Trypanosoma cruzi Produces the Specialized Proresolving Mediators Resolvin D1, Resolvin D5, and Resolvin E2.

Trypanosoma cruzi is a protozoan parasite that causes Chagas disease (CD). CD is a persistent, lifelong infection affecting many organs, most notably the heart, where it may result in acute myocarditis and chronic cardiomyopathy. The pathological features include myocardial inflammation and fibrosis. In the Brazil strain-infected CD-1 mouse, which recapitulates many of the features of human infection, we found increased plasma levels of resolvin D1 (RvD1), a specialized proresolving mediator of inflammation, during both the acute and chronic phases of infection (>100 days postinfection) as determined by enzyme-linked immunosorbent assay (ELISA). Additionally, ELISA on lysates of trypomastigotes of both strains Tulahuen and Brazil revealed elevated levels of RvD1 compared with lysates of cultured epimastigotes of T. cruzi, tachyzoites of Toxoplasma gondii, trypomastigotes of Trypanosoma brucei, cultured L6E9 myoblasts, and culture medium containing no cells. Lysates of T. cruzi-infected myoblasts also displayed increased levels of RvD1. Lipid mediator metabolomics confirmed that the trypomastigotes of T. cruzi produced RvD1, RvD5, and RvE2, which have been demonstrated to modulate the host response to bacterial infections. Plasma RvD1 levels may be both host and parasite derived. Since T. cruzi synthesizes specialized proresolving mediators of inflammation, as well as proinflammatory eicosanoids, such as thromboxane A2, one may speculate that by using these lipid mediators to modulate its microenvironment, the parasite is able to survive.

Dantrolene improves in vitro structural changes induced by serum from Trypanosoma cruzi-infected mice.

Dystrophin, an important protein of the dystrophin-glycoprotein complex, has been implicated in the pathogenesis of experimental Chagas disease. It is important for the maintenance of cell shape and contraction force transmission. Dystrophin loss has been related to end-stage cardiac myopathies and proposed as a common route for myocardial dysfunction and progression to advanced heart failure. Evidence suggests that calpains, calcium-dependent proteases, digest dystrophin when the calcium concentration is compatible with their activation. The objective of this in vitro study was to test the hypothesis that dantrolene, a calcium channel blocker, improves structural changes induced by serum from Trypanosoma cruzi-infected mice. Cultured neonatal cardiac myocytes were incubated with serum from T. cruzi-infected mice and treated with dantrolene for 24 h. Immunofluorescence and immunoblotting were performed to evaluate dystrophin and calpain-1 protein expression. The levels of dystrophin decreased 13 % and calpain increased 17 % after incubation of cultured neonatal cardiac myocytes with serum from T. cruzi-infected mice. The treatment with dantrolene restored the dystrophin and calpain levels near control levels. Our results demonstrate that alterations in calcium homeostasis in cardiac myocytes are responsible, in part, for cardiac structural changes in experimentally induced T. cruzi myocarditis and that calpain inhibitors may be beneficial in Chagasic heart disease.

MicroPET/SPECT/CT imaging of small animal models of disease.

For the greater part of the last century, basic science research has been limited to in vitro studies of cellular processes and ex vivo tissue examination from suitable animal models of disease. In the last three decades, however, new techniques have been developed that permit the imaging of live animals using X-rays, radiotracer emissions, magnetic resonance signals, sound waves and optical fluorescence, and bioluminescence. The objective of this review is to provide a broad overview of common animal imaging modalities, with a focus on positron emission tomography (PET), single photon emission computed tomography (SPECT), and computed tomography (CT). Important examples, benefits, and limits of microPET/SPECT/CT technologies in current use, and their central role in improving our understanding of biological behavior and in facilitating the development of treatments from bench to bedside are included.

Imaging of small-animal models of infectious diseases.

Infectious diseases are the second leading cause of death worldwide. Noninvasive small-animal imaging has become an important research tool for preclinical studies of infectious diseases. Imaging studies permit enhanced information through longitudinal studies of the same animal during the infection. Herein, we briefly review recent studies of animal models of infectious disease that have used imaging modalities.

