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Gene expression in macrophages stimulated with LPS in conditions allowing or inhibiting NFAT activation


ABSTRACT: Macrophages and dendritic cells (DCs) differently contribute to the generation of coordinated immune system responses against infectious agents. They interact with microbes through germline-encoded pattern-recognition receptors (PRRs), which recognize molecular patterns expressed by various microorganisms. Upon antigen binding, PRRs instruct DCs for the appropriate priming of natural killer cells, followed by specific T-cell responses. Once completed the effector phase, DCs reach the terminal differentiation stage and eventually die by apoptosis. By contrast, following antigen recognition, macrophages initiate first the inflammatory process and then switch to an anti-inflammatory phenotype for the restoration of tissue homeostasis. Following lipopolysaccharide (LPS)-stimulation the initiation of the apoptotic pathway in DCs is due the activation of NFAT proteins. DC stimulation with lipopolysaccharide (LPS) induces Src-family kinase and phospholipase C (PLC)γ2 activation, influx of extracellular Ca2+ and calcineurin-dependent nuclear NFAT translocation. The initiation of this pathway is independent of TLR4 engagement, and dependent exclusively on CD14. We asked whether macrophage survival after LPS encounter was due to their inability to activate the Ca2+ pathway. As matter of fact, bone marrow-derived macrophages were unable to mobilize Ca2+ and to translocate NFAT to the. To further investigate whether the Ca2+-NFAT pathway played any role in LPS-stimulated macrophages, we performed a comparative kinetic microarray analysis in conditions allowing or inhibiting NFAT activation. We show here that no modulation of gene expression can be attributed to NFAT. Gene expression analyses were performed using Affymetrix GeneChips in the following groups of murine macrophaghes: 1) CD14-deficient macrophages stimulated with LPS; 2) wt macrophages stimulated with LPS in presence of EGTA; 3) wt macrophages stimulated with LPS. The following kinetic time points were examined: 0, 6 and 24 hours following LPS activation. This experimental setting allowed us to select for effects due to Ca2+ fluxes and exclude the effects due to other causes, particularly the block of TRIF recruitment in CD14-deficient cells and the EGTA effects unrelated to Ca2+ chelation.

ORGANISM(S): Mus musculus

SUBMITTER: Ivan Zanoni 

PROVIDER: E-GEOD-15721 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Toll-like receptors (TLRs) are the best characterized pattern recognition receptors. Individual TLRs recruit diverse combinations of adaptor proteins, triggering signal transduction pathways and leading to the activation of various transcription factors, including nuclear factor kappaB, activation protein 1 and interferon regulatory factors. Interleukin-2 is one of the molecules produced by mouse dendritic cells after stimulation by different pattern recognition receptor agonists. By analogy wit  ...[more]

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