Alterations in myocardial gene expression associated with experimental Trypanosoma cruzi infection

Transcriptional Studies on Trypanosoma cruzi - Host Cell Interactions: A Complex Puzzle of Variables

Chagas Disease, caused by the protozoan parasite Trypanosoma cruzi, affects nearly eight million people in the world. T. cruzi is a complex taxon represented by different strains with particular characteristics, and it has the ability to infect and interact with almost any nucleated cell. The T. cruzi-host cell interactions will trigger molecular signaling cascades in the host cell that will depend on the particular cell type and T. cruzi strain, and also on many different experimental variables. In this review we collect data from multiple transcriptomic and functional studies performed in different infection models, in order to highlight key differences between works that in our opinion should be addressed when comparing and discussing results. In particular, we focus on changes in the respiratory chain and oxidative phosphorylation of host cells in response to infection, which depends on the experimental model of T. cruzi infection. Finally, we also discuss host cell responses which reiterate independently of the strain, cell type and experimental conditions.

Host-pathogen transcriptomics: Trypanosoma cruzi as a model for studying RNA contamination

Cellular infection assays constitute essential tools to understand host-pathogen interactions, particularly for intracellular microorganisms that are produced in cell lines are needed to propagate the microorganism. In this work, we demonstrate that RNA derived from Vero cells is an important contaminant to consider in order to avoid false positive results in transcriptomic experiments. We study the cross-contamination on a Trypanosoma cruzi cell infection model, the etiological agent of Chagas disease. We implemented the most frequently used trypanosome-purification protocols and, for all of them, we detected RNAs derived from Vero cells in trypomastigote extracts. For some of the protocols we also detected Vero RNAs in infected human cells. We also found this type of contamination in microarray experiments of human samples infected with T. cruzi. Concerning Illumina RNA-Seq data, we found that the contamination with Vero cells is probably introducing spurious results. Finally, we recommend a protocol to purify trypomastigotes, which showed a high percentage of trypomastigote recovery and the absence of Vero contamination in infected human samples. Avoiding this type of contamination should be an important factor to consider during experimental design, in order to minimize false positive results in transcriptomic studies as well as RNA contamination in vaccine production. SIGNIFICANCE: Transcriptomic studies are widely used to understand host-pathogen interactions. When the pathogen is an intracellular microorganism, an additional mammalian cell system can be needed to propagate it. In this work we demonstrate that pathogens purified from infected monolayers can carry RNAs from these mammalian cells, and that this ambient RNA contamination is probably producing false positive results in subsequent transcriptomic studies performed with qRT-PCR, microarrays or Next Generation Sequencing.

Close encounters between Trypanosoma cruzi and the host mammalian cell: Lessons from genome-wide expression studies

Trypanosoma cruzi is the etiologic agent of Chagas disease, a life-threatening disease that affects different tissues. Within its mammalian host, T. cruzi develops molecular strategies for successful invasion of different cell types and adaptation to the intracellular environment. Conversely, the host cell responds to the infection by activating intracellular pathways to control parasite replication. Here, we reviewed genome-wide expression studies based on microarray and RNA-seq data from both parasite and host genes generated from animal models of infection as well as from Chagas disease patients. As expected, analyses of T. cruzi genes highlighted changes related to parasite energy metabolism and cell surface molecules, whereas host cell transcriptome emphasized the role of immune response genes. Besides allowing a better understanding of mechanisms behind the pathogenesis of Chagas disease, these studies provide essential information for the development of new therapies as well as biomarkers for diagnosis and assessment of disease progression.

Early Trypanosoma cruzi Infection Triggers mTORC1-Mediated Respiration Increase and Mitochondrial Biogenesis in Human Primary Cardiomyocytes

