Transcription of Tnfaip3 is regulated by NF-kB and p38 via C/EBPβ in activated macrophages
Ontology highlight
ABSTRACT: Macrophages play a pivotal role in the immune system through recognition and elimination of microbial pathogens. Toll-like receptors (TLRs) on macrophages interact with microbial substances and initiate signal transduction through intracellular adapters. TLR4, which is important for the response to lipopolysaccharide (LPS), triggers downstream signaling mediators and eventually activates IkB kinase (IKK) complex and mitogen-activated protein kinases (MAPKs) such as p38. Previous reports revealed that, in addition to NF-kB, the induction of some LPS-inducible genes in macrophages required another transcription factor whose activity depends on p38. However, these transcription factors remained to be identified. Among these genes, NF-kB and C/EBPβ, a p38 downstream transcription factor, were predicted to co-regulate genes in LPS-stimulated BMDMs. Based on the subsequent results of a chromatin immunoprecipitation assay, we demonstrated that Tnfaip3 is regulated by both NF-kB and p38-dependent C/EBPβ. These results elucidate our understanding of the tight regulation of innate immunity.
Project description:Macrophages play a pivotal role in the immune system through recognition and elimination of microbial pathogens. Toll-like receptors (TLRs) on macrophages interact with microbial substances and initiate signal transduction through intracellular adapters. TLR4, which is important for the response to lipopolysaccharide (LPS), triggers downstream signaling mediators and eventually activates IkB kinase (IKK) complex and mitogen-activated protein kinases (MAPKs) such as p38. Previous reports revealed that, in addition to NF-kB, the induction of some LPS-inducible genes in macrophages required another transcription factor whose activity depends on p38. However, these transcription factors remained to be identified. Among these genes, NF-kB and C/EBPβ, a p38 downstream transcription factor, were predicted to co-regulate genes in LPS-stimulated BMDMs. Based on the subsequent results of a chromatin immunoprecipitation assay, we demonstrated that Tnfaip3 is regulated by both NF-kB and p38-dependent C/EBPβ. These results elucidate our understanding of the tight regulation of innate immunity. In order to identify p38-activated transcription factors that cooperate with NF-kB in response to LPS stimulation, microarrays were used to identify genes regulated by both NF-kB and p38 using wild-type, IKK-depleted, and p38 inhibitor-treated mouse bone marrow-derived macrophages (BMDMs). In silico analysis of transcription factor binding sites was used to predict the potential synergistic transcription factors from the co-expressed genes.
Project description:The inhibitor of kB kinase (IKK) is the master regulator of the nuclear factor kB (NF-kB) pathway, involved in inflammatory, immune and apoptotic responses. In the ‘canonical’ NF-kB pathway, IKK phosphorylates inhibitor of kB (IkB) proteins and this triggers ubiquitin-mediated degradation of IkB, leading to release and nuclear translocation of NF-B transcription factors.
The data presented show that the IKK and IKK subunits recognize a YDDX docking site located within the disordered C-terminal region of IkBa. Our results also suggest that IKK contributes to the docking interaction with higher affinity as compared to IKK.
Project description:Sensing of microbial products by innate immune cells skew their transcriptional program to optimize anti-microbial defences. Chromatin remodeling by histone deacetylases (HDACs) plays a fundamental role in tailoring gene expression. HDAC inhibitors are among the most promising anti-cancer drugs and possess intrinsic anti-inflammatory properties. Yet, the influence of HDAC inhibition on innate immune responses to microbial infection is unknown. Here we show that HDAC inhibitors repress the expression of less than 10% of the genes expressed at baseline in BM-derived macrophages. In sharp contrast, HDAC inhibitors strongly interfere with transcriptome remodeling induced by LPS and Pam3CSK4, affecting the expression of 30-70% of genes modulated by microbial stimuli. Strikingly, HDAC inhibitors target the expression of numerous genes involved in anti-microbial host defences, encoding for microbial sensors, cytokines, chemokines, growth factors and their receptors, adhesion and signaling molecules, and molecules involved in antigen processing and presentation. At the molecular level, HDAC inhibitors do not impair mitogen-activated protein kinase, NF-kB, interferon-related factor signal and STAT1 transduction pathways, but inhibit NF-kB p65 recruitment to the promoter region of HDAC inhibitor-sensitive genes. HDAC inhibitors also inhibit the response of mouse and human DCs, splenocytes and whole blood to a broad range of microbial products and microorganisms. In agreement with these in vitro findings, HDAC inhibitors increase bacterial burden and sensitize mice to sub-lethal infection with Klebsiella pneumoniae and Candida albicans. Conversely, HDAC inhibitors confer protection in models of Pam3CSK4-induced fulminant toxic shock and severe sepsis following cecal ligation and puncture. Overall, these data substantiate the concept of immunomodulation by HDAC inhibitors, and suggest that these drugs could represent efficacious adjunctive therapy of severe sepsis. Mus musculus cells were grown in presence of LPS or LPS + TSA and pam or pam + TSA and hybrydised against a cRNA pool UMRR (from Mus musculus cells).
