Trypanosoma cruzi highjacks TrkC to enter cardiomyocytes and cardiac fibroblasts while exploiting TrkA for cardioprotection against oxidative stress

Impact of Laboratory-Adapted Intracellular Trypanosoma cruzi Strains on the Activity Profiles of Compounds with Anti-T. cruzi Activity

Chagas disease is caused by infection with the protozoan parasite, Trypanosoma cruzi. The disease causes ~12,000 deaths annually and is one of the world's 20 neglected tropical diseases, as defined by the World Health Organisation. The drug discovery pipeline for Chagas disease currently has few new clinical candidates, with high attrition rates an ongoing issue. To determine if the Trypanosoma cruzi strain utilised to assess in vitro compound activity impacts activity, a comparison of laboratory-adapted T. cruzi strains from differing geographical locations was undertaken for a selection of compounds with anti-T. cruzi activity. To minimise the possible effect of differences in experimental methodology, the same host cell and multiplicity of infection were utilised. To determine whether the compound exposure time influenced results, activity was determined following exposure for 48 and 72 h of incubation. To ascertain whether replication rates affected outcomes, comparative rates of replication of the T. cruzi strains were investigated, using the nucleoside analogue, 5-ethynyl-2'-deoxyuridine. Minimal differences in the in vitro activity of compounds between strains were observed following 48 h incubation, whereas significant differences were observed following 72 h incubation, in particular for the cytochrome P450 inhibitors tested and the cell cycle inhibitor, camptothecin. Thus, the use of panels of laboratory adapted strains in vitro may be dependent on the speed of action that is prioritised. For the identification of fast-acting compounds, an initial shorter duration assay using a single strain may be used. A longer incubation to identify compound activity may alternatively require profiling of compounds against multiple T. cruzi strains.

microRNA-454-mediated NEDD4-2/TrkA/cAMP axis in heart failure: Mechanisms and cardioprotective implications

The current study aimed to investigate the mechanism by which miR-454 influences the progression of heart failure (HF) in relation to the neural precursor cell expressed, developmentally downregulated 4-2 (NEDD4-2)/tropomyosin receptor kinase A (TrkA)/cyclic adenosine 3',5'-monophosphate (cAMP) axis. Sprague-Dawley rats were used to establish a HF animal model via ligation of the left anterior descending branch of the coronary artery. The cardiomyocyte H9c2 cells were treated with H₂ O₂ to stimulate oxidative stress injury in vitro. RT-qPCR and Western blot assay were subsequently performed to determine the expression patterns of miR-454, NEDD4-2, TrkA, apoptosis-related proteins and cAMP pathway markers. Dual-luciferase reporter gene assay coupled with co-immunoprecipitation was performed to elucidate the relationship between miR-454, NEDD4-2 and TrkA. Gain- or loss-of-function experiments as well as rescue experiments were conducted via transient transfection (in vitro) and adenovirus infection (in vivo) to examine their respective functions on H9c2 cell apoptosis and myocardial damage. Our results suggested that miR-454 was aberrantly downregulated in the context of HF, while evidence was obtained suggesting that it targeted NEDD4-2 to downregulate NEDD4-2 in cardiomyocytes. miR-454 exerted anti-apoptotic and protective effects on cardiomyocytes through inhibition of NEDD4-2, while NEDD4-2 stimulated ubiquitination and degradation of TrkA protein. Furthermore, miR-454 activated the cAMP pathway via the NEDD4-2/TrkA axis, which ultimately suppressed cardiomyocyte apoptosis and attenuated myocardial damage. Taken together, the key findings of the current study highlight the cardioprotective role of miR-454, which is achieved through activation of the cAMP pathway by impairing NEDD4-2-induced TrkA ubiquitination.

