CCR5, an important receptor related to cell recruitment and inflammation, is expressed during experimental Toxoplasma gondii infection. However, its role in the immunopathology of toxoplasmosis is not clearly defined yet. Thus, we inoculated WT and CCR5-/- mice with a sub lethal dose of the parasite by oral route. CCR5-/- mice were extremely susceptible to infection, presenting higher parasite load and lower tissue expression of IL-12p40, IFN-γ, TNF, IL-6, iNOS, Foxp3, T-bet, GATA-3 and PPARα. Although both groups presented inflammation in the liver with prominent neutrophil infiltration, CCR5-/- mice had extensive tissue damage with hepatocyte vacuolization, steatosis, elevated serum triglycerides and transaminases. PPARα agonist Gemfibrozil improved the vacuolization but did not rescue CCR5-/- infected mice from high serum triglycerides levels and enhanced mortality. We also found intense inflammation in the ileum of CCR5-/- infected mice, with epithelial ulceration, augmented CD4 and decreased frequency of NK cells in the gut lamina propria. Most interestingly, these findings were accompanied by an outstanding accumulation of neutrophils in the ileum, which seemed to be involved in the gut immunopathology, once the depletion of these cells was accompanied by reduced local damage. Altogether, these data demonstrated that CCR5 is essential to the control of T. gondii infection and to maintain the metabolic, hepatic and intestinal integrity. These findings add novel information on the disease pathogenesis and may be relevant for directing future approaches to the treatment of multi-deregulated diseases.
In the present work we examine the contribution of 5-lipoxygenase- (5-LO-) derived lipid mediators to immune responses during the acute phase of Trypanosoma cruzi infection in 5-LO gene knockout (5-LO−/−) mice and wild-type (WT) mice. Compared with WT mice, the 5-LO−/− mice developed less parasitemia/tissue parasitism, less inflammatory cell infiltrates, and a lower mortality. This resistance of 5-LO−/− mice correlated with several differences in the immune response to infection, including reduced PGE2 synthesis; sustained capacity of splenocytes to produce high levels of interleukin (IL)-12 early in the infection; enhanced splenocyte production of IL-1β, IL-6, and IFN-γ; rapid T-cell polarization to secrete high quantities of IFN-γ and low quantities of IL-10; and greater numbers of CD8+CD44highCD62Llow memory effector T cells at the end of the acute phase of infection. The high mortality in WT mice was associated with increased production of LTB4/LTC4, T cell bias to produce IFN-γ, high levels of serum nitrite, and marked protein extravasation into the peritoneal cavity, although survival was improved by treatment with a cys-LT receptor 1 antagonist. These data also provide evidence that 5-LO-derived mediators negatively affect host survival during the acute phase of T. cruzi infection.
Paracoccidioidomycosis (PCM) is a systemic mycosis caused by the thermodimorphic fungus Paracoccidioides brasiliensis. Leukotrienes and lipoxins are lipid mediators produced after 5-lipoxygenase (5-LO) activation that exhibit pro- and anti-inflammatory roles, respectively. Here, we have investigated the contribution of 5-LO enzymatic activity in PCM using an experimental model of P. brasiliensis infection. B6.129 wild-type (B6.129) and 5-LO-deficient (5-LO−/−) mice were intravenously inoculated with a virulent strain of P. brasiliensis (Pb18), and the survival rate of the infected mice was investigated on different days after yeast infection. 5-LO−/− mice exhibited an increased survival rate associated with a decreased number of CFU. The resistance of 5-LO−/− during PCM was associated with augmented nitric oxide (NO) production and the formation of compact granulomas. In addition, the absence of 5-LO was associated with a diminished number of CD4+ CD25+ regulatory T cells, higher levels of gamma interferon and interleukin-12, and increased T-bet (a T-box transcription factor that directs Th1 lineage commitment) mRNA levels in the lungs. Taken together, our results show for the first time that 5-LO enzymatic activity increases susceptibility to P. brasiliensis, suggesting that this pathway may be a potential target for therapeutic intervention during PCM.
Sepsis, a major cause of morbidity/mortality in intensive care units worldwide, is commonly associated with cardiac dysfunction, which worsens the prognosis dramatically for patients. Although in recent years the concept of septic cardiomyopathy has evolved, the importance of myocardial structural alterations in sepsis has not been fully explored. This study offers novel and mechanistic data to clarify subcellular events that occur in the pathogenesis of septic cardiomyopathy and myocardial dysfunction in severe sepsis. Cultured neonatal mice cardiomyocytes subjected to serum obtained from mice with severe sepsis presented striking increment of [Ca2+]i and calpain-1 levels associated with decreased expression of dystrophin and disruption and derangement of F-actin filaments and cytoplasmic bleb formation. Severe sepsis induced in mice led to an increased expression of calpain-1 in cardiomyocytes. Moreover, decreased myocardial amounts of dystrophin, sarcomeric actin, and myosin heavy chain were observed in septic hearts associated with depressed cardiac contractile dysfunction and a very low survival rate. Actin and myosin from the sarcomere are first disassembled by calpain and then ubiquitinated and degraded by proteasome or sequestered inside specialized vacuoles called autophagosomes, delivered to the lysosome for degradation forming autophagolysosomes. Verapamil and dantrolene prevented the increase of calpain-1 levels and preserved dystrophin, actin, and myosin loss/reduction as well cardiac contractile dysfunction associated with strikingly improved survival rate. These abnormal parameters emerge as therapeutic targets, which modulation may provide beneficial effects on future vascular outcomes and mortality in sepsis. Further studies are needed to shed light on this mechanism, mainly regarding specific calpain inhibitors.
