Project description:Glucocorticoids are primary stress hormones and their synthetic derivatives are widely used clinically. The therapeutic efficacy of these steroids is limited by severe side effects and glucocorticoid resistance. Multiple glucocorticoid receptor (GR) isoforms are produced by alternative translation initiation; however, the role individual isoforms play in controlling tissue-specific responses to glucocorticoids in vivo is unknown. We have generated knockin mice that exclusively express the most active receptor isoform, GR-C3. The GR-C3 knockin mice die at birth due to respiratory distress but can be completely rescued by antenatal glucocorticoid administration. Rescued GR-C3 mice exhibited alterations in circadian rhythm in a sexually dimorphic manner and in sensitivity to lipopolysaccharide (LPS)-induced endotoxemia. To evaluate the ability of glucocorticoids to protect against LPS-induced inflammation, we measured gene expression in spleens from WT and rescued GR-C3 knockin mice that had been treated with vehicle or LPS for 3 and 24 hours. The GR-C3 isoform was found to be deficient in its ability to repress a large cohort of immune and inflammatory genes.
Project description:Glucocorticoids are primary stress hormones and their synthetic derivatives are widely used clinically. The therapeutic efficacy of these steroids is limited by severe side effects and glucocorticoid resistance. Multiple glucocorticoid receptor (GR) isoforms are produced by alternative translation initiation; however, the role individual isoforms play in controlling tissue-specific responses to glucocorticoids in vivo is unknown. We have generated knockin mice that exclusively express the most active receptor isoform, GR-C3. The GR-C3 knockin mice die at birth due to respiratory distress but can be completely rescued by antenatal glucocorticoid administration. To evaluate the GR-C3 transcriptome, we prepared mouse embryonic fibroblasts (MEFs) from E12.5 wild-type (WT) and GR-C3 knockin embryos and treated the cells with vehicle or the synthetic glucocorticoid Dexamethasone (Dex) for 6 hours. The GR-C3 isoform was found to have a markedly different gene-regulatory profile than GR in WT MEFs.
Project description:Systemic inflammatory reactions mediated by chronic infections activate microglia in the central nervous system (CNS) and have been postulated to exacerbate neurodegenerative diseases. We now demonstrate in vivo that repeated systemic challenge of mice with bacterial lipopolysaccharides (LPS) maintains an elevated microglial inflammatory response and triggers neurodegeneration. Repeated chronic intraperitoneal application of LPS over four consecutive days induced loss of dopaminergic neurons in the substantia nigra, a process that was accompanied by decreased levels of dopamine in the striatum. In contrast, total cumulative LPS dose given intraperitoneally within a single acute application did not induce a decrease in dopamine levels nor neurodegeneration. Mice that received repeated systemic LPS application showed increased microglial activation, elevated production of proinflammatory cytokines and activation of the classical complement and its associated phagosome pathway in the brain. Loss of dopaminergic neurons induced by repeated systemic LPS application was rescued in complement C3 deficient mice, confirming an involvement of the complement system in neurodegeneration. Thus, our data demonstrate that repeated systemic exposure to bacterial LPS induces a microglial phagosomal inflammatory response, leading to complement-dependent damage of dopaminergic neurons.
Project description:We performed RNA sequencing in Mouse Embryonic Fibroblasts (MEFs) of GR wild-type and GR Zn. Cells were treated with: vehicle (EtOH), Dexamethasone (Dex), Lipopolysaccharide (LPS) or Dex+LPS. We show that GR Zn does not regulate any GR target gene
Project description:Analysis of spleens from ficolin knockout and wildtype mice treated without and with LPS to induce inflammation. Ficolins are pattern recognition molecules that initiate the lectin pathway of complement. Results provide insigt into the molecular basis of the inflammatory response of ficolin knockout mice.