Chagasic chronic cardiomyopathy is one of the most frequent and severe manifestations of Chagas disease, caused by the parasite Trypanosoma cruzi. The pathogenic and biochemical mechanisms responsible for cardiac lesions remain not completely understood, although it is clear that hypertrophy and subsequent heart dilatation is in part caused by the direct infection of cardiomyocytes. In this work, we evaluated the initial response of human cardiomyocytes to T. cruzi infection by transcriptomic profiling. Immediately after infection, cardiomyocytes dramatically change their gene expression patterns, up regulating most of the genes encoding for respiratory chain, oxidative phosphorylation and protein synthesis. We found that these changes correlate with an increase in basal and maximal respiration, as well as in spare respiratory capacity, which is accompanied by mitochondrial biogenesis pgc-1α independent. We also demonstrate that these changes are mediated by mTORC1 and reversed by rapamycin, resembling the molecular mechanisms described for the non-chagasic hypertrophic cardiomyopathy. The results of the present work identify that early during infection, the activation of mTORC1, mitochondrial biogenesis and improvement in oxidative phosphorylation are key biochemical changes that provide new insights into the host response to parasite infection and the pathogenesis of chronic chagasic cardiomyopathy. The finding that this phenotype can be reversed opens a new perspective in the treatment of Chagas disease, through the identification of host targets, and the use of combined parasite and host targeted therapies, in order to prevent chagasic cardiomyopathy.

Cell therapies for Chagas disease

In this review of cell therapies in Chagas disease, we cover aspects related to the disease, its treatment and world demographics, before proceeding to describe the preclinical and clinical trials performed using cell therapies in the search for an alternative therapy for the most severe and lethal form of this disease, chronic chagasic cardiomyopathy.

AKT network of genes and impaired myocardial contractility during murine acute Chagasic myocarditis

Chagasic disease is associated with high morbidity in Latin America. Acute Chagasic myocarditis is consistently found in acute infections, but little is known about its contribution to chronic cardiomyopathy. The aim of the study was to phenotypically characterize two strains of mice with differential Chagas infection susceptibility and correlate strain myocarditis phenotypes with heart tissue gene expression. C57BL/6J and Balb/c mice were injected intraperitoneally with 0 or 150-200 tissue-derived trypomastigotes (Tulahuen strain). Echocardiograms, brain natriuretic peptide, and troponin were measured. Heart tissue was harvested for histopathological analysis and gene expression profiling on microarrays. Genes differently expressed between infected Balb/c and C57BL/6J mice were identified. Echocardiograms showed differences in Balb/c versus C57BL/6J infected mice in heart rate (413 versus 476 beats per minute; P = 0.0001), stroke volume (31.9 ± 9.3 versus 39.2 ± 5.5 μL; P = 0.03), and cardiac output (13.1 ± 3.5 versus 18.7 ± 3.2 μL/min; P = 0.002). Gene expression at 4 weeks analysis showed 32 statistically significant (q value < 0.05) differentially expressed genes between infected Balb/c and C57BL/6J mice that were enriched for genes related to the protein kinase B (AKT) pathway. These specific phenotypic features of cardiac response during acute Chagasic myocarditis may, in part, be related to host AKT network regulation.

The quality of methods reporting in parasitology experiments

There is a growing concern both inside and outside the scientific community over the lack of reproducibility of experiments. The depth and detail of reported methods are critical to the reproducibility of findings, but also for making it possible to compare and integrate data from different studies. In this study, we evaluated in detail the methods reporting in a comprehensive set of trypanosomiasis experiments that should enable valid reproduction, integration and comparison of research findings. We evaluated a subset of other parasitic (Leishmania, Toxoplasma, Plasmodium, Trichuris and Schistosoma) and non-parasitic (Mycobacterium) experimental infections in order to compare the quality of method reporting more generally. A systematic review using PubMed (2000-2012) of all publications describing gene expression in cells and animals infected with Trypanosoma spp was undertaken based on PRISMA guidelines; 23 papers were identified and included. We defined a checklist of essential parameters that should be reported and have scored the number of those parameters that are reported for each publication. Bibliometric parameters (impact factor, citations and h-index) were used to look for association between Journal and Author status and the quality of method reporting. Trichuriasis experiments achieved the highest scores and included the only paper to score 100% in all criteria. The mean of scores achieved by Trypanosoma articles through the checklist was 65.5% (range 32-90%). Bibliometric parameters were not correlated with the quality of method reporting (Spearman's rank correlation coefficient <-0.5; p>0.05). Our results indicate that the quality of methods reporting in experimental parasitology is a cause for concern and it has not improved over time, despite there being evidence that most of the assessed parameters do influence the results. We propose that our set of parameters be used as guidelines to improve the quality of the reporting of experimental infection models as a pre-requisite for integrating and comparing sets of data.

