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:Aim： Use microarray analysis to understand the molecular mechanism underlying the effect of aristolochic acid (AA), a major active component of plants from the Aristolochiaceae family, in normal human kidney (HK-2) cells. Methods： HK-2 cells were treated with AA for 24 hours and cell viability was measured by a 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide assay. Complementary DNA microarrays were used to investigate the gene expression pattern of HK-2 cells exposed to AA and the results of this study were in triplicate. Quantitative real-time RT-PCR assay was used to verify the microarray data for selected nuclear factor kappa B (NF-κB)-regulated genes. Furthermore, subcellular localization of NF-κB p65 was visualized by immunofluorescence confocal microscopy in HK-2 cells. NF-κB activity was examined by luciferase reporter assay in HK-2/NF-κB transgenic cells. Results： AA exhibited a dose-dependent cytotoxic effect in HK-2 cells and induced alterations in gene expression profiles related to DNA damage response, stress response, etc. In addition, 9 biological pathways associated with immunomodulatory functions were down-regulated in AA-treated HK-2 cells. Network analysis revealed that NF-κB played a central role in the network topology. Among NF-kB-regulated genes, 8 differentially expressed genes were verified by real-time RT-PCR. The inhibition of NF-κB activity by AA was further confirmed by immunofluorescence confocal microscopy and by NF-κB luciferase reporter assay. Conclusion： Our data revealed that AA could suppress NF-κB activity in normal human cells, perhaps partially accounting for the reported anti-inflammatory effects of some plants from the genus Aristolochia. HK-2 cells were grown in keratinocyte serum-free basal medium (Gibco) supplemented with 5 ng/ml of recombinant epidermal growth factor and 50 μg/ml of bovine pituitary extract without antibiotics in 5 % CO2 at 370C. HK-2 cells were seeded in 25-T flasks and incubated for 24 h before aristolochic acid treatment. Aristolochic acid (10 90 μM) were added to HK-2 cells for 24 h. The control cells received equal amounts of water only.

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The RNA-binding protein TTP is a global post-transcriptional regulator of feedback control in inflammation [iCLIP-seq]

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