Endothelial Cells Activated by Extracellular Histones Promote Foxp3+ Suppressive Treg Cells In Vitro

International audienceHistones are widely recognized as pro-inflammatory mediators upon their release from the nucleus into the extracellular space. However, their impact on endothelial cell immunogenicity is unknown. Endothelial cells, Human Microvascular Endothelial cells 1 (HMEC1), have been exposed to recombinant histones in order to study their effect on the endothelial phenotype. We then studied the differentiation of CD4+-T lymphocytes subpopulations after three days of interaction with endothelial cells in vitro and observed that histone-treated endothelial cells differentiate a suppressive FoxP3+ T regulator subpopulation that expressed Human Leucocyte Antigen DR (HLA-DR) and Cytotoxic T-Lymphocyte-Associated protein 4 (CTLA4). Toll-Like Receptor 4 (TLR4) inhibition significantly decreased the expansion of these Treg cells. Moreover, blockade of Interleukin (IL)-6 and Intercellular Adhesion Molecule (ICAM)-1 in cocultures significantly decreased the expansion of Tregs, suggesting an IL-6 and ICAM-1 dependent pathway. Thus, beyond their inflammatory effects, extracellular histones may induce an increase of immunosuppressive Treg population via their action on endothelial cells. Further studies are needed to evaluate the impact on immunosuppression of an increase of peripheral suppressive Treg via endothelial cell activation by histones in vivo

Immunomodulation of endothelial cells induced by macrolide therapy in a model of septic stimulation

International audienceObjectives: Sepsis is defined as the host's inflammatory response to a lifethreatening infection. The endothelium is implicated in immunoregulation during sepsis. Macrolides have been proposed to display immunomodulatory properties. The goal of this study was to analyze whether macrolides can exert immunomodulation of endothelial cells (ECs) in an experimental model of sepsis. Methods: Human ECs were stimulated by proinflammatory cytokines and lipopolysaccharide before exposure to macrolides. ECs phenotypes were analyzed by flow cytometry. Cocultures of ECs and peripheral blood mononuclear cells (PBMCs) were performed to study the ECs ability to alter T-cell viability and differentiation in the presence of macrolides. Soluble factor production was assessed. Results: ECs act as non-professional antigen presenting cells and expressed human leukocyte antigen (HLA) antigens, the adhesion molecules CD54, CD106, and the coinhibitory molecule CD274 after septic stimulation. Incubation with macrolides induced a significant decrease of HLA class I and HLA class II HLA-DR on septic-stimulated ECs, but did not alter either CD54, CD106, nor CD274 expression. Interleukin-6 (IL-6) and IL-8 production by stimulated ECs were unaltered by incubation with macrolides, whereas Clarithromycin exposure significantly decreased IL-6 gene expression. In cocultures of septic ECs with PBMCs, neither the proportion of CD4 + , CD8 + T nor their viability was altered by macrolides. T-helper lymphocyte subsets Th1, Th17, and Treg polarization by stimulated ECs were unaltered by macrolides. Conclusion: This study reports phenotypic and gene expression changes in septic-stimulated ECs exposed to macrolides, without resulting in altered immunogenicity of ECs in co-cultures with PBMCs. In vivo studies may help This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited