Increased oxidative stress is correlated with mitochondrial dysfunction in chagasic patients

Secretome profiling reveals acute changes in oxidative stress, brain homeostasis, and coagulation following short-duration spaceflight

As spaceflight becomes more common with commercial crews, blood-based measures of crew health can guide both astronaut biomedicine and countermeasures. By profiling plasma proteins, metabolites, and extracellular vesicles/particles (EVPs) from the SpaceX Inspiration4 crew, we generated "spaceflight secretome profiles," which showed significant differences in coagulation, oxidative stress, and brain-enriched proteins. While >93% of differentially abundant proteins (DAPs) in vesicles and metabolites recovered within six months, the majority (73%) of plasma DAPs were still perturbed post-flight. Moreover, these proteomic alterations correlated better with peripheral blood mononuclear cells than whole blood, suggesting that immune cells contribute more DAPs than erythrocytes. Finally, to discern possible mechanisms leading to brain-enriched protein detection and blood-brain barrier (BBB) disruption, we examined protein changes in dissected brains of spaceflight mice, which showed increases in PECAM-1, a marker of BBB integrity. These data highlight how even short-duration spaceflight can disrupt human and murine physiology and identify spaceflight biomarkers that can guide countermeasure development.

Mapping the transporter-substrate interactions of the Trypanosoma cruzi NB1 nucleobase transporter reveals the basis for its high affinity and selectivity for hypoxanthine and guanine and lack of nucleoside uptake

Trypanosoma cruzi is a protozoan parasite and the etiological agent of Chagas disease, a debilitating and sometimes fatal disease that continues to spread to new areas. Yet, Chagas disease is still only treated with two related nitro compounds that are insufficiently effective and cause severe side effects. Nucleotide metabolism is one of the known vulnerabilities of T. cruzi, as they are auxotrophic for purines, and nucleoside analogues have been shown to have genuine promise against this parasite in vitro and in vivo. Since purine antimetabolites require efficient uptake through transporters, we here report a detailed characterisation of the T. cruzi NB1 nucleobase transporter with the aim of elucidating the interactions between TcrNB1 and its substrates and finding the positions that can be altered in the design of novel antimetabolites without losing transportability. Systematically determining the inhibition constants (Ki) of purine analogues for TcrNB1 yielded their Gibbs free energy of interaction, ΔG0. Pairwise comparisons of substrate (hypoxanthine, guanine, adenine) and analogues allowed us to determine that optimal binding affinity by TcrNB1 requires interactions with all four nitrogen residues of the purine ring, with N1 and N9, in protonation state, functioning as presumed hydrogen bond donors and unprotonated N3 and N7 as hydrogen bond acceptors. This is the same interaction pattern as we previously described for the main nucleobase transporters of Trypanosoma brucei spp. and Leishmania major and makes it the first of the ENT-family genes that is functionally as well as genetically conserved between the three main kinetoplast pathogens.

Arrhythmogenic Manifestations of Chagas Disease: Perspectives From the Bench to Bedside

Chagas cardiomyopathy caused by infection with the intracellular parasite Trypanosoma cruzi is the most common and severe expression of human Chagas disease. Heart failure, systemic and pulmonary thromboembolism, arrhythmia, and sudden cardiac death are the principal clinical manifestations of Chagas cardiomyopathy. Ventricular arrhythmias contribute significantly to morbidity and mortality and are the major cause of sudden cardiac death. Significant gaps still exist in the understanding of the pathogenesis mechanisms underlying the arrhythmogenic manifestations of Chagas cardiomyopathy. This article will review the data from experimental studies and translate those findings to draw hypotheses about clinical observations. Human- and animal-based studies at molecular, cellular, tissue, and organ levels suggest 5 main pillars of remodeling caused by the interaction of host and parasite: immunologic, electrical, autonomic, microvascular, and contractile. Integrating these 5 remodeling processes will bring insights into the current knowledge in the field, highlighting some key features for future management of this arrhythmogenic disease.

Platelets, Macrophages, and Thromboinflammation in Chagas Disease

Chagas disease (CD) is a major health problem in the Americas and an emerging health problem in Europe and other nonendemic countries. Several studies have documented persistence of the protozoan parasite Trypanosoma cruzi, and oxidative and inflammatory stress are major pathogenic factor. Mural and cardiac thrombi, cardiac arrhythmias, and cardiomyopathy are major clinical features of CD. During T. cruzi infection, parasite-released factors induce endothelial dysfunction along with platelet (PLT) and immune-cell activation. PLTs have a fundamental role in maintaining hemostasis and preventing bleeding after vascular injury. Excessive activation of PLTs and coagulation cascade can result in thrombosis and thromboembolic events, which are recognized to occur in seropositive individuals in early stages of CD when clinically symptomatic heart disease is not apparent. Several host and parasite factors have been identified to signal hypercoagulability and increase the risk of ischemic stroke in early phases of CD. Further, PLT interaction with immune cells and their role in host defense against pathogens and inflammatory processes have only recently been recognized and evolving. In the context of parasitic diseases, PLTs function in directly responding to T. cruzi infection, and PLT interactions with immune cells in shaping the proinflammatory or immunoregulatory function of monocytes, macrophages, and neutrophils remains elusive. How T. cruzi infection alters systemic microenvironment conditions to influence PLT and immune-cell interactions is not understood. In this review, we discuss the current literature, and extrapolate the mechanistic situations to explain how PLT and innate immune cell (especially monocytes and macrophages) interactions might be sustaining hypercoagulability and thromboinflammation in chronic CD.