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.

Gender differences in adiponectin modulation of cardiac remodeling in mice deficient in endothelial nitric oxide synthase.

Left ventricular hypertrophy (LVH) is a risk factor for cardiovascular disease, a leading cause of death. Alterations in endothelial nitric oxide synthase (eNOS), an enzyme involved in regulating vascular tone, and in adiponectin, an adipocyte-derived secretory factor, are associated with cardiac remodeling. Deficiency of eNOS is associated with hypertension and LVH. Adiponectin exhibits vaso-protective, anti-inflammatory, and anti-atherogenic properties. We hypothesized that increased levels of adiponectin would alleviate cardiac pathology resulting from eNOS deficiency, while decreased levels of adiponectin would exacerbate the pathology. Male and female mice, deficient in eNOS, and either lacking or over-expressing adiponectin, were fed high fat diet (HFD) or normal chow. Cardiac magnetic resonance imaging was performed to serially assess heart morphology and function up to 40 weeks of age. Thirty-two weeks of HFD feeding led to significantly greater LV mass in male mice deficient in eNOS and either lacking or over-expressing adiponectin. Heart function was significantly reduced when the mice were deficient in either eNOS, adiponectin or both eNOS and adiponectin; for female mice, heart function was only reduced when both eNOS and adiponectin were lacking. Thus, while over-expression of adiponectin in the eNOS deficient HFD fed male mice preserved function at the expense of significantly increased LV mass, female mice were protected from decreased function and increased LVH by over-expression of adiponectin. Our results demonstrate a sexual dimorphism in response of the heart to alterations in eNOS and adiponectin during high fat feeding and suggest that adiponectin might require eNOS for some of its metabolic effects.

Genetic ablation or chemical inhibition of phosphatidylcholine transfer protein attenuates diet-induced hepatic glucose production.

UNLABELLED: Phosphatidylcholine transfer protein (PC-TP, synonym StARD2) is a highly specific intracellular lipid binding protein that is enriched in liver. Coding region polymorphisms in both humans and mice appear to confer protection against measures of insulin resistance. The current study was designed to test the hypotheses that Pctp-/- mice are protected against diet-induced increases in hepatic glucose production and that small molecule inhibition of PC-TP recapitulates this phenotype. Pctp-/- and wildtype mice were subjected to high-fat feeding and rates of hepatic glucose production and glucose clearance were quantified by hyperinsulinemic euglycemic clamp studies and pyruvate tolerance tests. These studies revealed that high-fat diet-induced increases in hepatic glucose production were markedly attenuated in Pctp-/- mice. Small molecule inhibitors of PC-TP were synthesized and their potencies, as well as mechanism of inhibition, were characterized in vitro. An optimized inhibitor was administered to high-fat-fed mice and used to explore effects on insulin signaling in cell culture systems. Small molecule inhibitors bound PC-TP, displaced phosphatidylcholines from the lipid binding site, and increased the thermal stability of the protein. Administration of the optimized inhibitor to wildtype mice attenuated hepatic glucose production associated with high-fat feeding, but had no activity in Pctp-/- mice. Indicative of a mechanism for reducing glucose intolerance that is distinct from commonly utilized insulin-sensitizing agents, the inhibitor promoted insulin-independent phosphorylation of key insulin signaling molecules. CONCLUSION: These findings suggest PC-TP inhibition as a novel therapeutic strategy in the management of hepatic insulin resistance.

Fat apoptosis through targeted activation of caspase 8: a new mouse model of inducible and reversible lipoatrophy.