Dengue is a prevalent arthropod-borne viral disease in tropical and subtropical areas of the globe. Dengue clinical manifestations include asymptomatic infections; undifferentiated fever; dengue fever, which is characterized by fever, headache, retroorbital pain, myalgia, and arthralgia; and a severe form of the disease denominated dengue haemorrhagic fever/dengue shock syndrome, characterized by haemoconcentration, thrombocytopenia, and bleeding tendency. However, atypical manifestations, such as liver, central nervous system, and cardiac involvement, have been increasingly reported. We report an atypical and rare presentation of dengue disease marked by a dramatic and fatal cardiogenic shock due to acute myocarditis. Histopathological analysis of heart tissue showed several multifocal areas of muscle necrosis and intense interstitial oedema associated with clusters of virus particles inside the cardiomyocytes and in the interstitial space, providing evidence of a possible direct action of dengue virus on myocardium.
Acute heart failure; acute myocarditis; cardiogenic shock; dengue fever
The cardiovascular manifestations of Chagas disease are well known. However, the contribution of the vasculature and specifically the microvasculature has received little attention. This chapter reviews the evidence supporting the notion that alterations in the microvasculature especially in the heart contribute to the pathogenesis of chagasic cardiomyopathy. These data may also be important in understanding the contributions of the microvasculature in the aetiologies of other cardiomyopathies. The role of endothelin-1 and of thromboxane A2 vascular spasm and platelet aggregation is also discussed. Further, these observations may provide target(s) for intervention.
In the clinical setting, the early detection of myocardial injury induced by doxorubicin (DXR) is still considered a challenge. To assess whether ultrasonic tissue characterization (UTC) can identify early DXR-related myocardial lesions and their correlation with collagen myocardial percentages, we studied 60 rats at basal status and prospectively after 2mg/Kg/week DXR endovenous infusion. Echocardiographic examinations were conducted at baseline and at 8,10,12,14 and 16 mg/Kg DXR cumulative dose. The left ventricle ejection fraction (LVEF), shortening fraction (SF), and the UTC indices: corrected coefficient of integrated backscatter (IBS) (tissue IBS intensity/ phantom IBS intensity) (CC-IBS) and the cyclic variation magnitude of this intensity curve (MCV) were measured. The variation of each parameter of study through DXR dose was expressed by the average and standard error at specific DXR dosages and those at baseline. The collagen percent (%) was calculated in six control group animals and 24 DXR group animals. CC-IBS increased (1.29±0.27 x 1.1±0.26-basal; p=0.005) and MCV decreased (9.1± 2.8 x 11.02±2.6-basal; p=0.006) from 8 mg/Kg to 16mg/Kg DXR. LVEF presented only a slight but significant decrease (80.4±6.9% x 85.3±6.9%-basal, p=0.005) from 8 mg/Kg to 16 mg/Kg DXR. CC-IBS was 72.2% sensitive and 83.3% specific to detect collagen deposition of 4.24%(AUC=0.76). LVEF was not accurate to detect initial collagen deposition (AUC=0.54). In conclusion: UTC was able to early identify the DXR myocardial lesion when compared to LVEF, showing good accuracy to detect the initial collagen deposition in this experimental animal model.
Doxorubicin; Ultra-sonic tissue characterization; Echocardiography; Rats
The thermally dimorphic fungus Paracoccidioides brasiliensis (Pb) is the causative agent of paracoccidioidomycosis (PCM), one of the most frequent systemic mycosis that affects the rural population in Latin America. PCM is characterized by a chronic inflammatory granulomatous reaction, which is consequence of a Th1-mediated adaptive immune response. In the present study we investigated the mechanisms involved in the immunoregulation triggered after a prior contact with cell-free antigens (CFA) during a murine model of PCM. The results showed that the inoculation of CFA prior to the infection resulted in disorganized granulomatous lesions and increased fungal replication in the lungs, liver and spleen, that paralleled with the higher levels of IL-4 when compared with the control group. The role of IL-4 in facilitating the fungal growth was demonstrated in IL-4-deficient- and neutralizing anti-IL-4 mAb-treated mice. The injection of CFA did not affect the fungal growth in these mice, which, in fact, exhibited a significant diminished amount of fungus in the tissues and smaller granulomas. Considering that in vivo anti-IL-4-application started one week after the CFA-inoculum, it implicates that IL-4-CFA-induced is responsible by the mediation of the observed unresponsiveness. Further, the characterization of CFA indicated that a proteic fraction is required for triggering the immunosuppressive mechanisms, while glycosylation or glycosphingolipids moieties are not. Taken together, our data suggest that the prior contact with soluble Pb antigens leads to severe PCM in an IL-4 dependent manner.
