The protozoan parasite Trypanosoma cruzi is able to target the thymus and induce alterations of the thymic microenvironmental and lymphoid compartments. Acute infection results in severe atrophy of the organ and early release of immature thymocytes into the periphery. To date, the pathophysiological effects of thymic changes promoted by parasite-inducing premature release of thymocytes to the periphery has remained elusive. Herein, we show that sphingosine-1-phosphate (S1P), a potent mediator of T cell chemotaxis, plays a role in the exit of immature double-negative thymocytes in experimental Chagas disease. In thymuses from T. cruzi-infected mice we detected reduced transcription of the S1P kinase 1 and 2 genes related to S1P biosynthesis, together with increased transcription of the SGPL1 sphingosine-1-lyase gene, whose product inactivates S1P. These changes were associated with reduced intrathymic levels of S1P kinase activity. Interestingly, double-negative thymocytes from infected animals expressed high levels of the S1P receptor during infection, and migrated to lower levels of S1P. Moreover, during T. cruzi infection, this thymocyte subset expresses high levels of IL-17 and TNF-α cytokines upon polyclonal stimulation. In vivo treatment with the S1P receptor antagonist FTY720 resulted in recovery the numbers of double-negative thymocytes in infected thymuses to physiological levels. Finally, we showed increased numbers of double-negative T cells in the peripheral blood in severe cardiac forms of human Chagas disease. The formation of mature lineage-committed T cells requires the specialized environment of the thymus, a central organ of the immune system supporting the development of self-tolerant T cells. Key events of intrathymic T-cell development include lineage commitment, selection events and thymic emigration. This organ undergoes physiological involution during aging. However, acute thymic atrophy can occur in the presence autoimmune diseases, malignant tumors and infections caused by intracellular pathogens. The present study shows that the protozoan parasite Trypanosoma cruzi changes the thymic microenvironmental and lymphoid compartments, resulting in premature release of very immature CD4⁻CD8⁻ double-negative thymocytes, TCRneg/low, which bear a pro-inflammatory activation profile. Strikingly, we also found elevated levels of these undifferentiated T lymphocytes in the peripheral blood of patients in severe cardiac forms of chronic Chagas disease. Importantly, we provided evidence that migration of CD4⁻CD8⁻ T cells from infected mouse thymus is due to sphingosine-1-phosphate receptor-1-dependent chemotaxis. These findings point to an important role for bioactive signaling sphingolipids in the thymic escape of immature thymocytes to the periphery in Chagas disease.

Migration and invasion are hallmarks of cancer cells that allow their dissemination to other tissues. Studying the cellular and molecular basis of cancer cell migration can help us to understand and control cancer metastasis. Many membrane molecules have been described as being involved in tumor cell migration, and among them is cholesterol. In the present study we investigated the role of membrane cholesterol in the migration of breast tumor cells. The human mammary gland/breast epithelial cell line MDA-MB 231 was used and membrane cholesterol was depleted with methyl-β-cyclodextrin (MbCD). Cell migration was measured in a cell-based scratch assay and the involvement of the Wnt signaling was tested using Lef-1/TCF reporter activation in permanently transfected MDA-MB 231 cells. Cell morphology was analyzed using fluorescent phalloidin to label F-actin structures. Our results show that membrane cholesterol depletion reduces cell migration, induces changes in cell morphology and in membrane protrusions. Cholesterol depletion also induces an increase in the secretion of IL-10, a cytokine involved in the control of cell migration. In addition, we show that these effects do not involve the activation of the canonical Wnt/beta-catenin pathway. Interestingly, Wnt5a inhibited cell migration in similar levels as MbCD, pointing to a role for the non-canonical Wnt pathway and IL-10 in this process. Taken together, our results suggest a correlation between membrane cholesterol, non-canonical Wnt signaling, IL-10 secretion and breast tumor cell migration. These results could contribute to the understanding of breast tumor cell migration and may be used in the development of new therapeutic strategies targeted to breast cancer metastasis.

Several studies have correlated protein restriction associated with other nutritional deficiencies with the development of cardiovascular and renal diseases. The driving hypothesis for this study was that Ang II signaling pathways in the heart and kidney are affected by chronic protein, mineral and vitamin restriction. Wistar rats aged 90 days were fed from weaning with either a control or a deficient diet that mimics those used in impoverished regions worldwide. Such restriction simultaneously increased ouabain-insensitive Na⁺-ATPase and decreased (Na⁺+K⁺)ATPase activity in the same proportion in cardiomyocytes and proximal tubule cells. Type 1 angiotensin II receptor (AT₁R) was downregulated by that restriction in both organs, whereas AT₂R decreased only in the kidney. The PKC/PKA ratio increased in both tissues and returned to normal values in rats receiving Losartan daily from weaning. Inhibition of the MAPK pathway restored Na⁺-ATPase activity in both organs. The undernourished rats presented expanded plasma volume, increased heart rate, cardiac hypertrophy, and elevated systolic pressure, which also returned to control levels with Losartan. Such restriction led to electrical cardiac remodeling represented by prolonged ventricular repolarization parameters, induced triggered activity, early after-depolarization and delayed after-depolarization, which were also prevented by Losartan. The mechanisms responsible for these alterations are underpinned by an imbalance in the PKC- and PKA-mediated pathways, with participation of angiotensin receptors and by activation of the MAPK/ERK1/2 pathway. These cellular and molecular alterations culminate in cardiac electric remodeling and in the onset of hypertension in adulthood.