We describe the generation and characterization of the first inducible 'fatless' model system, the FAT-ATTAC mouse (fat apoptosis through targeted activation of caspase 8). This transgenic mouse develops identically to wild-type littermates. Apoptosis of adipocytes can be induced at any developmental stage by administration of a FK1012 analog leading to the dimerization of a membrane-bound, adipocyte-specific caspase 8-FKBP fusion protein. Within 2 weeks of dimerizer administration, FAT-ATTAC mice show near-knockout levels of circulating adipokines and markedly reduced levels of adipose tissue. FAT-ATTAC mice are glucose intolerant, have diminished basal and endotoxin-stimulated systemic inflammation, are less responsive to glucose-stimulated insulin secretion and show increased food intake independent of the effects of leptin. Most importantly, we show that functional adipocytes can be recovered upon cessation of treatment, allowing the study of adipogenesis in vivo, as well as a detailed examination of the importance of the adipocyte in the regulation of multiple physiological functions and pathological states.

An Msh2 conditional knockout mouse for studying intestinal cancer and testing anticancer agents.

BACKGROUND & AIMS: Mutations in the DNA mismatch repair (MMR) gene MSH2 cause Lynch syndromes I and II and sporadic colorectal cancers. Msh2(null) mice predominantly develop lymphoma and do not accurately recapitulate the colorectal cancer phenotype. METHODS: We generated and examined mice with a conditional Msh2 disruption (Msh2(LoxP)), permitting tissue-specific gene inactivation. ECMsh2(LoxP/LoxP) mice carried an EIIa-Cre transgene, and VCMsh2(LoxP/LoxP) mice carried a Villin-Cre transgene. We combined the VCMsh2(LoxP) allele with either Msh2(Delta7null) (VCMsh2(LoxP/null)) or Msh2(G674D) mutations (VCMsh2(LoxP/G674D)) to create allelic phase mutants. These mice were given cisplatin or 5-fluorouracil/leucovorin and oxaliplatin (FOLFOX), and their tumors were measured by magnetic resonance imaging. RESULTS: Embryonic fibroblasts from ECMsh2(LoxP/LoxP) mice do not express MSH2 and are MMR deficient. Reverse transcription, polymerase chain reaction, and immunohistochemistry from VCMsh2(LoxP/LoxP) mice demonstrated specific loss of Msh2 messenger RNA and protein from epithelial cells of the intestinal tract. Microsatellite instability was observed in all VCMsh2 strains and limited to the intestinal mucosa. Resulting adenomas and adenocarcinomas had somatic truncation mutations to the adenomatous polyposis coli (Apc) gene. VCMsh2(LoxP/LoxP) mice did not develop lymphoma. Comparison of allelic phase tumors revealed significant differences in multiplicity and size. When treated with cisplatin or FOLFOX, tumor size was reduced in VCMsh2(LoxP/G674D) but not VCMsh2(LoxP/null) tumors. The apoptotic response to FOLFOX was partially sustained in the intestinal mucosa of VCMsh2(LoxP/G674D) animals. CONCLUSIONS: Msh2(LoxP/LoxP) mice in combination with appropriate Cre recombinase transgenes have excellent potential for preclinical modeling of Lynch syndrome, MMR-deficient tumors of other tissue types, and use in drug development.

Lack of association between adiponectin levels and atherosclerosis in mice.

OBJECTIVE: Adiponectin is an adipocyte-derived, secreted protein that is implicated in protection against a cluster of related metabolic disorders. Mice lacking adiponectin display impaired hepatic insulin sensitivity and respond only partially to peroxisome proliferator-activated receptor gamma agonists. Adiponectin has been associated with antiinflammatory and antiatherogenic properties; however, the direct involvement of adiponectin on the atherogenic process has not been studied. METHODS AND RESULTS: We crossed adiponectin knockout mice (Adn(-/-)) or mice with chronically elevated adiponectin levels (Adn(Tg)) into the low-density lipoprotein receptor-null (Ldlr(-/-)) and the apoliprotein E-null (Apoe(-/-)) mouse models. Adiponectin levels did not correlate with a suppression of the atherogenic process. Plaque volume in the aortic root, cholesterol accumulation in the aorta, and plaque morphology under various dietary conditions were not affected by circulating adiponectin levels. In light of the strong associations reported for adiponectin with cardiovascular disease in humans, the lack of a phenotype in gain- and loss-of-function studies in mice suggests a lack of causation for adiponectin in inhibiting the buildup of atherosclerotic lesions. CONCLUSIONS: These data indicate that the actions of adiponectin on the cardiovascular system are complex and multifaceted, with a minimal direct impact on atherosclerotic plaque formation in preclinical rodent models.

