Neurodegeneration and neuroregeneration in Chagas disease

System-based insights into parasitological and clinical treatment failure in Chagas disease

Infectious disease treatment success requires symptom resolution (clinical treatment success), which often but not always involves pathogen clearance. Both of these treatment goals face disease-specific and general challenges. In this review, we summarize the current state of knowledge in mechanisms of clinical and parasitological treatment failure in the context of Chagas disease, a neglected tropical disease causing cardiac and gastrointestinal symptoms. Parasite drug resistance and persistence, drug pharmacokinetics and dynamics, as well as persistently altered host immune responses and tissue damage are the most common reasons for Chagas disease treatment failure. We discuss the therapeutics that failed before regulatory approval, limitations of current therapeutic options and new treatment strategies to overcome persistent parasites, inflammatory responses, and metabolic alterations. Large-scale omics analyses were critical in generating these insights and will continue to play a prominent role in addressing the challenges still facing Chagas disease drug treatment.

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

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

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.

Pro-arrhythmogenic effects of Trypanosoma cruzi conditioned medium proteins in a model of bovine chromaffin cells

Asymptomatic sudden death is the principal cause of mortality in Chagas disease. There is little information about molecular mechanisms involved in the pathophysiology of malignant arrhythmias in Chagasic patients. Previous studies have involved Trypanosoma cruzi secretion proteins in the genesis of arrhythmias ex vivo, but the molecular mechanisms involved are still unresolved. Thus, the aim was to determine the effect of these secreted proteins on the cellular excitability throughout to test its effects on catecholamine secretion, sodium-, calcium-, and potassium-conductance and action potential (AP) firing. Conditioned medium was obtained from the co-culture of T. cruzi and Vero cells (African green monkey kidney cells) and ultra-filtered for concentrating immunogenic high molecular weight parasite proteins. Chromaffin cells were assessed with the parasite and Vero cells control medium. Parasite-secreted proteins induce catecholamine secretion in a dose-dependent manner. Additionally, T. cruzi conditioned medium induced depression of both calcium conductance and calcium and voltage-dependent potassium current. Interestingly, this fact was related to the abolishment of the hyperpolarization phase of the AP produced by the parasite medium. Taken together, these results suggest that T. cruzi proteins may be involved in the genesis of pro-arrhythmic conditions that could influence the appearance of malignant arrhythmias in Chagasic patients.

Nerve Growth Factor, Stress and Diseases

Stress is a constant threat for homeostasis and is represented by different extrinsic and intrinsic stimuli (stressors, Hans Selye's "noxious agents"), such as aggressive behavior, fear, diseases, physical activity, drugs, surgical injury, and environmental and physiological changes. Our organisms respond to stress by activating the adaptive stress system to activate compensatory responses for restoring homeostasis. Nerve Growth Factor (NGF) was discovered as a signaling molecule involved in survival, protection, differentiation, and proliferation of sympathetic and peripheral sensory neurons. NGF mediates stress with an important role in translating environmental stimuli into physiological and pathological feedbacks since NGF levels undergo important variations after exposure to stressful events. Psychological stress, lifestyle stress, and oxidative stress are well known to increase the risk of mental disorders such as schizophrenia, major depressive disorders, bipolar disorder, alcohol use disorders and metabolic disorders such as metabolic syndrome. This review reports recent works describing the activity of NGF in mental and metabolic disorders related to stress.

Parasite-host glycan interactions during Trypanosoma cruzi infection: trans-Sialidase rides the show

Many important pathogen-host interactions rely on highly specific carbohydrate binding events. In the case of the protozoan Trypanosoma cruzi, the causative agent of Chagas disease, glycointeractions involving sialic acid (SA) residues are pivotal for parasite infectivity, escape from immune surveillance and pathogenesis. Though unable to synthesize SA de novo, T. cruzi displays a unique trans-Sialidase (TS) enzyme, which is able to cleave terminal SA residues from host donor glycoconjugates and transfer them onto parasite surface mucins, thus generating protective/adhesive structures. In addition, this parasite sheds TS into the bloodstream, as a way of modifying the surface SA signature, and thereby the signaling/functional properties of mammalian host target cells on its own advantage. Here, we discuss the pathogenic aspects of T. cruzi TS: its molecular adaptations, the multiplicity of interactions in which it is involved during infections, and the array of novel and appealing targets for intervention in Chagas disease provided by TS-remodeled sialoglycophenotypes.

