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Effects of Free and Nanoencapsulated Benznidazole in Acute Trypanosoma cruzi Infection: Role of Cholinergic Pathway and Redox Status

Background/Objectives: The Trypanosoma cruzi infection promotes an intense inflammatory process that affects several tissues. The cholinergic system may exert a regulatory immune response and control the inflammatory process. This study aimed to evaluate the comparative effect of free and nanoencapsulated benznidazole in acute T. cruzi infection to assess hematological, biochemical, and oxidative status triggered by the cholinergic system. Methods: For this, fifty female Swiss mice were distributed in eight groups, i.e., uninfected and infected animals under four treatment protocols: untreated (control-CT); vehicle treatment (Eudragit L 100-EL-100); benznidazole treatment (BNZ); and nanoencapsulated benznidazole treatment (NBNZ). After eight treatment days, the animals were euthanized for sample collection. Results: The peak of parasitemia was at day 7 p.i., and the BNZ and NBNZ controlled and reduced the parasite rate but showed no efficacy in terms of total elimination of parasites analyzed by RT-PCR in both infected groups. The infection promotes significant anemia, leukopenia, and thrombocytopenia, which the BNZ improves. There was an increase in AChE activity during infection, leading to a pro-inflammatory response and an increase in M1 and M2 mACh receptors in the BNZ group, showing that the treatment interacted with the cholinergic pathway. In addition, a pro-oxidative response was characterized in the infection and mainly in the infected BNZ and NBNZ groups. The histopathological analysis showed significative splenomegaly and inflammatory infiltrate in the heart, liver, and spleen. Conclusions: The administration of the BNZ or NBNZ reverses hematological, hepatic, and renal alterations through cholinergic signaling and stimulates a pro-inflammatory response during acute T. cruzi infection.

The mitochondrial uncoupler 2,4-dinitrophenol modulates inflammatory and oxidative responses in Trypanosoma cruzi-induced acute myocarditis in mice

By uncoupling oxidative phosphorylation, 2,4-dinitrophenol (DNP) attenuates reactive oxygen species (ROS) biosynthesis, which are known to aggravate infectious myocarditis in Chagas disease. Thus, the impact of DNP-based chemotherapy on Trypanosoma cruzi-induced acute myocarditis was investigated. C56BL/6 mice uninfected and infected untreated and treated daily with 100 mg/kg benznidazole (Bz, reference drug), 5 and 10 mg/kg DNP by gavage for 11 days after confirmation of T. cruzi infection were investigated. Twenty-four hours ​after the last treatment, the animals were euthanized and the heart was collected for microstructural, immunological and biochemical analyses. T. cruzi inoculation induced systemic inflammation (e.g., cytokines and anti-T. cruzi IgG upregulation), cardiac infection (T. cruzi DNA), oxidative stress, inflammatory infiltrate and microstructural myocardial damage in untreated mice. DNP treatment aggravated heart infection and microstructural damage, which were markedly attenuated by Bz. DNP (10 mg/kg) was also effective in attenuating ROS (total ROS, H2O2, and O2-), nitric oxide (NO), lipid (malondialdehyde - MDA) and protein (protein carbonyl - PCn) oxidation, TNF, IFN-γ, IL-10, and MCP-1/CCL2, anti-T. cruzi IgG, cardiac troponin I levels, as well as inflammatory infiltrate and cardiac damage in T. cruzi-infected mice. Our findings indicate that DNP aggravated heart infection and microstructural cardiomyocytes damage in infected mice. These responses were related to the antioxidant and anti-inflammatory properties of DNP, which favors infection by weakening the pro-oxidant and pro-inflammatory protective mechanisms of the infected host. Conversely, Bz-induced cardioprotective effects combined effective anti-inflammatory and antiparasitic responses, which protect against heart infection, oxidative stress, and microstructural damage in Chagas disease.

Identification of host antioxidant effectors as thioridazine targets: Impact on cardiomyocytes infection and Trypanosoma cruzi-induced acute myocarditis

Phenothiazines inhibit antioxidant enzymes in trypanosomatids. However, potential interferences with host cell antioxidant defenses are central concerns in using these drugs to treat Trypanosoma cruzi-induced infectious myocarditis. Thus, the interaction of thioridazine (TDZ) with T. cruzi and cardiomyocytes antioxidant enzymes, and its impact on cardiomyocytes and cardiac infection was investigated in vitro and in vivo. Cardiomyocytes and trypomastigotes in culture, and mice treated with TDZ and benznidazole (Bz, reference antiparasitic drug) were submitted to microstructural, biochemical and molecular analyses. TDZ was more cytotoxic and less selective against T. cruzi than Bz in vitro. TDZ-pretreated cardiomyocytes developed increased infection rate, reactive oxygen species (ROS) production, lipid and protein oxidation; similar catalase (CAT) and superoxide dismutase (SOD) activity, and reduced glutathione's (peroxidase - GPx, S-transferase - GST, and reductase - GR) activity than infected untreated cells. TDZ attenuated trypanothione reductase activity in T. cruzi, and protein antioxidant capacity in cardiomyocytes, making these cells more susceptible to H2O2-based oxidative challenge. In vivo, TDZ potentiated heart parasitism, total ROS production, myocarditis, lipid and protein oxidation; as well as reduced GPx, GR, and GST activities compared to untreated mice. Benznidazole decreased heart parasitism, total ROS production, heart inflammation, lipid and protein oxidation in T. cruzi-infected mice. Our findings indicate that TDZ simultaneously interact with enzymatic antioxidant targets in cardiomyocytes and T. cruzi, potentiating the infection by inducing antioxidant fragility and increasing cardiomyocytes and heart susceptibility to parasitism, inflammation and oxidative damage.

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.

Immunopathological Mechanisms Underlying Cardiac Damage in Chagas Disease

In Chagas disease, the mechanisms involved in cardiac damage are an active field of study. The factors underlying the evolution of lesions following infection by Trypanosoma cruzi and, in some cases, the persistence of its antigens and the host response, with the ensuing development of clinically observable cardiac damage, are analyzed in this review.

MC, Concepción JL, Cáceres AJ. Consumption of Galactose by Trypanosoma cruzi Epimastigotes Generates Resistance against Oxidative Stress

In this study, we demonstrate that Trypanosoma cruzi epimastigotes previously grown in LIT medium supplemented with 20 mM galactose and exposed to sub-lethal concentrations of hydrogen peroxide (100 μM) showed two-fold and five-fold viability when compared to epimastigotes grown in LIT medium supplemented with two different glucose concentrations (20 mM and 1.5 mM), respectively. Similar results were obtained when exposing epimastigotes from all treatments to methylene blue 30 μM. Additionally, through differential centrifugation and the selective permeabilization of cellular membranes with digitonin, we found that phosphoglucomutase activity (a key enzyme in galactose metabolism) occurs predominantly within the cytosolic compartment. Furthermore, after partially permeabilizing epimastigotes with digitonin (0.025 mg × mg-1 of protein), intact glycosomes treated with 20 mM galactose released a higher hexose phosphate concentration to the cytosol in the form of glucose-1-phosphate, when compared to intact glycosomes treated with 20 mM glucose, which predominantly released glucose-6-phosphate. These results shine a light on T. cruzi's galactose metabolism and its interplay with mechanisms that enable resistance to oxidative stress.

The protective effects of Clerodendranthus spicatus (Thunb.) C. Y. Wu extract on oxidative stress induced by 2,2'-azo (2-methylpropamidine) dihydrochloride in HL-1 mouse cardiomyocytes

To investigate the protective effects of Clerodendranthus spicatus (Thunb.) C. Y. Wu extract (CSTE) on oxidative stress injury in HL-1 mouse cardiomyocytes induced by 2,2'-azo (2-methylpropamidine) dihydrochloride (AAPH, 1 mmol/L), HL-1 cells were co-cultured with different concentrations (10–100 μg/mL) of the CSTE for 24 h. A cell damage model was established by continuously culturing the cells in Dulbecco's Modified Eagle Medium plus AAPH for 4 h. Cell survival rates were measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay, and by measuring intracellular malondialdehyde (MDA) content. MDA and total reactive oxygen species (ROS) levels were determined by thiobarbituric acid colorimetry and the 2',7'-dihydrodichlorofluorescent sodium yellow diacetate probe, respectively. Apoptosis was measured by flow cytometry. The intracellular catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), glutathione s-transferase (GST), γ-glutamylcysteine synthetase (γ-GCS), and glutathione (GSH) contents were determined by colorimetric methods. CSTE content was determined by high performance liquid chromatography. The CSTE pretreatment improved survival rates in damaged HL-1 cells, reduced total intracellular ROS and MDA levels, and reduced apoptosis. The CSTE also increased the activities of the antioxidant enzymes (CAT, SOD, GSH-Px, and GST), as well as the γ-GCS and GSH levels in damaged cells. Real-time fluorescence quantitative polymerase chain reaction analysis indicated that the CSTE upregulated CAT, SOD1, and GSH-Px mRNA expression levels. Additionally, the CSTE reduced MDA and ROS levels in HL-1 cells by improving the endogenous antioxidant system; thus, alleviating the oxidative stress damage caused by AAPH. Our compositional analyses revealed that the CSTE contained caffeic acid, isoquercetin, rosmarinic acid, luteolin, and baicalin. The CSTE demonstrates antioxidant and protective effects in myocardial cells.