Multi-therapeutic strategy targeting parasite and inflammation-related alterations to improve prognosis of chronic Chagas cardiomyopathy: a hypothesis-based approach

Chagas disease (CD), caused by infection by the protozoan parasite Trypanosoma cruzi, presents as main clinical manifestation the chronic chagasic cardiomyopathy (CCC). CCC afflicts millions of people, mostly in Latin America, and vaccine and effective therapy are still lacking. Comprehension of the host/parasite interplay in the chronic phase of T. cruzi infection may unveil targets for rational trait-based therapies to improve CCC prognosis. In the present viewpoint, I critically summarise a collection of data, obtained by our network of collaborators and other groups on CCC and preclinical studies on pathogenesis, targeting identification for intervention and the use of drugs with immunomodulatory properties to improve CCC. In the last two decades, models combining mouse lineages and T. cruzi strains allowed replication of crucial clinical, histopathological, and immunological traits of CCC. This condition includes conduction changes (heart rate changes, arrhythmias, atrioventricular blocks, prolongation of the QRS complex and PR and corrected QT intervals), ventricular dysfunction and heart failure, CD8-enriched myocarditis, tissue remodeling and progressive fibrosis, and systemic inflammatory profile, resembling "cytokine storm". Studies on Chagas' heart disease pathogenesis begins to unveil the molecular mechanisms underpinning the inflammation-related cardiac tissue damage, placing IFNγ, TNF and NFκB signaling as upstream regulators of miRNAs and mRNAs associated with critical biological pathways as cell migration, inflammation, tissue remodeling and fibrosis, and mitochondrial dysfunction. Further, data on preclinical trials using hypothesis-based tools, targeting parasite and inflammation-related alterations, opened paths for multi-therapeutic approaches in CCC. Despite the long path taken using experimental CD models replicating relevant aspects of CCC and testing new therapies and therapeutic schemes, these findings may get lost in translation, as conceptual and economical challenges, underpinning the valley of death across preclinical and clinical trials. It is hoped that such difficulties will be overcome in the near future.

Selenium, TGF-Beta and Infectious Endemic Cardiopathy: Lessons from Benchwork to Clinical Application in Chagas Disease

For over 60 years, selenium (Se) has been known as an essential microelement to many biological functions, including cardiovascular homeostasis. This review presents a compilation of studies conducted in the past 20 years related to chronic Chagas disease cardiomyopathy (CCC), caused by Trypanosoma cruzi infection, a neglected disease that represents a global burden, especially in Latin America. Experimental and clinical data indicate that Se may be used as a complementary therapy to prevent heart failure and improve heart function. Starting from the main questions “Is Se deficiency related to heart inflammation and arrhythmogenesis in CCC?” and “Could Se be recommended as a therapeutic strategy for CCC?”, we show evidence implicating the complex and multidetermined CCC physiopathology, discussing its possible interplays with the multifunctional cytokine TGF-β as regulators of immune response and fibrosis. We present two new proposals to face this global public health challenge in vulnerable populations affected by this parasitic disease: fibrosis modulation mediated by TGF-β pathways and the possible use of selenoproteins as antioxidants regulating the increased reactive oxygen stress present in CCC inflammatory environments. We assess the opportunity to consider the beneficial effects of Se in preventing heart failure as a concept to be applied for CCC 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.

Effects of Selenium treatment on cardiac function in Chagas heart disease: Results from the STCC randomized Trial

BACKGROUND

Chagas disease (caused by Trypanosoma cruzi infection) evolves to chronic chagasic cardiomyopathy (CCC) affecting 1.8 million people worldwide. This is the first randomized, placebo-controlled, double-blinded, clinical trial designed to estimate efficacy and safety of selenium (Se) treatment in CCC.

METHODS

66 patients with CCC stages B1 (left ventricular ejection fraction [LVEF] > 45% and no heart failure; n = 54) or B2 (LVEF < 45% and no heart failure; n = 12) were randomly assigned to receive 100 mcg/day sodium selenite (Se, n = 32) or placebo (Pla, n = 34) for one year (study period: May 2014-September 2018). LVEF changes over time and adverse effects were investigated. Trial registration number: NCT00875173 (clinicaltrials.gov).

FINDINGS

No significant differences between the two groups were observed for the primary outcome: mean LVEF after 6 (β= +1.1 p = 0.51 for Se vs Pla) and 12 months (β= +2.1; p = 0.23). In a subgroup analysis, statistically significant longitudinal changes were observed for mean LVEF in the stage B2 subgroup (β= +10.1; p = 0.02 for Se [n = 4] vs Pla [n = 8]). Se treatment was safe for CCC patients, and the few adverse effects observed were similarly distributed across the two groups.

INTERPRETATION

Se treatment did not improve cardiac function (evaluated from LVEF) in CCC. However, in the subgroup of patients at B2 stage, a potential beneficial influence of Se was observed. Complementary studies are necessary to explore diverse Se dose and/or associations in different CCC stages (B2 and C), as well as in A and B1 stages with longer follow-up.

FUNDING

Brazilian Ministry of Health, Fiocruz, CNPq, FAPERJ.

Central role of metabolism in Trypanosoma cruzi tropism and Chagas disease pathogenesis

Chagas disease is a neglected tropical disease caused by Trypanosoma cruzi parasites. During mammalian infection, T. cruzi alternates between an intracellular stage and extracellular stage. T. cruzi adapts its metabolism to this lifestyle, while also reshaping host metabolic pathways. Such host metabolic adaptations compensate for parasite-induced stress, but may promote parasite survival and proliferation. Recent work has demonstrated that metabolism controls parasite tropism and location of Chagas disease symptoms, and regulates whether infection is mild or severe. Such findings have important translational applications with regards to treatment and diagnostic test development, though further research is needed with regards to in vivo parasite metabolic gene expression, relationship between magnitude of local metabolic perturbation, parasite strain and disease location, and host-parasite-microbiota co-metabolism.

Oxidative stress implications for therapeutic vaccine development against Chagas disease

INTRODUCTION

Pathogenesis of Chagas disease (CD) caused by the protozoan parasite Trypanosoma cruzi (T. cruzi) involves chronic oxidative and inflammatory stress. In this review, we discuss the research efforts in therapeutic vaccine development to date and the potential challenges imposed by oxidative stress in achieving an efficient therapeutic vaccine against CD.

AREAS COVERED

This review covers the immune and nonimmune mechanisms of reactive oxygen species production and immune response patterns during T. cruzi infection in CD. A discussion on immunotherapy development efforts, the efficacy of antigen-based immune therapies against T. cruzi, and the role of antioxidants as adjuvants is discussed to provide promising insights to developing future treatment strategies against CD.

