Diabetes and Obesity Center, University of Louisville, Louisville, Kentucky 40202, USA.
J Biol Chem. 2012 Mar 30;287(14):11398-409. doi: 10.1074/jbc.M111.320416. Epub 2012 Jan 6.
Lipid peroxidation products, such as 4-hydroxy-trans-2-nonenal (HNE), cause endothelial activation, and they increase the adhesion of the endothelium to circulating leukocytes. Nevertheless, the mechanisms underlying these effects remain unclear. We observed that in HNE-treated human umbilical vein endothelial cells, some of the protein-HNE adducts colocalize with the endoplasmic reticulum (ER) and that HNE forms covalent adducts with several ER chaperones that assist in protein folding. We also found that at concentrations that did not induce apoptosis or necrosis, HNE activated the unfolded protein response, leading to an increase in XBP-1 splicing, phosphorylation of protein kinase-like ER kinase and eukaryotic translation initiation factor 2α, and the induction of ATF3 and ATF4. This increase in eukaryotic translation initiation factor 2α phosphorylation was prevented by transfection with protein kinase-like ER kinase siRNA. Treatment with HNE increased the expression of the ER chaperones, GRP78 and HERP. Exposure to HNE led to a depletion of reduced glutathione and an increase in the production of reactive oxygen species (ROS); however, glutathione depletion and ROS production by tert-butyl-hydroperoxide did not trigger the unfolded protein response. Pretreatment with a chemical chaperone, phenylbutyric acid, or adenoviral transfection with ATF6 attenuated HNE-induced monocyte adhesion and IL-8 induction. Moreover, phenylbutyric acid and taurine-conjugated ursodeoxycholic acid attenuated HNE-induced leukocyte rolling and their firm adhesion to the endothelium in rat cremaster muscle. These data suggest that endothelial activation by HNE is mediated in part by ER stress, induced by mechanisms independent of ROS production or glutathione depletion. The induction of ER stress may be a significant cause of vascular inflammation induced by products of oxidized lipids.
脂质过氧化产物，如 4-羟基-反式-2-壬烯醛（HNE），可引起内皮细胞激活，并增加内皮细胞与循环白细胞的黏附。然而，这些作用的机制尚不清楚。我们观察到，在 HNE 处理的人脐静脉内皮细胞中，一些蛋白-HNE 加合物与内质网（ER）共定位，并且 HNE 与几种帮助蛋白折叠的 ER 伴侣蛋白形成共价加合物。我们还发现，在没有诱导细胞凋亡或坏死的浓度下，HNE 激活未折叠蛋白反应，导致 XBP-1 剪接增加、蛋白激酶样内质网激酶和真核翻译起始因子 2α磷酸化，以及 ATF3 和 ATF4 的诱导。这种真核翻译起始因子 2α磷酸化的增加可通过转染蛋白激酶样内质网激酶 siRNA 来预防。HNE 处理增加了 ER 伴侣蛋白 GRP78 和 HERP 的表达。HNE 暴露导致还原型谷胱甘肽耗竭和活性氧（ROS）产生增加；然而，tert-butyl-hydroperoxide 引起的谷胱甘肽耗竭和 ROS 产生并没有引发未折叠蛋白反应。化学伴侣物苯丁酸预处理或 ATF6 的腺病毒转染减弱了 HNE 诱导的单核细胞黏附和 IL-8 诱导。此外，苯丁酸和牛磺酸结合的熊去氧胆酸减弱了 HNE 诱导的白细胞滚动及其在大鼠精索肌中的牢固黏附。这些数据表明，HNE 引起的内皮细胞激活部分是通过 ER 应激介导的，其机制独立于 ROS 产生或谷胱甘肽耗竭。ER 应激的诱导可能是氧化脂质产物引起血管炎症的一个重要原因。
