Cardiovascular Center and Division of Cardiology, Department of Internal Medicine, National Taiwan University College of Medicine, Taipei, Taiwan.
Department of Biochemistry and Molecular Biology, National Taiwan University College of Medicine, Taipei, Taiwan.
Mediators Inflamm. 2019 Aug 22;2019:6163130. doi: 10.1155/2019/6163130. eCollection 2019.
Electronegative low-density lipoprotein (LDL(-)) has been found in the plasma of familial hypercholesterolemia and acute myocardial infarction and has been implicated in atherosclerosis and cardiovascular disease. However, less is known about the involvement of LDL(-) in atherosclerosis-related inflammation. This study aims at investigating the inducibility of LDL(-) by atherogenic diet in rabbits and at exploring the proinflammatory potential of the diet-induced LDL(-) in macrophages. Rabbits were fed with an atherogenic diet; LDL was isolated from plasma by NaBr density gradient ultracentrifugation and was then resolved into nLDL and LDL(-) by anion-exchange chromatography. Isolated nLDL and LDL(-) were directly used or incubated with 10 M CuSO for 24 h to produce copper- (Cu-) ox-nLDL and Cu-ox-LDL(-). The effects of these LDLs on inflammation were evaluated in THP-1-derived macrophages. Macrophages were treated with nLDL, LDL(-), and extensively oxidized LDL (ox-LDL), then the levels of interleukin- (IL-) 1, IL-6, and tumor necrosis factor- (TNF-) in a culture medium were determined by ELISA, and the levels of total and phosphorylated IB, p65, p38, JNK, and ERK in cell lysates were determined by Western blotting. The LDL(-) induced significantly higher levels of IL-1, IL-6, and TNF- in the medium. The levels of phosphorylated/total IB, p65, p38, JNK, and ERK were also upregulated by LDL(-). In contrast, nLDL, Cu-ox-nLDL, and Cu-ox-LDL(-) exhibited much less effect. Knockdown of lectin-type oxidized LDL receptor- (LOX-) 1 resulted in significant reduction in LDL(-)-induced IL-1, IL-6, and TNF-. In addition, these LDL(-) effects were also markedly attenuated by inhibition of NF-B and ERK1/2. The data suggested that LDL(-) induced inflammation through LOX-1-, NF-B-, and ERK1/2-dependent pathways. Taken together, our results show that rabbits fed with atherogenic diet produce a highly proinflammatory LDL(-) that is more potent in inducing inflammation than nLDL and extensively oxidize LDL in macrophages. The results thus provide a novel link between diet-induced hypercholesterolemia and inflammation.
电负性低密度脂蛋白（LDL(-)）已在家族性高胆固醇血症和急性心肌梗死患者的血浆中发现，并与动脉粥样硬化和心血管疾病有关。然而，关于 LDL(-)在动脉粥样硬化相关炎症中的作用知之甚少。本研究旨在探讨致动脉粥样硬化饮食在兔体内诱导 LDL(-)的能力，并探讨饮食诱导的 LDL(-)在巨噬细胞中的促炎作用。兔子喂食致动脉粥样硬化饮食；通过 NaBr 密度梯度超速离心从血浆中分离 LDL，然后通过阴离子交换色谱将其分为 nLDL 和 LDL(-)。分离的 nLDL 和 LDL(-)直接使用或用 10 μM CuSO4孵育 24 小时，产生铜（Cu）氧化 nLDL 和 Cu 氧化 LDL(-)。用这些 LDL 评估其在 THP-1 衍生的巨噬细胞中的炎症作用。用 nLDL、LDL(-)和高度氧化的 LDL (ox-LDL)处理巨噬细胞，然后通过 ELISA 测定培养基中白细胞介素 (IL-) 1、IL-6 和肿瘤坏死因子 (TNF-)的水平，并用 Western 印迹测定细胞裂解物中总蛋白和磷酸化 IB、p65、p38、JNK 和 ERK 的水平。LDL(-)诱导培养基中 IL-1、IL-6 和 TNF-水平显著升高。LDL(-)还上调了磷酸化/总 IB、p65、p38、JNK 和 ERK 的水平。相比之下，nLDL、Cu-ox-nLDL 和 Cu-ox-LDL(-)的作用要小得多。Lectin 型氧化 LDL 受体（LOX-1）的敲低导致 LDL(-)诱导的 IL-1、IL-6 和 TNF-显著减少。此外，NF-B 和 ERK1/2 的抑制也显著减弱了这些 LDL(-)的作用。数据表明，LDL(-)通过 LOX-1、NF-B 和 ERK1/2 依赖性途径诱导炎症。总之，我们的结果表明，喂食致动脉粥样硬化饮食的兔子产生一种高度促炎的 LDL(-)，其在诱导巨噬细胞炎症方面比 nLDL 和高度氧化的 LDL 更有效。因此，该结果为饮食诱导的高胆固醇血症与炎症之间提供了新的联系。
