Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Valladolid, 47003 Valladolid, Spain.
Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), 28029 Madrid, Spain.
Cells. 2019 Aug 20;8(8):941. doi: 10.3390/cells8080941.
Human monocytes exposed to free arachidonic acid (AA), a secretory product of endothelial cells, acquire a foamy phenotype which is due to the accumulation of cytoplasmic lipid droplets with high AA content. Recruitment of foamy monocytes to the inflamed endothelium contributes to the development of atherosclerotic lesions. In this work, we investigated the potential role of AA stored in the neutral lipids of foamy monocytes to be cleaved by lipases and contribute to lipid mediator signaling. To this end, we used mass spectrometry-based lipidomic approaches combined with strategies to generate monocytes with different concentrations of AA. Results from our experiments indicate that the phospholipid AA pool in monocytes is stable and does not change upon exposure of the cells to the external AA. On the contrary, the AA pool in triacylglycerol is expandable and can accommodate relatively large amounts of fatty acid. Stimulation of the cells with opsonized zymosan results in the expected decreases of cellular AA. Under all conditions examined, all of the AA decreases observed in stimulated cells were accounted for by decreases in the phospholipid pool; we failed to detect any contribution of the triacylglycerol pool to the response. Experiments utilizing selective inhibitors of phospholipid or triacylglyerol hydrolysis confirmed that the phospholipid pool is the sole contributor of the AA liberated by stimulated cells. Thus, the AA in the triacylglycerol is not a source of free AA for the lipid mediator signaling during stimulation of human foamy monocytes and may be used for other cellular functions.
人类单核细胞暴露于内皮细胞的分泌产物游离花生四烯酸（AA）后，获得泡沫样表型，这是由于富含 AA 的细胞质脂质滴的积累。泡沫样单核细胞向炎症内皮细胞的募集有助于动脉粥样硬化病变的发展。在这项工作中，我们研究了储存于泡沫样单核细胞中性脂质中的 AA 被脂酶切割并有助于脂质介质信号的潜在作用。为此，我们使用了基于质谱的脂质组学方法，并结合了生成具有不同 AA 浓度的单核细胞的策略。我们实验的结果表明，单核细胞中磷脂 AA 池是稳定的，并且在细胞暴露于外部 AA 时不会改变。相反，甘油三酯中的 AA 池是可扩展的，可以容纳相对大量的脂肪酸。用包被的酵母聚糖刺激细胞会导致细胞内 AA 预期减少。在检查的所有条件下，刺激细胞中观察到的所有 AA 减少都归因于磷脂池的减少；我们未能检测到甘油三酯池对反应的任何贡献。利用磷脂或甘油三酯水解的选择性抑制剂进行的实验证实，磷脂池是受刺激细胞释放的 AA 的唯一来源。因此，在刺激人类泡沫样单核细胞期间，甘油三酯中的 AA 不是游离 AA 用于脂质介质信号的来源，并且可能用于其他细胞功能。
