Lipopolysaccharide (LPS)-stimulated macrophages express an aconitate decarboxylase (IRG1, also called ACOD1), leading to accumulation of the endogenous metabolite itaconate. However, the precise mechanisms by which elevated itaconate levels alter macrophage function are not clear. Our hypothesis is itaconate affects macrophage function through some uncertain mechanism. Based on this, we established a transcriptional and proteomic signature of macrophages stimulated by itaconate and identified the pathways of IL-1β secretion and altered iron metabolism. Consistently, the effect of IRG1 deficiency on IL-1β secretion and iron metabolism was confirmed in IRG1 knockout THP-1 cell lines. Several common inhibitors and other compounds were used to examine the molecular mechanisms involved. Only cysteine and antioxidants (catechin hydrate) could inhibit caspase-1 activation and IL-1β secretion in itaconate-stimulated macrophages. We further found that aconitase activity was decreased by itaconate stimulation. Our results demonstrate the counteracting effects of overexpression of mitochondrial aconitase (ACO2, a tricarboxylic acid cycle enzyme) or cytosolic aconitase (ACO1, an iron regulatory protein) on IL-1β secretion and altered iron metabolism. Both enzyme activities were inhibited by itaconate because of iron-sulfur (Fe-S) cluster destruction. Our findings indicate that the immunoregulatory functions of IRG1 and itaconate in macrophages are stressful Fe-S cluster of aconitases disrupting and iron metabolism rebalancing.

中文翻译：

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衣康酸盐通过压力铁硫簇破坏和铁代谢重新平衡来调节巨噬细胞功能

脂多糖 (LPS) 刺激的巨噬细胞表达乌头酸脱羧酶 (IRG1，也称为 ACOD1)，导致内源性代谢物衣康酸的积累。然而，衣康酸水平升高改变巨噬细胞功能的确切机制尚不清楚。我们的假设是衣康酸通过一些不确定的机制影响巨噬细胞功能。基于此，我们建立了衣康酸盐刺激的巨噬细胞的转录和蛋白质组学特征，并确定了 IL-1β 分泌和铁代谢改变的途径。一致地，IRG1 缺乏对 IL-1β 分泌和铁代谢的影响在 IRG1 敲除 THP-1 细胞系中得到证实。几种常见的抑制剂和其他化合物用于检查所涉及的分子机制。只有半胱氨酸和抗氧化剂（儿茶素水合物）可以抑制衣康酸盐刺激的巨噬细胞中的 caspase-1 激活和 IL-1β 分泌。我们进一步发现，衣康酸刺激降低了乌头酸酶活性。我们的结果证明了线粒体乌头酸酶（ACO2，一种三羧酸循环酶）或细胞质乌头酸酶（ACO1，一种铁调节蛋白）的过度表达对 IL-1β 分泌和铁代谢改变的抵消作用。由于铁硫 (Fe-S) 簇的破坏，这两种酶的活性都被衣康酸抑制。我们的研究结果表明，IRG1 和衣康酸在巨噬细胞中的免疫调节功能是应激性的 Fe-S 乌头酶簇破坏和铁代谢重新平衡。我们进一步发现，衣康酸刺激降低了乌头酸酶活性。我们的结果证明了线粒体乌头酸酶（ACO2，一种三羧酸循环酶）或细胞质乌头酸酶（ACO1，一种铁调节蛋白）的过度表达对 IL-1β 分泌和铁代谢改变的抵消作用。由于铁硫 (Fe-S) 簇的破坏，这两种酶的活性都被衣康酸抑制。我们的研究结果表明，IRG1 和衣康酸在巨噬细胞中的免疫调节功能是应激性的 Fe-S 乌头酶簇破坏和铁代谢重新平衡。我们进一步发现，衣康酸刺激降低了乌头酸酶活性。我们的结果证明了线粒体乌头酸酶（ACO2，一种三羧酸循环酶）或细胞质乌头酸酶（ACO1，一种铁调节蛋白）的过度表达对 IL-1β 分泌和铁代谢改变的抵消作用。由于铁硫 (Fe-S) 簇的破坏，这两种酶的活性都被衣康酸抑制。我们的研究结果表明，IRG1 和衣康酸在巨噬细胞中的免疫调节功能是应激性的 Fe-S 乌头酶簇破坏和铁代谢重新平衡。一种铁调节蛋白）对 IL-1β 分泌和铁代谢改变的影响。由于铁硫 (Fe-S) 簇的破坏，这两种酶的活性都被衣康酸抑制。我们的研究结果表明，IRG1 和衣康酸在巨噬细胞中的免疫调节功能是应激性的 Fe-S 乌头酶簇破坏和铁代谢重新平衡。一种铁调节蛋白）对 IL-1β 分泌和铁代谢改变的影响。由于铁硫 (Fe-S) 簇的破坏，这两种酶的活性都被衣康酸抑制。我们的研究结果表明，IRG1 和衣康酸在巨噬细胞中的免疫调节功能是应激性的 Fe-S 乌头酶簇破坏和铁代谢重新平衡。