EXPERT OPINION

Administration of therapeutic vaccines can be a good option to confront persistent parasitemia in CD by achieving a rapid, short-lived stimulation of type 1 cell-mediated immunity. At the same time, adjunct therapies could play a critical role in the preservation of mitochondrial metabolism and cardiac muscle contractility in CD. We propose combined therapy with antigen-based vaccine and small molecules to control the pathological oxidative insult would be effective in the conservation of cardiac structure and function in CD.

Alterations to the Cardiac Metabolome Induced by Chronic T. cruzi Infection Relate to the Degree of Cardiac Pathology

Chronic Chagasic cardiomyopathy (CCC) is a Neglected Tropical Disease caused by the parasite Trypanosoma cruzi. The pathognomonic findings in symptomatic CCC patients and animal models includes diffuse cardiac fibrosis and inflammation with persistent parasite presence in the heart. This study investigated chemical alterations in different regions of the heart in relation to cardiac pathology indicators to better understand the long-term pathogenesis of this neglected disease. We used data from echocardiography, fibrosis biomarkers, and histopathological analysis to fully evaluate cardiac pathology. Metabolites isolated from the pericardial and endocardial sides of the right ventricular myocardium were analyzed by liquid chromatography tandem mass spectrometry. The endocardial sections contained significantly less cardiac inflammation and fibrosis than the pericardial sections. Cardiac levels of acylcarnitines, phosphocholines, and other metabolites were significantly disrupted in accordance with cardiac fibrosis, inflammation, and serum fibrosis biomarker levels. These findings have potential implications in treatment and monitoring for CCC patients.

Sirtuin Control of Mitochondrial Dysfunction, Oxidative Stress, and Inflammation in Chagas Disease Models

Trypanosoma cruzi is a digenetic parasite that requires triatomines and mammalian host to complete its life cycle. T. cruzi replication in mammalian host induces immune-mediated cytotoxic proinflammatory reactions and cellular injuries, which are the common source of reactive oxygen species (ROS) and reactive nitrogen species (RNS) during the acute parasitemic phase. Mitochondrial dysfunction of electron transport chain has been proposed as a major source of superoxide release in the chronic phase of infection, which renders myocardium exposed to sustained oxidative stress and contributes to Chagas disease pathology. Sirtuin 1 (SIRT1) is a class III histone deacetylase that acts as a sensor of redox changes and shapes the mitochondrial metabolism and inflammatory response in the host. In this review, we discuss the molecular mechanisms by which SIRT1 can potentially improve mitochondrial function and control oxidative and inflammatory stress in Chagas disease.

Tryp-ing Up Metabolism: Role of Metabolic Adaptations in Kinetoplastid Disease Pathogenesis

Today, more than a billion people-one-sixth of the world's population-are suffering from neglected tropical diseases. Human African trypanosomiasis, Chagas disease, and leishmaniasis are neglected tropical diseases caused by protozoan parasites belonging to the genera Trypanosoma and Leishmania About half a million people living in tropical and subtropical regions of the world are at risk of contracting one of these three infections. Kinetoplastids have complex life cycles with different morphologies and unique physiological requirements at each life cycle stage. This review covers the latest findings on metabolic pathways impacting disease pathogenesis of kinetoplastids within the mammalian host. Nutrient availability is a key factor shaping in vivo parasite metabolism; thus, kinetoplastids display significant metabolic flexibility. Proteomic and transcriptomic profiles show that intracellular trypanosomatids are able to switch to an energy-efficient metabolism within the mammalian host system. Host metabolic changes can also favor parasite persistence, and contribute to symptom development, in a location-specific fashion. Ultimately, targeted and untargeted metabolomics studies have been a valuable approach to elucidate the specific biochemical pathways affected by infection within the host, leading to translational drug development and diagnostic insights.

Trypanosoma cruzi infection in Cyclophilin D deficient mice

Trypanosoma cruzi is the causative agent of Chagas disease, which is endemic in Latin America and around the world through mother to child transmission. The heart is the organ most frequently affected in the chronic stage of the human infection and depends on mitochondria for the required energy for its activity. Cyclophilins are involved in protein folding and the mitochondrial isoform, Cyclophilin D (CyPD), has a crucial role in the opening of the mitochondrial permeability transition pore. In the present study, we infected CyPD deficient mice, with ablation of the Ppif gene, with T. cruzi parasites and the course of the infection was analyzed. Parasite load, quantified by PCR, was significantly lower in skeletal and cardiac tissues of Ppif-/- mice compared to wild type mice. In vitro cultured cardiomyocytes and macrophages from mice lacking CyPD exhibited lower percentage of infected cells and number of intracellular parasites than those observed for wild type mice. Although histopathological analysis of heart and mRNA of heart cytokines showed differences between T. cruzi-infected mice compared to the uninfected animals, no significant differences were found mice due to the ablation of the Ppif gene. Our results suggest that cells deficient for mitochondrial CyPD, inhibited for the mitochondrial membrane potential collapse, reduces the severity of parasite aggression and spread of cellular infection.

Dual and Opposite Roles of Reactive Oxygen Species (ROS) in Chagas Disease: Beneficial on the Pathogen and Harmful on the Host

Chagas disease is a neglected tropical disease, which affects an estimate of 6-7 million people worldwide. Chagas disease is caused by Trypanosoma cruzi, which is a eukaryotic flagellate unicellular organism. At the primary infection sites, these parasites are phagocytized by macrophages, which produce reactive oxygen species (ROS) in response to the infection with T. cruzi. The ROS produce damage to the host tissues; however, macrophage-produced ROS is also used as a signal for T. cruzi proliferation. At the later stages of infection, mitochondrial ROS is produced by the infected cardiomyocytes that contribute to the oxidative damage, which persists at the chronic stage of the disease. The oxidative damage leads to a functional impairment of the heart. In this review article, we will discuss the mechanisms by which T. cruzi is able to deal with the oxidative stress and how this helps the parasite growth at the acute phase of infection and how the oxidative stress affects the cardiomyopathy at the chronic stage of the Chagas disease. We will describe the mechanisms used by the parasite to deal with ROS and reactive nitrogen species (RNS) through the trypanothione and the mechanisms used to repair the damaged DNA. Also, a description of the events produced by ROS at the acute and chronic stages of the disease is presented. Lastly, we discuss the benefits of ROS for T. cruzi growth and proliferation and the possible mechanisms involved in this phenomenon. Hypothesis is put forward to explain the molecular mechanisms by which ROS triggers parasite growth and proliferation and how ROS is able to produce a long persisting damage on cardiomyocytes even in the absence of the parasite.

