Virulence of Trypanosoma cruzi Strains Is Related to the Differential Expression of Innate Immune Receptors in the Heart

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

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

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

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

Molecular regulation of NLRP3 inflammasome activation during parasitic infection

Parasitic diseases are a serious global health concern, causing many common and severe infections, including Chagas disease, leishmaniasis, and schistosomiasis. The NLRP3 inflammasome belongs to the NLR (nucleotide-binding domain leucine-rich-repeat-containing proteins) family, which are cytosolic proteins playing key roles in the detection of pathogens. NLRP3 inflammasomes are activated in immune responses to Plasmodium, Leishmania, Toxoplasma gondii, Entamoeba histolytica, Trypanosoma cruzi, and other parasites. The role of NLRP3 is not fully understood, but it is a crucial component of the innate immune response to parasitic infections and its functions as a sensor triggering the inflammatory response to the invasive parasites. However, while this response can limit the parasites' growth, it can also result in potentially catastrophic host pathology. This makes it essential to understand how NLRP3 interacts with parasites to initiate the inflammatory response. Plasmodium hemozoin, Leishmania glycoconjugate lipophosphoglycan (LPG) and E. histolytica Gal/GalNAc lectin can stimulate NLRP3 activation, while the dense granule protein 9 (GRA9) of T. gondii has been shown to suppress it. Several other parasitic products also have diverse effects on NLRP3 activation. Understanding the mechanism of NLRP3 interaction with these products will help to develop advanced therapeutic approaches to treat parasitic diseases. This review summarizes current knowledge of the NLRP3 inflammasome's action on the immune response to parasitic infections and aims to determine the mechanisms through which parasitic molecules either activate or inhibit its action.

Cardiac Abnormalities in a Predictive Mouse Model of Chagas Disease

Chronic Chagas cardiomyopathy (CCC) results from infection with the protozoan parasite Trypanosoma cruzi and is a prevalent cause of heart disease in endemic countries. We previously found that cardiac fibrosis can vary widely in C3H/HeN mice chronically infected with T. cruzi JR strain, mirroring the spectrum of heart disease in humans. In this study, we examined functional cardiac abnormalities in this host:parasite combination to determine its potential as an experimental model for CCC. We utilised electrocardiography (ECG) to monitor T. cruzi-infected mice and determine whether ECG markers could be correlated with cardiac function abnormalities. We found that the C3H/HeN:JR combination frequently displayed early onset CCC indicators, such as sinus bradycardia and right bundle branch block, as well as prolonged PQ, PR, RR, ST, and QT intervals in the acute stage. Our model exhibited high levels of cardiac inflammation and enhanced iNOS expression in the acute stage, but denervation did not appear to have a role in pathology. These results demonstrate the potential of the C3H/HeN:JR host:parasite combination as a model for CCC that could be used for screening new compounds targeted at cardiac remodelling and for examining the potential of antiparasitic drugs to prevent or alleviate CCC development and progression.

Vascular Growth Factor Inhibition with Bevacizumab Improves Cardiac Electrical Alterations and Fibrosis in Experimental Acute Chagas Disease

Chagas disease (CD) caused by Trypanosoma cruzi is a neglected illness and a major reason for cardiomyopathy in endemic areas. The existing therapy generally involves trypanocidal agents and therapies that control cardiac alterations. However, there is no treatment for the progressive cardiac remodeling that is characterized by inflammation, microvasculopathy and extensive fibrosis. Thus, the search for new therapeutic strategies aiming to inhibit the progression of cardiac injury and failure is necessary. Vascular Endothelial Growth Factor A (VEGF-A) is the most potent regulator of vasculogenesis and angiogenesis and has been implicated in inducing exacerbated angiogenesis and fibrosis in chronic inflammatory diseases. Since cardiac microvasculopathy in CD is also characterized by exacerbated angiogenesis, we investigated the effect of inhibition of the VEGF signaling pathway using a monoclonal antibody (bevacizumab) on cardiac remodeling and function. Swiss Webster mice were infected with Y strain, and cardiac morphological and molecular analyses were performed. We found that bevacizumab significantly increased survival, reduced inflammation, improved cardiac electrical function, diminished angiogenesis, decreased myofibroblasts in cardiac tissue and restored collagen levels. This work shows that VEGF is involved in cardiac microvasculopathy and fibrosis in CD and the inhibition of this factor could be a potential therapeutic strategy for CD.

