低脂联素血症在高脂诱发动脉血栓形成中的作用及机制

Thrombus formation contributes greatly to cardia-cerebrovascular diseases. Hyperlipidemia plays a key role in thrombotic diseases. However, the molecular mechanisms of hyperlipidemia-induced thrombosis remain elusive. Our previous study demonstrated that treatment with adiponectin improves endothelial function and inhibits platelets aggregation. Preliminary experiments further revealed that the endothelial and platelet regulatory effects of adiponectin may involve attenuating oxidative/nitrative stress. Our recent clinical research showed that plasma levels of adiponectin is significantly reduced in hyperlipidemic patients. The current grant application is designed to demonstrate the following novel hypothesis: Endothelial dysfunction and platelet aggregation caused by hypoadiponectinemia is a crucial factor in hyperlipidemia-induced thrombosis, which is largely attributable to augmented oxidative/nitrative stress. Utilizing pharmacology and gene interference methods, we aim to: 1)Clarify the relationship of the levels/activity of adiponectin with activity of platelet in hyperlipidemia; 2)Determine the regulative effects of adiponectin on oxidative/nitrative stress levels of endothelium and platelet; 3)Identify the effects of hypoadiponectinemia in hyperlipidemia-induced thrombosis by utilizing a hyperlipidemic thrombus model and adiponectin knockout animals. Verifying these problems will help us to understand whether and how the adipokine adiponectin influences the cardiovascular system and provide novel targets for preventing and treating the thrombopoiesis in hyperlipidemia.

病理性血栓形成是多种心脑血管疾病的共同成因，而高脂血症是引发血栓性疾病的重要危险因素,但分子机理尚未完全阐明。我们前期研究表明，脂肪细胞因子脂联素具有改善内皮功能及抑制血小板活化作用，预实验研究进一步表明，氧化/硝化应激可能在其中发挥重要作用；我们新近的临床研究发现，高脂血症患者脂联素水平显著降低。据此我们提出科学假设：高脂血症时脂联素水平下降是导致内皮功能紊乱和血小板活化增强从而易形成血栓的重要环节，其机制与血管内皮及血小板氧化/硝化应激增强有关。本课题拟采用药理学与基因干预方法，揭示高脂血症血浆脂联素水平/活性与血小板活性的因果关系，阐明脂联素对血管内皮与血小板氧化/硝化应激的调节效应，并采用高脂血症血栓模型及脂联素敲除动物，验证低脂联素血症在高脂诱发血栓形成中的作用。阐明上述问题，可为深入认识脂联素心血管作用提供新的实验依据、并为防治高脂血症血栓性疾病提供新策略和新靶点。

高脂血症是引发血栓性疾病的重要危险因素之一。我们在前期临床研究中发现，高脂血症并发动脉粥样硬化患者的脂联素水平显著降低(Clin Endocrinol,2013)；前期研究还表明，脂联素具有改善内皮功能及抑制血小板活化作用(Am J Physiol,2007;Physiol Res,2011)。进一步的研究结果显示，氧化/硝化应激可能在其中发挥重要作用。据此我们提出科学假设：高脂血症时脂联素水平下降是导致血小板活化聚集从而易形成血栓的重要环节，其机制与血管内皮及血小板氧化/硝化应激增强有关。本课题采用了药理学与基因干预方法，观察高脂血症血浆脂联素水平/活性与血小板活性的联系，进一步探讨脂联素对血管内皮与血小板氧化/硝化应激的调节效应，并采用高脂血症动物及脂联素过表达及敲除小鼠验证之。在本项目资助下，申请者在国际上首次发现：①高脂血症时不仅脂联素水平显著降低，其对下游AMPK的磷酸化作用降低，表明脂联素活性亦显著降低。②与正常血小板相比，外源性脂联素对高脂血症血小板聚集的抑制作用显著降低。③分离正常及高脂血症大鼠血浆脂联素，并保证其活性的情况下，与正常大鼠来源的脂联素相比，高脂血症大鼠来源的脂联素对正常血小板聚集的抑制作用显著降低。④脂联素抑制血小板活化聚集的机制体现在：抑制血浆α颗粒膜蛋白GMP-140等血小板活性相关因子的表达；通过增强eNOS活性促进NO的生成；通过降低超氧阴离子、亚硝酸盐及硝基酪氨酸含量减少血小板氧化/硝化应激水平。以上实验结果明确了高脂血症中脂联素水平下降是导致血小板活化聚集增强的直接因素；证实了脂联素可通过降低血小板氧化/硝化应激抑制高脂血症动物模型血小板活化聚集。不仅从理论上深入认识了脂联素的心血管保护机制，而且为临床防治高脂血症血栓性疾病提供了新线索和新思路。