Shared neuroimmune and oxidative pathways underpinning Chagas disease and major depressive disorder

The cellular and molecular basis to understand the relationship between Chagas disease (CD), a infection caused by Trypanosoma cruzi, and depression, a common psychiatric comorbidity in CD patients, is largely unknown. Clinical studies show an association between CD and depression and preclinical evidence suggests that depressive-like behaviors in T. cruzi infected mice are due, at least partially, to immune dysregulation. However, mechanistic studies regarding this issue are still lacking. Herein, we present and discuss the state of art of data on CD and depression, and revise the mechanisms that may explain the development of depression in CD. We also discuss how the knowledge generated by current and future data may contribute to the discovery of new mechanisms underlying depressive symptoms associated with CD and, hence, to the identification of new therapeutic targets, which ultimately may change the way we see and treat CD and its psychiatric comorbidities.

Molecular dissection of Chagas induced cardiomyopathy reveals central disease associated and druggable signaling pathways

Chagas disease, the clinical presentation of T. cruzi infection, is a major human health concern. While the acute phase of Chagas disease is typically asymptomatic and self-resolving, chronically infected individuals suffer numerous sequelae later in life. Cardiomyopathies in particular are the most severe consequence of chronic Chagas disease and cannot be reversed solely by parasite load reduction. To prioritize new therapeutic targets, we unbiasedly interrogated the host signaling events in heart tissues isolated from a Chagas disease mouse model using quantitative, multiplexed proteomics. We defined the host response to infection at both the proteome and phospho-proteome levels. The proteome showed an increase in the immune response and a strong repression of several mitochondrial proteins. Complementing the proteome studies, the phospho-proteomic survey found an abundance of phospho-site alterations in plasma membrane and cytoskeletal proteins. Bioinformatic analysis of kinase activity provided substantial evidence for the activation of NDRG2 and JNK/p38 kinases during Chagas disease. A significant activation of DYRK2 and AMPKA2 and the inhibition of casein family kinases were also predicted. We concluded our analyses by linking the diseased heart proteome profile to known therapeutic interventions, uncovering a potential to target mitochondrial proteins, secreted immune effectors and core kinases for the treatment of chronic Chagas disease. Together, this study provides molecular insight into host proteome and phospho-proteome responses to T. cruzi infection in the heart for the first time, highlighting pathways that can be further validated for functional contributions to disease and suitability as drug targets.

Potential Role of Antioxidants as Adjunctive Therapy in Chagas Disease

Chagas disease (CD) is one of the most important neglected tropical diseases in the American continent. Host-derived nitroxidative stress in response to Trypanosoma cruzi infection can induce tissue damage contributing to the progression of Chagas disease. Antioxidant supplementation has been suggested as adjuvant therapy to current treatment. In this article, we synthesize and discuss the current evidence regarding the use of antioxidants as adjunctive compounds to fight harmful reactive oxygen species and lower the tissue oxidative damage during progression of chronic Chagas disease. Several antioxidants evaluated in recent studies have shown potential benefits for the control of oxidative stress in the host's tissues. Melatonin, resveratrol, the combination of vitamin C/vitamin E (vitC/vitE) or curcumin/benznidazole, and mitochondria-targeted antioxidants seem to be beneficial in reducing plasma and cardiac levels of lipid peroxidation products. Nevertheless, further research is needed to validate beneficial effects of antioxidant therapies in Chagas disease.

State-of-the-art in host-derived biomarkers of Chagas disease prognosis and early evaluation of anti-Trypanosoma cruzi treatment response

Chagas disease is caused by infection with the parasite Trypanosoma cruzi, which might lead to a chronic disease state and drive to irreversible damage to the heart and/or digestive tract tissues. Endemic in 21 countries in the Americas, it is the neglected disease with a highest burden in the region. Current estimates point at ~6 million people infected, of which ~30% will progress onto the symptomatic tissue disruptive stage. There is no vaccine but there are two anti-parasitic drugs available: benznidazole and nifurtimox. However, their efficacy is variable at the chronic symptomatic stage and both have frequent adverse effects. Since there are no prognosis markers, drugs should be administered to all T. cruzi-infected individuals in the indeterminate and early symptomatic stages. Nowadays, there are no tests-of-cure either, which greatly undermines patients follow-up and the search of safer and more efficacious drugs. Therefore, the identification and validation of biomarkers of disease progression and/or treatment response on which to develop tests of prognosis and/or cure is a major research priority. Both parasite- and host-derived markers have been investigated. In the present manuscript we present an updated outlook of the latter.

Reactive oxygen species and nitric oxide imbalances lead to in vivo and in vitro arrhythmogenic phenotype in acute phase of experimental Chagas disease

Chagas Disease (CD) is one of the leading causes of heart failure and sudden death in Latin America. Treatments with antioxidants have provided promising alternatives to ameliorate CD. However, the specific roles of major reactive oxygen species (ROS) sources, including NADPH-oxidase 2 (NOX2), mitochondrial-derived ROS and nitric oxide (NO) in the progression or resolution of CD are yet to be elucidated. We used C57BL/6 (WT) and a gp91PHOX knockout mice (PHOX-/-), lacking functional NOX2, to investigate the effects of ablation of NOX2-derived ROS production on the outcome of acute chagasic cardiomyopathy. Infected PHOX-/- cardiomyocytes displayed an overall pro-arrhythmic phenotype, notably with higher arrhythmia incidence on ECG that was followed by higher number of early afterdepolarizations (EAD) and 2.5-fold increase in action potential (AP) duration alternans, compared to AP from infected WT mice. Furthermore, infected PHOX-/- cardiomyocytes display increased diastolic [Ca2+], aberrant Ca2+ transient and reduced Ca2+ transient amplitude. Cardiomyocyte contraction is reduced in infected WT and PHOX-/- mice, to a similar extent. Nevertheless, only infected PHOX-/- isolated cardiomyocytes displayed significant increase in non-triggered extra contractions (appearing in ~75% of cells). Electro-mechanical remodeling of infected PHOX-/-cardiomyocytes is associated with increase in NO and mitochondria-derived ROS production. Notably, EADs, AP duration alternans and in vivo arrhythmias were reverted by pre-incubation with nitric oxide synthase inhibitor L-NAME. Overall our data show for the first time that lack of NOX2-derived ROS promoted a pro-arrhythmic phenotype in the heart, in which the crosstalk between ROS and NO could play an important role in regulating cardiomyocyte electro-mechanical function during acute CD. Future studies designed to evaluate the potential role of NOX2-derived ROS in the chronic phase of CD could open new and more specific therapeutic strategies to treat CD and prevent deaths due to heart complications.