Trypanosoma evansi impacts on embryonic neural progenitor cell functions

Trypanosoma evansi appears to have a significant tropism for brain tissue in its chronic and acute phases. The most common symptoms of this brain infection are motor incoordination, meningoencephalitis, demyelination, and anemia. There have only been few studies of the effects of T. evansi infection on neuronal differentiation and brain plasticity. Here, we investigated the impact of the congenital T. evansi infection on brain development in mice. We collected telencephalon-derived neural progenitor cells (NPCs) from T. evansi uninfected and infected mice, and cultivated them into neurospheres. We found that T. evansi significantly decreased the number of cells during development of neurospheres. Analysis of neurosphere differentiation revealed that T. evansi infection significantly increased neural migration. We also observed that T. evansi promoted expression of glial fibrillary acidic protein (GFAP) in infected cells. These data suggest that congenital T. evansi infection may affect embryonic brain development.

Effects of resveratrol on the differentiation fate of neural progenitor cells of mouse embryos infected with Trypanosoma cruzi

Chagas disease (CD) affecting about 7 million people is caused by the flagellate protozoan Trypanosoma cruzi. The central nervous system (CNS) is an important site for T. cruzi persistence in the host during the chronic phase of infection, because the protozoan may pass the blood-brain barrier and may cause motor and cognitive neuronal damage. Thinking about avoiding or minimizing these negative effects, it is hypothesized that resveratrol (RSV), a component with several medicinal properties has beneficial effects on the CNS. The objective of this study was to investigate, whether T. cruzi infection interferes with neurogenesis and gliogenesis of embryos of infected mice females, and whether RSV would be able to avoid or minimize these changes caused by CD. RSV is a polyphenol found in grapes and widely studied for its neuroprotective and antioxidant properties. In addition, we investigated the role caused by the parasite during congenital infection and CNS development. Embryos and their brains were PCR-positive for T. cruzi. For this study, NPCs obtained from telencephalon of infected and uninfected embryos and were cultured in presence of resveratrol for forming neurospheres. The results demonstrated that the congenital transmission of T. cruzi influences CNS formation and neural fate, decreasing the number of neuroespheres and causing an elongation in the phases of the cell cycle. In addition, the parasite promoted an increase in neugliogenesis. Resveratrol was neuroprotective and prevented negative effects of the infection. Thus, we suggest the use of resveratrol as a therapeutic target for the treatment of neuroinflammation or as neuroprotective agent during Chagas disease, as it improves gliogenesis and restores neural migration.

Endothelins in inflammatory neurological diseases

Endothelins were discovered more than thirty years ago as potent vasoactive compounds. Beyond their well-documented cardiovascular properties, however, the contributions of the endothelin pathway have been demonstrated in several neuroinflammatory processes and the peptides have been reported as clinically relevant biomarkers in neurodegenerative diseases. Several studies report that endothelin-1 significantly contributes to the progression of neuroinflammatory processes, particularly during infections in the central nervous system (CNS), and is associated with a loss of endothelial integrity at the blood brain barrier level. Because of the paucity of clinical trials with endothelin-1 antagonists in several infectious and non-infectious neuroinflammatory diseases, it remains an open question whether the 21 amino acid peptide is a mediator/modulator rather than a biomarker of the progression of neurodegeneration. This review focuses on the potential roles of endothelins in the pathology of neuroinflammatory processes, including infectious diseases of viral, bacterial or parasitic origin in which the synthesis of endothelins or its pharmacology have been investigated from the cell to the bedside in several cases, as well as in non-infectious inflammatory processes such as neurodegenerative disorders like Alzheimers Disease or central nervous system vasculitis.

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.

The Trypanosoma cruzi Surface, a Nanoscale Patchwork Quilt

The Trypanosoma cruzi trypomastigote membrane provides a major protective role against mammalian host-derived defense mechanisms while allowing the parasite to interact with different cell types and trigger pathogenesis. This surface has been historically appreciated as a rather unstructured 'coat', mainly consisting of a continuous layer of glycolipids and heavily O-glycosylated mucins, occasionally intercalated with different developmentally regulated molecules displaying adhesive and/or enzymatic properties. Recent findings, however, indicate that the trypomastigote membrane is made up of multiple, densely packed and discrete 10-150nm lipid-driven domains bearing different protein composition; hence resembling a highly organized 'patchwork quilt' design. Here, we discuss different aspects underlying the biogenesis, assembly, and dynamics of this cutting-edge fashion outfit, as well as its functional implications.

