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

巨噬细胞通过改变其新陈代谢对促炎和抗炎刺激(巨噬细胞极化)作出反应。反过来，中间代谢产物调节细胞内的信号和基因表达。因此，乙酰辅酶A除了通过驱动柠檬酸循环在能量生成中发挥作用外，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，它通过组蛋白乙酰化来支持基因表达，以响应癌细胞和脂肪细胞中营养水平的变化，以及小鼠巨噬细胞中细胞因子IL-4的作用。我们的初步数据显示，IL-4刺激的花生四烯酸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，我们先前已经证明，AMPK介导的对IL-4刺激的巨噬细胞ALOX15表达的抑制可能部分是通过改变组蛋白乙酰化来实现的。在这项建议中，我们的目的是阐明ACLY驱动的乙酰辅酶A的产生对IL-4反应的人巨噬细胞极化的影响。我们推测，ACLY通过与染色质上的基因调控元件物理结合，可能局部调节IL-4反应基因子集上的组蛋白乙酰化。其次，我们揭示了一种改变的蛋白质乙酰化模式，依赖于ACLY驱动的乙酰辅酶A。这将在蛋白质组学屏幕中解决。第三，我们研究了AMPK对蛋白质乙酰化的影响。我们认为AMPK抑制ACLY的活性，从而引起组蛋白乙酰化的改变，从而导致基因表达的变化。我们的研究有助于理解新陈代谢，特别是乙酰辅酶A的产生，如何与巨噬细胞极化有关。

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.