Unknown,Transcriptomics,Genomics,Proteomics

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Apoptosis genes specifically modulated by NFAT in LPS-activated dendritic cells

ABSTRACT: Dendritic cells (DCs) are a special class of leukocytes able to activate both innate and adaptive immune responses. 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. We have observed that following lipopolysaccharide (LPS)-stimulation the initiation of the apoptotic pathway in DCs is due the activation of NFAT proteins. Indeed, LPS induces Src-family kinase and phospholipase C (PLC)Î³2 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. According with this observation CD14-deficient DCs do not die following LPS stimulation. Nevertheless, CD14-deficient DC death following LPS activation can be restored by co-stimulating DCs with LPS and thapsigargin. Thapsigargin empties the intracellular calcium stores by blocking calcium pumping into the sarcoplasmic and endoplasmic reticulum and thereby activates plasma membrane calcium channels. This, in turn, allows an influx of calcium into the cytosol and NFAT activation. To identify the NFAT controlled apoptosis genes in LPS activated DCs we have performed a kinetic microarray analysis (0, 48 and 60 h) in conditions allowing or inhibiting NFAT activation. Four genes have been selected: Nur77, Gadd45g, Ddit3/Gadd153/Chop-10 and Tia1. To identify apoptosis genes selectively modulated by NFAT, a comparative kinetic (time points 0, 48 and 60 h) microarray analysis was performed in the following conditions: 1) wild type bone marrow derived DCs (wtBMDCs) stimulated with LPS; 2) CD14-deficient BMDCs stimulated with LPS; 3) wtBMDCs stimulated with LPS in presence of thapsigargin; 4) CD14-deficient BMDCs stimulated with LPS in presence of thapsigargin.

ORGANISM(S): Mus musculus

SUBMITTER: Ivan Zanoni

PROVIDER: E-GEOD-15720 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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CD14 regulates the dendritic cell life cycle after LPS exposure through NFAT activation.

Zanoni Ivan I Ostuni Renato R Capuano Giusy G Collini Maddalena M Caccia Michele M Ronchi Antonella Ellena AE Rocchetti Marcella M Mingozzi Francesca F Foti Maria M Chirico Giuseppe G Costa Barbara B Zaza Antonio A Ricciardi-Castagnoli Paola P Granucci Francesca F

Nature 20090614 7252

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]

PMID: 19525933

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Project description: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)Î³2 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.

Project description:Abstract Two major dendritic cell (DC) subsets have been described in the islets of mice: The immunogenic CD8Î±-CD11b+ DCs and the tolerogenic CD8Î±+CD103+ DCs. We have recently reported on reduced numbers of the minor population of tolerogenic CD8Î±+CD103+ DCs in the pancreas of 5 week old pre-diabetic non-obese diabetic (NOD) mice. Aim: To analyze also the larger subset of CD11c+CD8Î±- DCs isolated from the pancreas of pre-diabetic NOD mice 1) for maturation and tolerance inducing molecules found abnormally expressed on CD8Î±+CD103+ DCs, and 2) for genome-wide gene expression to further elucidate abnormalities in underlying gene expression networks. Methods: CD11c+CD8Î±- DCs were isolated from 5 week old C57BL/6 and NOD pancreas. Expression of cell surface markers including CD86, CCR5, CD11b, CD103, Clec9a, CD24 and CD200R3 were measured by FACS. Genome-wide gene expression by microarray was assessed during the steady state and after in vitro LPS stimulation. Results: The steady state pancreatic CD11c+ CD8Î±- DCs during the pre-diabetic stage showed: 1) A reduced expression of several gene networks important for the prime functions of the cell, such as for cell renewal, immune stimulation and immune tolerance induction, for migration and for the provision of growth factors for beta cell regeneration. This general deficiency state was corroborated by a reduced in vivo proliferation (BrdU incorporation) of the cells and the reduced expression in FACS analysis of CD86, CCR5, CD103, Clec9a, CD24 and CD200R3 on the cells. 2) A hyper reactivity of these cells to LPS correlated with an enhanced pro-inflammatory state characterized by altered expression of a number of classical pro-inflammatory factors and cytokines. Conclusion: The NOD CD11c+CD8Î±- DCs seem to be Janus-faced depending on the conditions: Deficient in steady state with reduced immune stimulation capabilities also for tolerance induction; over-inflammatory with a molecular profile suggesting a preferential stimulatory capacity for Th1 cells when encountering a Pathogen-Associated Molecular Pattern (PAMP) in the form of LPS. We used microarray gene expression analysis to explain the abnormal expression of several cell surface markers involved in tolerace, migration and maturation in the steady-state and to measure the effect of a PAMP such as LPS We isolated RNA from FACS sorted CD11c+CD8Î±- DCs in 10 pooled pancreases from pre-diabetic NOD and non-diabetic C57BL/6 mice at 5 weeks. In addition, we treated in another experiment the isolated pancreas DCs with LPS (and PBS), incubated for 18h and measured gene expression. We compared gene expression between strains NOD vs C57BL/6 under steady-state and after in-vitro LPS/PBS stimulation.

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Apoptosis genes specifically modulated by NFAT in LPS-activated dendritic cells

Publications

CD14 regulates the dendritic cell life cycle after LPS exposure through NFAT activation.

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