a decrease in electrocardiographic alterations, fewer modifications in the affinity and density of cardiac beta-receptors, and few isolated areas of fibrosis in the heart, whereas untreated mice presented areas of necrosis and fibre fragmentation 350 days p.i. (P<0.01). Survival in treated mice was 100% for benznidazole and 88% for thioridazine, independent of the parasite strain; survival for untreated mice was 30% and 40% for Tulahuen strain and SGO-Z12 isolate, respectively (P<0.01). No cardiotoxic effects of thioridazine were detected at the dose and treatment schedule used. These results show the benefit of treatment in the chronic phase of Chagas disease and that thioridazine should be considered as a promising agent for the treatment of Chagas disease.

[Analysis of the mitochondrial function and ultrastructure in healthy albino mice treated with heart failure medications] / Análisis de la función y ultraestructura mitocondrial en ratones albinos sanos tratados con medicamentos para insuficiencia cardíaca.

Background: Mitochondrial activity is essential for cardiac and skeletal muscle. The relationship between mitochondrial dysfunction and different cardiovascular conditions has been well described. Pharmacological treatment for heart failure involves different drugs as: angiotensin-converting enzyme inhibitors, B-adrenergic blockers, digitalis glycosides and diuretics. The clinical benefit from medication is clear, however, the role of this drugs in mitochondrial metabolisms is not well understood. Aim of the study: The objective of our study was to analyze structural and functional characteristics of cardiac and skeletal muscle mitochondria in mice treated with drugs normally used for heart failure and compare it to a control group. Methods: Twenty-five Albino Mice divided in five groups were treated with heart failure medication during 30 days (group I to IV). 30 days after treatment they were sacrificed, heart and skeletal muscle were analyzed and compared with a control group (V). Results: Enzymatic activity was slightly increased in groups treated with heart failure medication compared to control group (p>0.05). Mitochondrial morphology was significantly altered in groups treated compared to control group, in addition, mitochondrial area was significantly increased in the treated groups, in both cardiac and skeletal muscle. Conclusions: We concluded that heart failure medication could produce modifications in mitochondrial function; we believe that mitochondria maintains the enzymatic activity by increasing size and modifying morphology. Methods: Twenty-five Albino Mice divided in five groups were treated with heart failure medication during 30 days (group I to IV). 30 days after treatment they were sacrificed, heart and skeletal muscle were analyzed and compared with a control group (V). Results: Enzymatic activity was slightly increased in groups treated with heart failure medication compared to control group (p>0.05). Mitochondrial morphology was significantly altered in groups treated compared to control group, in addition, mitochondrial area was significantly increased in the treated groups, in both cardiac and skeletal muscle. Conclusions: We concluded that heart failure medication could produce modifications in mitochondrial function; we believe that mitochondria maintains the enzymatic activity by increasing size and modifying morphology. Results: Enzymatic activity was slightly increased in groups treated with heart failure medication compared to control group (p>0.05). Mitochondrial morphology was significantly altered in groups treated compared to control group, in addition, mitochondrial area was significantly increased in the treated groups, in both cardiac and skeletal muscle. Conclusions: We concluded that heart failure medication could produce modifications in mitochondrial function; we believe that mitochondria maintains the enzymatic activity by increasing size and modifying morphology. Conclusions: We concluded that heart failure medication could produce modifications in mitochondrial function; we believe that mitochondria maintains the enzymatic activity by increasing size and modifying morphology.

