Estruch M, Rajamäki K, Sanchez-Quesada J L, Kovanen P T, Öörni K, Benitez S, Ordoñez-Llanos J
Biomedical Research Institute Sant Pau (IIB-Sant Pau), Barcelona (Spain). C/Sant Antoni M. Claret, 167 08025 Barcelona, Spain.
Wihuri Research Institute (WRI). Haartmaninkatu, 8 FI-00290 Helsinki, Finland.
Biochim Biophys Acta. 2015 Nov;1851(11):1442-9. doi: 10.1016/j.bbalip.2015.08.009. Epub 2015 Aug 29.
Electronegative LDL (LDL(−)), a modified LDL fraction found in blood, induces the release of inflammatory mediators in endothelial cells and leukocytes. However, the inflammatory pathways activated by LDL(−) have not been fully defined. We aim to study whether LDL(−) induced release of the first-wave proinflammatory IL-1β in monocytes and monocyte-derived macrophages (MDM) and the mechanisms involved.
LDL(−) was isolated from total LDL by anion exchange chromatography. Monocytes and MDM were isolated from healthy donors and stimulated with LDL(+) and LDL(−) (100 mg apoB/L).
In monocytes, LDL(−) promoted IL-1β release in a time-dependent manner, obtaining at 20 h-incubation the double of IL-1β release induced by LDL(−) than by native LDL. LDL(−)-induced IL-1β release involved activation of the CD14-TLR4 receptor complex. LDL(−) induced priming, the first step of IL-1β release, since it increased the transcription of pro-IL-1β (8-fold) and NLRP3 (3-fold) compared to native LDL. Several findings show that LDL(−) induced inflammasome activation, the second step necessary for IL-1β release. Preincubation of monocytes with K+ channel inhibitors decreased LDL(−)-induced IL-1β release. LDL(−) induced formation of the NLRP3-ASC complex. LDL(−) triggered 2-fold caspase-1 activation compared to native LDL and IL-1β release was strongly diminished in the presence of the caspase-1 inhibitor Z-YVAD. In MDM, LDL(−) promoted IL-1β release, which was also associated with caspase-1 activation.
LDL(−) promotes release of biologically active IL-1β in monocytes and MDM by induction of the two steps involved: priming and NLRP3 inflammasome activation.
By IL-1β release, LDL(−) could regulate inflammation in atherosclerosis.
血液中发现的一种修饰型低密度脂蛋白——带负电荷的低密度脂蛋白（LDL(−)）可诱导内皮细胞和白细胞释放炎症介质。然而，LDL(−)激活的炎症途径尚未完全明确。我们旨在研究LDL(−)是否能诱导单核细胞和单核细胞衍生巨噬细胞（MDM）释放第一波促炎细胞因子白细胞介素-1β（IL-1β）及其相关机制。
通过阴离子交换色谱法从总低密度脂蛋白中分离出LDL(−)。从健康供体中分离出单核细胞和MDM，并用LDL(+)和LDL(−)（100 mg载脂蛋白B/L）进行刺激。
在单核细胞中，LDL(−)以时间依赖性方式促进IL-1β释放，在孵育20小时时，LDL(−)诱导的IL-1β释放量是天然低密度脂蛋白诱导量的两倍。LDL(−)诱导的IL-1β释放涉及CD14-TLR4受体复合物的激活。LDL(−)诱导了IL-1β释放的第一步——启动，因为与天然低密度脂蛋白相比，它使前体IL-1β（8倍）和NLRP3（3倍）的转录增加。多项研究结果表明，LDL(−)诱导了炎性小体激活，这是IL-1β释放的第二步。用钾通道抑制剂预孵育单核细胞可降低LDL(−)诱导的IL-1β释放。LDL(−)诱导了NLRP3-ASC复合物的形成。与天然低密度脂蛋白相比,LDL(−)触发的半胱天冬酶-1激活增加了2倍，并且在存在半胱天冬酶-1抑制剂Z-YVAD的情况下，IL-1β释放显著减少。在MDM中，LDL(−)促进IL-1β释放，这也与半胱天冬酶-1激活有关。
LDL(−)通过诱导启动和NLRP3炎性小体激活这两个步骤，促进单核细胞和MDM释放具有生物活性的IL-1β。
通过释放IL-1β，LDL(−)可能调节动脉粥样硬化中的炎症反应。
