Project description:The p38MAPK downstream targets MK 2 and 3 are critical for the regulation of the macrophage response towards bacterial lipopolysaccharid (LPS). The extent these two kinases act cooperatively in regulating LPS-induced inflammatory cytokine expression and their distinct regulatory effects are still unclear. To address this point, whole transcriptome analyses had been performed using bone marrow derived macrophages (BMDM) generated from MK2-/- or MK2/3-/- animals and from wildtype littermates. The BMDM were treated with 100 ng/ml LPS for 360 minutes or with medium as control. Thereafter, total mRNA was isolated and subjected to array analysis using the SurePrint G3 Mouse 8x60K Microarray Kit from Agilent.
Project description:The p38MAPK downstream targets MK 2 and 3 are critical for the regulation of the macrophage response towards bacterial lipopolysaccharid (LPS). The extent these two kinases act cooperatively in regulating LPS-induced inflammatory cytokine expression and their distinct regulatory effects are still unclear. To address this point, whole transcriptome analyses had been performed using bone marrow derived macrophages (BMDM) generated from MK2-/- or MK2/3-/- animals and from wildtype littermates. The BMDM were treated with 100 ng/ml LPS for 120 minutes or with medium as control. Thereafter, total mRNA was isolated and subjected to array analysis using the SurePrint G3 Mouse 8x60K Microarray Kit from Agilent.
Project description:Interleukin (IL)-1β is an endogenous pro-inflammatory pyrogen that affects both the innate and adaptive immune systems. Uncontrolled release of IL-1β is associated with sterile inflammatory diseases, such as arthritis, gout, and atherosclerosis as well as the development of tumors. In an initial investigation of the role of the MAPKAP kinase MK2 in IL-1β processing in macrophages, we found that Il1b mRNA and IL-1β protein levels were increased in unstimulated MK2-knockout (KO) macrophages. Additionally, we observed elevated basal IL-1β concentrations in the serum of MK2/3 double KO mice. Further analysis revealed an activation of the noncanonical NF-κB pathway in the absence of MK2 or its interacting activator p38α. Rescue by overexpression of MK2, its kinase-inactive mutant MK2K79R or p38α reduced activation of the noncanonical NF-κB pathway components as well as Il1b mRNA expression. Interestingly, the basal protein level of the tumor suppressor p53 is reduced in the absence of MK2 or p38α.We demonstrate that p53 interacts with mitochondrial caspase-3, which cleaves RelB and therefore inhibits the noncanonical NF-κB pathway, affecting subsequent Il1b and p53 expression. These results not only explain the increased basal levels in MK2-knockout macrophages, but also uncover a new autoregulatory mechanism of p53 expression. Additionally, they reveal a new mechanism that contributes to the long-discussed link between cancer and inflammation, in which the tumor suppressor p53 represses cytokine expression.
Project description:The mitogen-activated protein kinase (MAPK) p38 pathway is reported to regulate macrophage responses to lipopolysaccharide (LPS) at least partly via the phosphorylation of the mRNA-destabilizing factor tristetraprolin (TTP). LPS-activated MAPK p38 phosphorylates and activates the downstream kinase MAPK-activated protein kinase 2 (MK2), which then phosphorylates serines 52 and 178 of TTP, resulting in loss of mRNA-destabilizing activity. As a consequence, mRNAs that contain binding sites for TTP are stabilized in a manner that is acutely sensitive to the activity of the MAPK p38 pathway. Dual specificity phosphatase 1 (DUSP1) dephosphorylates and inactivates MAPK p38. Dusp1-/- macrophages overexpress a number of pro-inflammatory mediators, but their genome-wide responses to LPS have not yet been described in detail. Dusp1-/- mice are exceptionally sensitive to a wide variety of inflammatory challenges, including experimental models of endotoxemia or sepsis. It has been suggested (but not yet proven) that DUSP1 controls the inflammatory response of macrophages in part via the regulation of MAPK p38 activity and TTP phosphorylation status. We generated a mouse knock-in strain, in which codons 52 and 178 of the endogenous Zfp36 gene (which encodes TTP) were mutated to alanine codons. The mutation gives rise to a constitutively active form of TTP, which cannot be inactivated via the p38 MAPK pathway. The Zfp36aa/aa strain was