Introducción: la actividad mitocondrial es esencial para el músculo cardíaco y esquelético. La relación entre la disfunción mitocondrial y diferentes condiciones cardiovasculares ha sido bien descrita. El tratamiento farmacológico de la insuficiencia cardíaca implica diferentes medicamentos como: inhibidores de la enzima convertidora de la angiotensina, bloqueadores B-adrenérgicos, glucósidos digitálicos y diuréticos. Los beneficios clínicos del tratamiento son claros, sin embargo, el papel de estos fármacos en el metabolismo mitocondrial no esta bien establecido.Objetivo del estudio: El objetivo de nuestro estudio fue analizar las características estructurales y funcionales de las mitocondrias del músculo cardíaco y esquelético en ratones tratados con fármacos habitualmente utilizados para la insuficiencia cardíaca y compararlo con un grupo control.Métodos: Veinticinco ratones albinos divididos en cinco grupos fueron tratados con la medicación para insuficiencia cardíaca durante 30 días (grupo I a IV). 30 días después del tratamiento se sacrificaron, el corazón y el músculo esquelético se analizaron y se compararon con un grupo control (V).Resultados: La actividad enzimática se incrementó ligeramente en los grupos tratados con medicamentos insuficiencia cardiaca en comparación con el grupo control (p> 0,05). morfología mitocondrial se modificó significativamente en los grupos tratados en comparación con el grupo control, además, el área mitocondrial fue significativamente mayor en los grupos tratados, tanto en el músculo cardíaco y estriado.Conclusiones: Concluimos que la medicación insuficiencia cardíaca podría producir modificaciones en la función mitocondrial; creemos que las mitocondrias pueden mantener la actividad enzimática mediante el aumento de tamaño y modificación de la morfología. Objetivo: El objetivo de nuestro estudio fue analizar las características estructurales y funcionales de las mitocondrias del músculo cardíaco y esquelético en ratones tratados con fármacos habitualmente utilizados para la insuficiencia cardíaca y compararlo con un grupo control. Métodos: Veinticinco ratones albinos divididos en cinco grupos fueron tratados con la medicación para insuficiencia cardíaca durante 30 días (grupo I a IV). 30 días después del tratamiento se sacrificaron, el corazón y el músculo esquelético se analizaron y se compararon con un grupo control (V).Resultados: La actividad enzimática se incrementó ligeramente en los grupos tratados con medicamentos insuficiencia cardiaca en comparación con el grupo control (p> 0,05). morfología mitocondrial se modificó significativamente en los grupos tratados en comparación con el grupo control, además, el área mitocondrial fue significativamente mayor en los grupos tratados, tanto en el músculo cardíaco y estriado.Conclusiones: Concluimos que la medicación insuficiencia cardíaca podría producir modificaciones en la función mitocondrial; creemos que las mitocondrias pueden mantener la actividad enzimática mediante el aumento de tamaño y modificación de la morfología. Resultados: La actividad enzimática se incrementó ligeramente en los grupos tratados con medicamentos insuficiencia cardiaca en comparación con el grupo control (p> 0,05). morfología mitocondrial se modificó significativamente en los grupos tratados en comparación con el grupo control, además, el área mitocondrial fue significativamente mayor en los grupos tratados, tanto en el músculo cardíaco y estriado.Conclusiones: Concluimos que la medicación insuficiencia cardíaca podría producir modificaciones en la función mitocondrial; creemos que las mitocondrias pueden mantener la actividad enzimática mediante el aumento de tamaño y modificación de la morfología. Conclusiones: Concluimos que la medicación insuficiencia cardíaca podría producir modificaciones en la función mitocondrial; creemos que las mitocondrias pueden mantener la actividad enzimática mediante el aumento de tamaño y modificación de la morfología.

Changes in the cardiac beta-adrenergic system provoked by different T. cruzi strains.

BACKGROUND: It has been demonstrated that the beta-adrenergic signal transduction system is altered somewhere along its pathway in Trypanosoma cruzi infected hearts and we think that these alterations would differ according to the infection phase and the parasite strain. Their study would be important for the understanding of the disease's pathophysiology. METHODS: In the present work we studied important components of this system in mice hearts infected with T. cruzi, Tulahuen strain and with SGO-Z12 isolate, obtained from a patient of an endemic area, in the acute phase of the infection, determining: the plasma catecholamines levels, the beta-receptors density and affinity as well as their function, the cardiac concentration of cAMP and the cardiac contractility as the physiologic response to the initial stimulus. RESULTS: Plasma catecholamines levels were diminished in both infected groups when compared to the uninfected one (P < 0.01). The receptor's affinity was also diminished (P < 0.05) while their density was augmented only in the SGO-Z12 infected one (P < 0.01). The cAMP levels were higher in both infected groups (P < 0.01), the basal contractile force however increased only in the Tulahuen infected one (P < 0.01) while the response to catecholamines remained unchanged. The hearts infected with the SGO Z12 isolate presented an inferior response to epinephrine (P < 0.05) than the ventricles infected with the Tulahuen strain. CONCLUSIONS: This model represents an important approach to understand the biochemical, physiological and molecular changes in the cardiac beta-adrenergic signalling that clearly begin in the acute phase of Chagas' disease and reveal a clear differentiation in the alterations produced by different parasite strains.

Weekly electrocardiographic pattern in mice infected with two different Trypanosoma cruzi strains.

BACKGROUND: Chagas' disease, which is caused by Trypanosoma cruzi, affects 20 million people. The electrocardiographic alterations are usually the first evidence of disease progression. In this work, we evaluated if two different T. cruzi strains presented electrocardiographic and heart histopathological alterations that could be characteristic and only achieved to the parasite strain. The moment when the electric alterations began was also studied. METHODS: Albino mice (n=100) were inoculated with 50 (n=50) and 500 (n=50) trypomastigotes of T. cruzi, for Tulahuen strain and SGO-Z12 isolate, respectively. Electrocardiograms were obtained before infection and once a week from 7 to 147 days post infection (d.p.i). Dipolar and unipolar leads were analyzed. Hearts were removed by necropsy on 14, 90 and 147 d.p.i. Each heart was cut horizontally into 5-mum sections and they were stained with Hematoxilin-Eosine. RESULTS: At 147 d.p.i., 30% of Tul-infected mice were found alive, while in the SGO-Z12 infected group, 75% were alive at the same moment. The Tul-infected group showed more intraventricular blockage alterations than the other groups from 49 to 70 d.p.i, (p<0.01). No structural cardiac alterations were detected in SGO-Z12-infected mice at 7 d.p.i., while the Tul-infected group showed mononuclear cell infiltrates. At 147 d.p.i., fiber disorganization and cell infiltration were observed in the SGO-Z12 and Tul-infected groups. CONCLUSIONS: We demonstrated that T. cruzi Tulahuen strain and SGO-Z12 isolate determined different electrocardiographic alterations which were characteristic for each stage of the experimental Chagas' disease. These results highlight the importance of the T. cruzi strain in the severity of the cardiopathy.