Galectin-1 (Gal-1) is important in immune function and muscle regeneration, but its expression and localization in adult tissues and primary leukocytes remain unclear. To address this, we generated a specific monoclonal antibody against Gal-1, termed αhGal-1, and defined a sequential peptide epitope that it recognizes, which is preserved in human and porcine Gal-1, but not in murine Gal-1. Using αhGal-1, we found that Gal-1 is expressed in a wide range of porcine tissues, including striated muscle, liver, lung, brain, kidney, spleen, and intestine. In most types of cells, Gal-1 exhibits diffuse cytosolic expression, but in cells within the splenic red pulp, Gal-1 showed both cytosolic and nuclear localization. Gal-1 was also expressed in arterial walls and exhibited prominent cytosolic and nuclear staining in cultured human endothelial cells. However, human peripheral leukocytes and promyelocytic HL60 cells lack detectable Gal-1 and also showed very low levels of Gal-1 mRNA. In striking contrast, Gal-1 exhibited an organized cytosolic staining pattern within striated muscle tissue of cardiac and skeletal muscle and colocalized with sarcomeric actin on I bands. These results provide insights into previously defined roles for Gal-1 in inflammation, immune regulation and muscle biology.
galectin-1 expression; leukocytes; monoclonal antibody; muscle; tissue localization
Noninvasive assessment of cardiac structure and function is essential to understand the natural course of murine infection with Trypanosoma cruzi. Magnetic resonance imaging (MRI) and echocardiography have been used to monitor anatomy and function; positron emission tomography (PET) is ideal for monitoring metabolic events in the myocardium. Mice infected with T. cruzi (Brazil strain) were imaged 15–100 days post infection (dpi). Quantitative 18F-FDG microPET imaging, MRI and echocardiography were performed and compared. Tracer (18F-FDG) uptake was significantly higher in infected mice at all days of infection, from 15 to 100 dpi. Dilatation of the right ventricular chamber was observed by MRI from 30 to 100 dpi in infected mice. Echocardiography revealed significantly reduced ejection fraction by 60 dpi. Combination of these three complementary imaging modalities makes it possible to noninvasively quantify cardiovascular function, morphology, and metabolism from the earliest days of infection through the chronic phase.
This review focuses on the short and bewildered history of Brazilian scientist Carlos Chagas's discovery and subsequent developments, the anatomopathological features of chronic Chagas cardiomyopathy (CCC), an overview on the controversies surrounding theories concerning its pathogenesis, and studies that support the microvascular hypothesis to further explain the pathological features and clinical course of CCC. It is our belief that knowledge of this particular and remarkable cardiomyopathy will shed light not only on the microvascular involvement of its pathogenesis, but also on the pathogenetic processes of other cardiomyopathies, which will hopefully provide a better understanding of the various changes that may lead to an end-stage heart disease with similar features. This review is written to celebrate the 100th anniversary of the discovery of Chagas disease.
An intense inflammatory process is associated with Trypanosoma cruzi infection. We investigated the mediators that trigger leukocyte activation and migration to the heart of infected mice. It is known that nitric oxide (NO) modulates the inflammatory response. During T. cruzi infection increased concentrations of NO are produced by cardiac myocytes (CMs) in response to IFN-γ and TNF. Here, we investigated whether NO, IFN-γ and TNF regulate chemokine production by T. cruzi-infected CMs. In addition, we examined the effects of the NOS2 deficiency on chemokine expression both in cultured CMs and in hearts obtained from infected mice. After infection of cultured WT CMs with T. cruzi, the addition of IFN-γ and TNF increased both mRNA and protein levels of the chemokines CXCL1, CXCL2, CCL2, CCL3, CCL4 and CCL5. Interestingly, T. cruzi-infected NOS2-deficient CMs produced significantly higher levels of CCL2, CCL4, CCL5 and CXL2 in the presence of IFN-γ and TNF. Infection of NOS2-null mice resulted in a significant increase in the expression of both chemokine mRNA and protein levels in the heart of as compared with hearts obtained from infected WT mice. Our data indicate that NOS2 is a potent modulator of chemokine expression which is critical to trigger the generation of the inflammatory infiltrate in the heart during T. cruzi infection.
Chemokines; nitric oxide; Trypanosoma cruzi; myocarditis
This review is based on recently published data from our laboratory. We investigated the role of hypertension and laminar flow, hypercholesterolemia and laminar flow and turbulent blood flow/low wall shear stress, and turbulent blood flow/low wall shear stress associated with hypercholesterolemia on aorta remodeling of rats feeding normal diet or hypercholesterolemic diet. Our findings suggest that increased circumferential wall tension due to hypertension plays a key role in the remodeling through biomechanical effects on oxidative stress and increased TGF-β expression; the remodeling observed in the presence of hypercholesterolemia could be initiated by oxidative stress that is involved in several processes of atherogenesis and this remodeling is more pronounced in the presence of turbulent blood flow/low wall shear stress.