Precision Health for Chagas Disease: Integrating Parasite and Host Factors to Predict Outcome of Infection and Response to Therapy

Chagas disease, caused by the infection with the protozoan parasite Trypanosoma cruzi, is clinically manifested in approximately one-third of infected people by inflammatory heart disease (cardiomyopathy) and, to a minor degree, gastrointestinal tract disorders (megaesophagus or megacolon). Chagas disease is a zoonosis transmitted among animals and people through the contact with triatomine bugs, which are found in much of the western hemisphere, including most countries of North, Central and South America, between parallels 45° north (Minneapolis, USA) and south (Chubut Province, Argentina). Despite much research on drug discovery for T. cruzi, there remain only two related agents in widespread use. Likewise, treatment is not always indicated due to the serious side effects of these drugs. On the other hand, the epidemiology and pathogenesis of Chagas disease are both highly complex, and much is known about both. However, it is still impossible to predict what will happen in an individual person infected with T. cruzi, because of the highly variability of parasite virulence and human susceptibility to infection, with no definitive molecular predictors of outcome from either side of the host-parasite equation. In this Minireview we briefly discuss the current state of T. cruzi infection and prognosis and look forward to the day when it will be possible to employ precision health to predict disease outcome and determine whether and when treatment of infection may be necessary.

In vitro models for investigation of the host-parasite interface - possible applications in acute Chagas disease

Chagas disease (CD), caused by Trypanosoma cruzi, is the main parasitic disease in the Western Hemisphere, with an increasing number of cases, especially in non-endemic regions. The disease is characterized by cardiomegaly and mega viscera, nevertheless, the clinical outcome is hard to predict, underscoring the need for further research into the pathophysiology of CD. Even though most basic and translational research involving CD is performed using in vivo models, in vitro models arise as an ethical, rapidly evolving, and physiologically relevant alternative for CD research. In the present review, we discuss the past and recent in vitro models available to study the host-parasite interface in cardiac and intestinal CD, critically analyzing the possibilities and limitations of state-of-the-art alternatives for the CD host-parasite investigation.

Trypanosoma cruzi Neurotrophic Factor Facilitates Cardiac Repair in a Mouse Model of Chronic Chagas Disease

Most patients acutely infected with Trypanosoma cruzi undergo short-term structural and functional cardiac alterations that heal without sequelae. By contrast, in patients whose disease progresses to chronic infection, irreversible degenerative chronic Chagas cardiomyopathy (CCC) may develop. To account for the contrast between cardiac regeneration in high-parasitism acute infection and progressive cardiomyopathy in low-parasitism CCC, we hypothesized that T. cruzi expresses repair factors that directly facilitate cardiac regeneration. We investigated, as one such repair factor, the T. cruzi parasite-derived neurotrophic factor (PDNF), known to trigger survival of cardiac myocytes and fibroblasts and upregulate chemokine chemokine C-C motif ligand 2, which promotes migration of regenerative cardiac progenitor cells (CPCs). Using in vivo and in vitro models of Chagas disease, we tested whether T. cruzi PDNF promotes cardiac repair. Quantitative PCR and flow cytometry of heart tissue revealed that stem-cell antigen-1 (Sca-1⁺) CPCs expand in acute infection in parallel to parasitism. Recombinant PDNF induced survival and expansion of ex vivo CPCs, and intravenous administration of PDNF into naïve mice upregulated mRNA of cardiac stem-cell marker Sca-1. Furthermore, in CCC mice, a 3-week intravenous administration of PDNF protocol induced CPC expansion and reversed left ventricular T-cell accumulation and cardiac remodeling including fibrosis. Compared with CCC vehicle-treated mice, which developed severe atrioventricular block, PDNF-treated mice exhibited reduced frequency and severity of conduction abnormalities. Our findings are in support of the novel concept that T. cruzi uses PDNF to promote mutually beneficial cardiac repair in Chagas disease. This could indicate a possible path to prevention or treatment of CCC.

