Transcriptional analysis of PPARgamma activation in control and PPARgamma null macrophages [ChIP-seq]

The nuclear receptor Peroxisome Proliferator Activated Receptor gamma (PPARgamma) is known to regulate lipid metabolism in many tissues, including macrophages. Here we report that macrophage respiration is enhanced by rosiglitazone, an activating PPARgamma ligand, in a PPARgamma dependent manner. Moreover, PPARgamma is required for macrophage respiration even in the absence of exogenous ligand. Unexpectedly, the absence of PPARgamma dramatically affects the oxidation of glutamine. Both glutamine and PPARgamma have been implicated in alternative activation (AA) of macrophages and PPARgamma was required for IL4-dependent gene expression and stimulation of macrophage respiration. Remarkably, depletion of PPARgamma phenocopied the effects of glutamine depletion on transcription. Thus, PPARgamma supports alternative activation by facilitating glutamine metabolism. Yet PPARgamma expression is itself markedly increased by IL4. Thus, PPARgamma functions at the center of a feed forward loop that is central to AA of macrophages. Immuno-precipitation followed by high throughput sequencing of thioglycollate elicited macrophages harvested from four control and four PPARgammaKO mice.