The role of primary infection of Schwann cells in the aetiology of infective inflammatory neuropathies

Numerous different pathogens are responsible for infective peripheral neuropathies and this is generally the result of the indirect effects of pathogen infection, namely anti pathogen antibodies cross reacting with epitopes on peripheral nerve, auto reactive T cells attacking myelin, circulating immune complexes and complement fixation. Primary infection of Schwann cells (SC) associated with peripheral nerve inflammation is rare requiring pathogens to cross the Blood Peripheral Nerve Barrier (BPNB) evade anti-pathogen innate immune pathways and invade the SC. Spirochetes Borrelia bourgdorferi and Trepomema pallidum are highly invasive, express surface lipo proteins, but despite this SC are rarely infected. However, Trypanosoma cruzi (Chaga's disease) and Mycobacterium leprae. Leprosy are two important causes of peripheral nerve infection and both demonstrate primary infection of SC. This is due to two novel strategies; T. cruzi express a trans-silalidase that mimics host neurotrophic factors and infects SC via tyrosine kinase receptors. M. leprae demonstrates multi receptor SC tropism and subsequent infection promotes nuclear reprogramming and dedifferentiation of host SC into progenitor stem like cells (pSLC) that are vulnerable to M. leprae infection. These two novel pathogen evasion strategies, involving stem cells and receptor mimicry, provide potential therapeutic targets relevant to the prevention of peripheral nerve inflammation by inhibiting primary SC infection.

Treatment with bone marrow mesenchymal stem cells combined with plumbagin alleviates spinal cord injury by affecting oxidative stress, inflammation, apoptotis and the activation of the Nrf2 pathway

The aim of the present study was to investigate the protective effect exerted by bone marrow mesenchymal stem cells (BMSCs) in combination with plumbagin on spinal cord injury (SCI) and explore the mechanism behind this protective effect. Firstly, BMSCs were extracted from male Sprague-Dawley rats, cultured in vitro, and identified by hematoxylin. Sprague-Dawley rats were then randomly divided into a control group, SCI model group, BMSC-treated group, a plumbagin-treated group, and a BMSC and plumbagin-treated group. After treatment with BMSCs combined with plumbagin, a Basso, Beattie and Bresnahan (BBB) test was carried out and the spinal cord water content was examined in order to analyze the effect of BMSCs combined with plumbagin on SCI. The myeloperoxidase (MPO), superoxide dismutase (SOD), malondialdehyde (MDA), nuclear factor-κB (NF-κB) p65 unit, tumor necrosis factor-α (TNF-α) levels were also detected. Moreover, nuclear factor erythroid 2‑related factor 2 (Nrf2), phosphoinositide 3-kinase (PI3K), phosphorylated (p-)Akt, p-p38 mitogen-activated protein kinase (MAPK), and p-extracellular-signal-regulated kinase (ERK) protein expression levels were measured using western blot analysis. Treatment with BMSCs combined with plumbagin significantly improved locomotor recovery and reduced the spinal cord water content after SCI. The increased MPO, MDA, NF-κB p65 and TNF-α levels were significantly suppressed and the decreased SOD was significantly increased in SCI rats. The suppression of Nrf2, p-Akt and p-ERK, as well as the promotion of p-p38 MAPK, were reversed by treatment with BMSCs combined with plumbagin. These effects suggest that treatment with BMSCs combined with plumbagin alleviates SCI through its effects on oxidative stress, inflammation, apoptotis and activation of the Nrf2 pathway.

In Vivo Transplantation of Enteric Neural Crest Cells into Mouse Gut; Engraftment, Functional Integration and Long-Term Safety

Objectives

Enteric neuropathies are severe gastrointestinal disorders with unsatisfactory outcomes. We aimed to investigate the potential of enteric neural stem cell therapy approaches for such disorders by transplanting mouse enteric neural crest cells (ENCCs) into ganglionic and aganglionic mouse gut in vivo and analysing functional integration and long-term safety.

Design

Neurospheres generated from yellow fluorescent protein (YFP) expressing ENCCs selected from postnatal Wnt1-cre;R26R-YFP/YFP murine gut were transplanted into ganglionic hindgut of wild-type littermates or aganglionic hindgut of Ednrb^tm1Ywa mice (lacking functional endothelin receptor type-B). Intestines were then assessed for ENCC integration and differentiation using immunohistochemistry, cell function using calcium imaging, and long-term safety using PCR to detect off-target YFP expression.

Results

YFP+ ENCCs engrafted, proliferated and differentiated into enteric neurons and glia within recipient ganglionic gut. Transplanted cells and their projections spread along the endogenous myenteric plexus to form branching networks. Electrical point stimulation of endogenous nerve fibres resulted in calcium transients (F/F0 = 1.16±0.01;43 cells, n = 6) in YFP+ transplanted ENCCs (abolished with TTX). Long-term follow-up (24 months) showed transplanted ENCCs did not give rise to tumours or spread to other organs (PCR negative in extraintestinal sites). In aganglionic gut ENCCs similarly spread and differentiated to form neuronal and glial networks with projections closely associated with endogenous neural networks of the transition zone.

