Sialic acid removal by trans-sialidase modulates MMP-2 activity during Trypanosoma cruzi infection.

Matrix metalloproteinases (MMPs) not only play a relevant role in homeostatic processes but are also involved in several pathological mechanisms associated with infectious diseases. As their clinical relevance in Chagas disease has recently been highlighted, we studied the modulation of circulating MMPs by Trypanosoma cruzi infection. We found that virulent parasites from Discrete Typing Units (DTU) VI induced higher proMMP-2 and MMP-2 activity in blood, whereas both low (DTU I) and high virulence parasites induced a significant decrease in proMMP-9 plasma activity. Moreover, trans-sialidase, a relevant T. cruzi virulence factor, is involved in MMP-2 activity modulation both in vivo and in vitro. It removes α2,3-linked sialyl residues from cell surface glycoconjugates, which then triggers the PKC/MEK/ERK signaling pathway. Additionally, bacterial sialidases specific for this sialyl residue linkage displayed similar MMP modulation profiles and triggered the same signaling pathways. This novel pathogenic mechanism, dependent on sialic acid removal by the neuraminidase activity of trans-sialidase, can be exploited by different pathogens expressing sialidases with similar specificity. Thus, here we present a new pathogen strategy through the regulation of the MMP network.

Neutrophils from patients with the cardiac clinical form of Chagas disease release less NETs than neutrophils from healthy individuals.

INTRODUCTION: Chagas disease (CD) is a global health concern with approximately 12 000 deaths per year worldwide. In the chronic phase, about 30% of patients develop the cardiac clinical form, which presents symptoms associated with the presence of inflammatory cells in the cardiac tissue. Neutrophils are inflammatory cells able to modulate the chronic immune response against pathogens. These cells are capable of interacting with Trypanosoma cruzi, the aetiological agent of CD, and perform several effector functions, such as NET release. However, few studies have been carried out to investigate the role of these cells in the disease. AIMS: To investigate the release of NETs by neutrophils from CD patients by measuring the amount of DNA and elastase released. METHODS AND RESULTS: Measurement of DNA release by neutrophils from chronic CD patients presenting the indeterminate (IND group; n = 18) and cardiac (CARD group; n = 15) clinical forms and nonchagasic subjects (n = 18) stimulated with soluble antigen of T. cruzi was quantified using the Quant-iT™ PicoGreen® dsDNA assay kit. Patients from CARD group release less DNA (117.3 ± 21.85 ng/mL; *P = .0131) than neutrophils from control (177.7 ± 58.41 ng/mL). Elastase enzyme degranulation was measured using the substrate N-methoxysuccinyl-Ala-Ala-Pro-Val p-nitroanilide (SAAVNA). Absorbance values of elastase degranulation activity showed that only cells from healthy individuals presented a high release profile of elastase. Also, we found a negative correlation between DNA released concentration and risk of death (r = -.6574; *P = .0173); the lower the neutrophil DNA release from chagasic patients with cardiac event, the higher the risk of death. CONCLUSION: These preliminary data show that patients with the cardiac form of CD release less NETs than nonchagasic individuals, raising the possibility that lower release of NETs enhances risk of death in CD patients with cardiac events.

Manganese superoxide dismutase deficiency exacerbates the mitochondrial ROS production and oxidative damage in Chagas disease.

