Gharavi Nima M, Baker Nancy A, Mouillesseaux Kevin P, Yeung Winnie, Honda Henry M, Hsieh Xavier, Yeh Michael, Smart Eric J, Berliner Judith A
Division of Cardiology, Department of Medicine, University of California, Los Angeles, USA.
Circ Res. 2006 Mar 31;98(6):768-76. doi: 10.1161/01.RES.0000215343.89308.93. Epub 2006 Feb 23.
Oxidized-1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphorylcholine (Ox-PAPC), found in atherosclerotic lesions and other sites of chronic inflammation, activates endothelial cells (EC) to synthesize chemotactic factors, such as interleukin (IL)-8. Previously, we demonstrated that the sustained induction of IL-8 transcription by Ox-PAPC was mediated through the activation of sterol regulatory element-binding protein (SREBP). We now present evidence for the role of endothelial nitric oxide synthase (eNOS) in the activation of SREBP by Ox-PAPC. Ox-PAPC treatment of EC induced a dose- and time-dependent activation of eNOS, as measured by phosphorylation of serine 1177, dephosphorylation of threonine 495, and the conversion of L-arginine to L-citrulline. Activation of eNOS by Ox-PAPC was regulated through a phosphatidylinositol-3-kinase/Akt-mediated mechanism. These studies also demonstrated that pretreatment of EC with NOS inhibitor, Nomega-nitro-L-arginine-methyl ester (L-NAME), significantly inhibited Ox-PAPC-induced IL-8 synthesis. Because SREBP activation had been previously shown to regulate IL-8 transcription by Ox-PAPC, we examined the effects of L-NAME on Ox-PAPC-induced SREBP activation. Our data demonstrated that Ox-PAPC-induced SREBP activation and expression of SREBP target genes were significantly reduced by pretreatment with L-NAME. Interestingly, treatment of EC with NO donor, S-nitroso-N-acetylpenicillamine, did not activate SREBP, suggesting that NO alone was not sufficient for SREBP activation. Rather, our findings indicated that superoxide (O2*-), in combination with NO, regulated SREBP activation by Ox-PAPC. We found that Ox-PAPC treatment generated O2*- through an eNOS-mediated mechanism and that mercaptoethylguanidine, a peroxynitrite scavenger, reduced SREBP activation by Ox-PAPC. Taken together, these findings propose a novel role for eNOS in the activation of SREBP and SREBP-mediated inflammatory processes.
氧化型1-棕榈酰-2-花生四烯酰-sn-甘油-3-磷酸胆碱（Ox-PAPC）存在于动脉粥样硬化病变及其他慢性炎症部位，可激活内皮细胞（EC）合成趋化因子，如白细胞介素（IL）-8。此前，我们证明Ox-PAPC对IL-8转录的持续诱导是通过固醇调节元件结合蛋白（SREBP）的激活介导的。我们现在提供证据表明内皮型一氧化氮合酶（eNOS）在Ox-PAPC激活SREBP中发挥作用。用Ox-PAPC处理EC可诱导eNOS呈剂量和时间依赖性激活，这可通过丝氨酸1177的磷酸化、苏氨酸495的去磷酸化以及L-精氨酸向L-瓜氨酸的转化来衡量。Ox-PAPC对eNOS的激活是通过磷脂酰肌醇-3-激酶/蛋白激酶B（Akt）介导的机制调节的。这些研究还表明，用一氧化氮合酶抑制剂Nω-硝基-L-精氨酸甲酯（L-NAME）预处理EC可显著抑制Ox-PAPC诱导的IL-8合成。由于此前已表明SREBP激活可调节Ox-PAPC诱导的IL-8转录，我们研究了L-NAME对Ox-PAPC诱导的SREBP激活的影响。我们的数据表明，用L-NAME预处理可显著降低Ox-PAPC诱导的SREBP激活和SREBP靶基因的表达。有趣的是，用一氧化氮供体S-亚硝基-N-乙酰青霉胺处理EC并未激活SREBP，这表明单独的一氧化氮不足以激活SREBP。相反，我们的研究结果表明，超氧阴离子（O2*-）与一氧化氮结合可调节Ox-PAPC对SREBP的激活。我们发现Ox-PAPC处理通过eNOS介导的机制产生O2*-，而过氧亚硝酸盐清除剂巯基乙胍可降低Ox-PAPC对SREBP的激活。综上所述，这些研究结果揭示了eNOS在激活SREBP和SREBP介导的炎症过程中的新作用。