A systematic review of the Trypanosoma cruzi genetic heterogeneity, host immune response and genetic factors as plausible drivers of chronic chagasic cardiomyopathy

Chagas disease is a complex tropical pathology caused by the kinetoplastid Trypanosoma cruzi. This parasite displays massive genetic diversity and has been classified by international consensus in at least six Discrete Typing Units (DTUs) that are broadly distributed in the American continent. The main clinical manifestation of the disease is the chronic chagasic cardiomyopathy (CCC) that is lethal in the infected individuals. However, one intriguing feature is that only 30-40% of the infected individuals will develop CCC. Some authors have suggested that the immune response, host genetic factors, virulence factors and even the massive genetic heterogeneity of T. cruzi are responsible of this clinical pattern. To date, no conclusive data support the reason why a few percentages of the infected individuals will develop CCC. Therefore, we decided to conduct a systematic review analysing the host genetic factors, immune response, cytokine production, virulence factors and the plausible association of the parasite DTUs and CCC. The epidemiological and clinical implications are herein discussed.

Astrocyte Apoptosis and HIV Replication Are Modulated in Host Cells Coinfected with Trypanosoma cruzi

The protozoan Trypanosoma cruzi is the etiological agent of Chagas disease. In immunosuppressed individuals, as it occurs in the coinfection with human immunodeficiency virus (HIV), the central nervous system may be affected. In this regard, reactivation of Chagas disease is severe and often lethal, and it accounts for meningoencephalitis. Astrocytes play a crucial role in the environment maintenance of healthy neurons; however, they can host HIV and T. cruzi. In this report, human astrocytes were infected in vitro with both genetically modified-pathogens to express alternative fluorophore. As evidenced by fluorescence microscopy and flow cytometry, HIV and T. cruzi coexist in the same astrocyte, likely favoring reciprocal interactions. In this context, lower rates of cell death were observed in both T. cruzi monoinfected-astrocytes and HIV-T. cruzi coinfection in comparison with those infected only with HIV. The level of HIV replication is significantly diminished under T. cruzi coinfection, but without affecting the infectivity of the HIV progeny. This interference with viral replication appears to be related to the T. cruzi multiplication rate or its increased intracellular presence but does not require their intracellular cohabitation or infected cell-to-cell contact. Among several Th1/Th2/Th17 profile-related cytokines, only IL-6 was overexpressed in HIV-T. cruzi coinfection exhibiting its cytoprotective role. This study demonstrates that T. cruzi and HIV are able to coinfect astrocytes thus altering viral replication and apoptosis.

Automated high-content assay for compounds selectively toxic to Trypanosoma cruzi in a myoblastic cell line

Background

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, represents a very important public health problem in Latin America where it is endemic. Although mostly asymptomatic at its initial stage, after the disease becomes chronic, about a third of the infected patients progress to a potentially fatal outcome due to severe damage of heart and gut tissues. There is an urgent need for new drugs against Chagas disease since there are only two drugs available, benznidazole and nifurtimox, and both show toxic side effects and variable efficacy against the chronic stage of the disease.

Methodology/Principal Findings

Genetically engineered parasitic strains are used for high throughput screening (HTS) of large chemical collections in the search for new anti-parasitic compounds. These assays, although successful, are limited to reporter transgenic parasites and do not cover the wide T. cruzi genetic background. With the aim to contribute to the early drug discovery process against Chagas disease we have developed an automated image-based 384-well plate HTS assay for T. cruzi amastigote replication in a rat myoblast host cell line. An image analysis script was designed to inform on three outputs: total number of host cells, ratio of T. cruzi amastigotes per cell and percentage of infected cells, which respectively provides one host cell toxicity and two T. cruzi toxicity readouts. The assay was statistically robust (Z´ values >0.6) and was validated against a series of known anti-trypanosomatid drugs.

Conclusions/Significance

We have established a highly reproducible, high content HTS assay for screening of chemical compounds against T. cruzi infection of myoblasts that is amenable for use with any T. cruzi strain capable of in vitro infection. Our visual assay informs on both anti-parasitic and host cell toxicity readouts in a single experiment, allowing the direct identification of compounds selectively targeted to the parasite.