In this study, we have investigated the effects of manganese superoxide dismutase (SOD2 or MnSOD) deficiency on mitochondrial function and oxidative stress during Chagas disease. For this, C57BL/6 wild type (WT) and MnSOD+/- mice were infected with Trypanosoma cruzi (Tc), and evaluated at 150 days' post-infection that corresponded to chronic disease phase. Genetic deletion of SOD2 decreased the expression and activity of MnSOD, but it had no effect on the expression of other members of the SOD family. The myocardial expression and activity of MnSOD were significantly decreased in chronically infected WT mice, and it was further worsened in MnSOD+/- mice. Chronic T. cruzi infection led to a decline in mitochondrial complex I and complex II driven, ADP-coupled respiration and ATP synthesis in the myocardium of WT mice. The baseline oxidative phosphorylation (OXPHOS) capacity in MnSOD+/- mice was decreased, and it had an additive effect on mitochondrial dysregulation of ATP synthesis capacity in chagasic myocardium. Further, MnSOD deficiency exacerbated the mitochondrial rate of reactive oxygen species (ROS) production and myocardial oxidative stress (H2O2, protein carbonyls, malondialdehyde, and 4-hydroxynonenal) in Chagas disease. Peripheral and myocardial parasite burden and inflammatory response (myeloperoxidase, IL-6, lactate dehydrogenase, inflammatory infiltrate) were increased in all chagasic WT and MnSOD+/- mice. We conclude that MnSOD deficiency exacerbates the loss in mitochondrial function and OXPHOS capacity and enhances the myocardial oxidative damage in chagasic cardiomyopathy. Mitochondria targeted, small molecule mitigators of MnSOD deficiency will offer potential benefits in averting the mitochondrial dysfunction and chronic oxidative stress in Chagas disease.

Physiological and unappreciated roles of CaMKII in the heart.

In the cardiomyocyte, CaMKII has been identified as a nodal influencer of excitation-contraction and also excitation-transcription coupling. Its activity can be regulated in response to changes in intracellular calcium content as well as after several post-translational modifications. Some of the effects mediated by CaMKII may be considered adaptive, while effects of sustained CaMKII activity may turn into the opposite and are detrimental to cardiac integrity and function. As such, CaMKII has long been noted as a promising target for pharmacological inhibition, but the ubiquitous nature of CaMKII has made it difficult to target CaMKII specifically where it is detrimental. In this review, we provide a brief overview of the physiological and pathophysiological properties of CaMKII signaling, but we focus on the physiological and adaptive functions of CaMKII. Furthermore, special consideration is given to the emerging role of CaMKII as a mediator of inflammatory processes in the heart.

Association of caspase-1 polymorphisms with Chagas cardiomyopathy among individuals in Santa Cruz, Bolivia.

INTRODUCTION:: Trypanosoma cruzi (Tc) infection is usually acquired in childhood in endemic areas, leading to Chagas disease, which progresses to Chagas cardiomyopathy in 20-30% of infected individuals over decades. The pathogenesis of Chagas cardiomyopathy involves the host inflammatory response to T. cruzi, in which upstream caspase-1 activation prompts the cascade of inflammatory chemokines/cytokines, cardiac remodeling, and myocardial dysfunction. The aim of the present study was to examine the association of two caspase-1 single nucleotide polymorphisms (SNPs) with cardiomyopathy. METHODS:: We recruited infected (Tc+, n = 149) and uninfected (Tc-, n = 87) participants in a hospital in Santa Cruz, Bolivia. Cardiac status was classified (I, II, III, IV) based on Chagas cardiomyopathy-associated electrocardiogram findings and ejection fractions on echocardiogram. Genotypes were determined using Taqman probes via reverse transcription-polymerase chain reaction of peripheral blood DNA. Genotype frequencies were analyzed according to three inheritance patterns (dominant, recessive, additive) using logistic regression adjusted for age and sex. RESULTS:: The AA allele for the caspase-1 SNP rs501192 was more frequent in Tc+ cardiomyopathy (classes II, III, IV) patients compared to those with a normal cardiac status (class I) [odds ratio (OR) = -2.18, p = 0.117]. This trend approached statistical significant considering only Tc+ patients in class I and II (OR = -2.64, p = 0.064). CONCLUSIONS:: Caspase-1 polymorphisms may play a role in Chagas cardiomyopathy development and could serve as markers to identify individuals at higher risk for priority treatment.

