Transcriptional analysis of PPARgamma activation in control and PPARgamma null macrophages [GRO-seq]. Transcriptional analysis of PPARgamma activation in control and PPARgamma null macrophages [GRO-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. Overall design: Nascent RNA profiling of thioglycollate elicited macrophages untreated macrophages or macrophages treated for 24 hours with either DMSO or Rosiglitazone

核受体过氧化物酶体增殖物激活受体γ（Peroxisome Proliferator Activated Receptor gamma, PPARγ）已知可调控包括巨噬细胞在内的多种组织的脂质代谢。本研究发现，PPARγ的特异性激动剂罗格列酮（rosiglitazone）可通过PPARγ依赖性途径增强巨噬细胞的呼吸功能。进一步研究表明，即使在缺乏外源性配体的情况下，巨噬细胞的呼吸作用也依赖于PPARγ的存在。出乎意料的是，PPARγ的缺失会显著影响谷氨酰胺的氧化过程。谷氨酰胺与PPARγ均与巨噬细胞的替代性激活（alternative activation, AA）密切相关，且IL4依赖的基因表达以及巨噬细胞呼吸作用的激活均需要PPARγ的参与。值得注意的是，PPARγ的缺失可模拟谷氨酰胺缺失对转录过程的影响。综上，PPARγ通过促进谷氨酰胺代谢来支持巨噬细胞的替代性激活。而IL4本身也会显著上调PPARγ的表达水平，因此PPARγ处于调控巨噬细胞替代性激活的核心前馈环路的中心位置。整体实验设计：对硫代乙醇酸诱导的巨噬细胞进行新生RNA谱分析，实验分组包括未处理组、二甲基亚砜（DMSO）处理组以及罗格列酮处理24小时组。