Institute of Cellular Biology and Pathology N. Simionescu of the Romanian Academy, Bucharest, Romania.
Biochem Biophys Res Commun. 2013 Apr 26;434(1):173-8. doi: 10.1016/j.bbrc.2013.03.050. Epub 2013 Mar 26.
The role of HDL in the modulation of endoplasmic reticulum (ER) stress in macrophage-derived foam cells is not completely understood. Therefore, we aimed to investigate whether HDL may inhibit ER stress in correlation with the secretion of apoE and CETP from lipid-loaded macrophages. To this purpose, THP-1 macrophages were loaded with lipids by incubation with human oxidized LDL (oxLDL) and then exposed to human HDL3. ER stress signaling markers, protein kinase/Jun-amino-terminal kinase (SAPK/JNK p54/p46) and eukaryotic initiation factor-2α (eIF2α), as well as the secreted apoE and CETP, were evaluated by immunoblot analysis. Out of the many different bioactive lipids of oxLDL, we tested the effect of 9-hydroxy-octadecadienoic acid (9-HODE) and 4-hydroxynonenal (4-HNE) on ER stress. Tunicamycin was used as positive control for ER stress induction. Results showed that oxLDL, 9-HODE and 4-HNE induce ER stress in human macrophages by activation of eIF-2α and SAPK/JNK (p54/p46) signaling pathways. OxLDL stimulated apoE and CETP secretion, while tunicamycin determined a reduction of the secreted apoE and CETP, both in control and lipid-loaded macrophages. The addition of HDL3 to the culture medium of tunicamycin-treated cells induced: (i) the reduction of ER stress, expressed as decreased levels of eIF-2α and SAPK/JNK, and (ii) a partial recovery of the secreted apoE and CETP levels in lipid-loaded macrophages. These data suggest a new mechanism by which HDL3 diminish ER stress and stimulate cholesterol efflux from lipid-loaded macrophages.
高密度脂蛋白（HDL）在调节巨噬细胞源性泡沫细胞内质网（ER）应激中的作用尚不完全清楚。因此，我们旨在研究 HDL 是否可以通过与载脂蛋白 E（apoE）和胆固醇酯转移蛋白（CETP）从脂质负载的巨噬细胞分泌相关来抑制 ER 应激。为此，用人氧化低密度脂蛋白（oxLDL）孵育 THP-1 巨噬细胞使其负载脂质，然后用人 HDL3 处理。通过免疫印迹分析评估 ER 应激信号标志物蛋白激酶/Jun-N 末端激酶（SAPK/JNK p54/p46）和真核起始因子 2α（eIF2α）以及分泌的 apoE 和 CETP。在 oxLDL 的许多不同生物活性脂质中，我们测试了 9-羟基十八碳烯酸（9-HODE）和 4-羟基壬烯酸（4-HNE）对 ER 应激的影响。衣霉素被用作 ER 应激诱导的阳性对照。结果表明，oxLDL、9-HODE 和 4-HNE 通过激活 eIF-2α 和 SAPK/JNK（p54/p46）信号通路诱导人巨噬细胞 ER 应激。oxLDL 刺激 apoE 和 CETP 的分泌，而衣霉素则导致未负载和负载脂质的巨噬细胞中分泌的 apoE 和 CETP 减少。在衣霉素处理的细胞培养基中添加 HDL3 可诱导：（i）减少 ER 应激，表现为 eIF-2α 和 SAPK/JNK 水平降低，以及（ii）部分恢复负载脂质的巨噬细胞中分泌的 apoE 和 CETP 水平。这些数据表明了 HDL3 减少 ER 应激并刺激载脂蛋白从负载脂质的巨噬细胞中流出的一种新机制。