Association of caspase-1 polymorphisms with Chagas cardiomyopathy among individuals in Santa Cruz, Bolivia

Abstract INTRODUCTION: Trypanosoma cruzi (Tc) infection is usually acquired in childhood in endemic areas, leading to Chagas disease, which progresses to Chagas cardiomyopathy in 20-30% of infected individuals over decades. The pathogenesis of Chagas cardiomyopathy involves the host inflammatory response to T. cruzi, in which upstream caspase-1 activation prompts the cascade of inflammatory chemokines/cytokines, cardiac remodeling, and myocardial dysfunction. The aim of the present study was to examine the association of two caspase-1 single nucleotide polymorphisms (SNPs) with cardiomyopathy. METHODS: We recruited infected (Tc+, n = 149) and uninfected (Tc−, n = 87) participants in a hospital in Santa Cruz, Bolivia. Cardiac status was classified (I, II, III, IV) based on Chagas cardiomyopathy-associated electrocardiogram findings and ejection fractions on echocardiogram. Genotypes were determined using Taqman probes via reverse transcription-polymerase chain reaction of peripheral blood DNA. Genotype frequencies were analyzed according to three inheritance patterns (dominant, recessive, additive) using logistic regression adjusted for age and sex. RESULTS: The AA allele for the caspase-1 SNP rs501192 was more frequent in Tc+ cardiomyopathy (classes II, III, IV) patients compared to those with a normal cardiac status (class I) [odds ratio (OR) = −2.18, p = 0.117]. This trend approached statistical significant considering only Tc+ patients in class I and II (OR = −2.64, p = 0.064). CONCLUSIONS: Caspase-1 polymorphisms may play a role in Chagas cardiomyopathy development and could serve as markers to identify individuals at higher risk for priority treatment.

Synergic and antagonistic relationship between MMP-2 and MMP-9 with fibrosis and inflammation in Chagas' cardiomyopathy.

Cardiomyopathy is the most important clinical manifestation in the chronic phase of Chagas' disease because of its frequency, severity and impact on morbidity and mortality. The extracellular matrix degradation during cardiac remodeling in Trypanosoma cruzi infection is driven by matrix metalloproteinases (MMPs), primarily the MMP-2 and MMP-9 gelatinases. MMPs also regulate some molecules related to inflammation, such as growth factors, cytokines and chemokines. The involvement of MMP-2 and MMP-9 is not yet fully understood in Chagas' disease. It has been proposed that the gelatinases may have opposite effect on inflammation/regulation and cardiac remodeling. MMP-2 would participate in regulation, offering a protective role for cardiac damage in asymptomatic patients and would be a good marker for the initiation of changes in the heart. On the other hand, MMP-9 can be used as a marker for serious changes on the heart and would be associated with inflammation and fibrosis. Here, we consolidate all characteristics involving MMP-2 and MMP-9 in Chagas' disease based on current studies to clarify their participation on the inflammation/regulation and fibrosis, and the synergistic or antagonistic role between them.

Matrix metalloproteinases 2 and 9 are differentially expressed in patients with indeterminate and cardiac clinical forms of Chagas disease.

Dilated chronic cardiomyopathy (DCC) from Chagas disease is associated with myocardial remodeling and interstitial fibrosis, resulting in extracellular matrix (ECM) changes. In this study, we characterized for the first time the serum matrix metalloproteinase 2 (MMP-2) and MMP-9 levels, as well as their main cell sources in peripheral blood mononuclear cells from patients presenting with the indeterminate (IND) or cardiac (CARD) clinical form of Chagas disease. Our results showed that serum levels of MMP-9 are associated with the severity of Chagas disease. The analysis of MMP production by T lymphocytes showed that CD8(+) T cells are the main mononuclear leukocyte source of both MMP-2 and MMP-9 molecules. Using a new 3-dimensional model of fibrosis, we observed that sera from patients with Chagas disease induced an increase in the extracellular matrix components in cardiac spheroids. Furthermore, MMP-2 and MMP-9 showed different correlations with matrix proteins and inflammatory cytokines in patients with Chagas disease. Our results suggest that MMP-2 and MMP-9 show distinct activities in Chagas disease pathogenesis. While MMP-9 seems to be involved in the inflammation and cardiac remodeling of Chagas disease, MMP-2 does not correlate with inflammatory molecules.