The repositioned drugs disulfiram/diethyldithiocarbamate combined to benznidazole: Searching for Chagas disease selective therapy, preventing toxicity and drug resistance

Chagas disease (CD) affects at least 6 million people in 21 South American countries besides several thousand in other nations all over the world. It is estimated that at least 14,000 people die every year of CD. Since vaccines are not available, chemotherapy remains of pivotal relevance. About 30% of the treated patients cannot complete the therapy because of severe adverse reactions. Thus, the search for novel drugs is required. Here we tested the benznidazole (BZ) combination with the repositioned drug disulfiram (DSF) and its derivative diethyldithiocarbamate (DETC) upon Trypanosoma cruzi in vitro and in vivo. DETC-BZ combination was synergistic diminishing epimastigote proliferation and enhancing selective indexes up to over 10-fold. DETC was effective upon amastigotes of the BZ- partially resistant Y and the BZ-resistant Colombiana strains. The combination reduced proliferation even using low concentrations (e.g., 2.5 µM). Scanning electron microscopy revealed membrane discontinuities and cell body volume reduction. Transmission electron microscopy revealed remarkable enlargement of endoplasmic reticulum cisternae besides, dilated mitochondria with decreased electron density and disorganized kinetoplast DNA. At advanced stages, the cytoplasm vacuolation apparently impaired compartmentation. The fluorescent probe H2-DCFDA indicates the increased production of reactive oxygen species associated with enhanced lipid peroxidation in parasites incubated with DETC. The biochemical measurement indicates the downmodulation of thiol expression. DETC inhibited superoxide dismutase activity on parasites was more pronounced than in infected mice. In order to approach the DETC effects on intracellular infection, peritoneal macrophages were infected with Colombiana trypomastigotes. DETC addition diminished parasite numbers and the DETC-BZ combination was effective, despite the low concentrations used. In the murine infection, the combination significantly enhanced animal survival, decreasing parasitemia over BZ. Histopathology revealed that low doses of BZ-treated animals presented myocardial amastigote, not observed in combination-treated animals. The picrosirius collagen staining showed reduced myocardial fibrosis. Aminotransferase de aspartate, Aminotransferase de alanine, Creatine kinase, and urea plasma levels demonstrated that the combination was non-toxic. As DSF and DETC can reduce the toxicity of other drugs and resistance phenotypes, such a combination may be safe and effective.

4-nitrobenzoylcoumarin potentiates the antiparasitic, anti-inflammatory and cardioprotective effects of benznidazole in a murine model of acute Trypanosoma cruzi infection

The anti-inflammatory and cardioprotective potential of coumarin metabolites in infectious myocarditis remains overlooked. Thus, the impact of the synthetic 4-nitrobenzoylcoumarin (4NB) alone and combined with benznidazole (Bz) in a murine model of Trypanosoma cruzi-induced acute myocarditis was investigated. Swiss mice infected with T. cruzi were randomized in 8 groups: uninfected, infected untreated or treated with 50 and 100 mg/kg 4NB or Bz alone and combined. Treatments were administered by gavage for 20 days. Cytokines (IL-2, IL-6, IL-10, IL-17, TNFα, and IFN-γ), immunoglobulin reactivity index (total IgG, IgG1, IgG2a and IgG2b), atrial natriuretic peptide (ANP), parasitemia, serum transaminases, heart and liver cellularity were analyzed. T. cruzi infection induced blood parasitism, heart and liver inflammation, upregulated all cytokines, IgG reactivity index, ANP and transaminase levels, determining 43% mortality in untreated mice. Transaminase levels, mean parasitemia, heart inflammation and ANP were reduced in 4NB-treated mice, reaching a 100% survival rate. Total survival (100%) was also obtained in all combinations of Bz and 4NB, which were effective in reducing blood parasitism, transaminases, cytokines and ANP levels, IgG reactivity index, liver and heart interstitial cellularity compared to 50 mg/kg Bz. Our findings indicated that 4NB alone and combined with Bz was well tolerated, showing no evidence of hepatotoxicity. Mainly in combination, these drugs exerted protective effects against T. cruzi-induced acute myocarditis by attenuating blood parasitism, systemic and heart inflammation. Thus, combinations based on 4NB and Bz are potentially relevant to develop new and more effective drug regimens for the treatment of T. cruzi-induced myocarditis.

Treatment of Trypanosoma evansi-Infected Mice With Eucalyptus camaldulensis Led to a Change in Brain Response and Spleen Immunomodulation

Surra is a parasitic disease caused by the eukaryotic, unicellular hemoprotozoan, Trypanosoma evansi, which affects the development of animal production and is widespread among both domestic and wild animals. As such, in this research, we studied the antiparasitic activity and the ameliorative impact of Eucalyptus camaldulensis leaf extracts (ELE) against T. evansi-induced brain injury and spleen immune response in mice. As a result, we found that ELE decreased the amount of trypanosomes in the blood and improved the weight loss caused by infection. In addition, ELE reduced the parasite-induced brain and spleen histopathological damage. The parasite affected the levels of dopamine and serotonin, but after treatment with ELE, their concentrations significantly decreased to 154 ± 7 and 258 ± 11 μg/g, respectively. We clearly observed the antioxidant activity of ELE because of its ability to increase the induced change in the brain's total antioxidant capacity and the nitric oxide level. The histopathological changes in the spleen also improved after ELE application. Based on our results, we concluded that ELE possesses antitrypanosomal antioxidant and protective effects in the brains of mice infected with T. evansi. Additional phytochemical screening and molecular studies are required to understand the mechanism underlying the effect of ELE.

Sex Differences in Cardiac Pathology of SARS-CoV2 Infected and Trypanosoma cruzi Co-infected Mice

Coronavirus disease-2019 (COVID-19) caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2; CoV2) is a deadly contagious infectious disease. For those who survive COVID-19, post-COVID cardiac damage greatly increases the risk of cardiomyopathy and heart failure. Currently, the number of COVID-related cases are increasing in Latin America, where a major COVID comorbidity is Chagas' heart disease, which is caused by the parasite Trypanosoma cruzi. However, the interplay between indeterminate Chagas disease and COVID-19 is unknown. We investigated the effect of CoV2 infection on heart pathology in T. cruzi infected mice (coinfected with CoV2 during the indeterminate stage of T. cruzi infection). We used transgenic human angiotensin-converting enzyme 2 (huACE2/hACE2) mice infected with CoV2, T. cruzi, or coinfected with both in this study. We found that the viral load in the hearts of coinfected mice is lower compared to the hearts of mice infected with CoV2 alone. We demonstrated that CoV2 infection significantly alters cardiac immune and energy signaling via adiponectin (C-ApN) and AMP-activated protein kinase (AMPK) signaling. Our studies also showed that increased β-adrenergic receptor (b-AR) and peroxisome proliferator-activated receptors (PPARs) play a major role in shifting the energy balance in the hearts of coinfected female mice from glycolysis to mitochondrial β-oxidation. Our findings suggest that cardiac metabolic signaling may differently regulate the pathogenesis of Chagas cardiomyopathy (CCM) in coinfected mice. We conclude that the C-ApN/AMPK and b-AR/PPAR downstream signaling may play major roles in determining the progression, severity, and phenotype of CCM and heart failure in the context of COVID.

The Oxidative Stress and Chronic Inflammatory Process in Chagas Disease: Role of Exosomes and Contributing Genetic Factors

Chagas disease is a neglected tropical disease caused by the flagellated protozoa Trypanosoma cruzi that affects several million people mainly in Latin American countries. Chagas disease has two phases, which are acute and chronic, both separated by an indeterminate time period in which the infected individual is relatively asymptomatic. The acute phase extends for 40-60 days with atypical and mild symptoms; however, about 30% of the infected patients will develop a symptomatic chronic phase, which is characterized by either cardiac, digestive, neurological, or endocrine problems. Cardiomyopathy is the most important and severe result of Chagas disease, which leads to left ventricular systolic dysfunction, heart failure, and sudden cardiac death. Most deaths are due to heart failure (70%) and sudden death (30%) resulting from cardiomyopathy. During the chronic phase, T. cruzi-infected macrophages respond with the production of proinflammatory cytokines and production of superoxide and nitric oxide by the NADPH oxidase 2 (NOX2) and inducible nitric oxide synthase (iNOS) enzymes, respectively. During the chronic phase, myocardial changes are produced as a result of chronic inflammation, oxidative stress, fibrosis, and cell death. The cellular inflammatory response is mainly the result of activation of the NF-κB-dependent pathway, which activates gene expression of inflammatory cytokines, leading to progressive tissue damage. The persisting production of reactive oxygen species (ROS) is the result of mitochondrial dysfunction in the cardiomyocytes. In this review, we will discuss inflammation and oxidative damage which is produced in the heart during the chronic phase of Chagas disease and recent evidence on the role of macrophages and the production of proinflammatory cytokines during the acute phase and the origin of macrophages/monocytes during the chronic phase of Chagas disease. We will also discuss the contributing factors and mechanisms leading to the chronic inflammation of the cardiac tissue during the chronic phase of the disease as well as the innate and adaptive host immune response. The contribution of genetic factors to the progression of the chronic inflammatory cardiomyopathy of chronic Chagas disease is also discussed. The secreted extracellular vesicles (exosomes) produced for both T. cruzi and infected host cells can play key roles in the host immune response, and those roles are described. Lastly, we describe potential treatments to attenuate the chronic inflammation of the cardiac tissue, designed to improve heart function in chagasic patients.

