Unknown,Transcriptomics,Genomics,Proteomics

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Tissue-specific differences in PPARγ control of macrophage function.

ABSTRACT: PPARγ is known for its anti-inflammatory actions in macrophages. However, which macrophage populations express PPARγ in vivo and how it regulates tissue homeostasis in the steady state and during inflammation is not completely understood. We show that lung and spleen macrophages constitutively expressed PPARγ, while other macrophage populations did not. Recruitment of monocytes to sites of inflammation was associated with induction of PPARγ as they differentiated to macrophages. Its absence in these macrophages led to failed resolution of inflammation, characterized by persistent, low-level recruitment of leukocytes. Conversely, PPARγ agonists supported an earlier cessation in leukocyte recruitment during resolution of acute inflammation and likewise suppressed monocyte recruitment to chronically inflamed atherosclerotic vessels. In the steady state, PPARγ deficiency in macrophages had no obvious impact in the spleen but profoundly altered cellular lipid homeostasis in lung macrophages. Reminiscent of pulmonary alveolar proteinosis, LysM-Cre x PPARγflox/flox mice displayed mild leukocytic inflammation in the steady-state lung and succumbed faster to mortality upon infection with S. pneumoniae. Surprisingly, this mortality was not due to overly exuberant inflammation, but instead to impaired bacterial clearance. Thus, in addition to its anti-inflammatory role in promoting resolution of inflammation, PPARγ sustains functionality in lung macrophages and thereby has a pivotal role in supporting pulmonary host defense. The two major subsets of monocytes (Ly-6C+ and Ly-6Clo) from 12-week old C57Bl/6 mice were sorted and the RNA extracted and hybridized to Affymetrix GeneChip® 430 2.0 arrays. We pooled leukocytes from 5 mice for each sort and sorted 3 to 4 separate times for 3 to 4 biological replicates.

ORGANISM(S): Mus musculus

SUBMITTER: Emmanuel GAUTIER

PROVIDER: E-GEOD-32034 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Systemic analysis of PPARγ in mouse macrophage populations reveals marked diversity in expression with critical roles in resolution of inflammation and airway immunity.

Gautier Emmanuel L EL Chow Andrew A Spanbroek Rainer R Marcelin Genevieve G Greter Melanie M Jakubzick Claudia C Bogunovic Milena M Leboeuf Marylene M van Rooijen Nico N Habenicht Andreas J AJ Merad Miriam M Randolph Gwendalyn J GJ

Journal of immunology (Baltimore, Md. : 1950) 20120801 5

Although peroxisome proliferator-activated receptor γ (PPARγ) has anti-inflammatory actions in macrophages, which macrophage populations express PPARγ in vivo and how it regulates tissue homeostasis in the steady state and during inflammation remains unclear. We now show that lung and spleen macrophages selectively expressed PPARγ among resting tissue macrophages. In addition, Ly-6C(hi) monocytes recruited to an inflammatory site induced PPARγ as they differentiated to macrophages. When PPARγ wa ...[more]

PMID: 22855714

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Project description:Dunster2014 - WBC Interactions (Model1) This is a sub-model of a three-step inflammatory response modelling study. The model includes distinct populations of white blood cells namely, macrophages and active and apoptotic neutrophil populations. Neutrophil apoptosis rate is predicted to be crucial for the qualitative nature of the system. This model is described in the article: The resolution of inflammation: a mathematical model of neutrophil and macrophage interactions. Dunster JL, Byrne HM, King JR. Bull. Math. Biol. 2014 Aug; 76(8): 1953-1980 Abstract: There is growing interest in inflammation due to its involvement in many diverse medical conditions, including Alzheimer's disease, cancer, arthritis and asthma. The traditional view that resolution of inflammation is a passive process is now being superceded by an alternative hypothesis whereby its resolution is an active, anti-inflammatory process that can be manipulated therapeutically. This shift in mindset has stimulated a resurgence of interest in the biological mechanisms by which inflammation resolves. The anti-inflammatory processes central to the resolution of inflammation revolve around macrophages and are closely related to pro-inflammatory processes mediated by neutrophils and their ability to damage healthy tissue. We develop a spatially averaged model of inflammation centring on its resolution, accounting for populations of neutrophils and macrophages and incorporating both pro- and anti-inflammatory processes. Our ordinary differential equation model exhibits two outcomes that we relate to healthy and unhealthy states. We use bifurcation analysis to investigate how variation in the system parameters affects its outcome. We find that therapeutic manipulation of the rate of macrophage phagocytosis can aid in resolving inflammation but success is critically dependent on the rate of neutrophil apoptosis. Indeed our model predicts that an effective treatment protocol would take a dual approach, targeting macrophage phagocytosis alongside neutrophil apoptosis. This model is hosted on BioModels Database and identified by: BIOMD0000000616. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

Project description:Iron is an essential component of the erythrocyte protein hemoglobin and is crucial to oxygen transport in vertebrates. In the steady state, erythrocyte production is in equilibrium with erythrocyte removal1. In various pathophysiological conditions, erythrocyte life span is severely compromised, which threatens the organism with anemia and iron toxicity 2,3. Here we identify anon-demand mechanism specific to the liver that clears erythrocytes and recycles iron. We showthat Ly-6Chigh monocytes ingest stressed and senescent erythrocytes, accumulate in the liver, and differentiate to ferroportin 1 (FPN1)-expressing macrophages that can deliver iron to hepatocytes. Monocyte-derived FPN1+ Tim-4neg macrophages are transient, reside alongside embryonically-derived Tim-4high Kuppfer cells, and depend on Csf1 and Nrf2. The spleenlikewise recruits iron-loaded Ly-6Chigh monocytes, but they do not differentiate into ironrecycling macrophages due to the suppressive action of Csf2, and are instead shuttled to the livervia coordinated chemotactic cues. Inhibiting this mechanism by preventing monocyte recruitment to the liver leads to kidney failure and liver damage. These observations identify the liver as the primary organ supporting emergency erythrocyte removal and iron recycling, and uncover a mechanism by which the body adapts to fluctuations in erythrocyte integrity. Pregnant CX3CR1-CreERT+/+ Stopfl/fl tdTomato mice were injected subcutaneously with tamoxifen (8 mg/animal in 400 µl corn oil s.c.) on days 13.5and 15.5 p.c to induce tdTomato expression in embryonic monocytes/macrophages. At the age of 3 months, the progeny was transplanted with GFP bone marrow after busulfan pre-conditioning. After establishment of stable chimerism among blood leukocytes (3 weeks), mice were transfused with stressed red blood cells (sRBC). Embryonic (eKCs, CD45+ CD11b- F4/80+ GFP- tdTomato+) and monocyte-derived Kupffer cells (mKCs, CD45+ CD11b- F4/80+ GFP+ tdTomato-) of the liver were FACS-sorted 7 days after sRBC treatment and subjected to whole-genome expression profiling

Dataset Information

Tissue-specific differences in PPARγ control of macrophage function.

Publications

Systemic analysis of PPARγ in mouse macrophage populations reveals marked diversity in expression with critical roles in resolution of inflammation and airway immunity.

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