Project description:Macrophages are key immune cells in inflammatory bowel disease (IBD) that can exhibit different phenotypes and promote inflammation. Alcohol consumption is associated with increased risk and severity of IBD. We performed in vitro and in vivo experiments with dextran sodium sulfate-induced mice colitis model, peritoneal macrophages and RAW264.7 cell line to investigate the effect and mechanism of alcohol on macrophages in colitis. Our study has found that alcohol exacerbates colitis in mice, increases the aggregation of colonic macrophages, and promotes the production of various inflammatory factors. Alcohol increases lipopolysaccharides (LPS)-induced calcium influx in macrophages, which is inhibited by the TRPV1 antagonist Capsazepine (CPZ). Alcohol and LPS together induce M2b polarization of macrophages and promote the phosphorylation and nuclear translocation of P38, ERK1/2 and NF-κB, and could be inhibited by CPZ and NOD2 inhibitor. Thus, alcohol can aggravate experimental colitis in mice and promote macrophage M2b polarization through the TRPV1-MAPK/NF-kB pathways.
Project description:The bacterial product lipopolysaccharide (LPS) stimulates nuclear factor kB (NF-kB) signaling, which results in the production of proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), as part of the immune response. NF-kB target genes also include those encoding proteins that inhibit NF-kB signaling through negative feedback loops. By simultaneously studying the dynamics of the nuclear translocation of the NF-kB subunit RelA and the activity of a Tnf-driven reporter in a mouse macrophage cell line, Sung et al. found that the gene encoding RelA was also a target of NF-kB. Synthesis of RelA occurred only at higher concentrations of LPS and constituted a positive feedback loop that dominated over existing negative feedback mechanisms. Genes expressed in response to a high concentration of LPS were enriched for those involved in innate immune responses. Together, these data suggest that the RelA-dependent positive feedback loop enables macrophages to mount an effective immune only above a critical concentration of LPS. Bone-marrow-derived macrophage (BMDM) cells were stimulated with zero, low, and high concentration of LPS separately for 4hrs. Two replicates for each condition.
Project description:The bacterial product lipopolysaccharide (LPS) stimulates nuclear factor kB (NF-kB) signaling, which results in the production of proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), as part of the immune response. NF-kB target genes also include those encoding proteins that inhibit NF-kB signaling through negative feedback loops. By simultaneously studying the dynamics of the nuclear translocation of the NF-kB subunit RelA and the activity of a Tnf-driven reporter in a mouse macrophage cell line, Sung et al. found that the gene encoding RelA was also a target of NF-kB. Synthesis of RelA occurred only at higher concentrations of LPS and constituted a positive feedback loop that dominated over existing negative feedback mechanisms. Genes expressed in response to a high concentration of LPS were enriched for those involved in innate immune responses. Together, these data suggest that the RelA-dependent positive feedback loop enables macrophages to mount an effective immune only above a critical concentration of LPS.
Project description:The five NF-kB family members and three nuclear IkB proteins play diverse biological roles, but the mechanisms by which distinct NF-kB and NF-kB: IkB complexes contribute to selective gene transcription remain poorly understood. Using nascent transcript RNA-seq, we observed considerable overlap between p50-dependent and IkBz-dependent genes in Toll-like receptor 4 (TLR4)-activated macrophages. Key inflammatory and immunoregulatory genes, including Il6, Il1b, Nos2, Lcn2, and Batf, were among the p50-IkBz co-dependent genes. IkBz typically bound genomic sites occupied earlier by NF-kB dimers. However, p50-IkBz co-dependence did not coincide with preferential binding of either protein, as p50, IkBz, and RelA co-occupied thousands of sites. A common feature of p50-IkBz co-dependent genes was close proximity to a p50/RelA/IkBz co-bound site exhibiting p50-dependent binding of RelA and IkBz. This result and others suggest that IkBz function is not restricted to p50 homodimers. Notably, IkBz and the p50-IkBz target genes comprise a high percentage of genes that exhibited the greatest differential expression between TLR4-stimulated and tumor necrosis factor receptor (TNFR)-stimulated macrophages, with ectopic IkBz rescuing a subset of these genes. These results reveal a defined p50-IkBz pathway that selectively activates a set of key inflammatory and immunoregulatory genes and serves as an important contributor to the differential responses to TNFR and TLR4.
Project description:The five NF-kB family members and three nuclear IkB proteins play diverse biological roles, but the mechanisms by which distinct NF-kB and NF-kB:IkB complexes contribute to selective gene transcription remain poorly understood. Using nascent transcript RNA-seq, we observed considerable overlap between p50-dependent and IkBz-dependent genes in Toll-like receptor 4 (TLR4)-activated macrophages. Key inflammatory and immunoregulatory genes, including Il6, Il1b, Nos2, Lcn2, and Batf, were among the p50-IkBz co-dependent genes. IkBz typically bound genomic sites occupied earlier by NF-kB dimers. However, p50-IkBz co-dependence did not coincide with the preferential binding of either protein, as p50, IkBz, and RelA co-occupied thousands of sites. A common feature of p50-IkBz co-dependent genes was close proximity to a p50/RelA/IkBz co-bound site exhibiting p50-dependent binding of RelA and IkBz. This result and others suggest that IkBz function is not restricted to p50 homodimers. Notably, IkBz and the p50-IkBz target genes comprise a high percentage of genes that exhibited the greatest differential expression between TLR4-stimulated and tumor necrosis factor receptor (TNFR)-stimulated macrophages, with ectopic IkBz rescuing a subset of these genes. These results reveal a defined p50-IkBz pathway that selectively activates a set of key inflammatory and immunoregulatory genes and serves as an important contributor to the differential responses to TNFR and TLR4.