Physical Exercise Promotes a Reduction in Cardiac Fibrosis in the Chronic Indeterminate Form of Experimental Chagas Disease

Chagas disease (CD), caused by the protozoan Trypanosoma cruzi, is a neglected tropical disease and a health problem in Latin America. Etiological treatment has limited effectiveness in chronic CD; thus, new therapeutic strategies are required. The practice of physical exercises has been widely advocated to improve the quality of life of CD patients. The most frequent clinical CD manifestation is the chronic indeterminate form (CIF), and the effect of physical exercises on disease progression remains unknown. Here, in a CIF model, we aimed to evaluate the effect of physical exercises on cardiac histological, parasitological, mitochondrial, and oxidative metabolism, electro and echocardiographic profiles, and immunological features. To establish a CIF model, BALB/c and C57BL/6 mice were infected with 100 and 500 trypomastigotes of the Y T. cruzi strain. At 120 days postinfection (dpi), all mouse groups showed normal PR and corrected QT intervals and QRS complexes. Compared to BALB/c mice, C57BL/6 mice showed a lower parasitemia peak, mortality rate, and less intense myocarditis. Thus, C57BL/6 mice infected with 500 parasites were used for subsequent analyses. At 120 dpi, a decrease in cardiac mitochondrial oxygen consumption and an increase in reactive oxygen species (ROS) were detected. When we increased the number of analyzed mice, a reduced heart rate and slightly prolonged corrected QT intervals were detected, at 120 and 150 dpi, which were then normalized at 180 dpi, thus characterizing the CIF. Y-infected mice were subjected to an exercise program on a treadmill for 4 weeks (from 150 to 180 dpi), five times per week in a 30–60-min daily training session. At 180 dpi, no alterations were detected in cardiac mitochondrial and oxidative metabolism, which were not affected by physical exercises, although ROS production increased. At 120 and 180 dpi, comparing infected and non-infected mice, no differences were observed in the levels of plasma cytokines, indicating that a crucial biomarker of the systemic inflammatory profile was absent and not affected by exercise. Compared with sedentary mice, trained Y-infected mice showed similar parasite loads and inflammatory cells but reduced cardiac fibrosis. Therefore, our data show that physical exercises promote beneficial changes that may prevent CD progression.

Mitochondria as a Cellular Hub in Infection and Inflammation

Mitochondria are the energy center of the cell. They are found in the cell cytoplasm as dynamic networks where they adapt energy production based on the cell’s needs. They are also at the center of the proinflammatory response and have essential roles in the response against pathogenic infections. Mitochondria are a major site for production of Reactive Oxygen Species (ROS; or free radicals), which are essential to fight infection. However, excessive and uncontrolled production can become deleterious to the cell, leading to mitochondrial and tissue damage. Pathogens exploit the role of mitochondria during infection by affecting the oxidative phosphorylation mechanism (OXPHOS), mitochondrial network and disrupting the communication between the nucleus and the mitochondria. The role of mitochondria in these biological processes makes these organelle good targets for the development of therapeutic strategies. In this review, we presented a summary of the endosymbiotic origin of mitochondria and their involvement in the pathogen response, as well as the potential promising mitochondrial targets for the fight against infectious diseases and chronic inflammatory diseases.

Involvement of ectonucleotidases and purinergic receptor expression during acute Chagas disease in the cortex of mice treated with resveratrol and benznidazole

Chagas disease (CD) is caused by the parasite Trypanosoma cruzi. CD affects people worldwide, primarily in tropical areas. The central nervous system (CNS) is an essential site for T. cruzi persistence during infection. The protozoan may pass through the blood-brain barrier and may cause motor and cognitive neuronal damage. Once in the CNS, T. cruzi triggers immune responses that the purinergic system can regulate. Treatment for CD is based on benznidazole (BNZ); however, this agent has negative side-effects and is toxic to the host. For this reason, we investigated whether resveratrol (RSV), a potent antioxidant and neuroprotective molecule, would modulate purinergic signaling and RSV alone or in combination with BNZ would prevent changes in purinergic signaling and oxidative damage caused by T. cruzi. We infected mice with T. cruzi and treated them with RSV or BNZ for 8 days. Increases in ATP and ADP hydrolysis by NTPDase in the total cortex of infected animals were observed. The treatment with RSV in infected group diminished ATP, ADP, and AMP hydrolysis compared to infected group. The combination of RSV + BNZ decreased AMP hydrolysis in infected animals compared to the INF group, exerting an anti-inflammatory effect. RSV acted as a neuroprotector, decreasing adenosine levels. Infected animals presented an increase of P2X₇ and A_2A density of purine receptors. RSV reduced P2X₇ and A_2A and increased A1 density receptors in infected animals. In addition, infected animals showed higher TBARS and reactive oxygen species (ROS) levels than control. RSV diminished ROS levels in infected mice, possibly due to antioxidant properties. In short, we conclude that resveratrol could act as a neuroprotective molecule, probably preventing inflammatory changes caused by infection by T. cruzi, even though the mice experienced high levels of parasitemia.

Characterization and functional analysis of the proteins Prohibitin 1 and 2 in Trypanosoma cruzi

BACKGROUND

Chagas disease is the third most important neglected tropical disease. There is no vaccine available, and only two drugs are generally prescribed for the treatment, both of which with a wide range of side effects. Our study of T. cruzi PHBs revealed a pleiotropic function in different stages of the parasite, participating actively in the transformation of the non-infective replicative epimastigote form into metacyclic trypomastigotes and also in the multiplication of intracellular amastigotes.

METHODOLOGY/PRINCIPAL FINDINGS

To obtain and confirm our results, we applied several tools and techniques such as electron microscopy, immuno-electron microscopy, bioinformatics analysis and molecular biology. We transfected T. cruzi clones with the PHB genes, in order to overexpress the proteins and performed a CRISPR/Cas9 disruption to obtain partially silenced PHB1 parasites or completely silenced PHB2 parasites. The function of these proteins was also studied in the biology of the parasite, specifically in the transformation rate from non-infective forms to the metacyclic infective forms, and in their capacity of intracellular multiplication.

CONCLUSION/SIGNIFICANCE

This research expands our understanding of the functions of PHBs in the life cycle of the parasite. It also highlights the protective role of prohibitins against ROS and reveals that the absence of PHB2 has a lethal effect on the parasite, a fact that could support the consideration of this protein as a possible target for therapeutic action.

Starvation and pH stress conditions induced mitochondrial dysfunction, ROS production and autophagy in Trypanosoma cruzi epimastigotes

Chagas disease is a neglected illness endemic in Latin America that mainly affects rural populations. The etiological agent of Chagas disease is the protozoan Trypanosoma cruzi, which has three different parasite stages and a dixenous life cycle that includes colonization of the vertebrate and invertebrate hosts. During its life cycle, T. cruzi is subjected to stress conditions, including variations in nutrient availability and pH, which impact parasite survival and differentiation. The plasticity of mitochondrial function in trypanosomatids has been defined as mitochondrial activity related to substrate availability. Thus, mitochondrial remodeling and autophagy, which is a constitutive cellular process of turnover and recycling of cellular components, may constitute a response to the nutritional and pH stress in the host. To assess these processes, epimastigotes were subjected to acidic, alkaline, and nutritional stress conditions, and mitochondrial function and its influence on the autophagic process were evaluated. Our data demonstrated that the three stress conditions affected the mitochondrial structure, inducing organelle swelling and impaired oxidative phosphorylation. Stressed epimastigotes produced increased ROS levels and overexpressed antioxidant enzymes. The stress conditions resulted in an increase in the number of autophagosomes and exacerbated the expression of different autophagy-related genes (Atgs). A correlation between mitochondrial dysfunction and autophagic phenotypes was also observed. After 24 h, acid stress and nutritional deprivation induced metacyclogenesis phenotypes (mitochondrial remodeling and autophagy). On the other hand, alkaline stress was transient due to insect blood feeding and culminated in an increase in autophagic flux as a survival mechanism.