Bone marrow-derived cell therapy in chagasic cardiac disease: a review of pre-clinical and clinical results

Chagas disease is caused by a protozoan parasite Trypanosoma cruzi, which infects people through blood sucking insects. It is endemic in Latin America and the disease is being spread to developed countries as a result of the migration of infected individuals. In its chronic stage, Chagas disease can lead to a severe cardiomyopathy for which there is currently no cure. End-stage patients require heart transplantation, thus demanding new therapeutic modalities. Cell-based therapy has been proposed as an alternative for various forms of heart disease. Here we review the experimental evidence that led to the use of bone marrow-derived cells in putative therapy for chronic chagasic cardiomyopathy in animal models and in clinical trials, discussing the reasons for failure of the translation of results from mice to men.

Pathogenesis of Chagas disease cardiomyopathy

Chagas disease, or American trypanosomiasis, is a parasitic infection caused by the flagellate protozoan Trypanosoma cruzi. Chagas disease is mainly affecting rural populations in Mexico and Central and South America. The World Health Organization estimates that 300 000 new cases of Chagas disease occur every year and approximately 20 000 deaths are attributable to Chagas. However, this organisation classified Chagas disease as a neglected tropical disease. The economic burden of this disease is significant. In many Latin American countries, the direct and indirect costs, including the cost of health care in dollars and loss of productivity, attributable to Chagas disease ranges from $40 million to in excess of $800 million per nation per annum. So, it remains a contemporary public health concern. In chronic phase, mortality is primarily due to the rhythm disturbances and congestive heart failure that result from the chronic inflammatory cardiomyopathy (CCC) due to the persistence presence of parasites in the heart tissue. Mechanisms underlying differential progression to CCC are still incompletely understood. In the last decades immunological proteomic genetic approaches lead to significant results which help to disperse the veil covering the knowledge of the pathogenic process. Here, we reported these significant progresses.

Gap junctions and chagas disease

Gap junction channels provide intercellular communication between cells. In the heart, these channels coordinate impulse propagation along the conduction system and through the contractile musculature, thereby providing synchronous and optimal cardiac output. As in other arrhythmogenic cardiac diseases, chagasic cardiomyopathy is associated with decreased expression of the gap junction protein connexin43 (Cx43) and its gene. Our studies of cardiac myocytes infected with Trypanosoma cruzi have revealed that synchronous contraction is greatly impaired and gap junction immunoreactivity is lost in infected cells. Such changes are not seen for molecules forming tight junctions, another component of the intercalated disc in cardiac myocytes. Transcriptomic studies of hearts from mouse models of Chagas disease and from acutely infected cardiac myocytes in vitro indicate profound remodelling of gene expression patterns involving heart rhythm determinant genes, suggesting underlying mechanisms of the functional pathology. One curious feature of the altered expression of Cx43 and its gene expression is that it is limited in both extent and location, suggesting that the more global deterioration in cardiac function may result in part from spread of damage signals from more seriously compromised cells to healthier ones.

Neurodegeneration and neuroregeneration in Chagas disease

Autonomic dysfunction plays a significant role in the development of chronic Chagas disease (CD). Destruction of cardiac parasympathetic ganglia can underlie arrhythmia and heart failure, while lesions of enteric neurons in the intestinal plexuses are a direct cause of aperistalsis and megasyndromes. Neuropathology is generated by acute infection when the parasite, though not directly damaging to neuronal cells, elicits immune reactions that can become cytotoxic, inducing oxidative stress and neurodegeneration. Anti-neuronal autoimmunity may further contribute to neuropathology. Much less clear is the mechanism of subsequent neuronal regeneration in patients that survive acute infection. Morphological and functional recovery of the peripheral neurons in these patients correlates with the absence of CD clinical symptoms, while persistent neuronal deficiency is observed for the symptomatic group. The discovery that Trypanosoma cruzi trans-sialidase can moonlight as a parasite-derived neurotrophic factor (PDNF) suggests that the parasite might influence the balance between neuronal degeneration and regeneration. PDNF functionally mimics mammalian neurotrophic factors in that it binds and activates neurotrophin Trk tyrosine kinase receptors, a mechanism which prevents neurodegeneration. PDNF binding to Trk receptors triggers PI3K/Akt/GSK-3β and MAPK/Erk/CREB signalling cascades which in neurons translates into resistance to oxidative and nutritional stress, and inhibition of apoptosis, whereas in the cytoplasm of infected cells, PDNF represents a substrate-activator of the host Akt kinase, enhancing host-cell survival until completion of the intracellular cycle of the parasite. Such dual activity of PDNF provides sustained activation of survival mechanisms which, while prolonging parasite persistence in host tissues, can underlie distinct outcomes of CD.