NADPH oxidase inhibition ameliorates Trypanosoma cruzi-induced myocarditis during Chagas disease.

Trypanosoma cruzi, the aetiological agent of Chagas disease, invades nucleated mammalian cells including macrophages. In this study, we investigated the crosstalk between T. cruzi-induced immune activation of reactive oxygen species (ROS) and pro-inflammatory responses, and their role in myocardial pathology. Splenocytes of infected mice (C3H/HeN) responded to Tc-antigenic stimulus by more than a two-fold increase in NADPH oxidase (NOX) activity, ROS generation, cytokine production (IFN-γ > IL-4 > TNFα > IL1-ß≈ IL6), and predominant expansion of CD4(+) and CD8(+) T cells. Inhibition of NOX, but not of myeloperoxidase and xanthine oxidase, controlled the ROS (>98%) and cytokine (70-89%) release by Tc-stimulated splenocytes of infected mice. Treatment of infected mice with apocynin (NOX inhibitor) in drinking water resulted in a 50-90% decline in endogenous NOX/ROS and cytokine levels, and splenic phagocytes' proliferation. The splenic percentage of T cells was maintained, though more than a 40% decline in splenic index (spleen weight/body weight) indicated decreased T-cell proliferation in apocynin-treated/infected mice. The blood and tissue parasite burden were significantly increased in apocynin-treated/infected mice, yet acute myocarditis, ie inflammatory infiltrate consisting of macrophages, neutrophils, and CD8(+) T cells, and tissue oxidative adducts (eg 8-isoprostanes, 3-nitrotyrosine, and 4-hydroxynonenal) were diminished in apocynin-treated/infected mice. Consequently, hypertrophy (increased cardiomyocytes' size and ß-MHC, BNP, and ANP mRNA levels) and fibrosis (increased collagen, glycosaminoglycans, and lipid contents) of the heart during the chronic phase were controlled in apocynin-treated mice. We conclude that NOX/ROS is a critical regulator of the splenic response (phagocytes, T cells, and cytokines) to T. cruzi infection, and bystander effects of heart-infiltrating phagocytes and CD8(+) T cells resulting in cardiac remodelling in chagasic mice.

[Role of nitric oxide in the development of cardiac lesions during the acute phase of experimental infection by Trypanosoma cruzi]. / Papel do óxido nítrico no desenvolvimento de lesões cardíacas na fase aguda da infecção experimental pelo Trypanosoma cruzi.

Chagas disease is caused by Trypanosoma cruzi and the heart is the organ most affected. Nitric oxide has notable anti-Trypanosoma action, but with little evidence regarding its role in the mechanism for tissue injury. The objective of this study was to analyze the contribution of nitric oxide towards the development of inflammation and cardiac fibrosis during the acute phase of experimental infection by Y and Colombian strains of Trypanosoma cruzi. The inflammation was significantly more intense in animals infected with the Colombian strain, compared with those infected with the Y strain, both in C57BL/6 animals (3.98 vs 1.87%; p = 0.004) and in C57BL/6 animals deficient in inducible nitric oxide synthase (3.99 vs 2.4%; p = 0.013). The cardiac parasite load in inducible nitric oxide synthase-deficient C57BL/6 animals infected with the Colombian strain was significantly greater than in those infected with the Y strain (2.78 vs. 0.17 nests/mm(2); p = 0.004), and also significantly greater than in the C57BL/6 infected with both the Colombian strain (2.78 vs 1.33 nests/mm(2); p = 0.006) and Y strains (2.78 vs 0.53 nests/mm(2); p = 0.005). The data confirm that nitric oxide has a role in parasite load control and suggest that it has a role in tissue protection, through controlling inflammation and potentially reducing cardiac lesions during the acute phase of Chagas disease.

Role of NO synthase in the development of Trypanosoma cruzi-induced cardiomyopathy in mice.