PARP1-cGAS-NF-κB pathway of proinflammatory macrophage activation by extracellular vesicles released during Trypanosoma cruzi infection and Chagas disease

Trypanosoma cruzi (T. cruzi) is the etiological agent of Chagas cardiomyopathy. In the present study, we investigated the role of extracellular vesicles (Ev) in shaping the macrophage (Mφ) response in progressive Chagas disease (CD). We purified T. cruzi Ev (TcEv) from axenic parasite cultures, and T. cruzi-induced Ev (TEv) from the supernatants of infected cells and plasma of acutely and chronically infected wild-type and Parp1-/- mice. Cultured (Raw 264.7) and bone-marrow Mφ responded to TcEV and TEv with a profound increase in the expression and release of TNF-α, IL-6, and IL-1β cytokines. TEv produced by both immune (Mφ) and non-immune (muscle) cells were proinflammatory. Chemical inhibition or genetic deletion of PARP1 (a DNA repair enzyme) significantly depressed the TEv-induced transcriptional and translational activation of proinflammatory Mφ response. Oxidized DNA encapsulated by TEv was necessary for PARP1-dependent proinflammatory Mφ response. Inhibition studies suggested that DNA-sensing innate immune receptors (cGAS>>TLR9) synergized with PARP1 in signaling the NFκB activation, and inhibition of PARP1 and cGAS resulted in >80% inhibition of TEv-induced NFκB activity. Histochemical studies showed intense inflammatory infiltrate associated with profound increase in CD11b+CD68+TNF-α+ Mφ in the myocardium of CD wild-type mice. In comparison, chronically infected Parp1-/- mice exhibited low-to-moderate tissue inflammation, >80% decline in myocardial infiltration of TNF-α+ Mφ, and no change in immunoregulatory IL-10+ Mφ. We conclude that oxidized DNA released with TEv signal the PARP1-cGAS-NF-κB pathway of proinflammatory Mφ activation and worsens the chronic inflammatory pathology in CD. Small molecule antagonists of PARP1-cGAS signaling pathway would potentially be useful in reprogramming the Mφ activation and controlling the chronic inflammation in CD.

Epidemiology and pathogenesis of maternal-fetal transmission of Trypanosoma cruzi and a case for vaccine development against congenital Chagas disease

Trypanos o ma cruzi (T. cruzi or Tc) is the causative agent of Chagas disease (CD). It is common for patients to suffer from non-specific symptoms or be clinically asymptomatic with acute and chronic conditions acquired through various routes of transmission. The expecting women and their fetuses are vulnerable to congenital transmission of Tc. Pregnant women face formidable health challenges because the frontline antiparasitic drugs, benznidazole and nifurtimox, are contraindicated during pregnancy. However, it is worthwhile to highlight that newborns can be cured if they are diagnosed and given treatment in a timely manner. In this review, we discuss the pathogenesis of maternal-fetal transmission of Tc and provide a justification for the investment in the development of vaccines against congenital CD.

Measuring mitochondrial respiration in adherent cells infected with Trypanosoma cruzi Chagas, 1909 using Seahorse extracellular flux analyser

Infection with Trypanosoma cruzi Chagas, 1909 is reported to increase the production of reactive oxygen species in patients with Chagas disease. Mitochondria dysfunction, host inflammatory response and inadequate antioxidant response are described as the main factors leading to oxidative stress during acute and chronic stages of the disease. The Seahorse XFe24 extracellular flux platform allows energy metabolism determination through mitochondrial respiration and glycolysis measurements. XFe24 platform can be used in in vitro models of T. cruzi-infected cells, which allow the assessment and even modulation of endogenous conditions of infected cells, generating readouts of real-time cellular bioenergetics changes. In this protocol, we standardised the use of XFe24 technology in T. cruzi infected AC16 cardiomyocytes and SGHPL-5 trophoblasts. In addition, we provide a list of optimised assay specifications, advantages and critical steps to be considered during the process. Cardiomyocytes and trophoblasts are attractive target cells to evaluate the metabolic environment in acute, chronic and congenital Chagas transmission scenarios.

Could pre-infection exercise training improve the efficacy of specific antiparasitic chemotherapy for Chagas disease?

Considering a potential exercise-drug interaction, we investigated whether exercise training could improve the efficacy of specific antiparasitic chemotherapy in a rodent model of Chagas disease. Wistar rats were randomized into five groups: sedentary and uninfected (CT); sedentary and infected (SI); sedentary, infected and treated (SIT); trained and infected (TI); trained, infected and treated (TIT). After 9-weeks running training, the animals were infected with T. cruzi and followed up for 4 weeks, receiving 100 mg kg-1 day-1 benznidazole. No evidence of myocarditis was observed in CT animals. TI animals exhibited reduced parasitemia, myocarditis, and reactive tissue damage compared to SI animals, in addition to increased IFN-γ, IL-4, IL-10, heart non-protein antioxidant (NPA) levels and glutathione-s transferase activity (P < 0.05). The CT, SIT and TIT groups presented similar reductions in parasitemia, cytokines (IFN-γ, TNF-α, IL-4, IL-10, IL-17 and MCP-1), inflammatory infiltrate, oxidative heart damage and antioxidant enzymes activity compared to SI and TI animals, as well as reduced heart microstructural remodeling (P < 0.05). By modulating heart inflammation and redox metabolism, exercise training exerts a protective effect against T. cruzi infection in rats. However, the antiparasitic and cardioprotective effects of benznidazole chemotherapy are more pronounced, determining similar endpoints in sedentary and trained T. cruzi-infected rats.

Inhibition of ER Stress by 2-Aminopurine Treatment Modulates Cardiomyopathy in a Murine Chronic Chagas Disease Model

Trypanosoma cruzi infection results in debilitating cardiomyopathy, which is a major cause of mortality and morbidity in the endemic regions of Chagas disease (CD). The pathogenesis of Chagasic cardiomyopathy (CCM) has been intensely studied as a chronic inflammatory disease until recent observations reporting the role of cardio-metabolic dysfunctions. In particular, we demonstrated accumulation of lipid droplets and impaired cardiac lipid metabolism in the hearts of cardiomyopathic mice and patients, and their association with impaired mitochondrial functions and endoplasmic reticulum (ER) stress in CD mice. In the present study, we examined whether treating infected mice with an ER stress inhibitor can modify the pathogenesis of cardiomyopathy during chronic stages of infection. T. cruzi infected mice were treated with an ER stress inhibitor 2-Aminopurine (2AP) during the indeterminate stage and evaluated for cardiac pathophysiology during the subsequent chronic stage. Our study demonstrates that inhibition of ER stress improves cardiac pathology caused by T. cruzi infection by reducing ER stress and downstream signaling of phosphorylated eukaryotic initiation factor (P-elF2α) in the hearts of chronically infected mice. Importantly, cardiac ultrasound imaging showed amelioration of ventricular enlargement, suggesting that inhibition of ER stress may be a valuable strategy to combat the progression of cardiomyopathy in Chagas patients.

Targeting mitochondrial dysfunction and oxidative stress in heart failure: Challenges and opportunities

Mitochondrial dysfunction characterized by impaired bioenergetics, oxidative stress and aldehydic load is a hallmark of heart failure. Recently, different research groups have provided evidence that selective activation of mitochondrial detoxifying systems that counteract excessive accumulation of ROS, RNS and reactive aldehydes is sufficient to stop cardiac degeneration upon chronic stress, such as heart failure. Therefore, pharmacological and non-pharmacological approaches targeting mitochondria detoxification may play a critical role in the prevention or treatment of heart failure. In this review we discuss the most recent findings on the central role of mitochondrial dysfunction, oxidative stress and aldehydic load in heart failure, highlighting the most recent preclinical and clinical studies using mitochondria-targeted molecules and exercise training as effective tools against heart failure.

Purinergic Antagonist Suramin Aggravates Myocarditis and Increases Mortality by Enhancing Parasitism, Inflammation, and Reactive Tissue Damage in Trypanosoma cruzi-Infected Mice

Suramin (Sur) acts as an ecto-NTPDase inhibitor in Trypanosoma cruzi and a P2-purinoceptor antagonist in mammalian cells. Although the potent antitrypanosomal effect of Sur has been shown in vitro, limited evidence in vivo suggests that this drug can be dangerous to T. cruzi-infected hosts. Therefore, we investigated the dose-dependent effect of Sur-based chemotherapy in a murine model of Chagas disease. Seventy uninfected and T. cruzi-infected male C57BL/6 mice were randomized into five groups: SAL = uninfected; INF = infected; SR5, SR10, and SR20 = infected treated with 5, 10, or 20 mg/kg Sur. In addition to its effect on blood and heart parasitism, the impact of Sur-based chemotherapy on leucocytes myocardial infiltration, cytokine levels, antioxidant defenses, reactive tissue damage, and mortality was analyzed. Our results indicated that animals treated with 10 and 20 mg/kg Sur were disproportionally susceptible to T. cruzi, exhibiting increased parasitemia and cardiac parasitism (amastigote nests and parasite load (T. cruzi DNA)), intense protein, lipid and DNA oxidation, marked myocarditis, and mortality. Animals treated with Sur also exhibited reduced levels of nonprotein antioxidants. However, the upregulation of catalase, superoxide dismutase, and glutathione-S-transferase was insufficient to counteract reactive tissue damage and pathological myocardial remodeling. It is still poorly understood whether Sur exerts a negative impact on the purinergic signaling of T. cruzi-infected host cells. However, our findings clearly demonstrated that through enhanced parasitism, inflammation, and reactive tissue damage, Sur-based chemotherapy contributes to aggravating myocarditis and increasing mortality rates in T. cruzi-infected mice, contradicting the supposed relevance attributed to this drug for the treatment of Chagas disease.