The transcriptome landscape of 3D-cultured placental trophoblasts reveals activation of TLR2 and TLR3/7 in response to low Trypanosoma cruzi parasite exposure

Vertical transmission of Trypanosoma cruzi (T. cruzi) become a globalized health problem accounting for 22% of new cases of Chagas disease (CD). Congenital infection is now considered the main route of CD spread in non-endemic countries where no routine disease testing of pregnant women is implemented. The main mechanisms that lead to fetal infection by T. cruzi remain poorly understood. Mother-to-child transmission may occur when bloodstream trypomastigotes interact with the syncytiotrophoblasts (SYNs) that cover the placenta chorionic villi. These highly specialized cells function as a physical barrier and modulate immune responses against pathogen infections. To model the human placenta environment, we have previously used a three-dimensional (3D) cell culture system of SYNs that exhibits differentiation characteristics comparable to placental trophoblasts. Further, we have shown that 3D-grown SYNs are highly resistant to T. cruzi infection. In this work, we used RNA sequencing and whole transcriptome analysis to explore the immunological signatures that drive SYNs' infection control. We found that the largest category of differentially expressed genes (DEGs) are associated with inflammation and innate immunity functions. Quantitative RT-PCR evaluation of selected DEGs, together with detection of cytokines and chemokines in SYNs culture supernatants, confirmed the transcriptome data. Several genes implicated in the Toll-like receptors signaling pathways were upregulated in 3D-grown SYNs. In fact, TLR2 blockade and TLR3/7 knockdown stimulated T. cruzi growth, suggesting that these molecules play a significant role in the host cell response to infection. Ingenuity Pathway Analysis of DEGs predicted the activation of canonical pathways such as S100 protein family, pathogen induced cytokine storm, wound healing, HIF1α signaling and phagosome formation after T. cruzi exposure. Our findings indicate that SYNs resist infection by eliciting a constitutive pro-inflammatory response and modulating multiple defense mechanisms that interfere with the parasite's intracellular life cycle, contributing to parasite killing and infection control.

What Do You Need to Know before Studying Chagas Disease? A Beginner's Guide

Chagas disease is one of the most important tropical infections in the world and mainly affects poor people. The causative agent is the hemoflagellate protozoan Trypanosoma cruzi, which circulates among insect vectors and mammals throughout the Americas. A large body of research on Chagas disease has shown the complexity of this zoonosis, and controlling it remains a challenge for public health systems. Although knowledge of Chagas disease has advanced greatly, there are still many gaps, and it is necessary to continue generating basic and applied research to create more effective control strategies. The aim of this review is to provide up-to-date information on the components of Chagas disease and highlight current trends in research. We hope that this review will be a starting point for beginners and facilitate the search for more specific information.

Mitochondrial DNA induces nucleus pulposus cell pyroptosis via the TLR9-NF-κB-NLRP3 axis

BACKGROUND

Nucleus pulposus cell (NPC) death and progressive reduction play important roles in intervertebral disc degeneration (IVDD). As part of a damage-associated molecular pattern, mitochondrial DNA (mtDNA) can be recognized by TLR9 and triggers the expression of NF-κB and NLRP3 inflammasomes, inducing pyroptosis and inflammatory response. However, whether mtDNA induces NPC pyroptosis via the TLR9-NF-κB-NLRP3 axis and promotes IVDD remains uncertain.

METHODS

We constructed an in vitro NPC oxidative stress injury model to clarify the mechanism of mtDNA release, TLR9-NF-κB signaling pathway activation, and NPC injury. We further verified the mechanism of action underlying the inhibition of mtDNA release or TLR9 activation in NPC injury in vitro. We then constructed a rat punctured IVDD model to understand the mechanism inhibiting mtDNA release and TLR9 activation in IVDD.

RESULTS

We used human NP specimen assays to show that the expression levels of TLR9, NF-κB, and NLRP3 inflammasomes correlated with the degree of IVDD. We demonstrated that mtDNA mediated TLR9-NF-κB-NLRP3 axis activation in oxidative stress-induced human NPC pyroptosis in vitro. Oxidative stress can damage the mitochondria of NPCs, causing the opening of the mitochondrial permeability transition pores (mPTP) and leading to the release of mtDNA into the cytosol. Furthermore, inhibition of mPTP opening or TLR9 activation blocked TLR9-NF-κB-NLRP3 axis activation and thereby mediated NPC pyroptosis and IVDD.

CONCLUSION

mtDNA plays a key role in mediating NPC pyroptosis and IVDD via the TLR9-NF-κB-NLRP3 axis. Our findings provide new potential targets for IVDD.

