Project description:Primary human macrophages were cultured 1, 3 or 6 days with different stimuli. Macrophages are key cell types of the innate immune system regulating host defense, inflammation, tissue homeostasis and cancer. Within this functional spectrum diverse and often opposing phenotypes are displayed which are dictated by environmental clues and depend on highly plastic transcriptional programs. Among these the ‘classical’ (M1) and ‘alternative’ (M2) macrophage polarization phenotypes are the best characterized. Understanding macrophage polarization in humans may reveal novel therapeutic intervention possibilities for chronic inflammation, wound healing and cancer. Systematic loss of function screening in human primary macrophages is limited due to lack of robust gene delivery methods and limited sample availability. To overcome these hurdles we developed cell-autonomous assays using the THP-1 cell line allowing genetic screens for human macrophage phenotypes. To confirm the relevance of the THP1-based system we performed microarray studies on THP1 cells and primary human cells subjected to various conditions.
Project description:Macrophages change their phenotype in response to complex (reinforcing or opposing) environmental cues. The molecular components providing the epigenomic basis of progressive or reinforcing polarization are largely unknown. Here we show that the normally ligand-activated nuclear receptor, Peroxisome Proliferator-Activated Receptor gamma (PPARγ), is a predominantly ligand-insensitive, epigenomic driver of a robust phenotypic change in macrophages uniquely upon repeated/reinforcing IL-4 stimulation. Ligand-insensitive PPARγ recruits P300, RAD21 and establishes a permissive chromatin environment, conferring transcriptional memory by facilitating the binding of STAT6 and RNAPII leading to more robust eRNA production upon IL-4 restimulation. PPARγ-mediated transcriptional memory allows the progressive, functional transition of macrophages upon repeated cytokine exposure by controlling the expression of an extracellular matrix remodeling related gene network, also expressed in macrophages from a mouse model of muscle regeneration and show progressive upregulation during the course of regeneration after muscle injury, coinciding with the appearance of IL-4 and PPARγ. Collectively, in contrast to the current prevailing view, alternative polarization gives rise to a predominantly ligand-insensitive PPARγ:RXR cistrome, regulating progressive/reinforcing macrophage polarization.
Project description:Macrophages change their phenotype in response to complex (reinforcing or opposing) environmental cues. The molecular components providing the epigenomic basis of progressive or reinforcing polarization are largely unknown. Here we show that the normally ligand-activated nuclear receptor, Peroxisome Proliferator-Activated Receptor gamma (PPARγ), is a predominantly ligand-insensitive, epigenomic driver of a robust phenotypic change in macrophages uniquely upon repeated/reinforcing IL-4 stimulation. Ligand-insensitive PPARγ recruits P300, RAD21 and establishes a permissive chromatin environment, conferring transcriptional memory by facilitating the binding of STAT6 and RNAPII leading to more robust eRNA production upon IL-4 restimulation. PPARγ-mediated transcriptional memory allows the progressive, functional transition of macrophages upon repeated cytokine exposure by controlling the expression of an extracellular matrix remodeling related gene network, also expressed in macrophages from a mouse model of muscle regeneration and show progressive upregulation during the course of regeneration after muscle injury, coinciding with the appearance of IL-4 and PPARγ. Collectively, in contrast to the current prevailing view, alternative polarization gives rise to a predominantly ligand-insensitive PPARγ:RXR cistrome, regulating progressive/reinforcing macrophage polarization.