Conclusions

Transplanted ENCCs successfully engrafted into recipient ganglionic and aganglionic gut showing appropriate spread, localisation and, importantly, functional integration without any long-term safety issues. This study provides key support for the development and use of enteric neural stem cell therapies.

The trans-sialidase, the major Trypanosoma cruzi virulence factor: Three decades of studies

Chagas' disease is a potentially life-threatening disease caused by the protozoan parasite Trypanosoma cruzi. Since the description of Chagas'disease in 1909 extensive research has identified important events in the disease in order to understand the biochemical mechanism that modulates T. cruzi-host cell interactions and the ability of the parasite to ensure its survival in the infected host. Exactly 30 years ago, we presented evidence for the first time of a trans-sialidase activity in T. cruzi (T. cruzi-TS). This enzyme transfers sialic acid from the host glycoconjugates to the terminal β-galactopyranosyl residues of mucin-like molecules on the parasite's cell surface. Thenceforth, many articles have provided convincing data showing that T. cruzi-TS is able to govern relevant mechanisms involved in the parasite's survival in the mammalian host, such as invasion, escape from the phagolysosomal vacuole, differentiation, down-modulation of host immune responses, among others. The aim of this review is to cover the history of the discovery of T. cruzi-TS, as well as some well-documented biological effects encompassed by this parasite's virulence factor, an enzyme with potential attributes to become a drug target against Chagas disease.

Chemical biology approaches to designing defined carbohydrate vaccines

Carbohydrate antigens have shown promise as important targets for developing effective vaccines and pathogen detection strategies. Modifying purified microbial glycans through synthetic routes or completely synthesizing antigenic motifs are attractive options to advance carbohydrate vaccine development. However, limited knowledge on structure-property correlates hampers the discovery of immunoprotective carbohydrate epitopes. Recent advancements in tools for glycan modification, high-throughput screening of biological samples, and 3D structural analysis may facilitate antigen discovery process. This review focuses on advances that accelerate carbohydrate-based vaccine development and various technologies that are driving these efforts. Herein we provide a critical overview of approaches and resources available for rational design of better carbohydrate antigens. Structurally defined and fully synthetic oligosaccharides, designed based on molecular understanding of antigen-antibody interactions, offer a promising alternative for developing future carbohydrate vaccines.

Trypanosoma cruzi Trans-sialidase: structural features and biological implications

Trypanosoma cruzi trans-sialidase (TcTS) has intrigued researchers all over the world since it was shown that T. cruzi incorporates sialic acid through a mechanism independent of sialyltransferases. The enzyme has being involved in a vast myriad of functions in the biology of the parasite and in the pathology of Chagas' disease. At the structural level experiments trapping the intermediate with fluorosugars followed by peptide mapping, X-ray crystallography, molecular modeling and magnetic nuclear resonance have opened up a three-dimensional understanding of the way this enzyme works. Herein we review the multiple biological roles of TcTS and the structural studies that are slowly revealing the secrets underlining an efficient sugar transfer activity rather than simple hydrolysis by TcTS.

Meeting report: Emerging respiratory viral infections and nonhuman primate case reports

A workshop on Emerging Respiratory Viral Infections and Spontaneous Diseases in nonhuman primates was sponsored by the concurrent Annual Meetings of the American College of Veterinary Pathologists and the American Society for Veterinary Clinical Pathology, held December 1-5, 2012, in Seattle, Washington. The session had platform presentations from Drs Karen Terio, Thijs Kuiken, Guy Boivin, and Robert Palermo that focused on naturally occurring influenza, human respiratory syncytial virus, and metapneumovirus in wild and zoo-housed great apes; the molecular biology and pathology of these viral respiratory diseases in nonhuman primate (NHP) models; and the therapeutic and vaccine approaches to prevention and control of these emerging respiratory viral infections. These formal presentations were followed by presentations of 14 unique case studies of rare or newly observed spontaneous lesions in NHPs (see online files for access to digital whole-slide images corresponding to each case report at http://scanscope.com/ACVP%20Slide%20Seminars/2012/Primate%20Pathology/view.apml). The session was attended by meeting participants that included students, pathology trainees, and experienced pathologists from academia and industry with an interest in respiratory and spontaneous diseases of NHPs.

