Functional genomic delineation of TLR-induced transcriptional networks

Elkon, Ran; Linhart, Chaim; Halperin, Yonit; Shiloh, Yosef; Shamir, Ron

doi:10.1186/1471-2164-8-394

Cited by 28 publications

(19 citation statements)

References 47 publications

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“…The IRF and STAT (IRF1, IRF2, IRF4, IRF7, IRF8, IRF9, STAT1, STAT2, STAT3, STAT4 and STAT5A) genes were seen to be differentially regulated following LPS stimulation and the peak of their expression was at 6 hours. This difference in induction of IRF and STAT transcription regulators following TLR4 and not TLR2 ligation is consistent with previous studies which have compared the temporal transcriptional response following TLR2 and TLR4 ligation in murine DCs and macrophages [10], [11]. The IFN signalling induced following TLR4 ligation and not TLR2 ligation can be accounted for by signalling through the MyD88 independent TRIF-TRAM, IRF3 pathway following TLR4 ligation resulting in induction of IFNβ, which then leads to positive feedback of IFN gene induction through induction of IRF7 amongst other IRFs [8].…”

Section: Discussionsupporting

confidence: 92%

“…Additionally a separate IFN-sensitive response element (ISRE) regulated set of genes expression was seen to be upregulated in the TLR4 (and TLR3) stimulations but not the TLR2 stimulation [10]. Importantly the temporal kinetics of these two groups of genes differed, with the genes predicted to be regulated by NFκB peaking in expression earlier than the predicted ISRE regulated genes.…”

Section: Introductionmentioning

confidence: 96%

“…Importantly the temporal kinetics of these two groups of genes differed, with the genes predicted to be regulated by NFκB peaking in expression earlier than the predicted ISRE regulated genes. In addition, genes thought to be regulated by both ISRE and NFκB had a greater magnitude of induction though similar temporal kinetics to the genes regulated only by ISRE [10]. However this study had limited time points available for the TLR2 stimulations and so the majority of the temporal analysis was undertaken using LPS stimulated samples.…”

Section: Introductionmentioning

confidence: 99%

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Identification of the Key Differential Transcriptional Responses of Human Whole Blood Following TLR2 or TLR4 Ligation In-Vitro

Blankley¹,

Graham²,

Howes³

et al. 2014

PLoS ONE

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The use of human whole blood for transcriptomic analysis has potential advantages over the use of isolated immune cells for studying the transcriptional response to pathogens and their products. Whole blood stimulation can be carried out in a laboratory without the expertise or equipment to isolate immune cells from blood, with the added advantage of being able to undertake experiments using very small volumes of blood. Toll like receptors (TLRs) are a family of pattern recognition receptors which recognise highly conserved microbial products. Using the TLR2 ligand (Pam3CSK4) and the TLR4 ligand (LPS), human whole blood was stimulated for 0, 1, 3, 6, 12 or 24 hours at which times mRNA was isolated and a comparative microarray was undertaken. A common NFκB transcriptional programme was identified following both TLR2 and TLR4 ligation which peaked at between 3 to 6 hours including upregulation of many of the NFκB family members. In contrast an interferon transcriptional response was observed following TLR4 but not TLR2 ligation as early as 1 hour post stimulation and peaking at 6 hours. These results recapitulate the findings observed in previously published studies using isolated murine and human myeloid cells indicating that in vitro stimulated human whole blood can be used to interrogate the early transcriptional kinetic response of innate cells to TLR ligands. Our study demonstrates that a transcriptomic analysis of mRNA isolated from human whole blood can delineate both the temporal response and the key transcriptional differences following TLR2 and TLR4 ligation.

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Identification of the Key Differential Transcriptional Responses of Human Whole Blood Following TLR2 or TLR4 Ligation In-Vitro

Blankley¹,

Graham²,

Howes³

et al. 2014

PLoS ONE

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“…47,48 Here, we show that TLR4 ligation increases hepcidin and represses ferroportin expression, while TLR2 ligation exclusively decreases ferroportin levels. To address the role of individual TLRs during the immune response most mechanistic studies apply synthetic ligands.…”