Chagas disease is a zoonosis caused by the protozoan parasite Trypanosoma cruzi. Endemic to Central and South America, it affects over 10 million people and many more live in risk transmission areas. Although mostly asymptomatic at its initial acute stage in humans, damages can occur over the years in many tissues such as T. cruzi-hosting heart and digestive track. For over 40 years the chemotherapy of Chagas disease has relied on the use of two drugs, benznidazole and nifurtimox, though both are known to lead to severe side effects which often prompt to the discontinuation of the treatments. Despite having good efficacy against the acute stage of infection, its efficacy against the chronic stage is under question. Therefore, there is an urgent unmet need of new anti-T. cruzi drugs. Several efforts have been made in the last years to establish reliable high throughput cell based in vitro assays to be used for drug discovery against Chagas. With the aim to contribute to this field here we describe the development of a new automated image-based assay to identify new compounds against T. cruzi that has been set up using the myoblastic rat cell line H9c2 as cell-cycling amastigotes hosting cells.

Parasite-derived neurotrophic factor/trans-sialidase of Trypanosoma cruzi links neurotrophic signaling to cardiac innate immune response

The Chagas' disease parasite Trypanosoma cruzi elicits a potent inflammatory response in acutely infected hearts that keeps parasitism in check and triggers cardiac abnormalities. A most-studied mechanism underlying innate immunity in T. cruzi infection is Toll-like receptor (TLR) activation by lipids and other parasite molecules. However, yet-to-be-identified pathways should exist. Here, we show that T. cruzi strongly upregulates monocyte chemoattractant protein 1 (MCP-1)/CCL2 and fractalkine (FKN)/CX3CL1 in cellular and mouse models of heart infection. Mechanistically, upregulation of MCP-1 and FKN stems from the interaction of parasite-derived neurotrophic factor (PDNF)/trans-sialidase with neurotrophic receptors TrkA and TrkC, as assessed by pharmacological inhibition, neutralizing antibodies, and gene silencing studies. Administration of a single dose of intravenous PDNF to naive mice results in a dose-dependent increase in MCP-1 and FKN in the heart and liver with pulse-like kinetics that peak at 3 h postinjection. Intravenous PDNF also augments MCP-1 and FKN in TLR signaling-deficient MyD88-knockout mice, underscoring the MyD88-independent action of PDNF. Although single PDNF injections do not increase MCP-1 and FKN receptors, multiple PDNF injections at short intervals up the levels of receptor transcripts in the heart and liver, suggesting that sustained PDNF triggers cell recruitment at infection sites. Thus, given that MCP-1 and FKN are chemokines essential to the recruitment of immune cells to combat inflammation triggers and to enhance tissue repair, our findings uncover a new mechanism in innate immunity against T. cruzi infection mediated by Trk signaling akin to an endogenous inflammatory and fibrotic pathway resulting from cardiomyocyte-TrkA recognition by matricellular connective tissue growth factor (CTGF/CCN2).

Endothelial transmigration by Trypanosoma cruzi

Chagas heart disease, the leading cause of heart failure in Latin America, results from infection with the parasite Trypanosoma cruzi. Although T. cruzi disseminates intravascularly, how the parasite contends with the endothelial barrier to escape the bloodstream and infect tissues has not been described. Understanding the interaction between T. cruzi and the vascular endothelium, likely a key step in parasite dissemination, could inform future therapies to interrupt disease pathogenesis. We adapted systems useful in the study of leukocyte transmigration to investigate both the occurrence of parasite transmigration and its determinants in vitro. Here we provide the first evidence that T. cruzi can rapidly migrate across endothelial cells by a mechanism that is distinct from productive infection and does not disrupt monolayer integrity or alter permeability. Our results show that this process is facilitated by a known modulator of cellular infection and vascular permeability, bradykinin, and can be augmented by the chemokine CCL2. These represent novel findings in our understanding of parasite dissemination, and may help identify new therapeutic strategies to limit the dissemination of the parasite.