back-crossed against C57/BL6 for > 10 generations. We also generated a double-targeted strain in which the Zfp36 mutation was combined with disruption of the Dusp1 gene. This expression array describes LPS responses of primary mouse bone marrow-derived macrophages of four genotypes, and closely matched genetic background: wild type (Dusp1+/+ : Zfp36+/+); TTP mutant (Zfp36aa/aa); DUSP1 knock out (Dusp1-/-); and double targeted (Dusp1-/- : Zfp36aa/aa). The data provide a comprehensive picture of the impact of Dusp1 deletion or TTP mutation on the responses of primary macrophages to LPS. They also demonstrate that the excessive inflammatory responses of Dusp1-/- macrophages are largely a consequence of the phosphorylation and inactivation of TTP. Genome wide expression profiles of wild type, Dusp1-/-, Zfp36aa/aa and Dusp1-/-/Zfp36aa/aa M-CSF derived macrophages, stimulated with LPS for 1 or 4 hours
Project description:The mitogen-activated protein kinase (MAPK) p38 pathway is reported to regulate macrophage responses to lipopolysaccharide (LPS) at least partly via the phosphorylation of the mRNA-destabilizing factor tristetraprolin (TTP). LPS-activated MAPK p38 phosphorylates and activates the downstream kinase MAPK-activated protein kinase 2 (MK2), which then phosphorylates serines 52 and 178 of TTP, resulting in loss of mRNA-destabilizing activity. As a consequence, mRNAs that contain binding sites for TTP are stabilized in a manner that is acutely sensitive to the activity of the MAPK p38 pathway. Dual specificity phosphatase 1 (DUSP1) dephosphorylates and inactivates MAPK p38. Dusp1-/- macrophages overexpress a number of pro-inflammatory mediators, but their genome-wide responses to LPS have not yet been described in detail. Dusp1-/- mice are exceptionally sensitive to a wide variety of inflammatory challenges, including experimental models of endotoxemia or sepsis. It has been suggested (but not yet proven) that DUSP1 controls the inflammatory response of macrophages in part via the regulation of MAPK p38 activity and TTP phosphorylation status. We generated a mouse knock-in strain, in which codons 52 and 178 of the endogenous Zfp36 gene (which encodes TTP) were mutated to alanine codons. The mutation gives rise to a constitutively active form of TTP, which cannot be inactivated via the p38 MAPK pathway. The Zfp36aa/aa strain was back-crossed against C57/BL6 for > 10 generations. We also generated a double-targeted strain in which the Zfp36 mutation was combined with disruption of the Dusp1 gene. This expression array describes LPS responses of primary mouse bone marrow-derived macrophages of four genotypes, and closely matched genetic background: wild type (Dusp1+/+ : Zfp36+/+); TTP mutant (Zfp36aa/aa); DUSP1 knock out (Dusp1-/-); and double targeted (Dusp1-/- : Zfp36aa/aa). The data provide a comprehensive picture of the impact of Dusp1 deletion or TTP mutation on the responses of primary macrophages to LPS. They also demonstrate that the excessive inflammatory responses of Dusp1-/- macrophages are largely a consequence of the phosphorylation and inactivation of TTP.
Project description:MicroRNAs regulated by lipopolysaccharide (LPS) target genes that contribute to the inflammatory phenotype. Here we showed that the protein kinase Akt1, which is activated by LPS, positively regulated miRNAs let-7e, miR-181c but negatively regulated miR-155 and miR-125b. In silico analyses and transfection studies revealed that let-7e repressed Toll-like receptor 4 (TLR4) whereas miR-155 repressed SOCS1, two proteins critical for LPS-driven TLR signalling, which regulate endotoxin sensitivity and tolerance. As a result, Akt1-/- macrophages exhibited increased responsiveness to LPS in culture and Akt1-/- mice did not develop endotoxin tolerance in vivo. Overexpression of let-7e and suppression of miR-155 in Akt1-/- macrophages restored sensitivity and tolerance to LPS in culture and in animals. These results indicate that Akt1 regulates the response of macrophages to LPS by controlling miRNA expression. The data deposited here contain the entire analysis of miRNA profile of Akt1+/+ and Akt1-/- thioglycollate elicited peritoneal macrophages following stimulation with LPS for 3 hours in culture. Thioglycollate elicited macrophages were cultured in complete DMEM medium, stimulated with LPS for 3 hours and RNA was extracted. Samples were analyzed using Taq-man PCR miRNA arrays (Dana Farber microarray Facility).