Optimized labeling of bone marrow mesenchymal cells with superparamagnetic iron oxide nanoparticles and in vivo visualization by magnetic resonance imaging.

BACKGROUND: Stem cell therapy has emerged as a promising addition to traditional treatments for a number of diseases. However, harnessing the therapeutic potential of stem cells requires an understanding of their fate in vivo. Non-invasive cell tracking can provide knowledge about mechanisms responsible for functional improvement of host tissue. Superparamagnetic iron oxide nanoparticles (SPIONs) have been used to label and visualize various cell types with magnetic resonance imaging (MRI). In this study we performed experiments designed to investigate the biological properties, including proliferation, viability and differentiation capacity of mesenchymal cells (MSCs) labeled with clinically approved SPIONs. RESULTS: Rat and mouse MSCs were isolated, cultured, and incubated with dextran-covered SPIONs (ferumoxide) alone or with poly-L-lysine (PLL) or protamine chlorhydrate for 4 or 24 hrs. Labeling efficiency was evaluated by dextran immunocytochemistry and MRI. Cell proliferation and viability were evaluated in vitro with Ki67 immunocytochemistry and live/dead assays. Ferumoxide-labeled MSCs could be induced to differentiate to adipocytes, osteocytes and chondrocytes. We analyzed ferumoxide retention in MSCs with or without mitomycin C pretreatment. Approximately 95% MSCs were labeled when incubated with ferumoxide for 4 or 24 hrs in the presence of PLL or protamine, whereas labeling of MSCs incubated with ferumoxide alone was poor. Proliferative capacity was maintained in MSCs incubated with ferumoxide and PLL for 4 hrs, however, after 24 hrs it was reduced. MSCs incubated with ferumoxide and protamine were efficiently visualized by MRI; they maintained proliferation and viability for up to 7 days and remained competent to differentiate. After 21 days MSCs pretreated with mitomycin C still showed a large number of ferumoxide-labeled cells. CONCLUSIONS: The efficient and long lasting uptake and retention of SPIONs by MSCs using a protocol employing ferumoxide and protamine may be applicable to patients, since both ferumoxides and protamine are approved for human use.

Obesity-associated improvements in metabolic profile through expansion of adipose tissue.

Excess caloric intake can lead to insulin resistance. The underlying reasons are complex but likely related to ectopic lipid deposition in nonadipose tissue. We hypothesized that the inability to appropriately expand subcutaneous adipose tissue may be an underlying reason for insulin resistance and beta cell failure. Mice lacking leptin while overexpressing adiponectin showed normalized glucose and insulin levels and dramatically improved glucose as well as positively affected serum triglyceride levels. Therefore, modestly increasing the levels of circulating full-length adiponectin completely rescued the diabetic phenotype in ob/ob mice. They displayed increased expression of PPARgamma target genes and a reduction in macrophage infiltration in adipose tissue and systemic inflammation. As a result, the transgenic mice were morbidly obese, with significantly higher levels of adipose tissue than their ob/ob littermates, leading to an interesting dichotomy of increased fat mass associated with improvement in insulin sensitivity. Based on these data, we propose that adiponectin acts as a peripheral "starvation" signal promoting the storage of triglycerides preferentially in adipose tissue. As a consequence, reduced triglyceride levels in the liver and muscle convey improved systemic insulin sensitivity. These mice therefore represent what we believe is a novel model of morbid obesity associated with an improved metabolic profile.