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.

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

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

Redox Balance Keepers and Possible Cell Functions Managed by Redox Homeostasis in Trypanosoma cruzi

The toxicity of oxygen and nitrogen reactive species appears to be merely the tip of the iceberg in the world of redox homeostasis. Now, oxidative stress can be seen as a two-sided process; at high concentrations, it causes damage to biomolecules, and thus, trypanosomes have evolved a strong antioxidant defense system to cope with these stressors. At low concentrations, oxidants are essential for cell signaling, and in fact, the oxidants/antioxidants balance may be able to trigger different cell fates. In this comprehensive review, we discuss the current knowledge of the oxidant environment experienced by T. cruzi along the different phases of its life cycle, and the molecular tools exploited by this pathogen to deal with oxidative stress, for better or worse. Further, we discuss the possible redox-regulated processes that could be governed by this oxidative context. Most of the current research has addressed the importance of the trypanosomes' antioxidant network based on its detox activity of harmful species; however, new efforts are necessary to highlight other functions of this network and the mechanisms underlying the fine regulation of the defense machinery, as this represents a master key to hinder crucial pathogen functions. Understanding the relevance of this balance keeper program in parasite biology will give us new perspectives to delineate improved treatment strategies.

Selenium and selenoproteins in prostanoid metabolism and immunity

Selenium (Se) is an essential trace element that functions in the form of the 21st amino acid, selenocysteine (Sec) in a defined set of proteins. Se deficiency is associated with pathological conditions in humans and animals, where incorporation of Sec into selenoproteins is reduced along with their expression and catalytic activity. Supplementation of Se-deficient population with Se has shown health benefits suggesting the importance of Se in physiology. An interesting paradigm to explain, in part, the health benefits of Se stems from the observations that selenoprotein-dependent modulation of inflammation and efficient resolution of inflammation relies on mechanisms involving a group of bioactive lipid mediators, prostanoids, which orchestrate a concerted action toward maintenance and restoration of homeostatic immune responses. Such an effect involves the interaction of various immune cells with these lipid mediators where cellular redox gatekeeper functions of selenoproteins further aid in not only dampening inflammation, but also initiating an effective and active resolution process. Here we have summarized the current literature on the multifaceted roles of Se/selenoproteins in the regulation of these bioactive lipid mediators and their immunomodulatory effects.

Immunity and vaccine development efforts against Trypanosoma cruzi

Trypanosoma cruzi (T. cruzi) is the causative agent for Chagas disease (CD). There is a critical lack of methods for prevention of infection or treatment of acute infection and chronic disease. Studies in experimental models have suggested that the protective immunity against T. cruzi infection requires the elicitation of Th1 cytokines, lytic antibodies and the concerted activities of macrophages, T helper cells, and cytotoxic T lymphocytes (CTLs). In this review, we summarize the research efforts in vaccine development to date and the challenges faced in achieving an efficient prophylactic or therapeutic vaccine against human CD.

Increased Sulfiredoxin Expression in Gastric Cancer Cells May Be a Molecular Target of the Anticancer Component Diallyl Trisulfide

Sulfiredoxin (Srx) is a newly discovered antioxidant enzyme playing a role in the catalytic reduction of oxidative modifications. Srx is overexpressed in a variety of cancers. It may promote carcinogenesis as well as tumor progression. In this study, we report for the first time that Srx expression might be positively associated with the development of gastric cancer and tumor malignancy. Immunohistochemistry showed that, compared to normal tissues (42%, 20/47), Srx expression in gastric tumors (85%, 40/47) was much more common (chi-square test, p<0.01). In addition, the staining of Srx was stronger in poorly differentiated gastric cancer than in well-differentiated gastric cancer. Western blotting showed that, in the gastric tumor cell line BGC823, the Srx protein was upregulated in response to H₂O₂ treatment, although it was inadequate to counteract the increased oxidative stress, as indicated by the gradually increasing level of malondialdehyde (MDA). In addition, Srx expression, MDA levels, and ROS levels in BGC823 cells were markedly inhibited upon treatment with diallyl trisulfide (DATS), a major constituent of garlic oil with proven anticancer effects. These results suggest that Srx may be an oxidative stress marker. Antioxidation may account for the anticancer potential of garlic.

Potential Utility of Protein Targets of Cysteine-S-Nitrosylation in Identifying Clinical Disease Status in Human Chagas Disease

Trypanosoma cruzi (Tc) infection causes Chagas disease (ChD) presented by dilated cardiomyopathy and heart failure. During infection, oxidative and nitrosative stresses are elicited by the immune cells for control the pathogen; however, excess nitric oxide and superoxide production can result in cysteine S-nitrosylation (SNO) of host proteins that affects cellular homeostasis and may contribute to disease development. To identify the proteins with changes in SNO modification levels as a hallmark of ChD, we obtained peripheral blood mononuclear cells (PBMC) from seronegative, normal healthy (NH, n = 30) subjects, and from seropositive clinically asymptomatic (ChD CA, n = 25) or clinically symptomatic (ChD CS, n = 28) ChD patients. All samples were treated (Asc+) or not-treated (Asc⁻) with ascorbate (reduces nitrosylated thiols), labeled with the thiol-labeling BODIPY FL-maleimide dye, resolved by two-dimensional electrophoresis (total 166 gels), and the protein spots that yielded significant differences in abundance or SNO level at p-value of ≤ 0.05_{t−test/Welch/BH} were identified by MALDI-TOF/TOF MS or OrbiTrap LC-MS/MS. Targeted analysis of a new cohort of PBMC samples (n = 10–14/group) was conducted to verify the differential abundance/SNO levels of two of the proteins in ChD (vs. NH) subjects. The multivariate adaptive regression splines (MARS) modeling, comparing differences in relative SNO level (Asc⁻/Asc+ ratio) of the protein spots between any two groups yielded SNO biomarkers that exhibited ≥90% prediction success in classifying ChD CA (582-KRT1 and 884-TPM3) and ChD CS (426-PNP, 582-KRT1, 486-ALB, 662-ACTB) patients from NH controls. Ingenuity Pathway Analysis (IPA) of the SNO proteome dataset normalized to changes in protein abundance suggested the proteins belonging to the signaling networks of cell death and the recruitment and migration of immune cells were most affected in ChD CA and ChD CS (vs. NH) subjects. We propose that SNO modification of the select panel of proteins identified in this study have the potential to identify ChD severity in seropositive individuals exposed to Tc infection.