Trypanosoma cruzi infection results in an increase in myocardial NO and intense inflammation. NO modulates the T. cruzi-induced myocardial inflammatory reaction. NO synthase (NOS)1-, NOS2-, and NOS3-null mice were infected with T. cruzi (Brazil strain). Infected NOS1-null mice had increased parasitemia, mortality, and left ventricular inner diameter (LVID). Chronically infected NOS1- and NOS2-null and wild-type mice (WT) exhibited increased right ventricular internal diameter (RVID), although the fold increase in the NOS2-null mice was smaller. Infected NOS3-null mice exhibited a significant reduction both in LVID and RVID. Reverse transcriptase-polymerase chain reaction showed expression of NOS2 and NOS3 in hearts of infected NOS1-null and WT mice, whereas infected NOS2-null hearts showed little change in expression of other NOS isoforms. Infected NOS3-null hearts showed an increase only in NOS1 expression. These results may indicate different roles for NOS isoforms in T. cruzi-induced cardiomyopathy.

Papel do óxido nítrico no desenvolvimento de lesões cardíacas na fase aguda da infecção experimental pelo Trypanosoma cruzi / Role of nitric oxide in the development of cardiac lesions during the acute phase of experimental infection by Trypanosoma cruzi

A doença de Chagas é causada pelo Trypanosoma cruzi e o coração é o órgão mais acometido. O óxido nítrico apresenta importante ação anti-Trypanosoma, porém, com pouca evidência de seu papel no mecanismo de lesão tecidual. O objetivo deste estudo foi analisar a contribuição do óxido nítrico no desenvolvimento da inflamação e da fibrose cardíaca na fase aguda da infecção experimental por cepas Y e Colombiana do Trypanosoma cruzi. A inflamação foi significativamente maior nos animais infectados pela cepa Colombiana, comparada com os infectados com a cepa Y, tanto nos animais C57BL/6 (3,98x1,87 por cento; p=0,004) quanto nos animais C57BL/6 deficientes na sintase do óxido nítrico induzível (3,99x2,4 por cento; p=0,013). O parasitismo cardíaco dos animais C57BL/6 deficientes na sintase do óxido nítrico induzível infectados pela cepa Colombiana foi significativamente maior que o destes mesmos animais infectados com a cepa Y (2,78x0,17 ninhos/mm²; p=0,004) assim como, os animais C57BL/6 infectados com a cepa Colombiana (2,78x1,33 ninhos/mm²; p=0,006) ou cepa Y (2,78x0,53 ninhos/mm²; p=0,005). Os dados reforçam o papel do óxido nítrico no controle do parasitismo e sugerem seu papel na proteção tecidual, controlando a inflamação e potencialmente diminuindo lesões cardíacas durante a fase aguda na doença de Chagas experimental.

Chagas disease is caused by Trypanosoma cruzi and the heart is the organ most affected. Nitric oxide has notable anti-Trypanosoma action, but with little evidence regarding its role in the mechanism for tissue injury. The objective of this study was to analyze the contribution of nitric oxide towards the development of inflammation and cardiac fibrosis during the acute phase of experimental infection by Y and Colombian strains of Trypanosoma cruzi. The inflammation was significantly more intense in animals infected with the Colombian strain, compared with those infected with the Y strain, both in C57BL/6 animals (3.98 vs 1.87 percent; p = 0.004) and in C57BL/6 animals deficient in inducible nitric oxide synthase (3.99 vs 2.4 percent; p = 0.013). The cardiac parasite load in inducible nitric oxide synthase-deficient C57BL/6 animals infected with the Colombian strain was significantly greater than in those infected with the Y strain (2.78 vs. 0.17 nests/mm²; p = 0.004), and also significantly greater than in the C57BL/6 infected with both the Colombian strain (2.78 vs 1.33 nests/mm²; p = 0.006) and Y strains (2.78 vs 0.53 nests/mm²; p = 0.005). The data confirm that nitric oxide has a role in parasite load control and suggest that it has a role in tissue protection, through controlling inflammation and potentially reducing cardiac lesions during the acute phase of Chagas disease.

