Magwenzi Simbarashe, Woodward Casey, Wraith Katie S, Aburima Ahmed, Raslan Zaher, Jones Huw, McNeil Catriona, Wheatcroft Stephen, Yuldasheva Nadira, Febbriao Maria, Kearney Mark, Naseem Khalid M
Centre for Cardiovascular and Metabolic Research, Hull-York Medical School, Thrombosis Research Laboratory (013/014), University of Hull, Hull, United Kingdom;
Division of Cardiovascular and Diabetes Research, Leeds Multidisciplinary Cardiovascular Research Centre, LIGHT Laboratories, University of Leeds, Leeds, United Kingdom; and.
Blood. 2015 Apr 23;125(17):2693-703. doi: 10.1182/blood-2014-05-574491. Epub 2015 Feb 20.
Oxidized low-density lipoprotein (oxLDL) promotes unregulated platelet activation in dyslipidemic disorders. Although oxLDL stimulates activatory signaling, it is unclear how these events drive accelerated thrombosis. Here, we describe a mechanism for oxLDL-mediated platelet hyperactivity that requires generation of reactive oxygen species (ROS). Under arterial flow, oxLDL triggered sustained generation of platelet intracellular ROS, which was blocked by CD36 inhibitors, mimicked by CD36-specific oxidized phospholipids, and ablated in CD36(-/-) murine platelets. oxLDL-induced ROS generation was blocked by the reduced NAD phosphate oxidase 2 (NOX2) inhibitor, gp91ds-tat, and absent in NOX2(-/-) mice. The synthesis of ROS by oxLDL/CD36 required Src-family kinases and protein kinase C (PKC)-dependent phosphorylation and activation of NOX2. In functional assays, oxLDL abolished guanosine 3',5'-cyclic monophosphate (cGMP)-mediated signaling and inhibited platelet aggregation and arrest under flow. This was prevented by either pharmacologic inhibition of NOX2 in human platelets or genetic ablation of NOX2 in murine platelets. Platelets from hyperlipidemic mice were also found to have a diminished sensitivity to cGMP when tested ex vivo, a phenotype that was corrected by infusion of gp91ds-tat into the mice. This study demonstrates that oxLDL and hyperlipidemia stimulate the generation of NOX2-derived ROS through a CD36-PKC pathway and may promote platelet hyperactivity through modulation of cGMP signaling.
氧化型低密度脂蛋白(oxLDL)在血脂异常疾病中促进血小板的失控活化。尽管oxLDL刺激活化信号传导,但目前尚不清楚这些事件如何导致血栓形成加速。在此,我们描述了一种oxLDL介导的血小板过度活跃的机制,该机制需要产生活性氧(ROS)。在动脉血流条件下,oxLDL触发血小板细胞内ROS的持续产生,这被CD36抑制剂阻断,被CD36特异性氧化磷脂模拟,并在CD36基因敲除(CD36(-/-))小鼠血小板中消失。oxLDL诱导的ROS产生被还原型烟酰胺腺嘌呤二核苷酸磷酸氧化酶2(NOX2)抑制剂gp91ds-tat阻断,且在NOX2基因敲除(NOX2(-/-))小鼠中不存在。oxLDL/CD36介导的ROS合成需要Src家族激酶以及蛋白激酶C(PKC)依赖的NOX2磷酸化和活化。在功能试验中,oxLDL消除了鸟苷3',5'-环磷酸(cGMP)介导的信号传导,并抑制了血流条件下的血小板聚集和黏附。这可通过对人血小板中NOX2的药理学抑制或小鼠血小板中NOX2的基因敲除来预防。在体外测试时,还发现高脂血症小鼠的血小板对cGMP的敏感性降低,向小鼠输注gp91ds-tat可纠正这一表型。这项研究表明,oxLDL和高脂血症通过CD36-PKC途径刺激NOX2衍生的ROS产生,并可能通过调节cGMP信号传导促进血小板过度活跃。