Biomarkers of Oxidative Stress and Inflammation in Chagasic Myocardiopathy

Introduction:

The fact that only part of the population that lives in endemic areas gets Chagas disease and that only some of the patients with chronic infection develop symptoms, supports the importance of investigating the factors of each host in the susceptibility and the development of the disease. Chronic pathological processes and progressive inflammation lead to alterations in the cellular antioxidant status. This imbalance would contribute to the destruction of the parasite and would be related to the cardiac damage observed in patients with chagasic cardiomyopathy.

Objective:

The objective of the present study was to determine the plasma activity of oxidative stress and inflammatory biomarkers: SOD, CAT, GPx, TBARS and TNF-α in chagasic patients with and without cardiomyopathy and healthy individuals.

Aim:

The aim of the present study is to demonstrate the predisposition to severe forms of chagasic heart disease by quantifying the biomarkers mentioned in blood from the study population.

Results and Conclusion:

The results show significant differences in the enzymatic activities in the different groups of patients, which would mean at the cellular level, an alteration of the antioxidant capacity. Contrary to what we expected (a depletion of these enzymes), patients show an increase in antioxidant activity, that is, they respond to the generation of free radicals. The same trend is observed in the case of TBARS that are elevated in the case of chagasic patients, indicating a high degree of lipid peroxidation and oxidative damage. Regarding TNF-α levels, we found statistically significant differences, which show an active and chronic inflammatory state in these patients. Although we have found significant differences between the CN group and the other groups of patients, we should indicate that between the MCC and ECsinMCC groups, the results obtained did not show marked differences. This is important since it has been shown that patients infected with Tc have a marked antioxidant potential and are able to respond to the oxidative stress induced by the parasite, although this would not be decisive in the evolution of the disease.

Pathology and Pathogenesis of Chagas Heart Disease

Chagas heart disease is an inflammatory cardiomyopathy that develops in approximately one-third of people infected with the protozoan parasite Trypanosoma cruzi. One way T. cruzi is transmitted to people is through contact with infected kissing bugs, which are found in much of the Western Hemisphere, including in vast areas of the United States. The epidemiology of T. cruzi and Chagas heart disease and the varied mechanisms leading to myocyte destruction, mononuclear cell infiltration, fibrosis, and edema in the heart have been extensively studied by hundreds of scientists for more than 100 years. Despite this wealth of knowledge, it is still impossible to predict what will happen in an individual infected with T. cruzi because of the tremendous variability in clonal parasite virulence and human susceptibility to infection and the lack of definitive molecular predictors of outcome from either side of the host-parasite equation. Further, while several distinct mechanisms of pathogenesis have been studied in isolation, it is certain that multiple coincident mechanisms combine to determine the ultimate outcome. For these reasons, Chagas disease is best considered a collection of related but distinct illnesses. This review highlights the pathology and pathogenesis of the most common adverse sequela of T. cruzi infection-Chagas heart disease-and concludes with a discussion of key unanswered questions and a view to the future.

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.

Infection by Trypanosoma cruzi parasitic protozoan remains endemic in Latin America. After acute parasitemia phase is controlled by host immune system, infected individuals remain clinically silent but manifest a number of micro and macro cardiac injuries for several years. Eventually many of the infected individuals develop chronic cardiomyopathy that leads to heart failure and sudden death. Cardiac muscle cells are rich in mitochondria and manganese superoxide dismutase (MnSOD) is the chief superoxide scavenging enzyme in the mitochondria. In this study, we show that a deficiency of MnSOD exacerbates the T. cruzi induced mitochondrial dysfunction of the electron transport chain and energy production in the heart. Further, MnSOD deficiency resulted in increased mitochondrial release of oxidants and caused excessive oxidative damage in the chagasic heart. Our results suggest that small molecule agonists of MnSOD will have potential utility as adjuvant therapy in preventing the development of chronic Chagas disease in infected individuals.

PARP1 depletion improves mitochondrial and heart function in Chagas disease: Effects on POLG dependent mtDNA maintenance

Chagasic cardiomyopathy is caused by Trypanosoma cruzi infection. Poly(ADP-ribose) polymerase 1 (PARP1) is known for its function in nuclear DNA repair. In this study, we have employed genetic deletion and chemical inhibition approaches to determine the role of PARP1 in maintaining mtDNA dependent mitochondrial function in Chagas disease. Our data show that expression of PARP1 and protein PARylation were increased by >2-fold and >16-fold, respectively, in the cytosolic, nuclear, and mitochondrial fractions of the human cardiac myocytes and the myocardium of wildtype (WT) mice chronically infected with T. cruzi. The nuclear and cytosolic PARP1/PAR did not interfere with the transcription and translation of the components of the mtDNA replisome machinery in infected cardiomyocytes and chagasic murine myocardium. However, PARP1 binding to Polymerase γ and mtDNA in mitochondria were increased, and associated with a loss in mtDNA content, mtDNA-encoded gene expression, and oxidative phosphorylation (OXPHOS) capacity, and an increase in mitochondrial ROS production in cells and heart of WT mice infected with T. cruzi. Subsequently, an increase in oxidative stress, and cardiac collagen deposition, and a decline in LV function was noted in chagasic mice. Genetic deletion of PARP1 or treatment with selective inhibitor of PARP1 (PJ34) improved the mtDNA content, mitochondrial function, and oxidant/antioxidant balance in human cardiomyocytes and chronically infected mice. Further, PARP1 inhibition was beneficial in preserving the cardiac structure and left ventricular function in chagasic mice. We conclude that PARP1 overexpression is associated with a decline in Pol γ-dependent maintenance of mtDNA content, mtDNA-encoded gene expression, and mitochondrial respiratory function, and subsequently contributes to an increase in mtROS and oxidative stress in chagasic myocardium. Inhibition of mitochondrial PARP1/PAR offers a novel therapy in preserving the mitochondrial and LV function in chronic Chagas disease.

ROS and Trypanosoma cruzi: Fuel to infection, poison to the heart

The activation of macrophage respiratory burst in response to infection with Trypanosoma cruzi inflicts oxidative damage to the host’s tissues. For decades, the role of reactive oxygen species (ROS) in the elimination of T. cruzi was taken for granted, but recent evidence suggests parasite growth is stimulated in oxidative environments. It is still a matter of debate whether indeed oxidative environments provide ideal conditions (e.g., iron availability in macrophages) for T. cruzi growth and whether indeed ROS signals directly to stimulate growth. Nitric oxide (NO) and ROS combine to form peroxynitrite, participating in the killing of phagocytosed parasites by activated macrophages. In response to infection, mitochondrial ROS are produced by cardiomyocytes. They contribute to oxidative damage that persists at the chronic stage of infection and is involved in functional impairment of the heart. In this review, we discuss how oxidative stress helps parasite growth during the acute stage and how it participates in the development of cardiomyopathy at the chronic stage.

Modulation of host central carbon metabolism and in situ glucose uptake by intracellular Trypanosoma cruzi amastigotes

Obligate intracellular pathogens satisfy their nutrient requirements by coupling to host metabolic processes, often modulating these pathways to facilitate access to key metabolites. Such metabolic dependencies represent potential targets for pathogen control, but remain largely uncharacterized for the intracellular protozoan parasite and causative agent of Chagas disease, Trypanosoma cruzi. Perturbations in host central carbon and energy metabolism have been reported in mammalian T. cruzi infection, with no information regarding the impact of host metabolic changes on the intracellular amastigote life stage. Here, we performed cell-based studies to elucidate the interplay between infection with intracellular T. cruzi amastigotes and host cellular energy metabolism. T. cruzi infection of non-phagocytic cells was characterized by increased glucose uptake into infected cells and increased mitochondrial respiration and mitochondrial biogenesis. While intracellular amastigote growth was unaffected by decreased host respiratory capacity, restriction of extracellular glucose impaired amastigote proliferation and sensitized parasites to further growth inhibition by 2-deoxyglucose. These observations led us to consider whether intracellular T. cruzi amastigotes utilize glucose directly as a substrate to fuel metabolism. Consistent with this prediction, isolated T. cruzi amastigotes transport extracellular glucose with kinetics similar to trypomastigotes, with subsequent metabolism as demonstrated in ¹³C-glucose labeling and substrate utilization assays. Metabolic labeling of T. cruzi-infected cells further demonstrated the ability of intracellular parasites to access host hexose pools in situ. These findings are consistent with a model in which intracellular T. cruzi amastigotes capitalize on the host metabolic response to parasite infection, including the increase in glucose uptake, to fuel their own metabolism and replication in the host cytosol. Our findings enrich current views regarding available carbon sources for intracellular T. cruzi amastigotes and underscore the metabolic flexibility of this pathogen, a feature predicted to underlie successful colonization of tissues with distinct metabolic profiles in the mammalian host.

The kinetoplastid protozoan, Trypanosoma cruzi, is a highly successful parasite with a broad mammalian host range and the capacity to colonize a variety of tissues within a given host to establish life-long infection. T. cruzi infection causes Chagas disease in humans, characterized by severe cardiomyopathy and gastrointestinal motility disorders, with limited treatment options. Despite the critical role of T. cruzi amastigotes in sustaining mammalian infection, little is known about their metabolic requirements or the range of nutrients available to these parasites in the host cell cytoplasm. Here, we demonstrate that T. cruzi infection triggers a host response in infected cells that includes increased mitochondrial respiration and biogenesis and increased glucose uptake into infected cells. We show that exogenous glucose supports optimal intracellular parasite replication and that cytosolic T. cruzi amastigotes access glucose in situ, potentially via a facilitated transport process characterized here. These findings expand our view of the range of carbons available to the intracellular parasite and suggest even greater metabolic flexibility of the tissue-infective stages of T. cruzi than previously appreciated, a capability predicted to contribute to successful host colonization.

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.

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.

S-Nitrosylation Proteome Profile of Peripheral Blood Mononuclear Cells in Human Heart Failure

Nitric oxide (NO) protects the heart against ischemic injury; however, NO- and superoxide-dependent S-nitrosylation (S-NO) of cysteines can affect function of target proteins and play a role in disease outcome. We employed 2D-GE with thiol-labeling FL-maleimide dye and MALDI-TOF MS/MS to capture the quantitative changes in abundance and S-NO proteome of HF patients (versus healthy controls, n = 30/group). We identified 93 differentially abundant (59-increased/34-decreased) and 111 S-NO-modified (63-increased/48-decreased) protein spots, respectively, in HF subjects (versus controls, fold-change | ≥1.5|, p ≤ 0.05). Ingenuity pathway analysis of proteome datasets suggested that the pathways involved in phagocytes' migration, free radical production, and cell death were activated and fatty acid metabolism was decreased in HF subjects. Multivariate adaptive regression splines modeling of datasets identified a panel of proteins that will provide >90% prediction success in classifying HF subjects. Proteomic profiling identified ATP-synthase, thrombospondin-1 (THBS1), and vinculin (VCL) as top differentially abundant and S-NO-modified proteins, and these proteins were verified by Western blotting and ELISA in different set of HF subjects. We conclude that differential abundance and S-NO modification of proteins serve as a mechanism in regulating cell viability and free radical production, and THBS1 and VCL evaluation will potentially be useful in the prediction of heart failure.