Microarray analysis of the mammalian thromboxane receptor-Trypanosoma cruzi interaction

Trypanosoma cruzi, the etiological agent of Chagas disease, causes vasculopathy and cardiomyopathy in humans and is associated with elevated levels of several vasoactive molecules such as nitric oxide, endothelin-1 and thromboxane A 2 (TXA 2). Parasite derived TXA 2 modulates vasculopathy and other pathophysiological features of Chagasic cardiomyopathy. Previously, we demonstrated that in response to infection with T. cruzi, TXA 2 receptor (TP) null mice displayed increased parasitemia; mortality and cardiac pathology compared with wild type (WT) and TXA 2 synthase null mice. In order to further study the role of TXA 2-TP signaling in the development of Chagas disease, GeneChip microarrays were used to detect transcriptome changes in rat fat pad endothelial cells (RFP-ECs) which is incapable of TXA 2 signaling (TP null) to that of control (wild type) and RFP-EC with reconstituted TP expression. Genes that were significantly regulated due to infection were identified using a time course of 2, 18 and 48 hrs post infection. We identified several key genes such as suppressor of cytokine signaling (SOCS-5), several cytokines (CSF-1, CXCF ligands), and MAP kinases (MAPK-1, Janus kinase) that were upregulated in the absence of TP signaling. These data underscore the importance of the interaction of the parasite with mammalian TP and may explain the increased mortality and cardiovascular pathology observed in infected TP null mice.

Gene network analysis during early infection of human coronary artery smooth muscle cells by Trypanosoma cruzi and Its gp83 ligand

Trypanosoma cruzi, the causative agent of Chagas' disease, infects heart and muscle cells leading to cardiac arrest, followed by death. The genetic architectures in the early T. cruzi infection process of human cells are unknown. To understand the genetic architectures of the early invasion process of T. cruzi, we conducted gene transcription microarray analysis, followed by gene network construction of the host cell response in primary human coronary artery smooth muscle (HCASM) cells infected with T. cruzi or exposed to T. cruzi gp83, a ligand used by the trypanosome to bind host cells. Using seven RT-PCR verified up-regulated genes (FOSB, ATF5, INPP1, CCND2, THBS1, LAMC1, and APLP2) as the seed for network construction, we built an interaction network of the early T. cruzi infection process containing 165 genes, connected by 598 biological interactions. This interactome network is centered on the BCL6 gene as a hub. Silencing the expression of two seed genes (THBS1 and LAMC1) by RNAi reduced T. cruzi infection. Overall, our results elucidate the significant and complex process involved in T. cruzi infection of HCASM cells at the transcriptome level. This is the first elucidation into the interactome network in human cells caused by T. cruzi and its gp83 ligand.

Gene expression changes associated with myocarditis and fibrosis in hearts of mice with chronic chagasic cardiomyopathy

Chronic chagasic cardiomyopathy is a leading cause of heart failure in Latin American countries. About 30% of Trypanosoma cruzi-infected individuals develop this severe symptomatic form of the disease, characterized by intense inflammatory response accompanied by fibrosis in the heart. We performed an extensive microarray analysis of hearts from a mouse model of this disease and identified significant alterations in expression of approximately 12% of the sampled genes. Extensive up-regulations were associated with immune-inflammatory responses (chemokines, adhesion molecules, cathepsins, and major histocompatibility complex molecules) and fibrosis (extracellular matrix components, lysyl oxidase, and tissue inhibitor of metalloproteinase 1). Our results indicate potentially relevant factors involved in the pathogenesis of the disease that may provide new therapeutic targets in chronic Chagas disease.