[Myocardial cellular damage and the activity of the mitochondrial ATP synthase in rats infected with a Colombian strain of Trypanosoma cruzi]. / Lesión celular del miocardio y actividad de la ATPsintasa mitocondrial en ratas infectadas con una cepa colombiana de Trypanosoma cruzi.

INTRODUCTION: Chagas disease is the main cause of cardiomyopathy in endemic regions of Latin America. Alterations in the cardiac mitochondrial energy metabolism caused by Trypanosoma cruzi can be involved in the development of this cardiomyopathy during the course of Chagas disease. OBJECTIVE: The cellular injury of the rat myocardium was investigated in rats infected with the Colombian Mg8 strain of Trypanosoma cruzi. The activity of mitochondrial ATP synthase was measured to determine the relationship heart damage with the energy metabolism. MATERIALS AND METHODS: Two groups of five rats each were infected with tripomastigotes, with 1 group of 6 rats serving as controls. The course of infection was characterized by parasitological, histopathological and molecular studies. The mitochondrial ATP synthase activity of the myocardium was evaluated in all rats. RESULTS: Peak parasitaemia (day 26 post infection) and the time of parasite clearance from circulating blood (day 60 post infection) were determined for acute and chronic phase models. The histopathological and molecular results showed that the Colombian Mg8 strain has tropism to the cardiac tissue and causes considerable cellular injury of the myocardium in rats during both phases. Despite the lesions observed in infected rats, no statistical difference in the activity of the mitochondrial ATPsynthase was observed between them and the non-infected rats. CONCLUSION: Mitochondrial energy metabolism of the cardiomyocites does not appear to change during cellular injury of rat myocardium associated with infection by the Colombian Mg8 T. cruzi strain.

Impaired mitochondrial respiratory chain and bioenergetics during chagasic cardiomyopathy development.

In this study, we evaluated the activities of respiratory chain complexes and oxidative phosphorylation (OXPHOS) capacity of the heart to gain insights into the pathological significance of mitochondrial dysfunction in chagasic cardiomyopathy (CCM). In a murine model of Trypanosoma cruzi infection, biochemical and histochemical analysis of the cardiac mitochondria revealed deficiency of the respiratory chain complexes (CI-CV) in infected mice; the inhibition of CI activity was more pronounced in the acute infection phase, CIII was constitutively repressed throughout the infection and disease phase, and the CV defects appeared in chronic phase only. A substantial decline in cardiac mtDNA content (54-60%) and mitochondria-encoded transcripts (50-65%) with disease development indicated that the alterations in mtDNA contribute to the quantitative deficiencies in respiratory chain activity in chagasic hearts. The observations of a selective inhibition of redox-sensitive CI and CIII complexes that are also the site of free radical generation in mitochondria, and the decline in cardiac mtDNA content in infected mice, all support the free radical hypothesis of mitochondria dysfunction in CCM. Consequently, OXPHOS-mediated ATP synthesis capacity of the cardiac mitochondria in infected mice was substantially reduced (37-50%), suggesting an energy homeostasis in the affected tissue.

Serum enzyme pattern and local enzyme gradients in chronic chagasic patients.

Histochemical studies of myocardial biopsies from chronic chagasic patients at different evolutive stages showed a pattern primarily characterized by a marked increment in tissue enzymes such as mono-amine oxidase and lysosomal acid phosphatase. This cellular damage can be reflected by changes in certain serum enzymes associated with myocardial metabolism, specially in the coronary sinus, where the blood metabolized by the heart is drained. However, little is known about the possible changes in blood enzyme activity during chronic Chagas disease. In this investigation, the activity of the following enzymes glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT), alkaline phosphatase (ALP), acid maltase (AM), lactate dehydrogenase (LDH), alpha-hydroxybutyric dehydrogenase (alpha-HBDH or LDH1) and creatine phosphokinase (CPK) was measured in blood serum of the superior cava vein (SCV), coronary sinus (CS) and pulmonary (PA) and femoral (FA) arteries of 45 chronic chagasic patients, ages between 20 and 55 yr, at different evolutive stages (groups IA, IB, II and III). The results demonstrate that the average activity of the enzymes studied in chagasic patients, except LDH and CPK, are significantly altered (p < 0.05) in the majority of the arterial and venous blood samples. The finding of released GOT, GPT, ALP, acid maltase and alpha-HBDH in groups IA and IB is an indication of early myocardial damage in chronic chagasic patients without clinical evidence of cardiac disease. In conclusion, it is suggested that the possible evolutive pattern for myocardial damage could be established by the increment in coronary sinus blood of the enzymes GOT, acid maltase and alpha-HBDH.

