Caspase-1-induced pyroptosis is an innate immune effector mechanism against intracellular bacteria

Macrophages mediate crucial innate immune responses via caspase-1-dependent processing and secretion of interleukin 1β (IL-1β) and IL-18. Although infection with wild-type Salmonella typhimurium is lethal to mice, we show here that a strain that persistently expresses flagellin was cleared by the cytosolic flagellin-detection pathway through the activation of caspase-1 by the NLRC4 inflammasome; however, this clearance was independent of IL-1β and IL-18. Instead, caspase-1-induced pyroptotic cell death released bacteria from macrophages and exposed the bacteria to uptake and killing by reactive oxygen species in neutrophils. Similarly, activation of caspase-1 cleared unmanipulated Legionella pneumophila and Burkholderia thailandensis by cytokine-independent mechanisms. This demonstrates that activation of caspase-1 clears intracellular bacteria in vivo independently of IL-1β and IL-18 and establishes pyroptosis as an efficient mechanism of bacterial clearance by the innate immune system

Caspase-1-induced pyroptosis is an innate immune effector mechanism against intracellular bacteria

Macrophages mediate crucial innate immune responses via caspase-1-dependent processing and secretion of interleukin 1β (IL-1β) and IL-18. Although infection with wild-type Salmonella typhimurium is lethal to mice, we show here that a strain that persistently expresses flagellin was cleared by the cytosolic flagellin-detection pathway through the activation of caspase-1 by the NLRC4 inflammasome; however, this clearance was independent of IL-1β and IL-18. Instead, caspase-1-induced pyroptotic cell death released bacteria from macrophages and exposed the bacteria to uptake and killing by reactive oxygen species in neutrophils. Similarly, activation of caspase-1 cleared unmanipulated Legionella pneumophila and Burkholderia thailandensis by cytokine-independent mechanisms. This demonstrates that activation of caspase-1 clears intracellular bacteria in vivo independently of IL-1β and IL-18 and establishes pyroptosis as an efficient mechanism of bacterial clearance by the innate immune system

The Glial Differentiation Factor Nuclear Factor One B (Nfib) Induces Differentiation and Inhibits Growth of Glioblastoma.

International audienceThe molecule CD90 is a N-glycosylated, glycophosphatidylinositol anchored cell surface protein, originally described on thymocytes. CD90 has been considered as a surrogate marker for a variety of stem cells and has recently been reported on glioblastoma stem cells. CD90 is also expressed on T lymphocytes, endothelial cells, fibroblasts and neurons. The function of CD90 is not fully elucidated. CD90 has been involved in cell-cell and cell-matrix interactions, in neurite outgrowth, T cell activation and apoptosis. In this study, we confirmed the expression of CD90 on human glioblastoma stem-like cells from serum-free neurosphere cultures. We also observed RNA and protein CD90 expression on primary cell lines from FSC-containing culture (adherent cell lines) and on freshly prepared glioblastoma specimen. In order to study the function of CD90 on glioblastoma cells, we used a silencing strategy to decrease the expression of CD90 on the immortalized U251 cell line. We then compared the viability, the tumor growth and the migration property of the wild-type CD90+ U251 cells and CD90 down-regulated U251 clones. The decrease of CD90 expression did not affect the viability and the tumor growth of U251 cells. In contrast, down-regulation of CD90 mediated the decreased ability of tumor cell migration using both scratch wound healing and boyden chamber migration assays. Experiments are currently on going to test the effect of CD90 expression on tumorigenicity in mice models. In total, this study might lead to better understand the role of CD90 on the pathology in particular in term of tumor migration/invasion of human glioblastoma