Institute of Molecular Biology and Biochemistry, Harrachgasse 21/III, Medical University Graz, 8010 Graz, Austria.
Atherosclerosis. 2011 Feb;214(2):338-44. doi: 10.1016/j.atherosclerosis.2010.11.007. Epub 2010 Nov 13.
Previously we identified palmitoyl-lysophosphatidylcholine (LPC 16:0), as well as linoleoyl-, arachidonoyl- and oleoyl-LPC (LPC 18:2, 20:4 and 18:1) as the most prominent LPC species generated by the action of endothelial lipase (EL) on high-density lipoprotein (HDL). In the present study, the impact of EL and EL-generated LPC on interleukin-8 (IL-8) synthesis was examined in vitro in primary human aortic endothelial cells (HAEC) and in mice.
Adenovirus-mediated overexpression of the catalytically active EL, but not its inactive mutant, increased endothelial synthesis of IL-8 mRNA and protein in a time- and HDL-concentration-dependent manner. While LPC 18:2 was inactive, LPC 16:0, 18:1 and 20:4 promoted IL-8 mRNA- and protein-synthesis, differing in potencies and kinetics. The effects of all tested LPC on IL-8 synthesis were completely abrogated by addition of BSA and chelation of intracellular Ca(2+). Underlying signaling pathways also included NFkB, p38-MAPK, ERK, PKC and PKA. In mice, adenovirus-mediated overexpression of EL caused an elevation in the plasma levels of MIP-2 (murine IL-8 analogue) accompanied by a markedly increased plasma LPC/PC ratio. Intravenously injected LPC also raised MIP-2 plasma concentration, however to a lesser extent than EL overexpression.
Our results indicate that EL and EL-generated LPC, except of LPC 18:2, promote endothelial IL-8 synthesis, with different efficacy and kinetics, related to acyl-chain length and degree of saturation. Accordingly, due to its capacity to modulate the availability of the pro-inflammatory and pro-adhesive chemokine IL-8, EL should be considered an important player in the development of atherosclerosis.
我们先前发现，棕榈酰溶血磷脂胆碱（LPC16:0）以及亚油酸酰基、花生四烯酸酰基和油酰基-LPC（LPC18:2、20:4 和 18:1）是内皮脂肪酶（EL）作用于高密度脂蛋白（HDL）时生成的最主要的 LPC 物质。在本研究中，我们在原代人主动脉内皮细胞（HAEC）和小鼠中检测了 EL 和 EL 生成的 LPC 对白细胞介素-8（IL-8）合成的影响。
通过腺病毒介导的催化活性 EL 的过表达，而不是其无活性突变体，以时间和 HDL 浓度依赖的方式增加内皮细胞 IL-8mRNA 和蛋白的合成。虽然 LPC18:2 无活性，但 LPC16:0、18:1 和 20:4 以不同的效力和动力学促进 IL-8mRNA 和蛋白的合成。所有测试的 LPC 对 IL-8 合成的作用都可以通过添加 BSA 和螯合细胞内 Ca2+完全消除。潜在的信号通路还包括 NFkB、p38-MAPK、ERK、PKC 和 PKA。在小鼠中，腺病毒介导的 EL 过表达导致 MIP-2（鼠类 IL-8 类似物）的血浆水平升高，同时血浆 LPC/PC 比值显著增加。静脉注射 LPC 也会升高 MIP-2 的血浆浓度，但程度低于 EL 过表达。
我们的结果表明，EL 和 EL 生成的 LPC（除了 LPC18:2）促进内皮细胞 IL-8 的合成，其效力和动力学不同，与酰基链长度和饱和度有关。因此，由于其调节促炎和促黏附趋化因子 IL-8 可用性的能力，EL 应被视为动脉粥样硬化发生的重要参与者。