Relevance of Trypanothione Reductase Inhibitors on Trypanosoma cruzi Infection: A Systematic Review, Meta-Analysis, and In Silico Integrated Approach

Due to the rudimentary antioxidant defenses in Trypanosoma cruzi, disruptors of redox balance are promising candidates for new antitrypanosomal drugs. We developed an integrated model based on systematic review, meta-analyses, and molecular modeling to evaluate the effect of trypanothione reductase (TR) inhibitors in T. cruzi infections. Our findings indicated that the TR inhibitors analyzed were effective in reducing parasitemia and mortality due to Trypanosoma cruzi infection in animal models. The most investigated drugs (clomipramine and thioridazine) showed no beneficial effects on the occurrence of infection-related electrocardiographic abnormalities or the affinity and density of cardiac β-adrenergic receptors. The affinity between the tested ligands and the active site of TR was confirmed by molecular docking. However, the molecular affinity score was unable to explain TR inhibition and T. cruzi death in vitro or the antiparasitic potential of these drugs when tested in preclinical models of T. cruzi infection. The divergence of in silico, in vitro, and in vivo findings indicated that the anti-T. cruzi effects of the analyzed drugs were not restricted to TR inhibition. As in vivo studies on TR inhibitors are still scarce and exhibit methodological limitations, mechanistic and highly controlled studies are required to improve the quality of evidence.

Characterization of Trypanosoma cruzi MutY DNA glycosylase ortholog and its role in oxidative stress response

Trypanosoma cruzi is a protozoan parasite and the causative agent of Chagas disease. Like most living organisms, it is susceptible to oxidative stress, and must adapt to distinct environments. Hence, DNA repair is essential for its survival and the persistence of infection. Therefore, we studied whether T. cruzi has a homolog counterpart of the MutY enzyme (TcMYH), important in the DNA Base Excision Repair (BER) mechanism. Analysis of T. cruzi genome database showed that this parasite has a putative MutY DNA glycosylase sequence. We performed heterologous complementation assays using this genomic sequence. TcMYH complemented the Escherichia coli MutY- strain, reducing the mutation rate to a level similar to wild type. In in vitro assays, TcMYH was able to remove an adenine that was opposite to 8-oxoguanine. We have also constructed a T. cruzi lineage that overexpresses MYH. Although in standard conditions this lineage has similar growth to control cells, the overexpressor is more sensitive to hydrogen peroxide and glucose oxidase than the control, probably due to accumulation of AP sites in its DNA. Localization experiments with GFP-fused TcMYH showed this enzyme is present in both nucleus and mitochondrion. QPCR and MtOX results reinforce the presence and function of TcMYH in these two organelles. Our data suggest T. cruzi has a functional MYH DNA glycosylase, which participates in nuclear and mitochondrial DNA Base Excision Repair.

Inhibition of NFE2L2-Antioxidant Response Element Pathway by Mitochondrial Reactive Oxygen Species Contributes to Development of Cardiomyopathy and Left Ventricular Dysfunction in Chagas Disease

AIMS

We investigated the effects of mitochondrial reactive oxygen species (mtROS) on nuclear factor (erythroid 2)-like 2 (NFE2L2) transcription factor activity during Trypanosoma cruzi (Tc) infection and determined whether enhancing the mtROS scavenging capacity preserved the heart function in Chagas disease.

RESULTS

C57BL/6 wild type (WT, female) mice infected with Tc exhibited myocardial loss of mitochondrial membrane potential, complex II (CII)-driven coupled respiration, and ninefold increase in mtROS production. In vitro and in vivo studies showed that Tc infection resulted in an ROS-dependent decline in the expression, nuclear translocation, antioxidant response element (ARE) binding, and activity of NFE2L2, and 35-99% decline in antioxidants' (gamma-glutamyl cysteine synthase [γGCS], heme oxygenase-1 [HO1], glutamate-cysteine ligase modifier subunit [GCLM], thioredoxin (Trx), glutathione S transferase [GST], and NAD(P)H dehydrogenase, quinone 1 [NQO1]) expression. An increase in myocardial and mitochondrial oxidative adducts, myocardial interventricular septum thickness, and left ventricle (LV) mass, a decline in LV posterior wall thickness, and disproportionate synthesis of collagens (COLI/COLIII), αSMA, and SM22α were noted in WT.Tc mice. Overexpression of manganese superoxide dismutase (MnSOD) in cultured cells (HeLa or cardiomyocytes) and MnSOD^tg mice preserved the NFE2L2 transcriptional activity and antioxidant/oxidant balance, and cardiac oxidative and fibrotic pathology were significantly decreased in MnSOD^tg.Tc mice. Importantly, echocardiography finding of a decline in LV systolic (stroke volume, cardiac output, ejection fraction) and diastolic (early/late peak filling ratio, myocardial performance index) function in WT.Tc mice was abolished in MnSOD^tg.Tc mice. Innovation and Conclusion: The mtROS inhibition of NFE2L2/ARE pathway constitutes a key mechanism in signaling the fibrotic gene expression and evolution of chronic cardiomyopathy. Preserving the NFE2L2 activity arrested the mitochondrial and cardiac oxidative stress, cardiac fibrosis, and heart failure in Chagas disease. Antioxid. Redox Signal. 27, 550-566.

Melatonin: Antioxidant and modulatory properties in age-related changes during Trypanosoma cruzi infection

The purpose of this study was to investigate the effects of melatonin on selected biomarkers of innate and humoral immune response as well as the antioxidant/oxidant status (superoxide dismutase-SOD and reduced glutathione levels (GSH) to understand whether age-related changes would influence the development of acute Trypanosoma cruzi (T. cruzi) infection. Young- (5 weeks) and middle-aged (18 months) Wistar rats were orally treated with melatonin (gavage) (05 mg/kg/day), 9 days after infection. A significant increase in both SOD activity and GSH levels was found in plasma from all middle-aged melatonin-treated animals. Melatonin triggered enhanced expression of major histocompatibility class II (MHC-II) antigens on antigen-presenting cell (APC) and peritoneal macrophages in all treated animals. High levels of CD4⁺ CD28-negative T cells (*P<.05) were detected in middle-aged control animals. Melatonin induced a significant reduction (***P<.001) in CD28-negative in CD4⁺ and CD8⁺ T cells in middle-aged control animals. Contrarily, the same group displayed upregulated CD4⁺ CD28⁺ T and CD8⁺ CD28⁺ T cells. Melatonin also triggered an upregulation of CD80 and CD86 expression in all young-treated groups. Significant percentages of B and spleen dendritic cells in middle-aged infected and treated animals were observed. Our data reveal new features of melatonin action in inhibiting membrane lipid peroxidation, through the reduction in 8-isoprostane, upregulating the antioxidant defenses and triggering an effective balance in the antioxidant/oxidant status during acute infection. The ability of melatonin to counteract the immune alterations induced by aging added further support to its use as a potential therapeutic target not only for T. cruzi infection but also for other immunocompromised states.

Evaluation of antioxidant therapy in experimental Chagas disease

INTRODUCTION:

Stimulation of inflammatory mediators such as cytokines and chemokines may cause oxidative stress in Chagas disease. In this study, we evaluated the merit of vitamins C and E as antioxidant therapy to minimize the oxidative stress-induced damage in an experimental model of Chagas disease.

METHODS:

Ninety-six Swiss mice were infected with Trypanosoma cruzi QM2 and treated with vitamins C, E, or both (C/E) for 60 and 120 days, and their effects compared to placebo administration were evaluated in the acute and chronic disease phases.

RESULTS:

There was no difference in parasitemia among treatment groups. However, histological analysis showed more severe inflammation in the skeletal muscle in the vitamin supplementation groups at both the acute and chronic phases. Biochemical analyses during the acute phase showed increased ferric-reducing ability of plasma (FRAP) and glutathione (GSH) levels in the vitamin C and C/E groups. In the chronic phase, a decrease in GSH levels was observed in the vitamin E group and a decrease in thiobarbituric acid reactive substances (TBARS) was observed in the vitamin C/E group. Moreover, there was a decrease in TBARS in the cardiac tissues of the vitamin C and C/E groups compared to that of the placebo group, although this level was greater in the vitamin E group than in the vitamin C group.

CONCLUSIONS:

The antioxidant action of vitamins C and E reduced oxidative stress in both the acute and chronic phases of Chagas disease, with a marked effect from joint administration, indicating their inherent synergism.