Transcriptomic signatures of alterations in a myoblast cell line infected with four distinct strains of Trypanosoma cruzi

We examined the extent to which different Trypanosoma cruzi strains induce transcriptomic changes in cultured L(6)E(9) myoblasts 72 hours after infection with Brazil (TC I), Y (TC II), CL (TC II), and Tulahuen (TC II) strains. Expression of 6,289 distinct, fully annotated unigenes was quantified with 27,000 rat oligonucleotide arrays in each of the four replicas of all control and infected RNA samples. Considering changes greater than 1.5-fold and P values < 0.05, the Tulahuen strain was the most disruptive to host transcriptome (17% significantly altered genes), whereas the Y strain altered only 6% of the genes. The significantly altered genes in the infected cells were largely different among the strains, and only 21 genes were similarly changed by all four strains. However, myoblasts infected with different strains showed proportional overall gene-expression alterations. These results indicate that infection with different parasite strains modulates similar but not identical pathways in the host cells.

Transcriptomic alterations in Trypanosoma cruzi-infected cardiac myocytes

Trypanosoma cruzi infection is a major cause of cardiomyopathy. Previous gene profiling studies of infected mouse hearts have revealed prominent changes in gene expression within many functional pathways. This variety of transcriptomic changes in infected mice raises the question of whether gene expression alterations in whole hearts are due to changes in infected cardiac myocytes or other cells or even to systemic effects of the infection on the heart. We employed microarrays to examine infected cardiac myocyte cultures 48 h post-infection. Statistical comparison of gene expression levels of 7624 well annotated unigenes in four independent cultures of infected and uninfected myocytes detected substantial (>or=1.5 absolute fold changes) in 420 (5.5%) of the sampled genes. Major categories of affected genes included those involved in immune response, extracellular matrix and cell adhesion. These findings on infected cardiac myocytes in culture reveal that alterations in cardiac gene expression described in Chagas disease are the consequence of both direct infection of the myocytes themselves as well as resulting from the presence of other cell types in the myocardium and systemic effects of infection.

Micro-positron emission tomography in the evaluation of Trypanosoma cruzi-induced heart disease: Comparison with other modalities

Noninvasive assessment of cardiac structure and function is essential to understand the natural course of murine infection with Trypanosoma cruzi. Magnetic resonance imaging (MRI) and echocardiography have been used to monitor anatomy and function; positron emission tomography (PET) is ideal for monitoring metabolic events in the myocardium. Mice infected with T. cruzi (Brazil strain) were imaged 15-100 days post infection (dpi). Quantitative (18)F-FDG microPET imaging, MRI and echocardiography were performed and compared. Tracer ((18)F-FDG) uptake was significantly higher in infected mice at all days of infection, from 15 to 100 dpi. Dilatation of the right ventricular chamber was observed by MRI from 30 to 100 dpi in infected mice. Echocardiography revealed significantly reduced ejection fraction by 60 dpi. Combination of these three complementary imaging modalities makes it possible to noninvasively quantify cardiovascular function, morphology, and metabolism from the earliest days of infection through the chronic phase.

Perspectives on Trypanosoma cruzi-induced heart disease (Chagas disease)

Chagas disease is caused by the parasite Trypanosoma cruzi. It is a common cause of heart disease in endemic areas of Latin America. The year 2009 marks the 100th anniversary of the discovery of T cruzi infection and Chagas disease by the Brazilian physician Carlos Chagas. Chagasic cardiomyopathy develops in from 10% to 30% of persons who are chronically infected with this parasite. Echocardiography and magnetic resonance imaging (MRI) are important modalities in the evaluation and prognostication of individuals with chagasic heart disease. The etiology of chagasic heart disease likely is multifactorial. Parasite persistence, autoimmunity, and microvascular abnormalities have been studied extensively as possible pathogenic mechanisms. Experimental studies suggest that alterations in cardiac gap junctions may be etiologic in the pathogenesis of conduction abnormalities. The diagnosis of chronic Chagas disease is made by serology. The treatment of this infection has shortcomings that need to be addressed. Cardiac transplantation and bone marrow stem cell therapy for persons with Chagas disease have received increasing research attention in recent years.

Perspectives on the Trypanosoma cruzi-host cell receptor interactions

Chagas disease is caused by the parasite Trypanosoma cruzi. The critical initial event is the interaction of the trypomastigote form of the parasite with host receptors. This review highlights recent observations concerning these interactions. Some of the key receptors considered are those for thromboxane, bradykinin, and for the nerve growth factor TrKA. Other important receptors such as galectin-3, thrombospondin, and laminin are also discussed. Investigation into the molecular biology and cell biology of host receptors for T. cruzi may provide novel therapeutic targets.