Differential regulation of nitric oxide synthase isoforms in experimental acute chagasic cardiomyopathy.

We have previously demonstrated induction and high level expression of IL-1beta, IL-6 and tumour necrosis factor-alpha in the myocardium during the acute stage of experimental Trypanosoma cruzi infection (Chagas' disease). The myocardial depressive effects of these cytokines are mediated in part by the induction of nitric oxide synthase (NOS), production of nitric oxide (NO) and formation of peroxynitrite. In this study we investigated the expression, activity and localization of NOS isoforms, and the levels of NO, malondialdehyde (a measure of oxidative stress), and peroxynitrite in rats at 1.5, 5, 10 and 15 days after infection with T. cruzi trypomastigotes. The myocardial inflammatory infiltrate and number of amastigote nests increased over the course of infection. A significant increase in tissue nitrate + nitrite levels, NOS2 mRNA, and NOS2 enzyme activity was observed at all time points in the infected compared with uninfected animals. The enzyme activity of constitutive NOS, tissue malondialdehyde levels, and NOS3 mRNA levels was only transiently increased after infection. The protein levels of the NOS isoforms paralleled their mRNA expression. While no positive nitrotyrosine immunoreactivity was detected in control myocardium, its levels increased in infected animals over time. Thus, by 1.5 days post-infection, when no parasite or immune cell infiltration could be detected, the myocardium expressed high levels of NOS and NO metabolites. Nevertheless, the early production of NO in the myocardium was not sufficient to clear the parasites.

Heart FoF1-ATPase changes during the acute phase of Trypanosoma cruzi infection in rats.

The kinetic properties of ATP hydrolysis and synthesis by FoF1-ATPase of heart mitochondria were evaluated during the acute phase of T. cruzi infection in rats. Mitochondria and submitochondrial particles were isolated 7 days (early stage) and 25 days (late stage) following infection of rats with 2 x 10(5) trypomastigote forms of the Y strain of T. cruzi. The kinetic properties for ATP hydrolysis were altered for the early but not the late stage, showing a changed pH profile, increased K0.5 values, and a decreased total Vmax. The Arrhenius' plot for membrane-associated enzyme showed a higher transition temperature with a lower value for the activation energy in body temperature. For the Triton X-100-solubilized enzyme, the plot was similar to the control. A decrease in the efficiency of ADP phosphorylation by mitochondria, measured by the firefly-luciferase luminescence, was observed only during the late stage and appeared to be correlated with a decrease in the affinity of the FoF1-ATPase for ADP. It is proposed that in the early stage, during the acute phase of T. cruzi infection in rats, heart FoF1-ATPase undergoes a membrane-dependent conformational change in order to maintain the phosphorylation potential of mitochondria, which would compensate for the uncoupling of mitochondrial function. Also, during both the early and late stages, the enzyme seems to be under the regulation of the endogenous inhibitor protein for the preservation of cellular ATP levels.

Verapamil ameliorates clinical, pathologic and biochemical manifestations of experimental chagasic cardiomyopathy in mice.