The benefits of using selenium in the treatment of Chagas disease: prevention of right ventricle chamber dilatation and reversion of Trypanosoma cruzi-induced acute and chronic cardiomyopathy in mice.

Cardiac damage is a frequent manifestation of Chagas disease, which is caused by the parasite Trypanosoma cruzi. Selenium (Se) is an essential micronutrient, the deficiency of which has been implicated in the development of cardiomyopathy. Our group has previously demonstrated that Se supplementation prevents myocardial damage during acute T. cruzi infection in mice. In this study, we analyzed the effect of Se treatment in cases of T. cruzi infection using prevention and reversion schemes. In the Se prevention scheme, mice were given Se supplements (2 ppm) starting two weeks prior to inoculation with T. cruzi(Brazil strain) and continuing until 120 days post-infection (dpi). In the Se reversion scheme, mice were treated with Se (4 ppm) for 100 days, starting at 160 dpi. Dilatation of the right ventricle was observed in the infected control group at both phases of T. cruzi infection, but it was not observed in the infected group that received Se treatment. Surviving infected mice that were submitted to the Se reversion scheme presented normal P wave values and reduced inflammation of the pericardium. These data indicate that Se treatment prevents right ventricular chamber increase and thus can be proposed as an adjuvant therapy for cardiac alterations already established by T. cruzi infection.

The role of selenium in intestinal motility and morphology in a murine model of Typanosoma cruzi infection.

Infection with Trypanosoma cruzi causes megasyndromes of the gastrointestinal (GI) tract in humans and animals. In the present study, we employed magnetic resonance imaging to non-invasively monitor the effect of selenium supplementation on alterations in the GI tract of T. cruzi-infected mice. CD1 mice infected with T. cruzi (Brazil strain) exhibited dilatation of the intestines similar to that we recently reported in infected C57Bl/6 mice. The average intestine lumen diameter increased by 65% and the increase was reduced to 29% in mice supplemented with 2 ppm selenium in the drinking water. When supplemented with 3 ppm selenium in chow the lumen diameter was also significantly reduced although the difference between the infected and infected supplemented mice was smaller. Intestinal motility in infected mice fed with selenium-enriched chow was increased compared with infected mice fed with normal unsupplemented chow and was not significantly different from intestinal motility in uninfected mice. We suggest that Se may be used to modulate the inflammatory, immunological, and/or antioxidant responses involved in intestinal disturbances caused by T. cruzi infection.

Regulation of energy substrate utilization and hepatic insulin sensitivity by phosphatidylcholine transfer protein/StarD2.

Phosphatidylcholine transfer protein (PC-TP, also known as StarD2) is a highly specific intracellular lipid binding protein with accentuated expression in oxidative tissues. Here we show that decreased plasma concentrations of glucose and free fatty acids in fasting PC-TP-deficient (Pctp(-/-)) mice are attributable to increased hepatic insulin sensitivity. In hyperinsulinemic-euglycemic clamp studies, Pctp(-/-) mice exhibited profound reductions in hepatic glucose production, gluconeogenesis, glycogenolysis, and glucose cycling. These changes were explained in part by the lack of PC-TP expression in liver per se and in part by marked alterations in body fat composition. Reduced respiratory quotients in Pctp(-/-) mice were indicative of preferential fatty acid utilization for energy production in oxidative tissues. In the setting of decreased hepatic fatty acid synthesis, increased clearance rates of dietary triglycerides and increased hepatic triglyceride production rates reflected higher turnover in Pctp(-/-) mice. Collectively, these data support a key biological role for PC-TP in the regulation of energy substrate utilization.

Maternal substrate utilization programs the development of the metabolic syndrome in male mice exposed to high fat in utero.