Trypanothione reductase inhibitors: Overview of the action of thioridazine in different stages of Chagas disease.

Thioridazine (TDZ) is a phenothiazine that has been shown to be one of the most potent phenothiazines to inhibit trypanothione reductase irreversibly. Trypanothione reductase is an essential enzyme for the survival of Trypanosoma cruzi in the host. Here, we reviewed the use of this drug for the treatment of T. cruzi experimental infection. In our laboratory, we have studied the effect of TDZ for the treatment of mice infected with different strains of T. cruzi and treated in the acute or in the chronic phases of the experimental infection, using two different schedules: TDZ at a dose of 80 mg/kg/day, for 3 days starting 1h after infection (acute phase), or TDZ 80 mg/kg/day for 12 days starting 180 days post infection (d.p.i.) (chronic phase). In our experience, the treatment of infected mice, in the acute or in the chronic phases of the infection, with TDZ led to a large reduction in the mortality rates and in the cardiac histological and electrocardiographical abnormalities, and modified the natural evolution of the experimental infection. These analyses reinforce the importance of treatment in the chronic phase to decrease, retard or stop the evolution to chagasic myocardiopathy. Other evidence leading to the use of this drug as a potential chemotherapeutic agent for Chagas disease treatment is also revised.

Trypanosoma cruzi reinfections in mice determine the severity of cardiac damage.

In two murine models we studied Trypanosoma cruzi reinfection in the acute and chronic phase of experimental Chagas' disease in order to elucidate the relevance of reinfections in determining the variability of cardiac symptoms and the irreversible cardiac damage. They were followed for 120 and 600 days post infection (p.i.) for the acute and chronic model, respectively. Reinfected mice reached higher parasitaemia levels than infected mice. The survival was 33 and 21% in the chronic phase for mice reinfected in the acute phase and 13% for mice reinfected in the chronic stage at the end of the experiments. Sixty-six percent of the infected group presented electrocardiographic abnormalities (heart frequency, prolonged PQ segment or QRS complex) in the chronic stage whereas 100% of the reinfected animals exhibited electric cardiac dysfunction since 90 and 390 days p.i. for the acute and chronic reinfected model, respectively (P<0.01). Heart histopathological studies showed fibrosis and necrosis areas and mononuclear infiltrates supporting the view that parasite persistence is a major factor in continuing the tissue inflammation. This work shows that T. cruzi reinfections could be related to the variability and severity of the clinical course of Chagas' disease and that parasite persistence is involved in exacerbation of the disease.

Circulating Trypanosoma cruzi populations differ from those found in the tissues of the same host during acute experimental infection.

We evaluated the presence and distribution of two Trypanosoma cruzi natural isolates in blood, heart, skeletal muscle, liver, and spleen tissues in the acute phase of the experimental infection (35 days postinfection) in order to determine if the populations present in blood were different to those found in the tissues of the same host. Thirty mice were infected with 50 forms of each isolate or with a combination of them. Presence and molecular characterization of the parasites in the host tissues were determined by specific PCR. Cardiac and skeletal muscle alterations were analyzed by histological studies. T. cruzi variability in the host tissues was analyzed through RFLP studies. Both isolates used consisted of a mixture of two T. cruzi lineages. Specific PCRs were positive for most of the samples from the 3 groups analyzed. Cardiac and skeletal muscle sections from the groups infected with one isolate presented mild to moderate inflammatory infiltrates; the group infected with both isolates showed severe inflammatory infiltrates and the presence of amastigote nests in both tissues. Different parasite populations were found in circulation and in the tissues from the same host. These results are important for patients with high probability of mixed infections in endemic areas and contribute to the knowledge of parasite/host interactions.

Functional and structural alterations of cardiac and skeletal muscle mitochondria in heart failure patients.

BACKGROUND AND AIMS: The fundamental mechanisms involved in the genesis and progression of heart failure are not clearly understood. The present study was conducted to analyze the cardiac mitochondrial involvement in heart failure, the possible parallelism between cardiac and skeletal muscle and if there is a link between clinical symptoms and mitochondrial damage. METHODS: Left ventricle and pectoral biopsies were obtained from patients with heart failure (n: 21) and patients with inter-auricular communication as the unique diagnosis for surgery (n: 6). Mitochondria were isolated from these tissues and studied through electron microscopy, spectrophotometry to measure the activity of respiratory complex III and immunohistochemistry to determine the presence of reactive oxygen species. RESULTS: More than 90% of cardiac and skeletal muscle mitochondria presented structural and functional alterations in relation to an increment in the reactive oxygen species production, even in patients without the presence of any clinical Framingham criteria. CONCLUSIONS: We demonstrated some parallelism between cardiac and skeletal muscle mitochondrial alterations in patients with heart failure and that these alterations begin before the major clinical Framingham criteria are installed, pointing to mitochondria as one of the possibly responsible factors for the evolution of cardiac disease.