Project description:The glucocorticoid receptor (GR) and ten-eleven translocation 2 (TET2) respectively play a crucial role in regulating immunity and inflammation, and GR interacts with TET2. However, their syn-ergetic roles in inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn’s disease (CD), remain unclear. This study aimed to investigate the co-target gene signatures of GR and TET2 in IBD and provide potential therapeutic interventions for IBD. By integrating public data, we identified 179 GR- and TET2-targeted differentially expressed genes (DEGs) in CD and 401 in UC. These genes were closely associated with immunometabolism, inflammatory responses, and cell stress pathways. In vitro inflammatory cellular models were constructed using LPS-treated HT29 and HCT116 cells, respectively. Drug repositioning based on the co-target gene signatures of GR and TET2 derived from transcriptomic data of UC, CD, and the in vitro model were performed using the Connectivity Map (CMap). BMS-536924 emerged as a top therapeutic candidate, and its validation experiment within the in vitro inflammatory model confirmed its ef-ficacy in mitigating the LPS-induced inflammatory response. This study sheds light on the path-ogenesis of IBD from a new perspective and may accelerate the development of novel therapeutic agents for inflammatory diseases including IBD.
Project description:An unresolved molecular paradox is how the glucocorticoid receptor (GR) activates some genes while potently repressing others. We carried out genome-wide localization and expression profiling experiments in primary bone marrow-derived mouse macrophages treated with Dexamethasone in the presence or absence of LPS. Unexpectedly, we find that the anti-inflammatory GR cistrome, which is principally composed of 'canonical' GREs colocalizing with NFkB and AP-1 co-enriched with the myeloid lineage factors C/EBP and Pu.1, is shaped by TLR4-directed chromatin dynamics, suggesting that context rather than sequence may be a critical determinant of function. Identification of GR, cJun, NFkB(p65) binding sites in primary bone-marrow derived macrophages unstimulated and LPS-stimulated (3hrs) that were untreated or pre-treated with Dexamethasone for 16 hrs
Project description:Despite the widespread use of glucocorticoids (GCs) for treating inflammatory conditions, the underlying mechanisms of their anti-inflammatory effects are not understood. Moreover, the majority of molecular investigations have examined the effects of glucocorticoid receptor (GR) activation prior to inflammatory challenges. However, clinically relevant situations are emulated by a GC intervention initiated in the midst of rampant inflammatory responses. To characterize the effects of a late GC treatment, we performed systematic profiling of macrophage transcriptional and regulatory landscapes with Dexamethasone (Dex) treatment either before or after stimulation by lipopolysaccharide (LPS). GR activation by Dex following LPS stimulation had a similar anti-inflammatory profile in comparison to GR pre-activation, while ameliorating the disruption of metabolic genes. Unexpectedly, the chromatin occupancy pattern of GR is not predictive of the Dex-regulated expression changes and shows little evidence for the widely accepted ‘trans-repression by tethering’ model. Rather, we find that GR activation results in global blockade of NF-κB binding to chromatin. Integrative analyses of gene expression, transcription factor occupancy, and chromatin accessibility data highlight distinct mechanisms through which GR controls inflammatory macrophages: prevention of NF-κB chromatin occupancy and activation of negative regulators such as Nfkbia, Dusp1, Tnfaip3, and Tsc22d3. Our investigation with differentially timed GC treatments reveals molecular mechanisms underlying therapeutic actions of GR for modulating the ‘inflamed epigenome’.
Project description:Despite the widespread use of glucocorticoids (GCs) for treating inflammatory conditions, the underlying mechanisms of their anti-inflammatory effects are not understood. Moreover, the majority of molecular investigations have examined the effects of glucocorticoid receptor (GR) activation prior to inflammatory challenges. However, clinically relevant situations are emulated by a GC intervention initiated in the midst of rampant inflammatory responses. To characterize the effects of a late GC treatment, we performed systematic profiling of macrophage transcriptional and regulatory landscapes with Dexamethasone (Dex) treatment either before or after stimulation by lipopolysaccharide (LPS). GR activation by Dex following LPS stimulation had a similar anti-inflammatory profile in comparison to GR pre-activation, while ameliorating the disruption of metabolic genes. Unexpectedly, the chromatin occupancy pattern of GR is not predictive of the Dex-regulated expression changes and shows little evidence for the widely accepted ‘trans-repression by tethering’ model. Rather, we find that GR activation results in global blockade of NF-κB binding to chromatin. Integrative analyses of gene expression, transcription factor occupancy, and chromatin accessibility data highlight distinct mechanisms through which GR controls inflammatory macrophages: prevention of NF-κB chromatin occupancy and activation of negative regulators such as Nfkbia, Dusp1, Tnfaip3, and Tsc22d3. Our investigation with differentially timed GC treatments reveals molecular mechanisms underlying therapeutic actions of GR for modulating the ‘inflamed epigenome’.