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

Chronic Chagas cardiomyopathy (CCC), caused by the obligate intracellular protozoan parasite Trypanosoma cruzi, is a major cause of morbidity and mortality in Latin America. CCC begins when T. cruzi enters cardiac cells for intracellular multiplication and differentiation, a process that starts with recognition of host-cell entry receptors. However, the nature of these surface molecules and corresponding parasite counter-receptor(s) is poorly understood. Here we show that antibodies against neurotrophin (NT) receptor TrkC, but not against family members TrkA and TrkB, prevent T. cruzi from invading primary cultures of cardiomyocytes and cardiac fibroblasts. Invasion is also selectively blocked by the TrkC ligand NT-3, and by antagonists of Trk autophosphorylation and downstream signalling. Therefore, these results indicate that T. cruzi gets inside cardiomyocytes and cardiac fibroblasts by activating TrkC preferentially over TrkA. Accordingly, short hairpin RNA interference of TrkC (shTrkC), but not TrkA, selectively prevents T. cruzi from entering cardiac cells. Additionally, T. cruzi parasite-derived neurotrophic factor (PDNF)/trans-sialidase, a TrkC-binding protein, but not family member gp85, blocks entry dose-dependently, underscoring the specificity of PDNF as TrkC counter-receptor in cardiac cell invasion. In contrast to invasion, competitive and shRNA inhibition studies demonstrate that T. cruzi-PDNF recognition of TrkA, but not TrkC on primary cardiomyocytes and the cardiomyocyte cell line H9c2 protects the cells against oxidative stress. Thus, this study shows that T. cruzi via PDNF favours neurotrophin receptor TrkC for cardiac cell entry and TrkA for cardiomyocyte protection against oxidative stress, and suggests a new therapeutic opportunity in PDNF and/or fragments thereof for CCC therapy as entry inhibitors and/or cardioprotection agonists.

Planar cell polarity genes control the connectivity of enteric neurons

A highly complex network of intrinsic enteric neurons is required for the digestive and homeostatic functions of the gut. Nevertheless, the genetic and molecular mechanisms that regulate their assembly into functional neuronal circuits are currently unknown. Here we report that the planar cell polarity (PCP) genes Celsr3 and Fzd3 are required during murine embryogenesis to specifically control the guidance and growth of enteric neuronal projections relative to the longitudinal and radial gut axes. Ablation of these genes disrupts the normal organization of nascent neuronal projections, leading to subtle changes of axonal tract configuration in the mature enteric nervous system (ENS), but profound abnormalities in gastrointestinal motility. Our data argue that PCP-dependent modules of connectivity established at early stages of enteric neurogenesis control gastrointestinal function in adult animals and provide the first evidence that developmental deficits in ENS wiring may contribute to the pathogenesis of idiopathic bowel disorders.

Sialic acid: a sweet swing between mammalian host and Trypanosoma cruzi

Commonly found at the outermost ends of complex carbohydrates in extracellular medium or on outer cell membranes, sialic acids play important roles in a myriad of biological processes. Mammals synthesize sialic acid through a complex pathway, but Trypanosoma cruzi, the agent of Chagas’ disease, evolved to obtain sialic acid from its host through a trans-sialidase (TcTS) reaction. Studies of the parasite cell surface architecture and biochemistry indicate that a unique system comprising sialoglycoproteins and sialyl-binding proteins assists the parasite in several functions including parasite survival, infectivity, and host–cell recognition. Additionally, TcTS activity is capable of extensively remodeling host cell glycomolecules, playing a role as virulence factor. This review presents the state of the art of parasite sialobiology, highlighting how the interplay between host and parasite sialic acid helps the pathogen to evade host defense mechanisms and ensure lifetime host parasitism.

Mechanisms of Trypanosoma cruzi persistence in Chagas disease

Trypanosoma cruzi infection leads to development of chronic Chagas disease. In this article, we provide an update on the current knowledge of the mechanisms employed by the parasite to gain entry into the host cells and establish persistent infection despite activation of a potent immune response by the host. Recent studies point to a number of T. cruzi molecules that interact with host cell receptors to promote parasite invasion of the diverse host cells. T. cruzi expresses an antioxidant system and thromboxane A(2) to evade phagosomal oxidative assault and suppress the host's ability to clear parasites. Additional studies suggest that besides cardiac and smooth muscle cells that are the major target of T. cruzi infection, adipocytes and adipose tissue serve as reservoirs from where T. cruzi can recrudesce and cause disease decades later. Further, T. cruzi employs at least four strategies to maintain a symbiotic-like relationship with the host, and ensure consistent supply of nutrients for its own survival and long-term persistence. Ongoing and future research will continue to help refining the models of T. cruzi invasion and persistence in diverse tissues and organs in the host.