Project description:Macrophages change their phenotype in response to complex (reinforcing or opposing) environmental cues. The molecular components providing the epigenomic basis of progressive or reinforcing polarization are largely unknown. Here we show that the normally ligand-activated nuclear receptor, Peroxisome Proliferator-Activated Receptor gamma (PPARγ), is a predominantly ligand-insensitive, epigenomic driver of a robust phenotypic change in macrophages uniquely upon repeated/reinforcing IL-4 stimulation. Ligand-insensitive PPARγ recruits P300, RAD21 and establishes a permissive chromatin environment, conferring transcriptional memory by facilitating the binding of STAT6 and RNAPII leading to more robust eRNA production upon IL-4 restimulation. PPARγ-mediated transcriptional memory allows the progressive, functional transition of macrophages upon repeated cytokine exposure by controlling the expression of an extracellular matrix remodeling related gene network, also expressed in macrophages from a mouse model of muscle regeneration and show progressive upregulation during the course of regeneration after muscle injury, coinciding with the appearance of IL-4 and PPARγ. Collectively, in contrast to the current prevailing view, alternative polarization gives rise to a predominantly ligand-insensitive PPARγ:RXR cistrome, regulating progressive/reinforcing macrophage polarization.
Project description:Macrophages change their phenotype in response to complex (reinforcing or opposing) environmental cues. The molecular components providing the epigenomic basis of progressive or reinforcing polarization are largely unknown. Here we show that the normally ligand-activated nuclear receptor, Peroxisome Proliferator-Activated Receptor gamma (PPARγ), is a predominantly ligand-insensitive, epigenomic driver of a robust phenotypic change in macrophages uniquely upon repeated/reinforcing IL-4 stimulation. Ligand-insensitive PPARγ recruits P300, RAD21 and establishes a permissive chromatin environment, conferring transcriptional memory by facilitating the binding of STAT6 and RNAPII leading to more robust eRNA production upon IL-4 restimulation. PPARγ-mediated transcriptional memory allows the progressive, functional transition of macrophages upon repeated cytokine exposure by controlling the expression of an extracellular matrix remodeling related gene network, also expressed in macrophages from a mouse model of muscle regeneration and show progressive upregulation during the course of regeneration after muscle injury, coinciding with the appearance of IL-4 and PPARγ. Collectively, in contrast to the current prevailing view, alternative polarization gives rise to a predominantly ligand-insensitive PPARγ:RXR cistrome, regulating progressive/reinforcing macrophage polarization.
Project description:Macrophages are key cell types of the innate immune system regulating host defense, inflammation, tissue homeostasis and cancer. Within this functional spectrum diverse and often opposing phenotypes are displayed which are dictated by environmental clues and depend on highly plastic transcriptional programs. Among these the ‘classical’ (M1) and ‘alternative’ (M2) macrophage polarization phenotypes are the best characterized. Understanding macrophage polarization in humans may reveal novel therapeutic intervention possibilities for chronic inflammation, wound healing and cancer. Systematic loss of function screening in human primary macrophages is limited due to lack of robust gene delivery methods and limited sample availability. To overcome these hurdles we developed cell-autonomous assays using the THP-1 cell line allowing genetic screens for human macrophage phenotypes. To confirm the relevance of the THP1-based system we performed microarray studies on THP1 cells and primary human cells subjected to various conditions. THP1 cells were treated with PMA (phorbol 12-myristate 13-acetate) to derive macrophages which were then cultured 1, 3 or 6 days with different stimuli.
Project description:Macrophage activation is associated with profound transcriptional reprogramming. Although much progress has been made in the understanding of macrophage activation, polarization and function, the transcriptional programs regulating these processes remain poorly characterized. We stimulated human macrophages with diverse activation signals, acquiring a dataset of 299 macrophage transcriptomes. Analysis of this dataset revealed a spectrum of macrophage activation states extending the current M1 versus M2-polarization model. Network analyses identified central transcriptional regulators associated with all macrophage activation complemented by regulators related to stimulus-specific programs. Applying these transcriptional programs to human alveolar macrophages from smokers and patients with chronic obstructive pulmonary disease (COPD) revealed an unexpected loss of inflammatory signatures in COPD patients. Finally, by integrating murine data from the ImmGen project we propose a refined, activation-independent core signature for human and murine macrophages. This resource serves as a framework for future research into regulation of macrophage activation in health and disease. Since transcriptional programs are further modulated on several levels including miRNAs we assessed the global spectrum of miRNA expression by miRNA-Seq in macrophages stimulated with IFNM-NM-3, IL4 or with the combination of TNFM-NM-1, PGE2 and P3C