Studies were conducted to determine whether maternal substrate utilization during pregnancy affects fetal growth and predisposes offspring to metabolic disease. Female wild-type (WT) and glucose transporter 4 heterozygous mice (G4+/-, a model of altered peripheral substrate utilization) were fed high-fat diet (HFD, 35.5% fat) or control chow (C, 9.5% fat) for 2 wk before mating, throughout pregnancy and lactation (IU/L). WT HFD females exhibited increased serum nonesterified fatty acid and lactate levels and increased hepatic mRNA expression of peroxisome proliferator-activated receptor gamma coactivator-1-beta and SREBP-1c, consistent with increased lipogenesis. G4+/- HFD females exhibited enhanced lipid clearance, and exposure to HFD did not increase hepatic gene expression. HFD independent of maternal genotype decreased fetal growth and birth weight. WT offspring were weaned onto a low-fat diet (5.6% fat). Male offspring of WT mothers exposed to HFD exhibited "catch-up" growth accompanied by increased adiposity, impaired glucose tolerance, and insulin sensitivity. In contrast, male offspring of G4+/- HFD mothers did not exhibit any characteristics of metabolic syndrome. These data suggest that differences in maternal substrate utilization influence offspring metabolic phenotype.

Role of transcription factor NFAT in glucose and insulin homeostasis.

Compromised immunoregulation contributes to obesity and complications in metabolic pathogenesis. Here, we demonstrate that the nuclear factor of activated T cell (NFAT) group of transcription factors contributes to glucose and insulin homeostasis. Expression of two members of the NFAT family (NFATc2 and NFATc4) is induced upon adipogenesis and in obese mice. Mice with the Nfatc2-/- Nfatc4-/- compound disruption exhibit defects in fat accumulation and are lean. Nfatc2-/- Nfatc4-/- mice are also protected from diet-induced obesity. Ablation of NFATc2 and NFATc4 increases insulin sensitivity, in part, by sustained activation of the insulin signaling pathway. Nfatc2-/- Nfatc4-/- mice also exhibit an altered adipokine profile, with reduced resistin and leptin levels. Mechanistically, NFAT is recruited to the transcription loci and regulates resistin gene expression upon insulin stimulation. Together, these results establish a role for NFAT in glucose/insulin homeostasis and expand the repertoire of NFAT function to metabolic pathogenesis and adipokine gene transcription.

Alterations in myocardial gene expression associated with experimental Trypanosoma cruzi infection.

Chagas disease, characterized by acute myocarditis and chronic cardiomyopathy, is caused by infection with the protozoan parasite Trypanosoma cruzi. We sought to identify genes altered during the development of parasite-induced cardiomyopathy. Microarrays containing 27,400 sequence-verified mouse cDNAs were used to analyze global gene expression changes in the myocardium of a murine model of chagasic cardiomyopathy. Changes in gene expression were determined as the acute stage of infection developed into the chronic stage. This analysis was performed on the hearts of male CD-1 mice infected with trypomastigotes of T. cruzi (Brazil strain). At each interval we compared infected and uninfected mice and confirmed the microarray data with dye reversal. We identified eight distinct categories of mRNAs that were differentially regulated during infection and identified dysregulation of several key genes. These data may provide insight into the pathogenesis of chagasic cardiomyopathy and provide new targets for intervention.

High fat diet aggravates cardiomyopathy in murine chronic Chagas disease.

Infection with Trypanosoma cruzi, the etiologic agent in Chagas disease, may result in heart disease. Over the last decades, Chagas disease endemic areas in Latin America have seen a dietary transition from the traditional regional diet to a Western style, fat rich diet. Previously, we demonstrated that during acute infection high fat diet (HFD) protects mice from the consequences of infection-induced myocardial damage through effects on adipogenesis in adipose tissue and reduced cardiac lipidopathy. However, the effect of HFD on the subsequent stages of infection - the indeterminate and chronic stages - has not been investigated. To address this gap in knowledge, we studied the effect of HFD during indeterminate and chronic stages of Chagas disease in the mouse model. We report, for the first time, the effect of HFD on myocardial inflammation, vasculopathy, and other types of dysfunction observed during chronic T. cruzi infection. Our results show that HFD perturbs lipid metabolism and induces oxidative stress to exacerbate late chronic Chagas disease cardiac pathology.