Regulation of Trypanosoma cruzi-Induced Myocarditis by Programmed Death Cell Receptor

Trypanosoma cruzi infection causes intense myocarditis, leading to cardiomyopathy and severe cardiac dysfunction. Protective adaptive immunity depends on balanced signaling through a T cell receptor and coreceptors expressed on the T cell surface. Such coreceptors can trigger stimulatory or inhibitory signals after binding to their ligands in antigen-presenting cells (APC). T. cruzi modulates the expression of coreceptors in lymphocytes after infection. Deregulated inflammation may be due to unbalanced expression of these molecules. Programmed death cell receptor 1 (PD-1) is a negative T cell coreceptor that has been associated with T cell anergy or exhaustion and persistent intracellular infections. We aimed to study the role of PD-1 during T. cruzi-induced acute myocarditis in mice. Cytometry assays showed that PD-1 and its ligands are strongly upregulated in lymphocytes and APC in response to T. cruzi infection in vivo and in vitro. Lymphocytes infiltrating the myocardium exhibited high levels of expression of these molecules. An increased cardiac inflammatory response was found in mice treated with blocking antibodies against PD-1, PD-L1, and to a lesser extent, PD-L2, compared to that found in mice treated with rat IgG. Similar results in PD-1(-/-) mice were obtained. Moreover, the PD-1 blockade/deficiency led to reduced parasitemia and tissue parasitism but increased mortality. These results suggest the participation of a PD-1 signaling pathway in the control of acute myocarditis induced by T. cruzi and provide additional insight into the regulatory mechanisms in the pathogenesis of Chagas` disease.

Immunohistochemical approach reveals involvement of inducible nitric oxide synthase in rat late development

To better understand the role of nitric oxide (NO) in mammal development, specifically in the transition of the fetal stages at birth, we studied the timing of cell-specific expression of inducible NO synthase (iNOS) isoform during gestational periods of rats, mainly at the late stages of intra-uterine development. Before experimentation, the samples were collected (from 17th to 21st gestational days), fixed in 10% buffered formalin and embedded in paraffin for histological procedures. Hereafter, the sections (5 mu m thickness) obtained from different embryos were immunostained by avidin-biotin-immunoperoxidase technique, by using antibody against iNOS isoform. The most of cell immunopositive was suggestive of granulocyte-like cells and those cells were resident close to the blood vessels in different organs, such as: lung, liver or bone marrow environment. Sometimes we noted immunopositive cells in the blood flow, as reported in the thymus. In agreement, iNOS expression, obtained by western blotting analysis, showed the same profile. Together, our data shows that iNOS expression increased gradually during the late stages of rat development (from E17 to E21) and it was executed by cells close to blood vessels. Thus, we can clearly to predict that this expression was finely modulated and it contributes for time-line dependent NO production during rat late development.