Parasite control and skeletal myositis in Trypanosoma cruzi-infected and exercised rats

Non-pharmacological strategies have been rarely described in the treatment of infectious diseases. Although exercise training has been recently incorporated in the clinical management of Chagas disease, the rationale basis that supports this indication is poorly understood. Thus, we investigated the effect of an aerobic exercise on the parasitism, inflammation and oxidative tissue damage in a murine model of Trypanosoma cruzi-induced skeletal myositis. Wistar rats were randomized into four groups: trained not infected (TNI) and infected (TI), sedentary not infected (SNI) and infected (SI). A running training program was administered 5days/week for 9 weeks. Then, infected animals were inoculated with T. cruzi and followed up for another 9 weeks. Exercise training induced beneficial adaptations by increasing time to fatigue and lactate threshold in TNI and TI animals. SI animals presented higher parasitemia, skeletal muscle parasitism, cell necrosis, leukocyte infiltration, cytokines levels, reactive oxygen species and nitric oxide production, thiobarbituric acid reactive substances, carbonyl proteins, myosin heavy chain I depletion, and increased catalase (CAT) and superoxide dismutase (SOD) activities. Beyond attenuation in all these variables, TI animals showed reduced TNF-α, CCL-2/MCP-1 and CX3CL1, and increased IL-10 muscle levels. Furthermore, these animals presented higher CAT and SOD activities and reduced lipid and protein oxidation. Taken together, our findings indicated that exercise training induced a protective phenotype in T. cruzi-infected mice, enhancing host defenses against the parasite and attenuating the pathological remodeling associated with skeletal myositis, aspects potentially associated to an improved immunological and redox balance in infected animals.

Effects of astaxanthin in mice acutely infected with Trypanosoma cruzi

During Trypanosoma cruzi infection, oxidative stress is considered a contributing factor for dilated cardiomyopathy development. In this study, the effects of astaxanthin (ASTX) were evaluated as an alternative drug treatment for Chagas disease in a mouse model during the acute infection phase, given its anti-inflammatory, immunomodulating, and anti-oxidative properties. ASTX was tested in vitro in parasites grown axenically and in co-culture with Vero cells. In vivo tests were performed in BALB/c mice (4-6 weeks old) infected with Trypanosoma cruzi and supplemented with ASTX (10 mg/kg/day) and/or nifurtimox (NFMX; 100 mg/kg/day). Results show that ASTX has some detrimental effects on axenically cultured parasites, but not when cultured with mammalian cell monolayers. In vivo, ASTX did not have any therapeutic value against acute Trypanosoma cruzi infection, used either alone or in combination with NFMX. Infected animals treated with NFMX or ASTX/NFMX survived the experimental period (60 days), while infected animals treated only with ASTX died before day 30 post-infection. ASTX did not show any effect on the control of parasitemia; however, it was associated with an increment in focal heart lymphoplasmacytic infiltration, a reduced number of amastigote nests in cardiac tissue, and less hyperplasic spleen follicles when compared to control groups. Unexpectedly, ASTX showed a negative effect in infected animals co-treated with NFMX. An increment in parasitemia duration was observed, possibly due to ASTX blocking of free radicals, an anti-parasitic mechanism of NFMX. In conclusion, astaxanthin is not recommended during the acute phase of Chagas disease, either alone or in combination with nifurtimox.

Diet Modulates Adipose Tissue Oxidative Stress in a Murine Acute Chagas Model

Chagas disease, also known as American trypanosomiasis, is a tropical parasitic disease caused by the protozoan Trypanosoma cruzi. T. cruzi targets adipose tissue, which serves as a reservoir of this parasite. T. cruzi infection of adipose tissue is characterized by increased lipolysis, oxidative stress, and parasitemia. High fat diet (HFD) decreases lipolysis and increases the survival rate in the mice infected with T. cruzi during acute infection. However, the effect of HFD on oxidative stress in adipose tissue has not been examined in detail. In the present study we evaluated the effect of HFD on oxidative stress markers in both white and brown adipose tissues (WAT and BAT) during acute infection. We used qPCR to examine the mRNA expression levels of genes involved in several antioxidant defence systems, such as those acting in ROS metabolism, peroxidases, and relevant oxygen transporter genes. The result of our study showed that HFD regulates the expression levels of oxidative stress genes in adipose tissues and that these effects are often different in WAT and BAT. For instance, while HFD down-regulated the levels of most antioxidant genes in both WAT and BAT, it differentially affected the expression pattern of genes involved in ROS metabolism (e.g. peroxidases) in WAT and BAT tissues of infected mice. Together with our previous studies, these findings show that infection and diet both regulate antioxidant enzymes and other oxidative stress defenses in mouse adipose tissues during acute T. cruzi infection.

Diet regulates liver autophagy differentially in murine acute Trypanosoma cruzi infection

Chagas disease is a tropical parasitic disease caused by the protozoan Trypanosoma cruzi, which affects about ten million people in its endemic regions of Latin America. After the initial acute stage of infection, 60-80% of infected individuals remain asymptomatic for several years to a lifetime; however, the rest develop the debilitating symptomatic stage, which affects the nervous system, digestive system, and heart. The challenges of Chagas disease have become global due to immigration. Despite well-documented dietary changes accompanying immigration, as well as a transition to a western style diet in the Chagas endemic regions, the role of host metabolism in the pathogenesis of Chagas disease remains underexplored. We have previously used a mouse model to show that host diet is a key factor regulating cardiomyopathy in Chagas disease. In this study, we investigated the effect of a high-fat diet on liver morphology and physiology, lipid metabolism, immune signaling, energy homeostasis, and stress responses in the murine model of acute T. cruzi infection. Our results indicate that in T. cruzi-infected mice, diet differentially regulates several liver processes, including autophagy, a stress response mechanism, with corresponding implications for human Chagas disease patients.

Nonsteroidal anti-inflammatory is more effective than anti-oxidant therapy in counteracting oxidative/nitrosative stress and heart disease in T. cruzi-infected mice

We compared the relevance of ibuprofen, vitamins C and E to control oxidative/nitrosative stress and heart disease in mice infected by Trypanosoma cruzi. Swiss mice were randomized into five groups: control, uninfected; infected without treatment; and infected treated with vitamins C, E or ibuprofen. Animals were inoculated with 2000 trypomastigote forms of T. cruzi. After 20 days, infected mice presented reduced vitamin C and E tissue levels, high cytokines (interferon gamma, tumour necrosis factor-α, interleukin 10 and chemokine ligand 2), prostaglandin F2α (PGF2α ) and nitric oxide (NO) cardiac production, intense myocarditis and reactive tissue damage, which was directly correlated with the intensity of the inflammatory infiltrate and the degree of pathological cardiac remodelling. Vitamins C and E supplementation were irrelevant to counteract reactive tissue damage and myocarditis in infected animals. Conversely, ibuprofen reduced tissue levels of cytokines, PGF2α and NO, as well as lipid and protein oxidation, antioxidant enzyme activity and the cardiac damage, without interfering with heart parasitism. Our results do not support the applicability of vitamin C and E supplementation in the management of acute Chagas cardiomyopathy. By controlling the inflammatory infiltrate, anti-inflammatory-based therapy proved to be a more rational strategy than a direct antioxidant therapy in attenuating oxidative/nitrosative stress and cardiac damage.

SIRT1-PGC1α-NFκB Pathway of Oxidative and Inflammatory Stress during Trypanosoma cruzi Infection: Benefits of SIRT1-Targeted Therapy in Improving Heart Function in Chagas Disease

Chronic chagasic cardiomyopathy (CCM) is presented by increased oxidative/inflammatory stress and decreased mitochondrial bioenergetics. SIRT1 senses the redox changes and integrates mitochondrial metabolism and inflammation; and SIRT1 deficiency may be a major determinant in CCM. To test this, C57BL/6 mice were infected with Trypanosoma cruzi (Tc), treated with SIRT1 agonists (resveratrol or SRT1720), and monitored during chronic phase (~150 days post-infection). Resveratrol treatment was partially beneficial in controlling the pathologic processes in Chagas disease. The 3-weeks SRT1720 therapy provided significant benefits in restoring the left ventricular (LV) function (stroke volume, cardiac output, ejection fraction etc.) in chagasic mice, though cardiac hypertrophy presented by increased thickness of the interventricular septum and LV posterior wall, increased LV mass, and disproportionate synthesis of collagens was not controlled. SRT1720 treatment preserved the myocardial SIRT1 activity and PGC1α deacetylation (active-form) that were decreased by 53% and 9-fold respectively, in chagasic mice. Yet, SIRT1/PGC1α-dependent mitochondrial biogenesis (i.e., mitochondrial DNA content, and expression of subunits of the respiratory complexes and mtDNA replication machinery) was not improved in chronically-infected/SRT1720-treated mice. Instead, SRT1720 therapy resulted in 2-10-fold inhibition of Tc-induced oxidative (H2O2 and advanced oxidation protein products), nitrosative (inducible nitric oxide synthase, 4-hydroxynonenal, 3-nitrotyrosine), and inflammatory (IFNγ, IL1β, IL6 and TNFα) stress and inflammatory infiltrate in chagasic myocardium. These benefits were delivered through SIRT1-dependent inhibition of NFκB transcriptional activity. We conclude that Tc inhibition of SIRT1/PGC1α activity was not a key mechanism in mitochondrial biogenesis defects during Chagas disease. SRT1720-dependent SIRT1 activation led to suppression of NFκB transcriptional activity, and subsequently, oxidative/nitrosative and inflammatory pathology were subdued, and antioxidant status and LV function were enhanced in chronic chagasic cardiomyopathy.