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confidence: 68%

A novel inflammatory pathway mediating rapid hepcidin-independent hypoferremia

Guida

Altamura

Klein

et al. 2015

Blood

149

131

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Key Points• Stimulation of Toll-like receptors 2 and 6 reduces ferroportin expression in mouse macrophages by hepcidin-independent mechanism(s).• Reduced expression of ferroportin in macrophages that recycle iron from red cells is sufficient to rapidly induce hypoferremia in mice.Regulation of iron metabolism and innate immunity are tightly interlinked. The acute phase response to infection and inflammation induces alterations in iron homeostasis that reduce iron supplies to pathogens. The iron hormone hepcidin is activated by such stimuli causing degradation of the iron exporter ferroportin and reduced iron release from macrophages, suggesting that hepcidin is the crucial effector of inflammatory hypoferremia. Here, we report the discovery of an acute inflammatory condition that is mediated by Toll-like receptors 2 and 6 (TLR2 and TLR6) and which induces hypoferremia in mice injected with TLR ligands. Stimulation of TLR2/TLR6 triggers profound decreases in ferroportin messenger RNA and protein expression in bone marrow-derived macrophages, liver, and spleen of mice without changing hepcidin expression. Furthermore, C326S ferroportin mutant mice with a disrupted hepcidin/ferroportin regulatory circuitry respond to injection of the TLR2/6 ligands FSL1 or PAM3CSK4 by ferroportin downregulation and a reduction of serum iron levels. Our findings challenge the prevailing role of hepcidin in hypoferremia and suggest that rapid hepcidin-independent ferroportin downregulation in the major sites of iron recycling may represent a first-line response to restrict iron access for numerous pathogens. (Blood. 2015;125(14): [2265][2266][2267][2268][2269][2270][2271][2272][2273][2274][2275] IntroductionIron plays a central role in host-pathogen interactions.1 Most pathogens require iron for proliferation and full virulence. The innate immune system fights infections by sequestration of iron in macrophages of the reticuloendothelial system. The resulting hypoferremia represents a major host defense strategy and promotes anemia of inflammation, a form of anemia commonly associated with infectious and inflammatory conditions as well as cancer. Toll-like receptors (TLRs) are key sensors of the innate immune system.3 They recognize pathogen-associated molecular patterns (PAMPs) and control the hypoferremic host response. Lipopolysaccharide (LPS) is a cell wall component of gram-negative bacteria recognized by TLR4. LPS injection into mice causes the release of proinflammatory cytokines and triggers a wellcharacterized acute phase response including induction of the hepatic iron hormone hepcidin 4-6 by interleukin-6 (IL-6). 7,8 Hepcidin binds to and causes internalization and degradation of the iron exporter ferroportin, which limits iron release from iron-exporting cells such as macrophages, hepatocytes, and duodenal enterocytes. Diminished iron export from macrophages that recycle iron from senescent red cells rapidly induces hypoferremia due to the high iron demand of erythropoiesis. 10,11 Excess levels of hepcidin have been recog...

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“…First, Elkon et al (42) combined computational analysis of expression profiles and cis -regulatory promoter sequences to dissect the TLR-induced transcriptional program. Their model demonstrated that NF-κB mainly regulates an early-induced and sustained response, whereas the ISRE element functions primarily in the induction of a delayed wave.…”

Section: Systems Analysis Of Innate Immunity: Case Studiesmentioning

confidence: 99%

Systems-Level Analysis of Innate Immunity

Zak

Tam

Aderem

2014

Annu. Rev. Immunol.

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Systems-level analysis of biological processes strives to comprehensively and quantitatively evaluate the interactions between the relevant molecular components over time, thereby enabling development of models that can be employed to ultimately predict behavior. Rapid development in measurement technologies (omics), when combined with the accessible nature of the cellular constituents themselves, is allowing the field of innate immunity to take significant strides toward this lofty goal. In this review, we survey exciting results derived from systems biology analyses of the immune system, ranging from gene regulatory networks to influenza pathogenesis and systems vaccinology.

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Functional genomic delineation of TLR-induced transcriptional networks

Cited by 28 publications

References 47 publications

Identification of the Key Differential Transcriptional Responses of Human Whole Blood Following TLR2 or TLR4 Ligation In-Vitro

Identification of the Key Differential Transcriptional Responses of Human Whole Blood Following TLR2 or TLR4 Ligation In-Vitro

A novel inflammatory pathway mediating rapid hepcidin-independent hypoferremia

Systems-Level Analysis of Innate Immunity

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