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.

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.

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.

[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.

Allopurinol is effective to modify the evolution of Trypanosoma cruzi infection in mice.

There is a real need for new and less toxic drugs for the treatment of Chagas disease, as nifurtimox and benznidazole are effective but toxic and provoke unpleasant side effects, especially in adult patients. Allopurinol, commonly used to treat the hiperuricemia, is also used by the Trypanosoma cruzi's hypoxantine guanine fosforyltransferase as an alternative substrate incorporating it into the parasite's ribonucleic acid, provoking the death of the parasite. However, the results of using allopurinol as chemotherapy for Chagas disease are not clear. For that, we investigated the evolution of the T. cruzi infection in mice treated with allopurinol (5, 10 or 15 mg/kg for 90 days) obtaining a reduction in the parasitaemia (p<0.05), no electrocardiographic alterations (p<0.05) and a conserved myocardial and cardiac beta-receptors' affinity values with the highest dose of the drug, compared to those of the uninfected mice. Cruzipain immunoglobulin G levels remained high in all the groups as well as the survival (70%, 90 days post-infection). Allopurinol prevented the acute phase evolving into the chronic cardiac disease.

Reinfections and Trypanosoma cruzi strains can determine the prognosis of the chronic chagasic cardiopathy in mice.

Chronic Chagas' disease represents the result of the interaction between the host and the parasite, producing different clinical features: from a mild disease to a severe heart failure. In the present investigation, we analyzed whether Trypanosoma cruzi strain and/or reinfections in the acute stage, determine changes in the chronic phase (135 days postinfection, d.p.i) that could explain the diverse evolution of cardiac lesions. After infection of albino Swiss mice (n = 170) with 50 blood trypomastigote of the T. cruzi, strain Tulahuen (n = 80) and the isolate SGO-Z12 (n = 90), respectively, and reinfections at 10 and 20 d.p.i. Parasitemia, survival, electrocardiography, affinity and density of cardiac beta-receptors and histopathology of the heart were studied. Parasitemias in reinfected mice were significantly higher than those in single-infected mice. Survival of SGO-Z12-infected group was significantly higher than the other groups (p < 0.01). All Tulahuen-reinfected mice and 55-67% of the infected and SGO-Z12-reinfected groups presented some electrocardiographic abnormality (p < 0.01). Hearts from single-infected mice presented fibber disorganization and necrosis; reinfected groups also exhibited fibber fragmentation and a diminished affinity and a higher beta-adrenergic receptors' density than the other groups (p < 0.05). Therefore, parasite strain and reinfections determine different cardiac damage, and either (or both) of these factors are involved in the severity of the clinical picture and the prognosis of the chronic cardiac disease.