Unknown,Transcriptomics,Genomics,Proteomics

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Microglia infection of Listeria monocytogenes is regulated by ActA virulence factor and TNF-α.

ABSTRACT: Cerebral listeriosis is characterized by neuronal apoptosis and microglial cell activation, but little is known about the bacterial virulence factors involved in this process and how bacterial dissemination is controlled. Here, we show that the cellular target of Listeria monocytogenes (LM) in murine hippocampal cultures is microglia rather than neurons or other glial cells, which are rarely infected. This in vitro model served to demonstrate that infected microglial cells release a soluble factor to the medium responsible for neuronal apoptosis. We investigated the production of this factor in a well-established murine microglia cell model BV2 cells, and compared with J-774 macrophage cells after infection with different LM bacterial mutants. Our purpose was to study in both cell types parameters such as the listericidal capacities, pro-inflammatory cytokines released, and bacterial factors involved in the intracellular cycle. Our data reveal that microglia shows unique features to handle a LM infection. Microglia is three times more permissive for LM intracellular growth than murine macrophages; while producing five times higher levels of pro-inflammatory cytokines IL-6, MCP-1 and TNF-α than macrophages. Using different LM mutants (i.e., LMWT, LM∆LLO, LM∆ActA or LM∆plcB) we conclude that LLO and ActA are not involved in LM proliferation within microglia cells, while they are required for survival within macrophages. Moreover, ActA controls TNF-α production, a cytokine involved in neural apoptosis. Transcriptional differential response of microglia infected with different LM mutants reflected ActA controls the TNF-a signaling pathway through out molecules and chemokines involved in this pathway such as NFkβ, MAPK-1, Ccl2, Ccl3, Ccl4 and CxCl10. The project implies the analysis of two replicates from three different conditions, in total 6 samples: microglia cells non-infected, microglia cells infected with Listeria monocytogenes (LM) wild type (LLO+), microglia cells infected with LM deficient in listeriolysin O (LLO-) and microglia cells infected with LM deficient in ActA (1942). References samples were microglia cells non-infected (NT). Infection with LM was performed for 1 hour, followed by 24 hours in medium with antibiotics to avoid bacterial extracellular growth. Gene expression analysis was performed using Partek Genomics Suite software (version 6.11.0801; Partek). GeneChip data were filtered to remove those probe sets with an intensity raw value close to background levels. Probe sets for each array are pre-processed using RMA. Also, probe sets whose expression change under all experimental conditions was below a threshold, based on the standard desviation of the normalised intensity values, were filtered.