Early nifurtimox-induced biochemical and ultrastructural alterations in rat heart

Nifurtimox (Nfx) and Benznidazole (Bz) are being used for the treatment of the acute phase of Chagas' disease. Recently, they were also considered for use in the indeterminate phase. Both the nitroheterocyclic drugs have serious toxic side effects. The mechanism of Nfx toxicity is associated with the formation of reactive oxygen species (ROS) generated during nitroreduction. Potential effects on cardiac function have not been established yet, despite the well-known cardiopathy often produced by the disease itself. We describe experiments testing some acute effects of Nfx on the male Sprague Dawley rat heart. Nifurtimox was present in the heart at 1, 3 and 6 h after intragastric (i.g) treatment. In vitro studies on Nfx microsomal and cytosolic nitroreductase activities showed that only the microsomal fraction had the ability to nitroreduce it. Cytochrome P450 and cytochrome P450 reductase would be involved in the process as suggested by their response to specific inhibitors. Nifurtimox increased the cardiac protein carbonyl content at 1 and 3 h and decreased the protein sulfhydryl content at 3 h. In addition, 24 h after treatment ultrastructural alterations such as marked cytoplasmic vacuolization, separation and loss of myofibrils and mitochondrial swelling were observed. Results suggest that Nfx administration might aggravate pre-existing adverse cardiac conditions. Human & Experimental Toxicology (2007) 26, 781 — 788

Improvement of kidney redox states contributes to the beneficial effects of dietary pomegranate peel against barium chloride-induced nephrotoxicity in adult rats

CONTEXT

Pomegranate (Punica granatum L., Punicaceae) is known to possess enormous antioxidant activity.

OBJECTIVE

This study investigates the protective effects of pomegranate peel against barium-mediated renal damage.

MATERIALS AND METHODS

Rats were exposed during 21 days either to barium (67 ppm), barium + pomegranate peel (5% of diet) or to only pomegranate peel (5% of diet).

RESULTS

Exposure rats to barium provoked a significant increase in kidney malondialdehyde (MDA), advanced oxidation protein products (AOPP) and hydrogen peroxide (H2O2) levels. Creatinine, urea and uric acid levels in plasma and urine were also modified. Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities, non protein thiol (NPSH) and reduced glutathione (GSH) levels were decreased. Metallothionein (MT) production was increased and their genes expressions were up-regulated. All these changes were improved by dietary pomegranate peel. Moreover, the distorted histoarchitecture in kidney of barium group was alleviated by pomegranate peel.

CONCLUSION

Our data showed, for the first time, the protective effects of pomegranate peel against barium-induced renal oxidative damage.

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.

•

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

•

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.

•

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

•

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

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.

Molecular mechanisms of myocarditis caused by Trypanosoma cruzi

PURPOSE OF REVIEW

American trypanosomiasis, or Chagas disease, is a lifelong and persistent infection caused by the protozoan Trypanosoma cruzi and is the most significant cause of morbidity and mortality in South and Central America. Owing to immigration and additional risks from blood transfusion and organ transplantation, the number of reported cases of Chagas disease has increased recently in Europe and the USA. The disease is caused by a moderate to intense lasting inflammatory response that triggers local expression of inflammatory mediators and activates and recruits leukocytes to various tissues to eliminate the parasites.

RECENT FINDINGS

This long-term inflammatory process triggers biochemical, physiological and morphological alterations and clinical changes in the digestive, nervous and cardiac (e.g. myocarditis, arrhythmias, congestive heart failure, autonomic dysfunctions and microcirculatory disturbances) systems. Indeed, the pathogenesis of Chagas disease is intricate and multifactorial, and the roles of the parasite and the immune response in initiating and maintaining the disease are still controversial.

SUMMARY

In this review, we discuss the current knowledge of 'strategies' employed by the parasite to persist in the host and host defence mechanisms against Trypanosoma cruzi infection, which can result in equilibrium (absence of the disease) or disease development, mainly in the cardiac systems.

Developments in the management of Chagas cardiomyopathy

Over 100 years have elapsed since the discovery of Chagas disease and there is still much to learn regarding pathogenesis and treatment. Although there are antiparasitic drugs available, such as benznidazole and nifurtimox, they are not totally reliable and often toxic. A recently released negative clinical trial with benznidazole in patients with chronic Chagas cardiomyopathy further reinforces the concerns regarding its effectiveness. New drugs and new delivery systems, including those based on nanotechnology, are being sought. Although vaccine development is still in its infancy, the reality of a therapeutic vaccine remains a challenge. New ECG methods may help to recognize patients prone to developing malignant ventricular arrhythmias. The management of heart failure, stroke and arrhythmias also remains a challenge. Although animal experiments have suggested that stem cell based therapy may be therapeutic in the management of heart failure in Chagas cardiomyopathy, clinical trials have not been promising.

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.

A change of heart: oxidative stress in governing muscle function?

Redox/cysteine modification of proteins that regulate calcium cycling can affect contraction in striated muscles. Understanding the nature of these modifications would present the possibility of enhancing cardiac function through reversible cysteine modification of proteins, with potential therapeutic value in heart failure with diastolic dysfunction. Both heart failure and muscular dystrophy are characterized by abnormal redox balance and nitrosative stress. Recent evidence supports the synergistic role of oxidative stress and inflammation in the progression of heart failure with preserved ejection fraction, in concert with endothelial dysfunction and impaired nitric oxide-cyclic guanosine monophosphate-protein kinase G signalling via modification of the giant protein titin. Although antioxidant therapeutics in heart failure with diastolic dysfunction have no marked beneficial effects on the outcome of patients, it, however, remains critical to the understanding of the complex interactions of oxidative/nitrosative stress with pro-inflammatory mechanisms, metabolic dysfunction, and the redox modification of proteins characteristic of heart failure. These may highlight novel approaches to therapeutic strategies for heart failure with diastolic dysfunction. In this review, we provide an overview of oxidative stress and its effects on pathophysiological pathways. We describe the molecular mechanisms driving oxidative modification of proteins and subsequent effects on contractile function, and, finally, we discuss potential therapeutic opportunities for heart failure with diastolic dysfunction.