Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Transcription profiling of mouse naive and tolerant macrophages stimulated with LPS

ABSTRACT: The inflammatory response initiated by microbial products signaling through Toll-like receptors (TLRs) of the innate immune system is essential for host defense against infection. Because inflammation can be harmful to host tissues, the innate response is highly regulated. Negative regulation of TLR4, the receptor for bacterial lipopolysaccharide (LPS), results in LPS tolerance, defined as hyporesponsiveness to repeated stimulation with LPS. LPS tolerance is thought to protect the host from excessive inflammation by turning off TLR4 signal, which then shuts down TLR-induced genes. However, TLR signaling induces hundreds of genes with very different functions. We reasoned that genes with different functions should have different requirements for regulation. Specifically, genes encoding proinflammatory mediators should be transiently inactivated to limit tissue damage, while genes encoding antimicrobial effectors, which directly target pathogens, should remain inducible in tolerant cells to protect the host from infection. Using an in vitro system of LPS tolerance in macrophages, here we show that TLR-induced genes may indeed be divided into two distinct categories based on their functions and regulatory requirements. Further, we show these distinct groups are regulated by gene-specific, and not signal-specific mechanisms. Experiment Overall Design: We examined gene expression using affymetrix genechips in 3 groups of murine bone-marrow derived macrophages: Naive (untreated), Naive stimulated with LPS, and Tolerant stimulated with LPS. Two biological replicates were performed for each group.

ORGANISM(S): Mus musculus

SUBMITTER: Simmie Foster

PROVIDER: E-GEOD-7348 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Gene-specific control of inflammation by TLR-induced chromatin modifications.

Foster Simmie L SL Hargreaves Diana C DC Medzhitov Ruslan R

Nature 20070530 7147

Toll-like receptors (TLRs) induce a multi-component inflammatory response that must be tightly regulated to avoid tissue damage. Most known regulatory mechanisms target TLR signalling pathways and thus broadly inhibit multiple aspects of the inflammatory response. Given the functional diversity of TLR-induced genes, we proposed that additional, gene-specific regulatory mechanisms exist to allow individual aspects of the TLR-induced response to be differentially regulated. Using an in vitro syste ...[more]

PMID: 17538624

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Project description:Siglec-E is a murine CD33-related siglec that functions as an inhibitory receptor and is expressed mainly on neutrophils and macrophage populations. Recent studies have suggested that siglec-E is an important negative regulator of LPS-TLR4 signalling and one report (Wu et al 2016) claimed that siglec-E is required for TLR4 endocytosis following uptake of Escherichia coli by macrophages and dendritic cells (DCs). Our attempts to reproduce these observations using cells from wildtype (WT) and siglec E deficient mice were unsuccessful. We used a variety of assays to determine if siglec-E expressed by different macrophage populations can regulate TLR-4 signalling in response to LPS, but found no consistent differences in cytokine secretion in vitro and in vivo, comparing 3 different strains of siglec-E-deficient mice with matched WT controls. No evidence was found that the siglec-E deficiency was compensated by expression of siglecs-F and –G, the other murine inhibitory CD33-related siglecs. Quantitative proteomics was used as an unbiased approach and provided additional evidence that siglec-E does not suppress inflammatory TLR4 signaling. Interestingly, proteomics revealed a siglec E dependent alteration in macrophage phenotype that could be relevant to functional responses in host defence. In support of this, siglec-E-deficient mice exhibited enhanced growth of Salmonella enterica serovar Typhimurium in the liver following intravenous infection, but macrophages lacking siglec-E did not show altered uptake or killing of bacteria in vitro. Using various cell types including bone marrow derived DCs (BMDC), splenic DCs and macrophages from WT and siglec-E-deficient mice, we showed that siglec-E is not required for TLR4 endocytosis following E.coli uptake or LPS challenge. We failed to see expression of siglec-E by BMDC even after LPS-induced maturation, but confirmed previous studies that splenic DCs express low levels of siglec-E. Taken together, our findings do not support a major role of siglec-E in regulation of TLR4 signalling functions or TLR4 endocytosis in macrophages or DCs. Instead, they reveal that induction of siglec-E by LPS can modulate the phenotype of macrophages, the functional significance of which is currently unclear.

Project description:Background: Toll-like family of receptors recognizes pathogen-associated molecular patterns (PAMPs) from different organisms. TLR4 is the receptor for bacterial lipopolysaccharide (LPS), dsRNA viral mimic poly(I:C) binds to TLR3, and bacterial CpG DNA signals through TLR9. TLR4 signaling is mediated by adaptor molecules Myd88 and TRIF while TLR3 pathway involves only the TRIF adaptor and TLR9 signals solely through Myd88. Methods: To identify genes other than those in TLR pathways that mediate macrophage response to different PAMPs, RAW264.7 cells were stimulated with LPS, poly(I:C), or CpG DNA, and RNA was profiled on microarrays 6 hrs and 24 hrs post-treatment. Gene expression data were analyzed to determine genes, pathways and transcriptional networks that are in common and unique to each of the three TLR stimuli. Potentially novel candidates revealed by this analysis were tested for their role in innate immunity using RNA interference. Results: Many genes are differentially regulated by LPS and poly(I:C) at both 6 hrs and 24 hrs following treatment, while CpG DNA elicits a much less pronounced transcriptional response. By analyzing gene expression data for networks and pathways, we prioritized differentially expressed genes that are in common to all three PAMPs as well as those shared by LPS and poly(I:C). Knockdown by RNA interference of two genes, Plec1 and TPST1, inhibited production of IL-6 in response to LPS in cultured macrophages. Conclusions: We have identified novel innate immunity genes that may be important in macrophage response to LPS, poly(I:C), and CpG DNA stimuli. Our results provide potential biomarkers and therapeutic targets that should be further investigated in mice and human populations. Keywords: time course For each treatment (Sigma LPS, LIST LPS, and media only), three biological replicates (separate macrophage cultures and RNA isolations) were profiled. Each sample was labeled with Cy3 and Cy5 and co-hybridized with Stratagene Universal Mouse Reference (dye flip techical replicates). Expression at 2 timepoints (6 and 24 hours post-treatment) was assessed.

Dataset Information

Transcription profiling of mouse naive and tolerant macrophages stimulated with LPS

Publications

Gene-specific control of inflammation by TLR-induced chromatin modifications.

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