Regulation of IL-4-induced human macrophage polarization by acetyl-CoA and AMP-activated protein kinase

巨噬细胞对促炎性刺激（巨噬细胞极化）的反应是通过改变它们的代谢。反过来，中间代谢物调节细胞内信号传导和基因表达。因此，乙酰辅酶a除了通过驱动柠檬酸循环产生能量外，还是蛋白质和组蛋白乙酰化的底物。ATP柠檬酸裂解酶（ACLY）是一种负责胞浆乙酰辅酶a生成的酶，在癌细胞和脂肪细胞营养水平改变的反应中，通过组蛋白乙酰化支持基因表达，同时也支持小鼠巨噬细胞细胞因子IL-4的表达。我们的初步数据显示，il -4刺激花生四烯酸15-脂氧合酶（ALOX15）的表达对ACLY抑制敏感。然而，ACLY和乙酰辅酶a对il -4诱导的人巨噬细胞极化的影响尚不清楚。此外，我们之前已经表明，在il -4刺激的巨噬细胞中，amp依赖性蛋白激酶（AMPK）介导的ALOX15表达抑制可能部分通过改变组蛋白乙酰化发生。在本研究中，我们旨在阐明acly驱动乙酰辅酶a生成对人巨噬细胞对IL-4的极化反应的影响。我们假设ACLY通过与染色质上的基因调控元件的物理关联，可能局部调节il -4应答基因子集上的组蛋白乙酰化。其次，我们揭示了蛋白质乙酰化的改变模式，依赖于acly驱动的乙酰辅酶a。这将在蛋白质组学屏幕中得到解决。第三，我们研究AMPK对蛋白乙酰化的影响。我们认为AMPK抑制ACLY的活性，从而引起组蛋白乙酰化的变化，从而引起基因表达的变化。我们的研究有助于理解代谢，特别是乙酰辅酶a的产生，是如何与巨噬细胞极化联系在一起的。

Macrophages respond to pro- versus anti-inflammatory stimuli (macrophage polarization) by altering their metabolism. In turn, intermediate metabolites regulate intracellular signaling and gene expression. Thus, acetyl-CoA, besides its role in energy generation by driving the citrate cycle, is a substrate for protein and histone acetylation. ATP citrate lyase (ACLY), an enzyme responsible for cytosolic acetyl-CoA generation, support gene expression through histone acetylation in responses to altered nutrient levels in cancer cells and adipocytes, but also to the cytokine IL-4 in murine macrophages. Our preliminary data show an IL-4-stimulated expression of arachidonate 15-lipoxygenase (ALOX15) to be sensitive to ACLY inhibition. However, the impact of ACLY and acetyl-CoA on IL-4-induced human macrophage polarization remains unclear. Furthermore, we have previously shown that AMP-dependent protein kinase (AMPK) - mediated inhibition of ALOX15 expression in IL-4-stimulated macrophages may partly occur through altered histone acetylation. In this proposal we aim to elucidate the influence of ACLY-driven acetyl-CoA generation on human macrophage polarization in response to IL-4. We postulate that ACLY, by physically associating with gene regulatory elements on chromatin, may locally regulate histone acetylation on a subset of IL-4-responsive genes. Second we reveal an altered pattern of protein acetylation, dependent on ACLY-driven acetyl-CoA. This will be address in a proteomic screen. Third, we investigate the influence of AMPK on protein acetylation. We suggest that AMPK inhibits the activity of ACLY, thereby eliciting changes of histone acetylation and thus, gene expression. Our study adds to understand how metabolism and, in particular, acetyl-CoA generation, connects to macrophage polarization.