Expression and the Peculiar Enzymatic Behavior of the Trypanosoma cruzi NTH1 DNA Glycosylase

Trypanosoma cruzi, the etiological agent of Chagas’ disease, presents three cellular forms (trypomastigotes, epimastigotes and amastigotes), all of which are submitted to oxidative species in its hosts. However, T. cruzi is able to resist oxidative stress suggesting a high efficiency of its DNA repair machinery.The Base Excision Repair (BER) pathway is one of the main DNA repair mechanisms in other eukaryotes and in T. cruzi as well. DNA glycosylases are enzymes involved in the recognition of oxidative DNA damage and in the removal of oxidized bases, constituting the first step of the BER pathway. Here, we describe the presence and activity of TcNTH1, a nuclear T. cruzi DNA glycosylase. Surprisingly, purified recombinant TcNTH1 does not remove the thymine glycol base, but catalyzes the cleavage of a probe showing an AP site. The same activity was found in epimastigote and trypomastigote homogenates suggesting that the BER pathway is not involved in thymine glycol DNA repair. TcNTH1 DNA-binding properties assayed in silico are in agreement with the absence of a thymine glycol removing function of that parasite enzyme. Over expression of TcNTH1 decrease parasite viability when transfected epimastigotes are submitted to a sustained production of H₂O₂.Therefore, TcNTH1 is the only known NTH1 orthologous unable to eliminate thymine glycol derivatives but that recognizes and cuts an AP site, most probably by a beta-elimination mechanism. We cannot discard that TcNTH1 presents DNA glycosylase activity on other DNA base lesions. Accordingly, a different DNA repair mechanism should be expected leading to eliminate thymine glycol from oxidized parasite DNA. Furthermore, TcNTH1 may play a role in the AP site recognition and processing.

Chemotherapeutic efficacy of phosphodiesterase inhibitors in chagasic cardiomyopathy

Molecular mechanisms of Trypanosoma cruzi (Tc)-induced Chagasic cardiomyopathy (CCM) are not well understood. The NO-cGMP-PKG1α pathway maintains cardiac homeostasis and inotropy and may be disturbed due to phosphodiesterase (PDE5)-mediated cGMP catabolism in CCM. To test this, C57BL/6 mice were infected with T. cruzi, and after the control of acute parasitemia (∼45 days post-infection), given sildenafil (SIL) (1 mg/kg) treatment for 3 weeks that ended long before the chronic disease phase (∼150 days post-infection). The PDE5 was increased and cGMP/PKG activity was decreased in chagasic myocardium. Transthoracic echocardiography revealed left ventricular (LV) systolic function, that is, stroke volume, cardiac output, and ejection fraction, was significantly decreased in chagasic mice. SIL treatment resulted in normal levels of PDE5 and cGMP/PKG activity and preserved the LV function. The cardioprotective effects of SIL were provided through inhibition of cardiac collagenosis and chronic inflammation that otherwise were pronounced in CCM. Further, SIL treatment restored the mitochondrial DNA–encoded gene expression, complex I–dependent (but not complex II–dependent) ADP-coupled respiration, and oxidant/antioxidant balance in chagasic myocardium. In vitro studies in cardiomyocytes verified that SIL conserved the redox metabolic state and cellular health via maintaining the antioxidant status that otherwise was compromised in response to T. cruzi infection. We conclude that SIL therapy was useful in controlling the LV dysfunction and chronic pathology in CCM.

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Mice infected with T. cruzi control acute parasitemia but develop chronic chagasic cardiomyopathy.

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Treatment with SIL (a phosphodiesterase inhibitor) during a therapeutic window of indeterminate phase provided powerful cardioprotective effects against chronic development of cardiomyopathy and LV dysfunction.

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SIL normalized the cGMP-dependent protein kinase activity and mitochondrial oxidative metabolism, and established the oxidant/antioxidant balance in chagasic myocardium.

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SIL prevented the oxidative/inflammatory adducts that precipitate cardiomyocytes death and cardiac remodeling in CCM.

Curcumin Enhances the Anti-Trypanosoma cruzi Activity of Benznidazole-Based Chemotherapy in Acute Experimental Chagas Disease

Although curcumin can increase the effectiveness of drugs against malaria, combination therapies using the molecule have never been investigated in Chagas disease (ChD). Therefore, we evaluated the efficacy of curcumin as a complementary strategy to benznidazole (Bz)-based chemotherapy in mice acutely infected with Trypanosoma cruzi Eighty-four 12-week-old Swiss mice were equally randomized into seven groups: uninfected (NI), T. cruzi infected and untreated (INF), infected and treated with 100 mg/kg of body weight Bz (B100), 50 mg/kg Bz (B50), 100 mg/kg curcumin (C100), 100 mg/kg Bz plus 100 mg/kg curcumin (B100 plus C100), and 50 mg/kg Bz plus 100 mg/kg curcumin (B50 plus C100). After microscopic identification of blood trypomastigotes (4 days after inoculation), both drugs were administered by gavage once a day for 20 days. Curcumin showed limited antiparasitic, anti-inflammatory, and antioxidant effects when administered alone. When curcumin and Bz were combined, there was a drastic reduction in parasitemia, parasite load, mortality, anti-T. cruzi IgG reactivity, circulating levels of cytokines (gamma interferon [IFN-γ], interleukin 4 [IL-4], and MIP1-α), myocardial inflammation, and morphological and oxidative cardiac injury; these results exceeded the isolated effects of Bz. The combination of Bz and curcumin was also effective at mitigating liver toxicity triggered by Bz, increasing the parasitological cure rate, and preventing infection recrudescence in noncured animals, even when the animals were treated with 50% of the recommended therapeutic dose of Bz. By limiting the toxic effects of Bz and enhancing its antiparasitic efficiency, the combination of the drug with curcumin may be a relevant therapeutic strategy that is possibly better tolerated in ChD treatment than Bz-based monotherapy.

Modulation of inflammatory and oxidative status by exercise attenuates cardiac morphofunctional remodeling in experimental Chagas cardiomyopathy

AIMS

The rational basis that explains the benefits of exercise therapy on Chagas cardiomyopathy (ChC) is poorly understood. This study investigated the impact of an exercise program on exercise performance, heart parasitism, immunoinflammatory response, fibrogenesis, oxidative damage, and cardiomyocytes contractility in experimental ChC.

MAIN METHODS

Wistar rats were subjected to a 9-week treadmill running training and challenged with Trypanosoma cruzi. Control animals remained sedentary. Physical and metabolic performance, cardiac morphology, cytokines, chemokines, nitric oxide, oxidative tissue damage, cardiomyocyte morphology and contractility were analyzed.

KEY FINDINGS

Exercise training was efficient to improve physical performance and anaerobic threshold in trained animals. By increasing cardiac and serum levels of cytokines (TNF-α, IFN-γ, and IL-6), chemokines (MCP-1 and CX3CL1), the myocardial activity catalase and superoxide dismutase, and reducing lipid and protein oxidation in cardiac tissue, exercise training seem to be a beneficial strategy to mitigate the progression and severity of Chagas-associated cardiomyopathy.

SIGNIFICANCE

The protective adaptations to the host triggered by exercise training contributed to reduce cardiac parasitism, inflammation, fibrosis and cardiomyocytes atrophy. Although exercise training does not affect nitric oxide levels in cardiac tissue from infected animals, this strategy enhanced the efficiency of endogenous antioxidant mechanisms, restricting oxidative tissue damage with positive repercussions to cardiomyocytes biomechanics in rats.

Changes in Proteome Profile of Peripheral Blood Mononuclear Cells in Chronic Chagas Disease

Trypanosoma cruzi (Tc) infection causes chagasic cardiomyopathy; however, why 30-40% of the patients develop clinical disease is not known. To discover the pathomechanisms in disease progression, we obtained the proteome signature of peripheral blood mononuclear cells (PBMCs) of normal healthy controls (N/H, n = 30) and subjects that were seropositive for Tc-specific antibodies, but were clinically asymptomatic (C/A, n = 25) or clinically symptomatic (C/S, n = 28) with cardiac involvement and left ventricular dysfunction. Protein samples were labeled with BODIPY FL-maleimide (dynamic range: > 4 orders of magnitude, detection limit: 5 f-mol) and resolved by two-dimensional gel electrophoresis (2D-GE). After normalizing the gel images, protein spots that exhibited differential abundance in any of the two groups were analyzed by mass spectrometry, and searched against UniProt human database for protein identification. We found 213 and 199 protein spots (fold change: |≥ 1.5|, p< 0.05) were differentially abundant in C/A and C/S individuals, respectively, with respect to N/H controls. Ingenuity Pathway Analysis (IPA) of PBMCs proteome dataset identified an increase in disorganization of cytoskeletal assembly and recruitment/activation and migration of immune cells in all chagasic subjects, though the invasion capacity of cells was decreased in C/S individuals. IPA predicted with high probability a decline in cell survival and free radical scavenging capacity in C/S (but not C/A) subjects. The MYC/SP1 transcription factors that regulate hypoxia and oxidative/inflammatory stress were predicted to be key targets in the context of control of Chagas disease severity. Further, MARS-modeling identified a panel of proteins that had >93% prediction success in classifying infected individuals with no disease and those with cardiac involvement and LV dysfunction. In conclusion, we have identified molecular pathways and a panel of proteins that could aid in detecting seropositive individuals at risk of developing cardiomyopathy.

