Sheltered in Stromal Tissue Cells, Trypanosoma cruzi Orchestrates Inflammatory Neovascularization via Activation of the Mast Cell Chymase Pathway.

Microangiopathy may worsen the clinical outcome of Chagas disease. Given the obstacles to investigating the dynamics of inflammation and angiogenesis in heart tissues parasitized by Trypanosoma cruzi, here we used intravital microscopy (IVM) to investigate microcirculatory alterations in the hamster cheek pouch (HCP) infected by green fluorescent protein-expressing T. cruzi (GFP-T. cruzi). IVM performed 3 days post-infection (3 dpi) consistently showed increased baseline levels of plasma extravasation. Illustrating the reciprocal benefits that microvascular leakage brings to the host-parasite relationship, these findings suggest that intracellular amastigotes, acting from inside out, stimulate angiogenesis while enhancing the delivery of plasma-borne nutrients and prosurvival factors to the infection foci. Using a computer-based analysis of images (3 dpi), we found that proangiogenic indexes were positively correlated with transcriptional levels of proinflammatory cytokines (pro-IL1ß and IFN-γ). Intracellular GFP-parasites were targeted by delaying for 24 h the oral administration of the trypanocidal drug benznidazole. A classification algorithm showed that benznidazole (>24 h) blunted angiogenesis (7 dpi) in the HCP. Unbiased proteomics (3 dpi) combined to pharmacological targeting of chymase with two inhibitors (chymostatin and TY-51469) linked T. cruzi-induced neovascularization (7 dpi) to the proangiogenic activity of chymase, a serine protease stored in secretory granules from mast cells.

The short chain fatty acid sodium butyrate regulates the induction of CD1a in developing dendritic cells.

Dendritic cells (DCs) are professional antigen-presenting cells with attributes for priming/activating T cells and mediating immune responses. Considering the importance of DCs in the initiation of immune responses, it will be of interest to study their mechanisms of regulation. Histone-modifying enzymes, such as histone deacetylases (HDACs), are critical in controlling chromatin organization. The aim of our study was to investigate DC differentiation under the influence of sodium butyrate (NaB), a short chain fatty acid that is a histone deacetylase inhibitor. Monocytes from healthy individuals were differentiated into immature DCs with IL-4 and GM-CSF in the presence or absence of NaB. DC differentiation was evaluated by CD14 and CD1a expression by flow cytometry. We observed that monocytes stimulated to differentiate in the presence of NaB displayed colony formation and dendritic cell morphology, lost CD14 and showed decreased secretion of IL-1ß. The acquisition of CD1a, however, was impaired. Being a natural short chain fatty acid, NaB may regulate CD1a acquisition independently of its HDAC inhibitory activity. We observed that the addition of peroxisome proliferator-activated receptor γ (PPAR-γ) antagonist (GW9662) did not reverse NaB effect, suggesting this was not the pathway involved. On the other hand, CD1a can also be induced by toll like receptors 2 (TLR 2) agonists, such as Pam3Cys, and NaB inhibited this effect. Our data suggest that the histone deacetylase inhibitor NaB instead of impairing DC differentiation inhibits the acquisition of CD1a induced both by cytokines and by TLR 2 agonist stimulus. Furthermore, this occurs at the transcriptional level as NaB led to a decrease in mRNA levels of CD1a and upregulation of CD1d.

Monocytes from HTLV-1-infected patients are unable to fully mature into dendritic cells.

Human T-cell lymphotropic virus type 1 (HTLV-1) is a causative agent of adult T-cell leukemia and HTLV-1-associated myelopathy/tropical spastic paraparesis. HTLV-1-associated myelopathy/tropical spastic paraparesis is a chronic inflammatory disease characterized by loss of motor movement in response to spinal marrow cell destruction by T lymphocytes. To perform their cellular function, T cells need to be activated by antigen-presenting cells, such as dendritic cells (DCs). The aim of this work was to analyze DC differentiation and activation from monocytes of HTLV-1-infected individuals. We demonstrated that monocytes from HTLV-1-infected patients who had been stimulated to differentiate had an impaired loss of CD14 expression, expressed low levels of CD1a, and maintained secretion of tumor necrosis factor-α compared with monocytes from noninfected donors. We further evaluated DC activation by tumor necrosis factor-α. We observed that in response to activation, DCs that were derived from noninfected donors had an increase in the percentage of CD83(+), CD86(+), and human leukocyte antigen-DR(+) cells, whereas in DCs derived from HTLV-1-infected patients, the percentage of CD83(+), CD86(+), and human leukocyte antigen-DR(+) cells remained similar to that of nonactivated cells. Moreover, these cells had an impaired capacity to stimulate allogeneic T lymphocytes. We demonstrated that DC maturation was altered in HTLV-1-infected patients, which could contribute to the development of HTLV-1-associated diseases.

Leukemic cell products down-regulate human dendritic cell differentiation.

The microenvironment produced by solid tumors is inhibitory to the immune system, inducing dendritic cell (DC) alterations, but there is a paucity of information regarding haematological malignances. The aim of this study was to investigate DC differentiation under the influence of leukemic cell products. Monocytes from healthy volunteers were cultured in the presence of IL-4 and GM-CSF for the generation of immature DCs. Supernatants from leukemic cultures were added to monocyte cultures during differentiation. The lineages used were K562, a chronic myeloid leukemia, HL-60, a promyelocytic leukemia and DAUDI, originated from Burkitt lymphoma. It was observed that the expression of CD14 remained high and the CD1a was low in the presence of tumor supernatants, while non-malignant supernatants did not affect these parameters. Furthermore, IL-1beta and TNF-alpha production by monocytes during differentiation was increased by the presence of tumor supernatants. The modifications on CD14 and CD1a expressions could be mimicked by the addition of exogenous IL-1beta and partially inhibited by the neutralization of IL-1beta. These results suggest that soluble products from leukemic cells interfere with DC differentiation and, in the present work, this effect could be mediated by monocyte-derived IL-1beta in response to tumor supernatants.