Nitazoxanide: A Drug Repositioning Compound with Potential Use in Chagas Disease in a Murine Model

Chagas disease (ChD), caused by Trypanosoma cruzi, is the most serious parasitosis in the western hemisphere. Benznidazole and nifurtimox, the only two trypanocidal drugs, are expensive, difficult to obtain, and have severe side effects. Nitazoxanide has shown to be effective against protozoa, bacteria, and viruses. This study aimed to evaluate the nitazoxanide efficacy against the Mexican T. cruzi Ninoa strain in mice. Infected animals were orally treated for 30 days with nitazoxanide (100 mg/kg) or benznidazole (10 mg/kg). The clinical, immunological, and histopathological conditions of the mice were evaluated. Nitazoxanide- or benznidazole-treated mice had longer survival and less parasitemia than those without treatment. Antibody production in the nitazoxanide-treated mice was of the IgG1-type and not of the IgG2-type as in the benznidazole-treated mice. Nitazoxanide-treated mice had significantly high IFN-γ levels compared to the other infected groups. Serious histological damage could be prevented with nitazoxanide treatment compared to without treatment. In conclusion, nitazoxanide decreased parasitemia levels, indirectly induced the production of IgG antibodies, and partially prevented histopathological damage; however, it did not show therapeutic superiority compared to benznidazole in any of the evaluated aspects. Therefore, the repositioning of nitazoxanide as an alternative treatment against ChD could be considered, since it did not trigger adverse effects that worsened the pathological condition of the infected mice.

A Review on the Immunological Response against Trypanosoma cruzi

Chagas disease is a chronic systemic infection transmitted by Trypanosoma cruzi. Its life cycle consists of different stages in vector insects and host mammals. Trypanosoma cruzi strains cause different clinical manifestations of Chagas disease alongside geographic differences in morbidity and mortality. Natural killer cells provide the cytokine interferon-gamma in the initial phases of T. cruzi infection. Phagocytes secrete cytokines that promote inflammation and activation of other cells involved in defence. Dendritic cells, monocytes and macrophages modulate the adaptive immune response, and B lymphocytes activate an effective humoral immune response to T. cruzi. This review focuses on the main immune mechanisms acting during T. cruzi infection, on the strategies activated by the pathogen against the host cells, on the processes involved in inflammasome and virulence factors and on the new strategies for preventing, controlling and treating this disease.

Neospora caninum Evades Immunity via Inducing Host Cell Mitophagy to Inhibit Production of Proinflammatory Cytokines in a ROS-Dependent Manner

Neospora caninum is an intracellular protozoan that mainly infects cattle to cause abortion and significant economic losses worldwide. A better understanding of the immune evasion mechanisms of N. caninum could help to search for an effective approach to prevent and treat neosporosis. Mitophagy is used by some viruses to evade host immune surveillance. However, host cell mitophagy and its effect on N. caninum infection is unclear. In the present study, N. caninum-induced host cell mitophagy and its role in parasite infection were investigated in vitro and in vivo. Furthermore, the regulation of N. caninum-induced host cell mitophagy on the production of Reactive Oxygen Species (ROS), the secretions of proinflammatory cytokines, and the signals of p38, ERK, and Nlrp3 inflammasome were explored. Our results showed that autophagosomes and co-localization of LC3 with mitochondria were observed in N. caninum-infected macrophages. The mtDNA/nDNA ratio and the levels of mitochondrial marker proteins (Hsp60 and Tim23) were decreased with the increase of N. caninum numbers or infection time. N. caninum could induce mitophagy in brain and peritoneal lavage fluid cells of mice. Promoting mitophagy via mitophagy inducers (CCCP) could shorten survival time, decrease body weight, increase parasite load, and attenuate secretion of cytokines in N. caninum infected mice. CCCP treatment decreased the production of cytokines and Reactive Oxygen Species (ROS), and increased parasite burden in N. caninum-infected macrophages. Furthermore, CCCP or NAC (ROS inhibitor) treatment could inhibit ERK signal, Nlrp3 inflammasome, and cytokine production, while promote p38 signal in N. caninum-infected macrophages. The opposite results were obtained when using a mitophagy inhibitor (Mdivi1). Taken together, N. caninum-induced mitophagy could regulate the activations of p38, ERK, Nlrp3 inflammasome to inhibit the production of inflammatory cytokines in a ROS-dependent manner to escape host immune surveillance.