EFFECTS OF VITAMIN C SUPPLEMENTATION ON THE CHRONIC PHASE OF CHAGAS DISEASE

Introduction:

In order to examine the effectiveness of vitamin C (ascorbic acid) in combating the oxidative insult caused by Trypanosoma cruzi during the development of the chronic phase of Chagas disease, Swiss mice were infected intraperitoneally with 5.0 × 10⁴ trypomastigotes of T. cruzi QM1strain.

Methods:

Mice were given supplements of two different doses of vitamin C for 180 days. Levels of lipid oxidation (as indicated by thiobarbituric acid reactive substances-TBARS), total peroxide, vitamin C, and reduced glutathione were measured in the plasma, TBARS, total peroxide and vitamin C were measured in the myocardium and histopathologic analysis was undertaken in heart, colon and skeletal muscle.

Results:

Animals that received a dose equivalent to 500 mg of vitamin C daily showed increased production of ROS in plasma and myocardium and a greater degree of inflammation and necrosis in skeletal muscles than those that received a lower dose or no vitamin C whatsoever.

Conclusion:

Although some research has shown the antioxidant effect of vitamin C, the results showed that animals subject to a 500 mg dose of vitamin C showed greater tissue damage in the chronic phase of Chagas disease, probably due to the paradoxical actions of the substance, which in this pathology, will have acted as a pro-oxidant or pro-inflammatory.

Evasion of the Immune Response by Trypanosoma cruzi during Acute Infection

Trypanosoma cruzi is the etiologic agent of Chagas disease, a neglected tropical disease that affects millions of people mainly in Latin America. To establish a life-long infection, T. cruzi must subvert the vertebrate host's immune system, using strategies that can be traced to the parasite's life cycle. Once inside the vertebrate host, metacyclic trypomastigotes rapidly invade a wide variety of nucleated host cells in a membrane-bound compartment known as the parasitophorous vacuole, which fuses to lysosomes, originating the phagolysosome. In this compartment, the parasite relies on a complex network of antioxidant enzymes to shield itself from lysosomal oxygen and nitrogen reactive species. Lysosomal acidification of the parasitophorous vacuole is an important factor that allows trypomastigote escape from the extremely oxidative environment of the phagolysosome to the cytoplasm, where it differentiates into amastigote forms. In the cytosol of infected macrophages, oxidative stress instead of being detrimental to the parasite, favors amastigote burden, which then differentiates into bloodstream trypomastigotes. Trypomastigotes released in the bloodstream upon the rupture of the host cell membrane express surface molecules, such as calreticulin and GP160 proteins, which disrupt initial and key components of the complement pathway, while others such as glycosylphosphatidylinositol-mucins stimulate immunoregulatory receptors, delaying the progression of a protective immune response. After an immunologically silent entry at the early phase of infection, T. cruzi elicits polyclonal B cell activation, hypergammaglobulinemia, and unspecific anti-T. cruzi antibodies, which are inefficient in controlling the infection. Additionally, the coexpression of several related, but not identical, epitopes derived from trypomastigote surface proteins delays the generation of T. cruzi-specific neutralizing antibodies. Later in the infection, the establishment of an anti-T. cruzi CD8(+) immune response focused on the parasite's immunodominant epitopes controls parasitemia and tissue infection, but fails to completely eliminate the parasite. This outcome is not detrimental to the parasite, as it reduces host mortality and maintains the parasite infectivity toward the insect vectors.

Discovery of Candidate Biomarkers

Properly performed, biomarker discovery can lead to effective candidates that can ultimately serve as predictors of disease, medical condition, define therapeutic parameters, and many other applications in medicine. Preferably, biomarkers comprise a panel of indicators, e.g. proteins and/or peptides that can be predictive or diagnostic of the medical condition of interest. Emphasis here is placed on "panel," as single candidates are rarely sufficient to provide the necessary sensitivity and specificity. To develop an effective panel that survives the development process described in Chap. 19 , proper experimental design and attention to important statistical parameters are critical to ensure success. Errors in discovery can lead to an inefficient use of expensive resources, as these may not be uncovered until the latter stages in biomarker development. Hence, accuracy, precision, and an estimate of the power of the proposed analyses are critical in the discovery of the panel of candidate biomarkers by proteomic methods, as is the selection of statistical approaches to refine and appropriately reduce the dataset for subsequent confirmatory assays.

Concomitant Benznidazole and Suramin Chemotherapy in Mice Infected with a Virulent Strain of Trypanosoma cruzi

Although suramin (Sur) is suggested as a potential drug candidate in the management of Chagas disease, this issue has not been objectively tested. In this study, we examined the applicability of concomitant treatment with benznidazole (Bz) and suramin in mice infected with a virulent strain of Trypanosoma cruzi. Eighty 12-week-old male C57BL/6 mice were equally randomized in eight groups: (i) noninfected mice (negative control) and mice infected with T. cruzi Y strain receiving (ii) no treatment (positive control), (iii) Bz, 100 mg/kg of body weight per day, (iv) Sur, 20 mg/kg/day, and (v to viii) Sur, 20 mg/kg/day, combined with Bz, 100, 50, 25, or 5 mg/kg/day. Bz was administered by gavage, and Sur was administered intraperitoneally. Sur dramatically increased the parasitemia, cardiac content of parasite DNA, inflammation, oxidative tissue damage, and mortality. In response to high parasitic load in cardiac tissue, Sur stimulated the immune system in a manner typical of the acute phase of Chagas disease, increasing tissue levels of gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α) and inducing a preferential IgG2a anti-T. cruzi serum pattern. When Sur and Bz were combined, the infection severity was attenuated, showing a dose-dependent Bz response. Sur therapy had a more harmful effect on the host than on the parasite and reduced the efficacy of Bz against T. cruzi infection. Considering that Sur drastically reinforced the infection evolution, potentiating the inflammatory process and the severity of cardiac lesions, the in vivo findings contradicted the in vitro anti-T. cruzi potential described for this drug.

Therapeutic Efficacy of a Subunit Vaccine in Controlling Chronic Trypanosoma cruzi Infection and Chagas Disease Is Enhanced by Glutathione Peroxidase Over-Expression

Trypanosoma cruzi-induced oxidative and inflammatory responses are implicated in chagasic cardiomyopathy. In this study, we examined the therapeutic utility of a subunit vaccine against T. cruzi and determined if glutathione peroxidase (GPx1, antioxidant) protects the heart from chagasic pathogenesis. C57BL/6 mice (wild-type (WT) and GPx1 transgenic (GPx^tg) were infected with T. cruzi and at 45 days post-infection (dpi), immunized with TcG2/TcG4 vaccine delivered by a DNA-prime/Protein-boost (D/P) approach. The plasma and tissue-sections were analyzed on 150 dpi for parasite burden, inflammatory and oxidative stress markers, inflammatory infiltrate and fibrosis. WT mice infected with T. cruzi had significantly more blood and tissue parasite burden compared with infected/GPx^tg mice (n = 5-8, p<0.01). Therapeutic vaccination provided >15-fold reduction in blood and tissue parasites in both WT and GPx^tg mice. The increase in plasma levels of myeloperoxidase (MPO, 24.7%) and nitrite (iNOS activity, 45%) was associated with myocardial increase in oxidant levels (3-4-fold) and non-responsive antioxidant status in chagasic/WT mice; and these responses were not controlled after vaccination (n = 5-7). The GPx^tg mice were better equipped than the WT mice in controlling T. cruzi-induced inflammatory and oxidative stress markers. Extensive myocardial and skeletal tissue inflammation noted in chagasic/WT mice, was significantly more compared with chagasic/GPx^tg mice (n = 4-6, p<0.05). Vaccination was equally effective in reducing the chronic inflammatory infiltrate in the heart and skeletal tissue of infected WT and GPx^tg mice (n = 6, p<0.05). Hypertrophy (increased BNP and ANP mRNA) and fibrosis (increased collagen) of the heart were extensively present in chronically-infected WT and GPx^tg mice and notably decreased after therapeutic vaccination. We conclude the therapeutic delivery of D/P vaccine was effective in arresting the chronic parasite persistence and chagasic pathology; and GPx1 over-expression provided additive benefits in reducing the parasite burden, inflammatory/oxidative stress and cardiac remodeling in Chagas disease.