OBJECTIVE Highly elevated plasma levels of interleukin-10 (IL-10) are causally associated with "Disappearing HDL Syndrome" and low plasma LDL-cholesterol, but the underlying mechanism is poorly understood. Fluid-phase endocytosis, a process highly dependent on actin dynamics, enables cells to internalize relatively high amounts of extracellular fluids and solutes. We sought to investigate whether IL-10 induces lipoprotein uptake by fluid-phase endocytosis in macrophages. METHODS AND RESULTS Macrophages (RAW264.7, Kupffer and human) were incubated with vehicle (PBS) or IL-10 (20 ng/ml) for 7 days. Uptake of HDL, LDL, and/or fluid-phase endocytosis probes (albumin-Alexa680®, 70 kDa FITC-Dextran and Lucifer Yellow, LY) was evaluated by FACS. Intracellular cofilin and phosphorylated cofilin (p-cofilin) levels were determined by immunoblotting. Macrophage uptake of lipoproteins and probes was non-saturable and increased after IL-10 incubation (p < 0.0001). Furthermore, pre-incubation with fluid-phase endocytosis inhibitors (LY294002, Latrunculin A, and Amiloride) significantly reduced uptake (p < 0.05). IL-10 increased the cofilin/p-cofilin ratio (p = 0.021), signifying increased cofilin activation and hence filamentous actin. Consistently, phalloidin staining revealed increased filamentous actin in macrophages after IL-10 treatment (p = 0.0018). Finally, RNA-seq analysis demonstrated enrichment of gene sets related to actin filament dynamics, membrane ruffle formation and endocytosis in IL-10-treated macrophages (p < 0.05). IL-10 did not alter mRNA levels of Ldlr, Vldlr, Scarb1, Cd36 or Lrp1. In primary human monocyte-derived macrophages and murine Kupffer cells, IL-10 incubation also increased uptake of lipoproteins, albumin and LY (p < 0.01). CONCLUSIONS Interleukin-10 induces the uptake of HDL and LDL by fluid-phase endocytosis by increasing actin-filament rearrangement in macrophages, thus providing a plausible mechanism contributing to "Disappearing HDL Syndrome".

中文翻译：

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白介素10通过刺激液相内吞作用来促进巨噬细胞对HDL和LDL的摄取。

目的血浆白细胞介素10（IL-10）的高度升高与“消失的HDL综合征”和血浆LDL-胆固醇低有因果关系，但其潜在机制尚不清楚。液相内吞作用是高度依赖肌动蛋白动力学的过程，可使细胞内化相对大量的细胞外液和溶质。我们试图研究IL-10是否通过巨噬细胞中的液相内吞作用诱导脂蛋白摄取。方法和结果将巨噬细胞（RAW264.7，Kupffer和人类）与溶媒（PBS）或IL-10（20 ng / ml）孵育7天。通过FACS评估了HDL，LDL和/或液相内吞探针（albumin-Alexa680®，70 kDa FITC-Dextran和Lucifer Yellow，LY）的摄取。通过免疫印迹测定细胞内cofilin和磷酸化cofilin（p-cofilin）的水平。IL-10孵育后，巨噬细胞对脂蛋白和探针的摄取不饱和，并且增加（p <0.0001）。此外，与液相内吞抑制剂（LY294002，Latrunculin A和Amiloride）预温育可显着降低摄取（p <0.05）。IL-10增加了cofilin / p-cofilin比率（p = 0.021），表明cofilin活化增加，因此丝状肌动蛋白增加。一致地，鬼笔环肽染色显示IL-10治疗后巨噬细胞中丝状肌动蛋白增加（p = 0.0018）。最后，RNA-seq分析表明，IL-10处理的巨噬细胞中与肌动蛋白丝动力学，膜褶皱形成和胞吞有关的基因集富集（p <0.05）。IL-10不会改变Ldlr，Vldlr，Scarb1，Cd36或Lrp1。在原代人单核细胞衍生的巨噬细胞和鼠Kupffer细胞中，IL-10孵育还增加了脂蛋白，白蛋白和LY的摄取（p <0.01）。结论Interleukin-10通过增加巨噬细胞中肌动蛋白丝的重排，通过液相内吞作用诱导HDL和LDL的摄取，从而为“消失的HDL综合征”提供了可能的机制。