The influence of long-term verapamil administration on the consequences of Trypanosoma cruzi infection in mice was studied with regard to animal mortality, morbidity, myocardial pathologic features and myocardial beta-adrenergic adenylate cyclase activity. Verapamil administration dramatically decreased the mortality rate from 60% to 6% during the 70 day period of infection. Three clinical stages of infection were evident. In the acute stage (17 days after infection with maximal parasitemia), verapamil treatment not only decreased the incidence of myocardial disease (fibrosis and inflammation), but also protected myocardial beta-adrenergic adenylate cyclase activity. In addition, there was no increase in total body weight, which was regarded as an index of right-sided heart failure. In the subacute stage (30 to 60 days after infection), administration of verapamil continued to decrease myocardial disease and preserve beta-adrenergic adenylate cyclase activity. In addition, verapamil ameliorated the morbidity and mortality associated with this stage of infection. The chronic stage of infection was characterized by a decrease in myocardial disease and in beta-adrenergic adenylate cyclase activity. Thus, independent of the state of infection, long-term verapamil treatment enhanced beta-adrenergic adenylate cyclase activity. In addition, verapamil ameliorated the morbidity associated with infection. Although the relation among these various effects of verapamil in the setting of T. cruzi infection remains to be determined, collectively the results suggested that verapamil administration attenuated the consequences of T. cruzi infection.

Myocardial adenylate cyclase activity in acute murine Chagas' disease.

We have studied the influence of myocardial infection with Trypanosoma cruzi on the beta-adrenergic adenylate cyclase complex in mouse myocardial membranes. The maximal rate of cAMP generation (Vmax) and the concentration of agonist associated with 50% of the maximal activity (apparent Kact) were determined for a series of agents. Six days after infection, the Vmax for isoproterenol significantly declines without a change in the apparent Kact. After 21 days of infection, both the Vmax and apparent Kact for isoproterenol are reduced. At 6 and 21 days of infection, the affinity of the beta-receptor for [125I]iodocyanopindolol declines from 0.84 to 3.6 and 3 nM, respectively, while the receptor density increases with the duration of infection from 33 to 57 and 82 fmol/mg protein, respectively. The Vmax (but not the apparent Kact) for forskolin and Mg2+- and Mn2+-associated activities declines also after 21 days. Another adenylate cyclase activity, which was stimulated by the nonhydrolyzable guanine nucleotide Gpp(NH)p, declines in relation to the duration of infection. Inhibitors of adenylate cyclase activity were also studied. Inhibition of adenylate cyclase activity by adenosine and by Gpp(NH)p (in the presence of forskolin) declines after 21 days of infection. The results suggested that the coupling proteins Ns and Ni, which mediate stimulatory or inhibitory control of receptors to adenylate cyclase activity, might be altered by infection. As monitored by cholera toxin- and pertussis toxin-dependent ADP ribosylation of their respective substrates, which include Ns and Ni proteins, respectively, there are declines in the availability of both substrates as a result of T. cruzi infection. For infected membranes, the addition of NADP enhances the magnitude of cholera toxin-dependent ADP ribosylation and renders the magnitude of pertussis toxin-dependent ADP ribosylation equal to that observed in uninfected membranes. The results support the hypothesis that infection with T. cruzi results in profound generalized alterations of the adenylate cyclase complex at several different sites.

Epidemiology of Chagas' disease in northern Chile: isozyme profiles of Trypanosoma cruzi from domestic and sylvatic transmission cycles and their association with cardiopathy.

Trypanosoma cruzi was isolated from 98 patients, 59 Triatoma infestans, 51 Triatoma spinolai, and 1 Octodon degus from northern Chile. With few exceptions, stocks originating from domestic hosts were classified, based on their isozyme profile, as principal zymodeme (Z)2, while sylvatic stocks from T. spinolai and the rodent O. degus showed Z1 profiles. These results indicate the existence of separate domestic and sylvatic transmission cycles. Clinical data and T. cruzi isozyme profiles from 107 chronic Chagas' disease patients showed no association between infecting T. cruzi zymodeme and the prevalence of chagasic cardiopathy. However, the age distributions of two groups of patients carrying different zymodemes were significantly different.