ORGANISM(S): Mus musculus

SUBMITTER: carmen alvarez-dominguez

PROVIDER: E-GEOD-32505 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Listeria monocytogenes (LM) is a Gram-positive, facultative intracellular bacterium responsible for disseminated infections in immunocompromised individuals which can result in septicaemia and meningitis (1). Effective control of listeriosis requires both innate and adaptive immune responses with the principal mediators of bacterial killing being neutrophils and macrophages (2). Key cytokines driving the innate immune response are IFN-γ (3) and TNF (4), which promote macrophage activation and drive the production of anti-microbial mediators such as reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI). Several studies using gene deficient mice demonstrated that ROI and RNI are required for optimal pathogen killing (5-8), but that macrophages also utilise an alternative, unknown mechanism besides ROI and RNI to efficiently control bacterial infection. Mice deficient for the transcription factor NF-IL6 are highly susceptible to a number of intracellular bacterial and fungal infections, including LM (9-12). NF-IL6-deficient mice infected with LM were unable to prevent bacterial dissemination, despite production of nitric oxide (NO), IFN-γ and TNF being equivalent to WT controls (12). From these results, we hypothesized that NF-IL6 acts downstream from IFN-γ and TNF during the activation of macrophage effector functions against LM (2). To facilitate the identification of putative effector genes in this unknown pathway, we compared gene expression profiles of WT and NF-IL6 deficient LM-infected macrophages by differential microarray. REFERENCES 1. Gellin, B. G. & Broome, C. V. (1989) Jama 261, 1313-1320. 2. Brombacher, F. & Kopf, M. (1996) Res Immunol 147, 505-511. 3. Buchmeier, N. A. & Schreiber, R. D. (1985) Proc Natl Acad Sci U S A 82, 7404-7408. 4. Havell, E. A. (1989) J Immunol 143, 2894-2899. 5. Dinauer, M. C., Deck, M. B., & Unanue, E. R. (1997) J Immunol 158, 5581-5583. 6. Endres, R., Luz, A., Schulze, H., Neubauer, H., Futterer, A., Holland, S. M., Wagner, H., & Pfeffer, K. (1997) Immunity 7, 419-432. 7. MacMicking, J. D., Nathan, C., Hom, G., Chartrain, N., Fletcher, D. S., Trumbauer, M., Stevens, K., Xie, Q. W., Sokol, K., Hutchinson, N., et al. (1995) Cell 81, 641-650. 8. Shiloh, M. U., MacMicking, J. D., Nicholson, S., Brause, J. E., Potter, S., Marino, M., Fang, F., Dinauer, M., & Nathan, C. (1999) Immunity 10, 29-38. 9. Pizarro-Cerda, J., Desjardins, M., Moreno, E., Akira, S., & Gorvel, J. P. (1999) J Immunol 162, 3519-3526. 10. Screpanti, I., Romani, L., Musiani, P., Modesti, A., Fattori, E., Lazzaro, D., Sellitto, C., Scarpa, S., Bellavia, D., Lattanzio, G., et al. (1995) Embo J 14, 1932-1941. 11. Sugawara, I., Mizuno, S., Yamada, H., Matsumoto, M., & Akira, S. (2001) Am J Pathol 158, 361-366. 12. Tanaka, T., Akira, S., Yoshida, K., Umemoto, M., Yoneda, Y., Shirafuji, N., Fujiwara, H., Suematsu, S., Yoshida, N., & Kishimoto, T. (1995) Cell 80, 353-361. Keywords: bone marrow derived macrophages, interferon-gamma, macrophage activation, macrophage effector activity, NF-IL6, gene-deficient mouse model, Listeria monocytogenes, intracellular pathogen

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Project description:GFAP and vimentin deficiency alters gene expression in astrocytes and microglia in wild-type mice and changes the transcriptional response of reactive glia in mouse model for Alzheimer's disease. Reactive astrocytes with an increased expression of intermediate filament (IF) proteins Glial Fibrillary Acidic Protein (GFAP) and Vimentin (VIM) surround amyloid plaques in Alzheimer's disease (AD). The functional consequences of this upregulation are unclear. To identify molecular pathways coupled to IF regulation in reactive astrocytes, and to study the interaction with microglia, we examined WT and APPswe/PS1dE9 (AD) mice lacking either GFAP, or both VIM and GFAP, and determined the transcriptome of cortical astrocytes and microglia from 15- to 18-month-old mice. Genes involved in lysosomal degradation (including several cathepsins) and in inflammatory response (including Cxcl5, Tlr6, Tnf, Il1b) exhibited a higher AD-induced increase when GFAP, or VIM and GFAP, were absent. The expression of Aqp4 and Gja1 displayed the same pattern. The downregulation of neuronal support genes in astrocytes from AD mice was absent in GFAP/VIM null mice. In contrast, the absence of IFs did not affect the transcriptional alterations induced by AD in microglia, nor was the cortical plaque load altered. Visualizing astrocyte morphology in GFAP-eGFP mice showed no clear structural differences in GFAP/VIM null mice, but did show diminished interaction of astrocyte processes with plaques. Microglial proliferation increased similarly in all AD groups. In conclusion, absence of GFAP, or both GFAP and VIM, alters AD-induced changes in gene expression profile of astrocytes, showing a compensation of the decrease of neuronal support genes and a trend for a slightly higher inflammatory expression profile. However, this has no consequences for the development of plaque load, microglial proliferation, or microglial activation. 2 cell types from 6 conditions: cortical microglia and cortical astrocytes from 15-18 month old APPswe/PS1dE9 mice compared to wildtype littermates. Biological replicates: microglia from APPswe/PS1dE9, N=7, microglia from WT, N=7, astrocytes from APPswe/PS1dE9, N=4, microglia from WT, N=4

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Microglia infection of Listeria monocytogenes is regulated by ActA virulence factor and TNF-α.

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